Types of grooves. Milling of shoulders and grooves. Device for processing balusters, pillars and other bodies of rotation

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Slot milling

A recess of metal in a part, limited by shaped or flat surfaces, is called a groove. Grooves can be rectangular, T-shaped, dovetail, shaped, through, open, closed, etc. Processing grooves is a common operation on milling machines of various types and is carried out with disk, end and shaped cutters (Fig. 5.23).

Through rectangular grooves are most often milled with disk three-sided cutters (Fig. 5.23, a), disk groove or end mills (Fig. 5.23, b). When milling precise slots, the width of the disk cutter (end mill diameter) must be less than the width of the slot, and milling to a given size is carried out in several passes. Machining grooves with end mills requires the right choice the direction of rotation of the machine spindle relative to the helical grooves of the cutters. It should be mutually opposite.

Milling of closed grooves is carried out on vertical milling machines using end mills (Fig. 5.23, d). The diameter of the cutters should be 1...2 mm less than the width of the groove. Plunging to a given cutting depth is carried out by moving the table with the workpiece in the longitudinal and vertical directions, then the longitudinal movement of the table feed is turned on and the groove is milled to the required length, followed by finishing passes along the sides of the groove.

Curvilinear grooves are milled to their full depth in one working stroke. According to this condition, the resulting feed motion is assigned, equal to the sum of the vectors of the transverse and longitudinal feed motion. To reduce infeeding in places where the directions of the grooves change, it is necessary to process with cutters with minimal overhangs and reduce feed rates.

Milling of grooves of special profiles - T-shaped, dovetail-type - is carried out on vertical or longitudinal milling machines in three (T-shaped grooves) or two (dovetail-type grooves) transitions. Taking into account the unfavorable operating conditions of T-shaped and single-angle cutters used in these operations, the feed per tooth S should not exceed 0.03 mm/tooth; cutting speed - 20...25 m/min.

Features of keyway milling

Keyways on shafts are divided into through, open, closed and semi-closed. They can be prismatic, segmental, wedge, etc. (corresponding to the sections of the keys). It is convenient to fix the shaft blanks on the machine table in prisms. For short workpieces, one prism is sufficient. For long shaft lengths, the workpiece is mounted on two prisms. The correct location of the prism on the machine table is ensured with the help of a tenon at the base of the prism, which fits into the groove of the table (Fig. 5.24).

Keyways are milled with slotted disk cutters, backed slotted cutters (GOST 8543-71), keyed cutters (GOST 9140-78) and mounted cutters. The slot or key cutter must be installed in the diametral plane of the workpiece.

Milling of open keyways with a groove exiting along a circle, the radius of which is equal to the radius of the cutter, is carried out using disk cutters. Grooves in which the groove is not allowed to exit along the radius of the circle are milled with end or key cutters.

Sockets for segment keys are milled with shank and attachment cutters on horizontal and vertical milling machines. The direction of feed movement is only towards the center of the shaft (Fig. 5.25, a).

To obtain grooves that are precise in width, processing is carried out on special key-milling machines with pendulum feed (Fig. 5.25, b). With this method, the cutter cuts 0.2...0.4 mm and mills the groove along the entire length, then cuts again to the same depth and mills the groove along the entire length, but in a different direction.

An operation similar to slot milling is grooving on blanks of cutting tools. The grooves can be located on the cylindrical, conical or end part of the workpieces. Single-angle or double-angle cutters are used as a tool for grooving.

When milling angular grooves on the cylindrical part of a cutting tool with a rake angle γ = 0° using single-angle cutters, the tops of the cutter teeth must pass through the diametrical plane of the workpiece. The cutter is installed using a square (Fig. 5.26, a) in the center of the spindle inserted into the conical hole so that the tops of the teeth of the cutters and the center are aligned, and then the workpiece is moved in the transverse direction by an amount equal to half its diameter, or along the line drawn at the end or the cylindrical surface of the workpiece, passing through its center plane (Fig. 5.26, b).

When processing corner grooves with a given positive value of the rake angle γ, the end surface of a single-angle cutter must be located from the center plane at a certain distance x (Fig. 5.26, c), which can be determined by the formula

where D is the diameter of the workpiece, mm; γ - front angle,°.

When setting up the processing of angular grooves, the tops of the teeth of a double-angle cutter should be set in the diametrical plane using one of the methods discussed above, and then the workpiece should be shifted relative to the cutter by an amount x (Fig. 5.26, d), which depends on the workpiece diameter D, profile depth groove h, working cutter angle 8 and cutter rake angle γ:

x = D/(2sin(γ+δ) - hsinδ/cosγ).

At γ= 0° x = (D/2 - /0)sinδ.

The workpiece can be installed and secured in one of the following ways: at the centers of the index head and tailstock, or at the centers on the mandrel.

Angle cutters are also used when milling angular grooves on a tapered surface. The cutters are installed relative to the diametrical plane of the workpiece in the same way as when milling angular grooves on a cylindrical surface.

When milling angular grooves on a conical surface, the workpiece can be secured in a three-jaw chuck, on an end mandrel inserted into the conical hole of the index head spindle or into the centers of the index head and tailstock. The last of the listed methods for installing the workpiece is used with a small taper angle.

Shoulder milling

Two mutually perpendicular planes form a ledge. The workpieces may have one or more ledges. Processing of shoulders is a common operation, which is carried out with disk or end mills, or a set of disk cutters (Fig. 5.27, a - c) on horizontal and vertical milling machines in the same way as processing grooves. Large ledges are milled with end mills (Fig. 5.27, d).

Face milling cutters are used when milling workpieces with wide shoulders on horizontal and vertical milling machines. A part with symmetrically located ledges is processed on two-position rotary tables. After milling the first shoulder, the part in the fixture is rotated 180°.

For easily processed materials and materials of average processing difficulty with a large milling depth, disc cutters with normal and large teeth are used. Milling of difficult-to-cut materials should be done with cutters with normal and fine teeth. When milling a shoulder, you should use a disk cutter whose width is 5...6 mm larger than the width of the shoulder. In this case, the accuracy of the width of the shoulder does not depend on the width of the cutter.

