Milling of shoulders and grooves. Milling with end mills Selecting cutting modes

In mechanical engineering, flat parts are often found that have ledges on one, two, three and even four sides. As an example in Fig. 194, and shows a prism for installing cylindrical parts during milling, which has two ledges.

Shoulder and groove milling

A ledge closed on both sides is called a groove. The grooves can have a rectangular shape - then they are called rectangular, or shaped - then they are called shaped. In Fig. 194, b shows a part with a rectangular groove, and in Fig. 194, in - a fork having a shaped groove.

Mills for processing ledges and grooves. 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 cutters. Disc cutters can be made with pointed and backed teeth (Fig. 195, a and b).

Disc cutters that have teeth on the cylindrical and on one of the two end surfaces are called double-sided

(Fig. 195, b), and those having teeth on both end surfaces are called three-sided (Fig. 195, d). Double-sided and three-sided disc cutters are made with pointed teeth.

To increase productivity, three-sided disc cutters are manufactured with large multi-directional teeth. In Fig. 195, d shows a cutter in which the teeth are alternately oriented in different directions, forming 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.

In Fig. 196 shows end mills proposed by the innovators of the Leningrad Kirov plant E.F. Savich, I.D. Leonov and V.Ya. Karasev. A state standard has been issued for these cutters (GOST 8237-57). Compared to previously manufactured cutters, the number of teeth in them has been reduced, the angle of inclination of the screw teeth has been increased to 30-45°, the height of the tooth has been increased and an uneven circumferential pitch of the teeth has been introduced. The back of the teeth of these cutters is made curved according to Fig. 51, v.

Milling cutters of this design provide increased productivity and cleanliness of the machined surface and eliminate vibration. End mills are made of two types: with a cylindrical shank (Fig. 196, a and b) and with a conical shank (Fig. 196, vig). Each of these types is manufactured in two versions: with a normal tooth (Fig. 196, abc) and with a large tooth (Fig. 196, b and d). The cutting part of end mills is made of high-speed steel.

End mills with large teeth are used for work with high feeds at large milling depths; cutters with normal teeth - for ordinary work.

Mills with a cylindrical shank are made with a diameter from 3 to 20 mm, with a conical shank - with a diameter from 16 to 50 mm.

Shoulder milling. Let's consider an example of milling two shoulders in a block on a horizontal milling machine (Fig. 197, left) 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 example it is necessary to work with a three-sided cutter, since it is necessary to alternately process one ledge on each side of the block.

For milling the shoulder, we will choose a three-sided cutter with multi-directional teeth with a diameter of 75 mm, a width of 10 mm, a hole diameter for the mandrel of 27 mm and a number of teeth of 18.

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 strengthen the vice on the machine table using a method known to us, after which we install the part in the vice at the required height (Fig. 198). We check the correct position (horizontalness) with a thickness gauge according to the marking marks, after which we 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.

We attach the disk cutter to the mandrel in the same way as a cylindrical cutter, maintaining the cleanliness of the mandrel, cutter and rings.

Setting up the machine for milling mode. We select the cutting mode when milling shoulders with high-speed disk cutters according to the table. 212 of the “Young Milling Machine Operator’s Handbook.”

Given: cutter diameter Z) = 75 mm, milling width B = 5 mm, cutting depth = 12 mm, surface finish V 5; According to the table, we select the cutting speed when feeding per tooth S3y6 = 0.05 mm/tooth.

The selected cutting speed a = 21.7 m/min corresponds to 92 rpm of the cutter and a feed of 83 mm/min. Then set the gearbox dial to 95 rpm and the feedbox dial to 75 mm/min.

Thus, we will mill the shoulder using a three-sided disk cutter 75x10x27 mm with multi-directional teeth (cutter material - high-speed steel P9 or P18) with a cutting depth of 12 mm, a milling width of 5 mm, a longitudinal feed of 75 mm/min or 0.04 mm/tooth and cutting speed of 22 m/min, we use cooling - emulsion.

Milling process. Milling each shoulder consists of the following basic techniques:

1) turn on the spindle rotation with the button;

take the chips, turn on the mechanical longitudinal feed (Fig. 199, a).

