How to make a keyway on a lathe. We cut splines and grooves How to cut closed grooves

The keyways (grooves) on the shafts are manufactured for parallel keys and keyways. Keyways for parallel keys can be closed on both sides (blind), closed on one side and through.

Keyways are manufactured in different ways depending on the keyway and shaft configuration and the tool used. They are carried out on horizontal milling or vertical milling machines for general purposes or on special machines.

Through and open on one side keyways are made by milling with disc cutters (Fig. 22, a).

Rice. 22. Methods of milling the keyways of the shafts: a- disc cutter with longitudinal feed; b- end mill with longitudinal feed; v- end mill with pendulum feed; G- disk milling cutter with vertical feed

The slot is milled in one or two passes. This method is the most productive and provides sufficient accuracy in the width of the groove, but its use is limited by the configuration of the grooves: closed grooves with rounding at the ends cannot be performed in this way. These slots are made with longitudinal feed end mills in one or more passes (Fig. 22, b).

Milling with an end mill in one pass is carried out in such a way that first the milling cutter with vertical feed goes to the full depth of the groove, then the longitudinal feed is switched on, with which the keyway is milled to the full length. This method requires a powerful machine, strong attachment of the cutter and abundant emulsion cooling. Due to the fact that the cutter works mainly with the peripheral part, the diameter of which decreases from regrinding to regrinding, as the number of regrindings increases, the machining accuracy (along the groove width) deteriorates.

To obtain accurate grooves in width, special key-milling machines with "pendulum feed" are used, working with double-helix end mills with frontal cutting edges. With this method, the cutter cuts to a depth of 0.1-0.3 mm and mills the groove to the entire length, then cuts again to the same depth as in the previous case, and mills the groove to the entire length, but in the opposite direction (Fig. 22, v). This is where the name "pendulum feed" comes from.

This method is the most rational for the manufacture of keyways in serial and mass production, since the accuracy of manufacturing the keyway provides interchangeability in the keyway. In addition, since the cutter works with the frontal part, it will be more durable, since the frontal part, rather than the peripheral part of the cutter, is worn out. The disadvantage of this method is poor performance. From this it follows that the pendulum feed method should be used in the manufacture of grooves that require interchangeability, and the one-pass milling method should be used in cases where the fit of the keys along the groove is allowed.

Keyways for segment keys are made by milling using disk cutters (Fig. 22, G). The through keyways of the shafts can be processed on planers (long grooves on planers, and short grooves on cross planers).

Keyways in the holes of the bushings of gear wheels, pulleys and other parts that are put on a shaft with a key are processed in individual and small-scale production on slotting machines, in large-scale and mass production - on broaching machines.

Typically, the lathe is used for boring, threading, reaming, countersinking and drilling, but their capabilities do not end there. I propose to consider a method of how to use it to hollow out the keyway on the bushing. For this I use a 1K62 screw-cutting lathe.

Set of tools

To complete the work, in addition to the machine, you will need:

boring cutter;
slotting cutter;
oil for lubrication.

Any boring tool can be used, of course within the capabilities of the bushing diameter. As for the slotting tool, its cross-section is matched to the required width of the keyway. Lubricating oil is only required when working with hard metal. For mild steels, provided that high-quality cutters are used, it is not necessary, since chamfering and chiselling does not cause critical overheating, which can accelerate the abrasion of the cutting edge of the tool.

Preparatory stage

The sleeve fits into a three-jaw chuck. Before chiselling, you must first prepare its inner and outer chamfer with a boring cutter. They are made only from the side from which the slotting tool will enter. This is the simplest process familiar even to an amateur turner, therefore it does not require separate consideration.

After preparing the chamfers on the machine, you need to set the minimum speed to prevent the spindle from turning. On many machine tools, the chuck can give a backlash under load, so in this case it is necessary to install a spacer. To do this, a bolt with a nut suitable in height is placed under it. When unscrewing it, the length of the stop increases, so it is tightly pressed against the chuck, thereby removing rolling.

The slotting tool is lightly clamped in the tool holder. It aligns to the center of the bushing, after which it is necessary to make fine adjustments. To do this, it is wound into the bushing, moving longitudinally with the support along the slide. The resulting scratch should run along the bore of the bushing from one edge to the other. There should be no scratch-free area in the cut line. If it is, then this is talking about the presence of a bias. When the cutter is set correctly, it must be clamped very firmly, since the load during chiselling is much higher than when performing standard turning work.

Chiseling process

Since the bushing has its own radius inside, it is necessary to cut it off before starting the groove depth reading in order to obtain a flat area, which will be the zero reference point. To do this, using a caliper, I move the cutter inside the sleeve along the longitudinal slide, removing the finest metal shavings. After its return to its original position, I approach the cutting edge along the transverse slide to the body of the sleeve by 0.1 mm. Again I make a longitudinal movement along the carriage. I repeat the process until the chute loses its radius. As soon as he leaves, this will be the zero point for the reference.

Now I'm starting to chisel the keyway. In my case, its depth should be 2.6 mm. Using a 0.1 mm step, it will take 26 cutter movements to reach this depth.

After deepening the groove by 2.6 mm, without changing the settings on the limb, make a few more repeated movements of the cutter in order to clean the plane from small burrs. Next, the sleeve is removed from the chuck. Its second end is rather rough, but it can be easily solved. The boring bar is reinstalled in the tool holder and the neat chamfers are removed. The sleeve can then be used as intended.

Chiseling on a lathe is a lengthy, although not complicated process. In my case, the longitudinal movement of the caliper is motorized, so everything is done relatively quickly. It is also possible to hammer a groove on budget machines with a manual drive, but in this case it will take much more time.

Set of tools

To complete the work, in addition to the machine, you will need:

boring cutter;
slotting cutter;
oil for lubrication.