Cutting blanks

The operations of completely separating part of the material from the workpiece, dividing the workpieces into separate parts, as well as the formation of one or several dimensional narrow grooves (slots, splines) are carried out with cutting and slotting cutters. The diameter of the cutting cutter should be chosen as small as possible. The smaller the diameter of the cutter, the higher its rigidity and vibration resistance. Workpieces are most often installed and secured in a vice (Fig. 5.28). It is preferable to cut thin sheet material and cut it into strips using down milling and small feeds (S_= 0.01...0.08 mm/tooth). Cutting speeds when cutting with cutting and slotting cutters made of high-speed steel, depending on the depth of milling and feed per tooth of the cutter, are: when processing workpieces made of gray cast iron v=12...65 m/min; from malleable cast iron - 27...75 m/min; made of steel - 24...60 m/min.

Inspection of grooves, ledges and cut workpieces

This operation is performed with a measuring instrument (Table 5.1).

Shoulder and groove milling

TO category:

Milling work

Shoulder and groove milling

A ledge is a recess limited by two mutually perpendicular planes forming a step. The part may have one, two or more ledges. A groove is a recess in a part, limited by planes or shaped surfaces. Depending on the shape of the recess, the grooves are divided into rectangular, T-shaped and shaped. Grooves of any profile can be through, open or with an exit and closed.

Processing of shoulders and grooves is one of the operations performed on milling machines. Milled shoulders and grooves are subject to different technical requirements depending on the purpose, serial production, dimensional accuracy, location accuracy and surface roughness. All these requirements determine the processing method.

Milling of shoulders and grooves is carried out with disk end mills, as well as a set of disk cutters. In addition, shoulders can be milled with end mills.

Milling shoulders and grooves with disc cutters. Disc cutters are designed for processing planes, shoulders and grooves. Disc cutters are distinguished between solid and inserted teeth. Solid disk cutters are divided into slotted (ST SEV 573-77), grooved backed (GOST 8543-71), three-sided with straight teeth (GOST 3755-78), three-sided with multi-directional small and normal teeth. Milling cutters with insert teeth are made three-sided (GOST 1669-78). Disc groove cutters have teeth only on the cylindrical part; they are used for milling shallow grooves. The main type of disk cutters are three-sided. They have teeth on the cylindrical surface and on both ends. They are used for processing ledges and deeper grooves. They provide a higher roughness class for the side walls of a groove or shoulder. To improve cutting conditions, three-sided disk cutters are equipped with inclined teeth with alternately alternating groove directions, i.e. one tooth has a right-hand groove direction, and the other adjacent to it has a left-hand direction. Therefore, such cutters are called multidirectional: Thanks to the alternating inclination of the teeth, the axial components of the cutting force of the right and left teeth are mutually balanced. These cutters have teeth on both ends. The main disadvantage of three-sided disk cutters is the reduction in width after the first regrinding along the end. When using adjustable cutters, consisting of two halves of the same thickness with overlapping teeth in the socket, after regrinding it is possible to restore the original size. This is achieved by using spacers of appropriate thickness made of copper or brass foil, which are placed in the socket between the cutters.

Rice. 1. Ledges

Rice. 2. Types of grooves by shape

Rice. 3. Manholes: through, with exit and closed

Disc cutters with insert knives equipped with hard alloy plates are three-sided (GOST 5348-69) and two-sided. Three-sided disk cutters are used for milling grooves, and two-sided ones are used for milling shoulders and planes. The insertion knives are fastened into the body of both types of cutters using axial corrugations and a wedge with an angle of 5°. The advantage of this method of attaching insert knives is the ability to compensate for wear and the layer removed during regrinding. Restoring the size in diameter is achieved by rearranging the knives by one or more corrugations, and in width - by correspondingly extending the knives. Three-sided cutters have knives with alternately alternating inclination with an angle of 10°, for double-sided ones - in one direction with an inclination angle of 10° (for right-cutting and left-cutting cutters).

The use of three-sided disk cutters with carbide inserts gives the highest productivity when processing grooves and shoulders. A disk cutter “holds” the size better than an end cutter.

Selecting the type and size of disk cutters. The type and size of the disk cutter are selected depending on the size of the surfaces being processed and the material of the workpiece. For given processing conditions, the type of cutter, the material of the cutting part and the main dimensions - B, D, d and z - are selected. For milling easily processed materials and materials of average processing difficulty with a large milling depth, cutters with normal large teeth are used. When processing difficult-to-cut materials and milling with small depths of cut, it is recommended to use cutters with normal and fine teeth.

The diameter of the cutter should be chosen as small as possible, since the smaller the diameter of the cutter, the higher its rigidity and vibration resistance. In addition, as the diameter increases, its durability increases.

Rice. 4. Selecting the diameter of disk cutters

In Fig. 5, a, b shows a diagram of milling two shoulders on a part. Milling of shoulders with disk cutters, as mentioned above, is usually carried out with a double-sided disk cutter. However, in our case, we should choose a three-sided disk cutter, since we need to process one shoulder on each side of the part in turn.

Rice. 5. Milling a shoulder with a disk cutter

Setting up a machine for milling through rectangular grooves using disk cutters. When milling shoulders, the accuracy of the width of the shoulder does not depend on the width of the cutter. Only one condition must be met: the width of the cutter must be greater than the width of the shoulder (if possible, no more than 3-5 mm).

When milling rectangular grooves, the width of the disk cutter should be equal to the width of the groove being milled in the case when the runout of the end teeth is zero. If there is runout of the cutter teeth, the size of the groove milled by such a cutter will be correspondingly larger than the width of the cutter. This should be kept in mind, especially when machining grooves that are precise in width.

Setting the cutting depth can be carried out according to the markings. To clearly highlight the marking lines, the workpiece is pre-painted with a chalk solution and recesses (cores) are applied to the line drawn by a surface scriber using a center punch. Setting the cutting depth along the marking line is carried out with trial passes. At the same time, make sure that the cutter cuts the allowance only half of the recesses from the center punch.