After processing the first shoulder, move the table to a distance equal to the width of the shoulder (17 mm) plus the width of the cutter (10 mm), i.e., 27 mm, and mill on the other side, observing all the described working techniques (Fig. 199.6) ;

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 the V5 mark on the drawing, we remove the part from the vice and hand it over to the master for inspection.

Milling through rectangular grooves. When milling through rectangular grooves, three-sided disk cutters are used, similar to the one shown in Fig. 195, g. The width of the cutter must correspond to the drawing size of the milled groove with permissible deviations, which is only true in cases where the installed cutter does not have an end 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 the groove, which can lead to defects.

That's why a three-sided cutter is selected based on a width slightly smaller than the width of the milled groove.

Since three-sided disk cutters are made with pointed teeth, after subsequent regrinding of the end teeth, the width of the cutter is reduced. 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 (Fig. 195, e), which allows you to adjust their size. Gaskets made of steel or copper foil are inserted into the socket of such a composite cutter.

The process of milling rectangular slots, i.e., installing the cutter, securing the part, as well as milling techniques, do not differ from the shoulder milling examples described above.

Cutting modes when milling grooves with three-sided disk cutters made of high-speed steel are selected according to table. 213 of the “Young Milling Machine Operator’s Handbook.”

Milling closed grooves. In Fig. 200 shows a drawing of a 15 mm thick plank in which it is necessary to mill a closed groove 16 mm wide and 32 mm long.

Such processing should be carried out with an end mill on a vertical milling machine.

Preparing for work. We will choose a 6N12 vertical milling machine for processing. To mill a groove with a width of £=16 mm, we take an end mill with a diameter of 16 mm with a tapered shank; such a cutter has a number of teeth z = 5.

The part enters the milling machine with a marked groove. Since the groove needs to be machined in the middle of the part, the part can be secured 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. 201).

After installing the part, the cutter is secured in the machine spindle.

Setting up the machine for milling mode. We select the cutting mode for milling grooves with high-speed end mills according to the table. 211 of the “Young Milling Machine Operator’s Handbook.”

Let's take the feed s3y6 - = 0.01 mm/tooth. With cutter diameter D -16 mm, groove width B = 16 mm, number of teeth 2 = 5, feed s3y6 = = 0.01 mm/tooth, according to the table we find o = 43.3 m/min, or i = 860 rpm , and 5 =

43 mm/min. Let's set the machine speed dial to 750 rpm and calculate the resulting cutting speed using formula (1):

Let's set the dial of the machine's feed box to a minute feed of 37.5 mm/min and calculate the resulting feed per tooth using formula (5):

Thus, we will mill the groove with an end mill D=16 mm made of P9 high-speed steel at a longitudinal feed of 37.5 mm/min, or 0.01 mm/tooth, and a cutting speed of 37.8 m/min; We use cooling - emulsion.

Milling process. In Fig. 202 shows the process of milling a groove 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, forward and backward movement to the table with the fixed part and after each double stroke, manually lifting the table by 4-5 mm until the groove is milled to its entire depth.

When milling closed slots, the cutter is in the most difficult conditions during cutting to depth, so the manual feed during cutting should be small.

The ledges in the stepped key according to Fig. 197 can also be milled on a vertical milling machine with an end mill with a diameter of 20 mm. Think about how to structure the operation. The cutting modes must be taken according to the table. 211 of the “Young Milling Operator’s Handbook” for feed per tooth = 0.03 mm/tooth.

Milling special slots

Parts with special grooves are widely used in mechanical engineering. Let's look at the two most common grooves , the method of processing them and the tools necessary when performing milling work.

Milling dovetail slots

The dovetail groove serves mainly as a guide for the moving elements of machines - these are consoles, table slides, lathe slide guides, milling machine shackles... The main tool for obtaining such a groove is an end angular mill named after the dovetail groove type tail". Dovetail cutters
are made single-angled (the cutting edge, as a rule, is only on
conical part of the cutter) or two-angle (cutting edge on two adjacent sides). Double angle cutters distribute the load more evenly, so they run smoother and are more durable. Dovetail cutters are made from high-speed steels R6M5, R9 and hard alloys VK8, T5K10 and T15K6.