When setting up a machine for processing grooves, it is very important to correctly position the cutter relative to the workpiece being processed. In the case when the workpiece is installed in a special device, its position relative to the cutter is determined by the device itself.

Precise installation of cutters to a given depth is carried out using special settings or dimensions provided in the device. In Fig. Figure 6 shows diagrams for installing cutters to size using settings. Dimension 1 is a hardened steel plate (Fig. 6, a) or a square (Fig. 6, b, c), fixed to the body of the device. A measuring probe 3-5 mm thick is placed between the set and the cutting edge of the cutter tooth to avoid contact of the cutter tooth with the hardened surface of the set. If the processing of the same surface is carried out in two passes (roughing and finishing), then probes of different thicknesses are used to install cutters of the same size.

Milling shoulders and grooves with a set of disc cutters. When processing a batch of identical parts, simultaneous milling of two shoulders, two or more grooves can be carried out by a set of cutters. To obtain the required distance between the shoulders and grooves, a corresponding set of mounting rings is placed on the mandrel between the cutters.

When processing workpieces with a set of cutters, one cutter is installed according to the dimensions, since the relative position of the set on the mandrel is achieved by selecting mounting rings. When installing cutters to a given size, they resort to using special installation templates. For precise installation of cutters, plane-parallel end blocks and indicator stops are used. In Fig. Figure 7 shows a diagram of the arrangement of indicator stops on a horizontal milling machine for precise installation of cutters during transverse and vertical movements of the table. Using such a device, you can raise and lower the table by a given amount with accelerated movement, without fear of making a mistake in the count.

The feasibility of processing shoulders and grooves with a set of cutters can be established based on the total time spent (calculation time) per part for the compared options for processing grooves.

Milling shoulders and grooves with end mills. Shoulders and grooves can be machined with end mills on vertical and horizontal milling machines. End mills (GOST 17026-71*) are designed for processing planes, shoulders and grooves. They are manufactured with cylindrical and conical shanks. End mills are manufactured with normal and large teeth. Mills with normal teeth are used for semi-finishing and finishing machining of shoulders and grooves. Mills with large teeth are used for roughing.

Roughing end mills with backed teeth (GOST 4675-71) are intended for rough processing of workpieces obtained by casting and forging.

Carbide end mills (GOST 20533-75-20539-75) are manufactured in two types: equipped with carbide crowns for diameters 10-20 mm and screw plates (for diameters 16-50 mm).

Rice. 6. Application of installations for milling cutters

Currently, tool factories produce solid carbide end mills with a diameter of 3-10 mm and end mills with a solid carbide working part soldered into a steel conical shank. The diameter of the cutters is 14-18 mm, the number of teeth is three. The use of carbide cutters is especially effective when processing grooves and shoulders in workpieces made of hardened and difficult-to-cut steels.

The accuracy of grooves in width when processing them with measuring tools, such as disk and end mills, largely depends on the accuracy of the cutters used, as well as on the accuracy, rigidity of the milling machines and on the runout of the cutter after fastening in the spindle. The disadvantage of a measuring tool is the loss of its nominal size due to wear and after regrinding. For end mills, after the first regrinding along a cylindrical surface, the diameter size is distorted, and they turn out to be unsuitable for obtaining the exact width of the groove.

You can get the exact size of the groove width by processing it in two passes: roughing and finishing. During finishing, the cutter will only calibrate the groove in width, maintaining its size for a long period of time.

IN Lately chucks for securing end mills have appeared, allowing the installation of a cutter with adjustable eccentricity, i.e., adjustable runout. In Fig. 8 shows a collet chuck used at the Leningrad Machine Tool Association named after. Y. M. Sverdlova. The hole in the chuck body is bored eccentrically by 0.3 mm relative to its shank. A sleeve for collets is inserted into this hole with the same eccentricity relative to the inner diameter. The bushing is attached to the body with two bolts. When the sleeve is turned with a nut and the bolts are slightly loosened, a conditional increase in the diameter of the cutter occurs (one division per limbg corresponds to an increase in the diameter of the cutter by 0.04 mm).

When machining grooves with an end mill, the chips must be directed upward along the helical groove so that they do not spoil the machined surface or cause breakage of the cutter tooth. This is possible in the case when the direction of the helical groove coincides with the direction of rotation of the cutter, i.e., when they are in the same direction. However, the axial component of the cutting force Px will be directed downward to push the cutter out of the spindle socket. Therefore, when machining grooves, the cutter must be fastened more securely than when machining an open plane with an end mill. The direction of rotation of the cutter and helical groove, as in the case of machining with face and cylindrical cutters, should be opposite, since in this case the axial component of the cutting force will be directed towards the spindle socket and tend to tighten the mandrel with the cutter into the spindle socket.

Rice. 8. Chuck for milling measuring grooves with standard cutters

Rice. 9. Milling an inclined plane in a vice

Rice. 10. Milling the recess of the body part

Other types of work performed by end mills. In addition to processing shoulders and grooves, end mills are used to perform other work on vertical and horizontal milling machines.

End mills are used for processing open planes: vertical, horizontal and inclined. In Fig. Figure 9 shows milling of an inclined plane in a universal vice. The techniques for processing planes with end mills are no different from the techniques for processing shoulders and grooves. End mills can be used to process various recesses (sockets). In Fig. Figure 10 shows the milling of a cavity using an end mill. Milling of recesses in the workpiece is carried out according to the markings. It is more convenient to first make preliminary milling of the recess contour (without reaching the marking lines), and then final milling of the contour.

In cases where it is necessary to mill a window rather than a recess, it is necessary to place an appropriate backing under the workpiece so as not to damage the vice when the end mill comes out.

Milling shoulders with an end mill. Shoulders can be milled on both vertical and horizontal milling machines. The processing of parts with symmetrically located shoulders can be carried out by securing the workpieces in two-position rotary tables. After milling the first shoulder, the fixture is rotated 180° and placed in the second position to mill the second shoulder.

When milling grooves and grooves, it is often preferable to use three-sided disc cutters rather than end mills.