Milling a dovetail groove is the final operation of milling a part; therefore, the selection of a tool and the correct securing of the workpiece are very important. The workpiece is aligned directly in a machine vice or, if the part is large, on the table of a milling machine using a height gauge, squares and indicators regarding the feed direction.

The groove is processed in two stages:

The first is to mill a rectangular groove using an end mill or, if conditions permit, a three-sided milling cutter.

The second - an angular cutter (“dovetail”) is used to process the sides one by one.

Taking into account the difficult cutting conditions, the tool feed must be slightly reduced - to approximately 40% of normal working conditions (for a given material, width of the material being cut, coolant supply, etc.).

Measurements are made using a caliper tool, angular dimensions are made with a universal goniometer (the cutter itself), templates from the base surface of the part, two calibrated cylindrical rollers according to special formulas.

When milling a dovetail groove, you need to pay attention to the following problems that may arise:

The depth of the groove and the angles of inclination of the sides are not the same along the entire length - the reason is inaccurate alignment of the part in the horizontal plane;

The angle of inclination of the sides does not correspond to the specified value - incorrect calculation of the cutter angle, wear of the cutter due to a mismatch between the processing mode and the tool material;

Different groove widths along the entire length - displacement of the machine table in the guide consoles;

Surface roughness - working with an incorrectly sharpened tool, inappropriate feed.

Breakage of the cutter - due to the heavy load when processing this groove on the mating cutting edges, the top of the cutter breaks - it is necessary to first round it, make it with a small radius.

Milling T-slots

T-slots are used mainly in mechanical engineering for fastening parts. They are widely used in tables of machine tools for various purposes (grinding, drilling, milling, planing, etc.). They are used to place the heads of fastening bolts in them, as well as to align the fixture on the machine table. T-slots are characterized by their overall depth, the thickness between the slot and the tabletop, and the width of the narrow top and wide bottom. Grooves of this type are regulated by the standard. Each size corresponds to strictly defined other sizes, because... For them, special bolts, fastening devices, and equipment are manufactured on an industrial scale.

To make a T-slot you need:

End mill with a diameter equal to the narrow width of the groove or a smaller diameter in multiple passes;

- when producing several grooves, it is more convenient to work with a three-sided cutter with a thickness equal to the narrow part of the T-shaped groove. The groove is obtained more accurately and the processing speed is higher than with an end mill, and the scrap rate is lower;

Special T-shaped end mill. The cutter for T-slots consists of a working part with the elements and geometry of disk slot cutters, conical
o or a cylindrical shank and a smooth cylindrical ground neck, the diameter of which is usually selected equal to the width of the narrow part of the groove (it can be smaller). The working part of the cutter can have multi-directional teeth and is mademade from high-speed steels R6M5, R18 or equipped with carbide inserts VK8, T5K10, T15K6, etc.;

Dovetail cutter or countersink for internal and external chamfering.

The sequence of milling a T-slot is similar to the milling of type slots
“dovetail”. Initially, a rectangular groove is milled with a width equal to or less than the narrow part of the groove and a depth equal to the depth of the groove.

Next, select a cutter for T-slots. Depending on the size of the groove, a decision is made about passing with one cutter or several, because When the depth and width of the groove are large, the working tool experiences heavy loads; select one or more cutters with the same height of the working part and, if desired,
elno, with the appropriate neck size. Thus, a more gentle processing mode is achieved, because the thickness of the cut layer in the workpiece decreases. When working, you need to pay special attention to removing chips, because... in closedIn the groove this becomes very important and it is necessary to provide a mandatory supply of coolant (cutting fluid) to remove excess heat in order to avoid overheating of the working cutter. The feed speed for this type of work must be reduced as much as possible.

The final operation involves removing external and internal chamfers. In this case, single-angle or double-angle end mills are used. Dl
For an external chamfer - it is possible to use countersinks, for an internal chamfer - dovetail cutters. The main condition is that the diameter of the corner cutter must be larger than the size of the narrow part of the T-slot to obtain a more even chamfer and greaterlabor productivity.

Measuring and controlling the dimensions of the T-shaped groove is carried out using calipers, height gauges, bore gauges, indicators, and also special templates.