The processed grooves or grooves can have different geometries - be short or long, open or closed, straight or curved, deep or shallow, wide or narrow
Usually the choice of tool is determined by the width and depth of the groove and, to some extent, its length
The type of machine and serial production determine which cutter should be used - end mill, long edge or disk
Three-sided disc cutters are a more efficient solution for machining long and deep slots, especially when using horizontal machines. However, the proliferation of vertical milling machines and machining centers means that end mills and long edge mills are also often used for a range of groove milling applications

Comparison of different types of cutters

Three-sided milling

+ Open grooves
+ Deep grooves
+ Adjustable width/tolerances
+ Milling with a set of cutters
+ Segment
+ Wide range of different widths/depths
– Closed grooves
– Straight grooves only
– Chip evacuation

End mills

+ Closed grooves
+ Shallow grooves
+ Non-linear slots
+ Versatility (additional methods):

Trochoidal milling of slots on parts made of difficult-to-cut materials (hardened steels, heat-resistant alloys, etc.)
Plunge milling for solving problems when working with large overhangs
Possibility of performing other types of semi-finish or fine milling operations
End mills can be used for more than just slot milling

– Deep grooves
– High cutting forces
– Tendency to vibration when pressing

Three-sided milling

Three-way disc cutters are more efficient when cutting long, deep, open slots and provide optimal stability and productivity in this type of milling. To simultaneously process several grooves in one plane, the operation can be carried out with a set of cutters.

Features of application

The size of the cutter, the pitch of the teeth and the location of the cutter together must ensure that at least one tooth is always in mesh
Control chip thickness to achieve optimal feed per tooth
When milling in difficult conditions, check the power and torque requirements. When attaching a cutter to a mandrel, the rigidity of the latter and the amount of adjustment overhang are extremely important.
It is necessary to ensure the rigidity and reliability of fastening the part and the mandrel itself in order to withstand the cutting forces of counter milling

Down milling:

Preferred milling method
Use a rigid stop in the direction of the tangential cutting forces to prevent the workpiece from shifting The feed direction coincides with the direction of the cutting forces, which imposes high requirements on the rigidity of the machine and the absence of gaps in the ball screw

Up milling:

A good alternative when there is insufficient rigidity or when working with difficult-to-cut materials
It is a good solution when problems arise with chip evacuation when cutting deep grooves.

Milling using a handwheel:

An additional milling method for low system rigidity and insufficient machine power characteristics
Position the handwheel as close to the tool as possible
Increasing the reliability of workpiece clamping always contributes to good machining results

Milling open slots with three-sided disc cutters

Calculation of feed per tooth

A critical factor when milling with three-sided disc cutters is to achieve a suitable feed per tooth, f z. Insufficient feed per tooth causes serious deficiencies, so special care must be taken when calculating.

Feed per tooth f z should be reduced when milling deep slots and increased when milling shallow slots to maintain the recommended maximum thickness shavings. For example, when milling a full slot width using M30 geometry, the initial maximum chip thickness should be 0.12 mm.

Note: Since two inserts work together when milling the entire width of a slot, half the number of inserts is used to calculate the feed z n.

a e/ D cap (%)	f z (mm/tooth)	h ex (mm)
25	0,14	0,12
10	0,20	0,12
5	0,28	0,12

Depth of cut

For deeper grooves, you can order a special cutter. When machining deep grooves, reduce the feed per tooth. If the groove is shallow, increase the feed.

Note: The depth of the machined groove can be limited by the diameter of the mandrel, the strength characteristics of the key joint and the conditions for chip evacuation.

Using a flywheel on horizontal machines

With three-sided milling, a small number of teeth are meshed, which causes vibrations during the cutting process. This has a negative impact on the processing result and productivity.

Mounting a flywheel on a milling arbor is often an effective method of combating vibration. Problems caused by insufficient power, torque and machine stability are often solved by the proper use of flywheels.
The need to use a flywheel is higher, the lower the power of the machine intended for processing or the higher the level of its wear
Position the handwheel as close to the tool as possible.
The use of a flywheel makes processing smoother, which in turn leads to reduced noise and vibration and increases tool life.
The flywheel is recommended to be used in conjunction with the counter milling method
To further increase stability when operating a 3-sided disc cutter, use the largest handwheel possible for the application.
As a flywheel, you can use several steel disks with holes corresponding to the diameter of the milling mandrel

Processing grooves with a set of cutters with staggered teeth

The 2-key cutters can be staggered to allow multiple slots to be cut at the same time. Offsetting the cutters relative to each other helps to avoid vibration. The need for flywheels is also reduced.

Milling of narrow and shallow slots and grooves

Universal cutters have multi-edge inserts various forms, suitable for most types of shallow grooves. Common applications include milling internal circlip and O-ring grooves, as well as small straight or circular external grooves, especially on non-rotating parts.

Internal grooving

When circular milling, it is necessary to program a smooth entry of the tool into cutting.
Consider the ratio of the cutter diameter to the hole diameter, D c/ D w. The smaller this ratio, the greater the length of the contact line between the tool and the material being processed.

Grooving with end mills

End mills are used when it is necessary to produce short, shallow grooves, particularly closed slots and pockets, and keyways. End mills are the only tools capable of milling closed slots with the following characteristics:

Straight, curved or angled
Wider than the diameter of the cutter used

Heavier slot milling is often done with long-edge cutters.

Tool selection

End and long edge milling cutters


	Solid Carbide End Mills	End mills for shoulder milling	Long edge cutters	End mills with replaceable heads
Spindle/machine size	ISO 30, 40, 50	ISO 40, 50	ISO 40, 50	ISO 30, 40, 50
Stability requirements	High	Average	High	Low
Roughing	Very good	Good	Very good	Acceptable
Finishing	Very good	Good	Acceptable	Very good
Depth of cut a p	Big	Average	Big	Small
Versatility	Very good	Good	Acceptable	Very good
Performance	Very good	Good	Very good	Good

Features of application

Use endmills for light-duty cutting with long predictable tool life in combination with high-performance chucks
To obtain the lowest possible overhang, minimize the distance from the chuck to the cutting edge
To obtain a satisfactory chip thickness, ensure proper feed per tooth. To avoid thin chips, which can cause vibration, burrs and poor surface finish, use cutters with coarse tooth pitches.
For optimum diameter/length ratio and stability, use the largest possible diameter tool
To achieve the most favorable cutting action, use climb milling
Ensure that chips are evacuated from the groove. Use compressed air to avoid chip accumulation
For optimal stability and support in the spindle direction, use the Coromant Capto® connection

Grooving with end mills

When milling a groove or slot, often called full-width milling, three surfaces are machined:

Slots that are closed at both ends—pockets—require end mills capable of axial feed
Milling the full width of a slot with an end mill is a complex operation. The axial depth of cut should generally be 70% of the cutting edge length. Machine rigidity and chip evacuation should also be taken into account when determining the optimal method for machining a slot.
End mills are sensitive to cutting forces. Limiting factors may include deflection and vibration, especially at high machining speeds and long overhangs.

Machining keyways

This operation requires specific instructions in addition to the general recommendations for milling planes and grooves. The direction of cutting forces and tool deflection when milling a closed keyway do not allow obtaining an accurate rectangular section. Machining accuracy can be increased if you use a cutter with a slightly smaller diameter and machine the groove in two passes:

Milling keyways - rough milling the full width of the keyway
Shoulder milling - processing a groove along the contour using the counter milling method to ensure perpendicularity of the walls.

At the finishing stages of machining, it is necessary to work with a small depth of cut in order to minimize tool deflection, which is a determining factor in the quality of the machined surface and the geometric accuracy of the groove (90° angle).

Milling keyways in two passes

Methods for routing a closed slot or pocket in a solid workpiece

In preparation for routing long, narrow, full-width slots, the most common pocket opening method after drilling is linear plunging.
– Deep grooves are processed in several passes

Trochoidal milling

+ Low radial cutting forces – less prone to vibration
+ Minimal deflection when milling deep grooves
+ Productive method for:

processing of high-hardness steels and heat-resistant alloys (ISO H and S)
vibration sensitive applications

+ The diameter of the cutter should be no more than 70% of the groove width
+ Good chip evacuation
+ A little heat is generated
– More programming required

Plunge milling

+ Shows excellent performance when prone to vibration:

with long tool overhang
when milling deep slots
in case of insufficient rigidity of the machine or setup

– Low performance in stable conditions
– Remain milling/finishing required
– Milling with end mills can cause chip evacuation difficulties
– Limited selection of tools

Rough milling of slots with long-edge cutters

High metal removal rate cutters are typically used for roughing
Shorter versions are capable of milling slots as deep as the cutter diameter on stable and powerful milling machines
For such operations, choose machines with a 50 cone, since the operation of cutters of this type is accompanied by high radial cutting forces
Check power and torque requirements as these are often the limiting factors for optimal results
Select the optimal tooth pitch for each type of operation

Longer cutter designs are mainly
designed for processing edges (along the contour).

Step	L	M	H
Application area	Long assemblies	Universal	Short assemblies
Shoulder milling	Great depth a p/ a e	Average depth a p/ a e	Shallow depth a p/ a e
	Shallow depth a p/ a e	Restrictions	__
v s m/min

Page 25 of 31

Chapter VIII

MILLING OF SHOULDERS, RECTANGULAR SLOTS AND GROOVES. CUTTING WORKS

§ 28. MILLING SHALLOWS AND SLOTS

In mechanical engineering, there are often flat parts that have ledges on one, two, three and even four sides. As an example in Fig. 122, and shows a prism for installing cylindrical parts during milling, which has two ledges. A ledge closed on both sides is called groove. The grooves can be rectangular And shaped. In Fig. 122, b shows a part with a rectangular groove, and in Fig. 122, in - fork with shaped groove.

Shoulder and groove cutters

Milling of shoulders and rectangular slots is carried out either with disk cutters on horizontal milling machines, or with end mills on vertical milling machines. Narrow cylindrical cutters are called disk. Disc cutters can be made with pointed and backed teeth (Fig. 123, a and b).

Disc cutters having teeth on the cylindrical and one end surfaces are called bilateral(Fig. 123, c), and disk cutters that also have teeth on both end surfaces are called tripartite(Fig. 123, d). Double-sided and three-sided disc cutters are made with pointed teeth. To increase productivity, three-sided disk cutters are manufactured with large multi-directional teeth. In Fig. 123, d shows a cutter in which the teeth, alternately in different directions, form end cutting edges through the tooth. This shape of the teeth, like the set teeth of circular and rip saws for wood, allows you to remove a larger amount of chips and better divert them. End mills are manufactured in two types: with cylindrical(Fig. 124, a and b) and c conical(Fig. 124, c and d) with a shank. Each of these types is manufactured in two versions: with a normal (Fig. 124, a and c) and with a large (Fig. 124, b and d) tooth. Cutting part end mills are made of high-speed steel and welded to a shank made of carbon steel.

end mills with large teeth are used for work with high feeds at great depths milling; cutters with normal teeth - for ordinary work. The direction of the screw grooves must be selected according to the table. 4. Milling cutters with a cylindrical shank are manufactured with a diameter of 3 to 20 mm, with a conical shank - diameter from 16 to 50 mm. For end mills in 1957, at the suggestion of the innovators of the Leningrad Kirov plant E.F. Savich, I.D. Leonov and V.Ya. Karasev state standard(GOST 8237-57). Compared to previously manufactured end mills, the new cutters have a reduced number of teeth, increased the angle of inclination of the helical groove to 30 - 45°, increased the tooth height and introduced an uneven circumferential tooth pitch. The back of the teeth is made curved according to Fig. 36, v. Milling cutters new design provide increased productivity, good surface finish and eliminate vibration when removing large chips.