When milling T-slots, the following types of defects can occur:

Good luck to everyone and success!

You can glue a shield from narrow bars, says A. Ilyin from the city of Shumerlya (Chuvashia), you just need to make a simple machine for milling grooves.

In the manufacture of some structures, in particular beehives, boards 350 mm wide are required. It is difficult to find and purchase boards of this width. Wide boards also have a drawback: they warp during the operation of the hives, so I decided to abandon wide boards. It is better to glue the shield from narrow boards or just bars. But the strength of the adhesive joint at the end of the grooved edges of the boards is too low, the tongue-and-groove joint is stronger, but its strength turned out to be insufficient, and the waste of material is large.

I found a solution like this. I process only those sides of the boards (bars) that will then be glued together. On the machine I mill a row of grooves 2 mm wide and 3 mm deep on the planed sides. I coat the surfaces to be glued with glue and connect the boards together so that the ridges and grooves on the boards fit into each other. The ridges fit tightly into the grooves, sometimes you even have to drive them in. You must work carefully so as not to jam the grooves upon impact. For these purposes, I usually use an auxiliary block, on one side of which grooves are milled. I place the block on the board and, aligning the grooves, hit it with a mallet. When the entire shield is assembled, I compress it with two clamps and dry it. I plane the glued board on both sides on a jointer to the required thickness. From such shields you can assemble a strong hive. I use flesh or casein glue. Any waterproof adhesives are suitable: K-17, VIAM-BZ, epoxy, etc.

My slot milling machine is made on a three-phase motor with a power of 0.3 kW, 2850 rpm. It is connected to a 220 V network using the usual “capacitor” delta circuit. Such low power is quite enough for work. A cutter head consisting of a tube with a nut, cutters and washers is fixed to the motor shaft. The cutters are made from ready-made cutters for metal work with a diameter of 100 mm. So that they can cut wood, some of the teeth are removed on an emery wheel and 4 teeth are left.

The cutter is assembled on a tube, washers of such thickness are installed between the individual cutters that there is a gap of 2 mm between them, the structure is tightened with a nut. In order for the machine to operate without vibration and shock, the cutting edges of the teeth are set offset relative to each other by 5-10 mm. The machine operates quietly and there are no workpiece emissions.

A table with a bounding frame (ruler) for uniform feeding of the workpiece is attached directly to the motor housing.

The machine is easy to carry, weighing no more than 8 kg. Attached to the table (workbench) with two screws.

Keys are used to connect various gear parts (gears, pulleys, etc.) to the shaft. To do this, key grooves are made on the shaft and the part connected to it (Fig. 63, a), into which a common parallel key (Fig. 63, b) is installed in the form of a rectangular bar or a segment key (Fig. 63, c) having the shape parts of the disk.

Special requirements for the accuracy of keyways are that their width is within the permissible deviations in the PN and strict symmetry of the groove to the shaft axis. To comply with these requirements, it is necessary to select the correct cutter, install it on the machine with minimal runout (no more than 0.02 mm on the side teeth) and align the device and the workpiece with respect to the direction of the longitudinal feed of the machine table.

For milling keyways on shafts, the standards provide for disc groove and three-sided solid cutters (see Fig. 52 and 54, a and b), which can be used to process open and semi-open grooves that have an exit along the radius of the cutter. Closed grooves are made with two-tooth keyed cutters (Fig. 64), the end teeth of which intersect in the center. Such cutters are ground mainly along the rear surfaces of the end teeth and can operate with axial feed.

Key cutters are made with cylindrical or conical shanks and are made of high-speed steel or equipped with carbide inserts. For milling hardened and difficult-to-cut materials, the production of monolithic carbide key cutters has been developed.

The grooves on the shafts for segment keys are machined with special mushroom cutters (Fig. 65, a) with cylindrical shanks or mounted cutters (Fig. 65, b) - for grooves of large diameter.

When machining keyways, the shafts can be secured in a machine vice, on prisms, directly on the machine table or in a special self-centering vice. When installing workpieces in a machine vice (Fig. 66), corner jaws made of soft sheet metal should be put on the jaws to protect the shaft surface from crushing. In these cases, it is also advisable to use special prismatic overhead jaws for the vice.