Milling shoulders with a disc cutter

Let's consider an example of milling two shoulders in a block on a horizontal milling machine (Fig. 125, right) to obtain a stepped key. Choosing a cutter. Milling ledges on a horizontal milling machine is usually done with a double-sided disk cutter, but in this case you should work with a three-sided cutter, since you need to alternately process one ledge on each side of the block. For milling the shoulder, we will choose a three-sided cutter with small multi-directional teeth with a diameter of 80 mm, width 10 mm, with hole diameter for mandrel 27 mm, with the number of teeth 18. A three-sided disk cutter was selected in accordance with GOST 9474-60. If there are cutters in the pantry that differ in diameter from those considered in this example, you should select a cutter of a suitable diameter, for example 75 mm with the corresponding number of teeth. The processing will be carried out on a horizontal milling machine with the workpiece secured in a machine vice. Preparing for work. We install, align and secure the vice on the machine table using a method known to us, after which we place the workpiece in the vice at the required height (Fig. 126). We check the correct position (horizontalness) using a thickness gauge according to the marking marks, and then firmly clamp the vice. The jaws of the vice must be covered with pads made of soft metal (brass, copper, aluminum) so as not to spoil the processed edges of the block.

>Attachment of the disk cutter to the mandrel is carried out in the same way as for a cylindrical cutter, maintaining the cleanliness of the mandrel, cutter and rings. . We set up the machine according to the specified cutting mode. Given: cutter diameter D = 80 mm, milling width IN = 5 mm, cutting depth t = 12 mm, surface finish 5, feed s tooth = 0.05 mm/tooth, cutting speed υ = 25 m/min. According to the ray diagram (see Fig. 54) cutting speed υ = 25 m/min And D = 80 mm corresponds to n 6 = 100 rpm. In this case, the minute feed will be: Set the gearbox dial to 100 rpm, and the feedbox dial to 80 mm/min. Thus, we will mill the shoulder using a three-sided disk cutter 80X110X27 mm with multi-directional teeth (cutter material - high-speed steel P18) with a cutting depth of 12 mm, milling width 5 mm, longitudinal feed 80 mm/min, or 0.05 mm/tooth, and cutting speed 25 m/min; We use cooling - emulsion. Shoulder milling. Milling each shoulder consists of the following basic techniques: 1. Turn on the spindle rotation with the button. 2. By rotating the longitudinal, transverse and vertical feed handles, bring the workpiece under the cutter until it lightly touches the side surface. Then, by rotating the vertical feed handle, lower the table and by rotating the cross feed handle, move the table in the direction of the cutter by 5 mm using the cross feed dial. Raise the table until the cutter lightly touches the top plane of the workpiece. By rotating the longitudinal feed handle, remove the workpiece from under the cutter and raise the table by 12 mm using the vertical feed dial. Turn off rotation. Lock the vertical and cross slides. 3. Set the cams for mechanically switching off the longitudinal feed of the table to the milling length. Turn on the rotation, turn on the cooling, manually feed the workpiece by rotating the table longitudinal feed handle towards the rotating cutter, turn on the mechanical longitudinal feed. After processing the first ledge (Fig. 127, a), move the table a distance equal to the width of the ledge (17 mm), plus the width of the cutter (10 mm), i.e. at 27 mm, and mill on the other side, observing all the work techniques outlined (Fig. 127.6).

4. Upon completion of processing the part, without removing it from the vice, use a caliper to measure the depth and width of the ledge on each side according to the dimensions of the drawing with a tolerance of ±0.2 mm. If the dimensions of the part correspond to the drawing and the processing surface is clean, as required by sign 5 on the drawing, we remove the part from the vice and hand it over to the master for inspection.

Shoulder milling with an end mill

Milling of shoulders can be performed on a vertical milling machine, using for this purpose an end mill in accordance with GOST 8237-57 (see Fig. 124). We will choose for processing vertically milling machine 6M12P. Let's consider an example of milling two shoulders in a block with an end mill (Fig. 125) to obtain a stepped key. Choosing a cutter. Choose an end mill with a diameter of 16 mm with a cylindrical shank and normal teeth. This cutter has five teeth. In order for the chips to be transported upward during processing, the direction of the helical grooves must be to the right when the spindle rotates to the right. Preparing for work. The workpiece is secured in a vice in the same way as described when processing with a disk cutter. We fix the end mill in the chuck (see Fig. 48), carefully wiping the cutter shank, expansion sleeve and chuck nut. Setting for cutting mode. Under the same processing conditions as the previous example (milling width, cutting depth and machining cleanliness), the feed per cutter tooth is set to 0.03 mm, since the cutting conditions here are more difficult. The cutting speed υ is set to 25 m/min. Under these conditions, the spindle speed according to formula (2a):

and the minute feed according to formula (4): Set the gearbox dial to 500 rpm and feed box dial at 80 mm/min. Thus, shoulder milling with an end mill will produce the same cutting speed and feed rate as milling with a disc mill. Shoulder milling. Milling of each shoulder is carried out as described when processing with a disk cutter. In Fig. 128 shows shoulder milling.

Milling through rectangular slots

When milling through rectangular grooves, three-sided disk cutters (Fig. 123, e) or end mills (Fig. 124) are used. When milling rectangular slots, the width of the disk cutter or the diameter of the end mill must correspond to the drawing size of the milled groove with permissible deviations, which is only true in cases where the installed disk cutter has no face runout, and the end mill has no radial runout. If the cutter beats, then the width of the milled groove will be greater than the width of the cutter, or, as they say, the cutter will break groove, which can lead to marriage. Therefore, a three-sided cutter is chosen in width slightly less than the width of the groove being milled. Since three-sided disk cutters are made with pointed teeth, after subsequent regrinding of the end teeth, the width of the cutter will decrease. Consequently, this cutter after sharpening will no longer be suitable for milling a rectangular groove in the next batch of parts. To maintain the required width of three-sided disk cutters after regrinding, they are made in composites with teeth overlapping each other (see Fig. 123, d), which allows you to adjust their size. For this purpose, gaskets made of steel or copper foil are inserted into the socket of such a composite cutter. End mills do not allow you to adjust their diameter, so cutting precise grooves is only possible with a new cutter. Recently, chucks have appeared for securing end mills, allowing you to install the cutter with adjustable eccentricity in relation to the spindle, i.e. with some adjustable runout, which allows you to mill precise grooves with an end mill that has lost its size after regrinding. The process of milling rectangular slots, i.e. installing a cutter, securing the workpiece, as well as milling techniques do not differ from the shoulder milling techniques described above.