Prisms 4 (Fig. 67) have a groove 1 with a profile angle of 90° and guide keys 5, with the help of which the prisms are aligned with the table groove. The workpiece 3 is pressed against the prisms by clamps 2.

Long shafts are often mounted directly on the table along the chamfers of the T-shaped groove and secured at the ends with clamps.

Self-centering vices (Fig. 68) can be used to install shaft-type workpieces on both horizontal milling and vertical milling machines, which is achieved by having two mutually perpendicular supporting planes 8. The workpiece is placed with its cylindrical surface on a prism 5 and When rotating, handwheel 1 is clamped with jaws 3 and 6, which rotate on axes 2 and 7. To install large-diameter shafts, prism 5 can be rotated and installed in a vice with the other side. Adjustable stop 4 serves to secure the shaft to the required length position.

Techniques for milling keyways differ practically little from the corresponding techniques for processing general-purpose slots. A special feature here is the methods for installing the cutter symmetrically to the shaft axis and controlling the transverse location of the groove on it.

The workpiece of the shaft being processed is usually fixed on the machine so that it has a free end. In this case, the cutter is brought until it touches the side generatrix of the workpiece cylinder (Fig. 69, a), and then, using already known actions, the table is shifted in the transverse direction by a distance

where d is the shaft diameter, mm; b - groove width, mm.

Control of the location of the cutter relative to the shaft axis is carried out using a square and calipers according to size S (Fig. 69, b), which is determined by the formula

where T is the width of the angle flange, mm; B - cutter width, mm.

If the size S is the same on both sides of the shaft, then the cutter is positioned correctly.

When the end of the workpiece does not protrude from the device, the cutter can be positioned symmetrically to the shaft axis using a relatively simple device (Fig. 69, c), which consists of a stand 1 and a movable prism 2. The prism is installed on the surface of the shaft using the lower V-shaped groove, and in The cutter is inserted into the upper groove until the corners of the teeth touch its sides. The accuracy of the symmetrical location of the keyway is checked using a template (Fig. 69, d).

In mass production, machines with modular program control are widely used for machining keyways. 6D95, working with non-dimensional end mills. The required accuracy of the groove width on these machines is achieved due to the adjustable oscillating (oscillating) movement of the cutter in the direction perpendicular to the longitudinal feed.

TO category:

Milling work

Milling keyways on shafts

Keyed connections are very common in mechanical engineering. They can be with prismatic, segmental, wedge and other key sections. The working drawings of the shaft must contain dimensions for a shaft with a feather key and for a shaft with a segment key.

Keyways are divided into through, open (with exit) and closed. Milling keyways is a very responsible operation. The nature of the fit of the parts mating to the shaft depends on the accuracy of the keyway. Strict technical requirements apply to milled keyways. The width of the keyway must be made according to the 2nd or 3rd accuracy class: the depth of the keyway must be made according to the 5th accuracy class; The length of the groove for the key is according to the 8th accuracy class. Failure to comply with these requirements when milling keyways entails labor-intensive fitting work during assembly - sawing down keys or other mating parts.

In addition to the above requirements, with regard to the accuracy of the keyway, there is also a requirement regarding the accuracy of its location and surface roughness. The side faces of the keyway must be located symmetrically relative to the plane passing through the shaft axis; The surface roughness of the side walls should be within the 5th roughness class, and sometimes higher.

By comparing the tolerances on cutters with the tolerances on the size of the keyway, one can be convinced of the difficulty of making a groove of the required accuracy on machines using measuring tools. Let's take as an example a groove with a width of 12psh

Practice shows that for machining a keyway, a groove that fits within the tolerance field of the PN must be carefully selected. cutters and make test passes. In serial and mass production, they tend to replace keyed connections with splined ones whenever possible.

Disc groove cutters (ST SEV 573-77) are intended for milling shallow grooves. They have teeth only on the cylindrical part.

Groove cutters backed according to GOST 8543-71 are also intended for processing grooves. They are sharpened only on the front surface. The advantage of these cutters is that they do not lose their width after regrinding. They are available in diameters from 50 to 100 mm, from 4 to 16 mm.

Key cutters in accordance with GOST 9140-78 are used for milling keyways and are manufactured with a cylindrical and conical shank. Key cutters have two cutting teeth with end cutting

common edges that perform the main cutting work. The cutting edges of the cutter are not directed outward, like a drill, but into the body of the tool. Such cutters can work with axial feed (like a drill) and with longitudinal feed. Resharpening of cutters is carried out along the end teeth, as a result of which the diameter of the cutter remains practically unchanged. This is very important for machining grooves.

Milling cutters with a cylindrical shank are manufactured for diameters from 2 to 20 mm, with a conical shank - from 16 to 40 mm. Currently, tool factories produce solid carbide key cutters with a diameter of 3, 4, 6, 8 and 10 mm with a helical flute angle of 20° from VK8 alloy. These cutters are mainly used for machining hardened steels and difficult-to-cut materials. The use of these cutters allows you to increase labor productivity by 2-3 times and increase the roughness class of the treated surface.

Shank cutters for slots for segment keys in accordance with GOST 6648-68* are intended for milling all slots for segment keys with a diameter of 4-5 mm.

Mounted cutters for grooves for segmental keys in accordance with GOST 6648-68* are intended for milling all grooves for segmental keys with a diameter of 55-80 mm.

Securing workpieces. Shaft blanks for milling keyways and flats into them are conveniently secured in prisms. For short workpieces, one prism is sufficient. For longer shaft lengths, the workpiece is mounted on two prisms. The correct positioning of the prism on the machine table is ensured by a tenon at the base of the prism, which fits into the groove of the table, as shown in the figure on the right. The shafts are secured with clamps. To avoid shaft deflection when fastening, it is necessary to ensure that the clamps rest on the shaft above the prisms. A thin copper or brass gasket should be placed under the clamps so as not to damage the final processed cylindrical surface of the shaft. In Fig. Figure 4 shows a vice for securing shafts. The vice can be fixed on the table either in the position shown in the figure, or it can be rotated 90°. They are therefore suitable for securing shafts on both horizontal and vertical milling machines. The shaft is mounted with a cylindrical surface on a prism and, when the handwheel rotates, it is clamped with jaws that rotate around the fingers. The prism can be installed in a vice on the other side of the larger diameter shaft. The stop is used to set the shaft along its length.

Rice. 1. Shaft with keyways

Rice. 2. Layout of tolerance fields for keyway and cutter

Rice. 3. Securing the shaft on the oisms

Rice. 4. Vise for securing shafts

In Fig. Figure 5 shows a magnetic prism with a permanent magnet. The prism body consists of two parts, between which a barium oxide magnet is placed. To secure the roller, simply turn the switch handle 90°. The clamping force is quite sufficient for milling keyways, flats, etc. on the rollers. Simultaneously with securing the part, the prism is attracted to the supporting surface of the machine table.

Milling through keyways. Keyways are milled after finishing the cylindrical surface. Through and open grooves with a groove exiting along a circle, the radius of which is equal to the radius of the cutter, are processed with disk cutters. The excess of the groove width compared to the width of the cutter is 0.1 mm or more. After sharpening disk slot cutters, the width of the cutter is slightly reduced, so the use of cutters is possible only up to certain limits, after which they are used for other work when the width size is not so important.

In Fig. Figure 6 shows the installation of the workpiece and cutter when milling a through keyway. When installing a cutter on a mandrel, it is necessary to ensure that the cutter has minimal runout at the end. The workpiece is secured in a machine vice with copper or brass jaws.

With a correctly installed vice, the accuracy of installing the shaft fixed in it does not need to be checked. The cutter should be installed so that it is located symmetrically relative to the diametrical plane passing through the shaft axis. To fulfill this condition, use the following technique. After fixing the cutter and checking its runout with an indicator, the cutter is first installed in the diametrical plane of the shaft. Precise installation is carried out with a square and caliper.

To install the cutter, it is necessary to place it in the transverse direction at size S from the side of one of the ends of the shaft protruding above the vice. Check this size with a caliper. Then place a square on the other side of the shaft, as shown in Fig. 7 dotted line, and check size S again.