Milling closed slots

In plank thickness 15 mm(Fig. 129) it is necessary to mill a closed groove with a width of 16 mm and length 32 mm.

Such processing should be carried out with an end mill on a vertical milling or horizontal milling machine with an overhead vertical milling head. Choosing a cutter. For vertical processing we will choose a 6M12P milling machine and an end mill with a diameter of 16 mm with a cylindrical shank and normal teeth (number of teeth z=5). Preparing for work. The workpiece enters the milling machine with a marked groove. Since the groove needs to be machined in the middle of the workpiece, it can be fixed at the level of the jaws of the vice, but the parallel pads must be positioned so that the end mill can have an exit between them (Fig. 130).

After installing the workpiece, the cutter is secured in the machine spindle. To do this, insert the end mill shank into the chuck according to Fig. 48, and the cartridge itself is fixed in the conical socket of the spindle. Setting up the machine for milling mode. The cutter feed is set to 0.01 mm/tooth, cutting speed 25 m/min, which corresponds to 500 rpm with cutter diameter D = 16 mm. In this case, the minute feed according to formula (4): Since the smallest feed on the machine is 31.5 mm/min, select this feed. Let's set the dial of the machine's feed box to a minute feed of 31.5 mm/min and calculate the resulting feed per 1 tooth using formula (5): Thus, we will mill the groove using an end mill D = 16 mm made of high-speed steel P18 at cutting speed 25 m/min, or 500 rpm, and when serving 31.5 mm/min, or 0.013 mm/tooth. We use cooling - emulsion. Milling a groove,In Fig. 131 shows how a groove is milled in a plank. Usually, after installing the cutter in its original position, a small manual vertical feed is first given so that the cutter cuts to a depth of 4-5 mm. After this, the mechanical longitudinal feed is turned on, giving, as indicated by the arrow, movement of the table with the fixed workpiece back and forth, lifting the table by 4-5 mm after each double manual stroke until the groove is milled along the entire length.

High-speed shoulder and slot milling

High-speed milling operators widely use high-speed milling of shoulders and grooves using disk cutters with hard alloy inserts. When machining ledges and grooves at high speed, it is necessary mill according to feed. In Fig. 132 and 133 show the designs of disk cutters for high-speed cutting used at the Leningrad Kirov plant.

In Fig. 132 shows a cutter with soldered plates hard alloy 2 to steel body 1 . Such cutters are used for small milling widths. One of the advantages of cutters with brazed inserts is the possibility of frequent tooth spacing, which is important for smooth operation. Another advantage is the ability to use the plate in work almost to its entire size. The main disadvantages of these cutters are the inability to adjust the width and diameter, the difficulty of replacing teeth if they break, and the difficulty of soldering. In Fig. 133 shows a disk cutter for high-speed milling with inserts into the body 1 serrated knives 2 , equipped with hard alloy plates. Wedges are used to secure the knives in the body. 3 . For milling shoulders and wide grooves, it is more advisable to use disk cutters with inserted carbide knives.

Possible shoulder milling methods

In Fig. 134 three options for milling ledges on a block are given.

In Fig. 134, and each shoulder is milled with one three-sided disk cutter. This method is usually used when processing a small number of workpieces. In Fig. 134, b both shoulders are simultaneously milled with a set of two double-sided disk cutters of the same diameter. To obtain a given size between the shoulders, a corresponding set of rings is placed on the mandrel between the cutters (see Fig. 44, c). This method is more productive and is used when processing a batch of identical workpieces. In Fig. 134, both shoulders are sequentially processed with one double-sided disk cutter on a two-position device. After milling the first shoulder (first position), the fixture is rotated and placed in the second position to mill the second shoulder. This processing method requires special equipment and is used in the manufacture of a batch of identical parts. Compared to processing using the first method (Fig. 134, a), it provides greater accuracy and reduces the time for rearranging the part for milling the second shoulder, but it is less productive than the second method (Fig. 134,6). Depending on the number of workpieces put into processing simultaneously (batch size), each of the three options outlined for milling shoulders may turn out to be the most rational.

GROOTS CAN BE MADE EVERYWHERE

With a groove connection, the end of one part fits into a shallow groove cut across the grain of the other. This connection is an improvement on the simple butt connection. The groove shoulders provide decent strength. In fact, such a connection cannot be broken, for example, by pressing on a shelf. If it fits tightly, it can withstand oblique loads well, when the force is directed diagonally across the body. Installing back walls in cabinets or chests of drawers and bottoms in drawers further strengthens the entire structure. Finally, the groove makes assembly easier by defining the position of the parts and keeping them from slipping.

Using just two types of groove connections, you can make almost any body part. The main joint, where the groove engages the full thickness of the adjacent piece, allows for the assembly of bookcases, toy chests, wall shelves, or any other cabinets in which the side walls extend beyond the adjacent pieces (Figure 1).

Rice. 1. Main groove connection.
Rice. 2. Modified groove/tenon connection.

If these "through" angles are unsuitable or unsightly, use a modified joint (Figure 2) called mortise/tenon.

Drawers are also boxes. They are easily made using a basic mortise joint and a mortise/tenon joint (Figure 3). Example ZA is the strongest of them; in examples ZV and ZS, you can weaken the front wall. If you want to hide the ends of the drawer sides shown in 30, cover them with a false front or use a quarter joint as shown in 30, reinforced with nails or dowels.

Rice. 3. Grooves in drawers.

BASIC CONNECTION IN GROOVE

Cutting grooves on a tabletop circular saw with a set of groove discs is much faster than manually. But long or wide pieces are difficult to maneuver around the table. A pendulum saw solves this problem, but it has an inherent drawback - usually its console is not enough to cut across wide parts.

A router helps solve this problem. But this also has its drawbacks.