Rice. 5. Magnetic prism for securing shafts

simultaneously slowly lift the table until it touches the cutter and move it in the longitudinal direction. Having established the moment of contact of the cutter with the shaft, move the table away from under the cutter. Turn off the machine and rotate the vertical feed handle to raise the table to the depth of the keyway.

Milling closed keyways. Milling of closed keyways can be done on horizontal milling machines. To secure the shaft, use special self-centering vices or prisms. Since the milling installation according to Fig. 9, but differs from the installation in Fig. 9, b only by the location of the spindle, we will analyze only the order of milling the keyway on a horizontal milling machine.

Rice. 9. Milling closed keyways

Another way to install (“bullseye”) a keyed or end mill in the diametral plane of the cutter is as follows. The shaft is positioned as accurately as possible (by eye) relative to the cutter and the rotating cutter is slowly brought into contact with the shaft being processed until a barely noticeable trace of the cutter appears on the surface of the shaft. If this mark is obtained in the form of a complete circle, then this means that the cutter is located in the diametrical plane of the shaft. If the mark has the shape of an incomplete circle, then it is necessary to move the table.

Setting to groove depth. The shaft being processed, the diametral plane of which coincides with the axis of the cutter, is brought into contact with the cutter. In this position of the table, note the indication of the dial of the transverse or vertical feed screw, then move or raise the table to cutting depth B.

Closed keyways that allow fit are milled in one of two ways:
a) manual cutting to a certain depth and longitudinal mechanical feed, then cutting again to the same depth and longitudinal feed, but in a different direction;
b) manual cutting to the full depth of the groove and further mechanical longitudinal feed. This method is used when milling with keyway cutters with a diameter of over 12-14 mm.

Rice. 10. Installation diagram of the end mill in diameter! shaft plane

The width of the keyway should be checked using a gauge according to the tolerance specified in the drawing.

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.

Milling the grooves of segment keys is carried out using shank or mounted cutters for segment keys, the diameter of which must be equal to double the radius of the groove. The feed is carried out in a vertical direction, perpendicular to the shaft axis (Fig. 11).

Milling of shafts on key-milling machines. To obtain grooves that are precise in width, processing is carried out on special key-milling machines with pendulum feed, working with two-tooth key cutters. With this method, the cutter cuts 0.2-0.4 mm and mills the groove along the entire length, then again cuts to the same depth as in the previous case, and mills the groove again along the entire length, but in a different direction. This is where the name of the method comes from - “pendulum feed”.

Rice. 11. Milling keyways for segmental keys

Rice. 12. Scheme for milling keyways using the “pendulum feed” method

Rice. 13. Control of groove size using gauges

At the end of milling, the spindle automatically returns to its original position and the longitudinal feed of the milling head is turned off. This method is the most rational for the manufacture of keyed shafts in serial and mass production, as it produces an accurate groove that ensures interchangeability in the keyed connection. In addition, since the cutter works with end cutting edges, it is more durable, since it does not wear out along the periphery. The disadvantage of this method is that it takes significantly more time compared to milling in one or two passes.

Milling of grooves on automated key-milling machines with a non-measured tool is carried out with an oscillating (oscillating) movement of the tool. By adjusting the oscillation range from zero to the required value, it is possible to mill keyways with the required width accuracy.

When milling with oscillation, the width of the cutter is less than the width of the groove being machined. Thus, the MA-57 machine is intended for milling open keyways on electric motor shafts using three-sided disk cutters in automated production. The 6D92 machine is designed for milling closed keyways using non-dimensional end mills. The required groove width is achieved due to the fact that the cutter is given an oscillating movement in the direction perpendicular to the longitudinal feed. The machine can be built into an automatic line.

Control of the dimensions of grooves and grooves. Control of the dimensions of grooves and grooves can be done using both line measuring instruments (vernier calipers, vernier depth number) and gauges. Measuring and counting the dimensions of grooves using universal tools does not differ from measuring other linear dimensions (length, width, thickness, diameter). The width of the groove can be controlled by round and sheet limit plug gauges. In Fig. 13, a shows the control of the width of the groove, given the size of 20+cm mm. In this case, the pass side of the caliber has a size of 20.0 mm, and the non-pass side has a size of 20.1 mm.

The symmetry of the location of the keyway relative to the shaft axis is controlled by special templates and devices.