First, if you are selecting more than one pair of grooves, setting the ruler for each side can be time consuming. Therefore, use an insert with a width equal to the distance from the rib of the router base to the cutter. To install the ruler, slide the insert along the marked shoulder line on the work piece (Figure 4).

Rice. 4. Insert for router.

Second, the thickness of the workpiece is almost never matched to the cutter to ensure a tight-fitting joint. Solid wood parts can be planed or sanded, but plywood parts are difficult to trim. Cutting a groove to fit is more clear. But this requires two passes with a router - one for each shoulder.

Faced closely with the selection of grooves, you can make a simple device (photo A).

GROVING DEVICE

The device consists of two rulers (one for each groove shoulder) and two strips that rest on the edges of the workpiece. One ruler and one strip are T-shaped fastened at right angles. Gaps along the other strip and ruler allow you to install boards up to 300mm wide and select grooves up to 38mm wide. Two clamps in an adjustable bar rest against the workpiece and lock the fixture in place.

To operate, you need a set of guide bushings for the router. With bushings, the rulers should be slightly offset to the side relative to the width of the groove itself.

The device is made of poplar, but Karelian birch plywood or MDF is also suitable. The T-nuts and MB screws are recessed, so the router can slide along the rules without hindrance.

Having finished manufacturing, you need to make inserts for installing the rulers. Plane a piece of cutting board approximately 450 mm long, 150 mm wide and 20 mm thick to the same thickness along the entire length. It all depends on the size of the sleeve and the cutter. Leave the jig in place while you make and fit four inserts, each approximately 50mm long, about 25mm wide and equal to the thickness of the gaps. Ideally, the thickness of the inserts should be equal to half the difference in the diameters of the cutter and sleeve.

Precise adjustment of the inserts is accomplished by using them with rulers installed when routing on a short piece that has been sawed off previously. Loosen the adjustable ruler, place the scrap between the rulers and two inserts on each side.

Tighten the screws. Remove the inserts and trim and mill the groove. If the trim does not fit into the groove, adjust the thickness of the inserts.

OPERATING THE DEVICE

Marking the grooves is very simple. Determine the shoulder line for each groove by making a pencil mark on the face of the piece to be worked. You can put the two side walls together and mark all the grooves at once, or mark the second side wall after routing the first.

Once the jig is aligned and the cuts are marked, align the straight edge with the mark (photo C), lightly tighten the clamps and make a pass with the router, then move the jig to the next mark. A well-chosen groove should fit the tenon without gaps or backlash (photo D).

GROOVE/TENK CONNECTION

Like the main groove, the groove/tenon connection (Fig. 5) can be made in several ways: on a circular saw and by milling. Regardless of the method, the proportions of the connection are as follows: the tenon is about 1/4-1/3 of the thickness of the part on which it is cut, and approximately 1/4-1/3 of the thickness of the part with the groove. To ensure a tight and good connection, it is necessary to cut the grooves slightly deeper than the length of the tenons.

SAWING A GROOVE/TENK CONNECTION ON A CIRCULAR

Since this is a very simple connection, it is easier and faster to combine marking and installation. Check the settings on the scrap boards (Fig. 6 and 7).

It's easier to fit the tenon to the mortise, so make the mortise first. Set the depth of the cut by measuring or by eye, pressing the disc against the part in which the groove will be. Then set a ruler to cut out the inner shoulder of the groove (Fig. 6, step 2), make a cut in all parts with grooves, rearrange the ruler and cut out the second shoulders.

Narrow parts, such as the sides of bookcases, can be sawed using a dividing head, keeping the end of the work piece in contact with a straightedge as you work. You can also attach a limiter to a ruler in front of the disk so that the end of the part rests against it.

The most accurate way to select a groove on a circular saw is to place the workpiece on the table and, pressing it against the ruler, cut out the shoulder. Then place the part on the end and cut out the thickness of the tenon. This method allows you to accurately control the thickness of the tenon, but it is inconvenient for long parts or those that are sawed across. It is better to make tenons on these parts using several horizontal cuts. After sawing the shoulder, press the piece against the ruler and use a dividing head to cut out the excess wood in several passes. Unlike the first method, here the thickness of the tenon depends on the thickness of the workpiece.

No matter how carefully the tenons are made, there is usually some variation in their size, especially when sawing into solid wood. Here we can advise you to cut the tenons a little thicker, and then, when fitting, trim them with a plane for the shoulders. The blade of a shoulder plane runs across its entire narrow sole, so you can cut right into the corner of a tenon shoulder.

MILLING THE GROOVE/TENK JOINT

For large and wide parts of housings or long and narrow parts, milling grooves is relatively simple and safe. Select a cutter of the correct diameter, attach a ruler to the base of the router and make passes with it, moving the ruler along the end of the part
(Fig. 8). Many routers are sold with a ruler, but to improve the quality of work, it must be pressed to the base with a clamp or screws.

The most accurate way to mill a tenon is to clearly set its thickness between the ruler and the cutter (Fig. 9). To support the base of the router, use a clamp to press a piece of thick board flush with the end of the workpiece.

HOMEMADE DEVICE FOR SELECTING GROOTS

Although the device looks complicated, it is quite easy to make (Fig. 10). Cut the workpieces to size, and then carefully plan the planes and edges. Then select a groove in the fixed bar for the fixed ruler using a few cuts on a circular saw. Then, to ensure a tight fit and square edges, use a sharp chisel to trim its shoulders. The half-wood connection on the adjustable ruler is made so that its upper surface is in the same plane as the fixed ruler.

Mill out all the cracks in the planks and rulers using a ruler pressed to the base of the router (Fig. 8). First, releasing the cutter approximately 3 mm in each pass, mill narrow through slots in several passes. Next, mill out pockets for the screw heads and T-nuts.

Small clamps are used as clamps. The pressure pad is a T-shaped nut at the end of the screw. The locknut prevents the pad from coming loose when it presses against the workpiece. Select the grooves in the adjustable bar so that the clamps can hide behind its edge.
Rice. 10. Device for making grooves.

(clickable picture)