Preparatory stage

Chiseling process

Now I'm starting to chisel the keyway. In my case, its depth should be 2.6 mm. Using a 0.1 mm step, it will take 26 cutter movements to reach this depth.

Milling grooves is a responsible procedure, the accuracy and correctness of its implementation directly affects the reliability and quality of mates in various mechanical devices where keys are used.

1 Types of keyways and requirements for their processing

Keyed connections can be found in a wide variety of devices. They are most often used in the engineering industry. Keys for such mates are wedge, segmental and prismatic; products with other types of sections are less common.

Keyways are usually subdivided into the following types:

with an exit (in other words - open);
end-to-end;
closed.

Any of these grooves must be milled as accurately as possible, since the reliability of the fit of the products mated with the shaft on the key depends on the quality of the operation performed. The accuracy of the grooves after processing should have the following indicators:

8th class of accuracy - length;
Grade 5 - depth;
3 or 2 class - width.

The quality of accuracy must be strictly observed. Otherwise, after milling, you will have to perform laborious and very complex fitting work, in particular, sawing down the mating structural elements or directly the keys.

Regulatory documents put forward strict requirements for the accuracy of the location of the keyway, as well as the value of the roughness of its surface.

The roughness quality of the walls of the (side) groove cannot be lower than the fifth class, and its edges must be placed absolutely symmetrically with respect to the plane passing through the axis of the shaft.

2 Keyway cutters

To ensure the required quality of accuracy of various grooves, different types of groove cutters are used for their processing:

Backed up according to Gosstandart 8543. They can have a cross section of 4-15 and 50-100 mm. After regrinding, such a tool does not change in its width. Re-ground cutters are sharpened exclusively along the front surface.
Disc according to standard 573. Their teeth are located on the cylindrical part. The disc cutter is recommended for shallow groove cutting.
With cylindrical and tapered shank. They come in a cross section of 16–40 mm (conical) and 2–20 mm (cylindrical). For the manufacture of such cutters, carbide alloys are usually used (for example, VK8). The tool has a 20-degree slope angle. The carbide cutting attachment makes it possible to mill shoulders and grooves from hard-to-machine materials and hardened steels. Such a tool several times increases the quality of accuracy and surface roughness, and also significantly increases the productivity of work.
Fitted for the keys of the segment type according to Gosstandart 6648. Cutters that allow you to process any kind of grooves for keyways with a cross section from 55 to 80 mm. The same standard also describes a tail tool for such keys. With their help, products are milled with a cross section of no more than 5 mm.

The main tool for machining grooves are special key cutters manufactured according to Gosstandart 9140. They have two teeth with cutting end edges and have a conical or cylindrical shank. They are ideal for machining a keyway, since the working edges of these cutters are directed into the tool body, and not outward.

Key cutters work with both longitudinal and axial feed (as on), they guarantee the necessary quality of the roughness of the shoulders and grooves after processing. The regrinding of such a tool is carried out along the teeth located in the end part of the cutter, due to which its initial section hardly changes.

3 Features of processing key steps and grooves

Keying elements are milled on shafts. For convenient fastening of the shaft blanks, a prism is used - a special device that facilitates the processing process. If the shaft is long, two prisms are used, if it is short, one is enough.

The prismatic shoulder and slot fixture should be positioned as accurately as possible. This is achieved due to the presence of a spike at its base, which is inserted into the groove of the desktop. Clamps are used to secure the shafts. They rest directly on the shaft, which eliminates the possibility of deflection of the latter. Usually, a brass or copper (small in thickness) plate is placed under the clamps. It protects the finished product surface from damage.

The shafts are fastened in a conventional vise, which is mounted on a table so that they can be turned 90 degrees. Due to the possibility of rotation, the vice can be easily installed on vertical and horizontal milling units.

On the prism, the shaft is fixed with jaws (by means of a handwheel it is clamped), rotating around the fingers. The described device for processing ledges and keyways has a stop in its design. It allows the shaft to be mounted lengthwise.

The most commonly used prisms with a permanent magnet (oxide-barium). The prismatic body is made of two parts. A magnet is installed between these halves. As you can see, the device for milling ledges and keyways is quite simple, but at the same time guarantees efficient processing of products.

4 How are closed slots milled?

Closed groove processing is carried out on horizontal milling units. For work, the device described above is used, which is supplied with prisms or self-centering vices. The shafts are mounted on them in a standard way.

In addition, there is another option for installing the shafts. Experts call it "bullseye editing." In this case, the shaft is positioned in relation to the working tool (end or keyway cutter for shoulders and slots) by eye. Then the cutting device is started and carefully brought to the shaft until the moment of their interaction.

When the cutter and the shaft come into contact, a faint trace of the working tool remains on the latter. When the trail is in the form of an incomplete circle, the table needs to be slightly displaced. If the worker sees a full circle in front of him, no additional action is needed, you can start milling.

Closed grooves, which are subsequently slightly fitted, are processed according to two different schemes:

By plunging the cutter (manual operation) to the full depth of the shoulder and mechanical feed in the longitudinal direction.
Manual plunge into the tool at a given depth and mechanical longitudinal feed in one direction, and then another plunge and feed, but in the opposite direction.

The first technique for machining shoulders and grooves is used for cutters with a section of 12-14 mm. In other cases, the second scheme is recommended.

5 Subtleties of processing open and through grooves and ledges

Such elements are milled only after all work on their cylindrical surface is completely completed. The disk tool is used in situations where the cutter and groove radii are the same.

Please note that the operation of cutters is allowed up to a certain point. With each new sharpening of the tool, its width becomes smaller by a certain amount. After several such operations, the cutters become unsuitable for working with grooves, they can be used to perform other operations that do not impose high demands on geometric parameters in width.

The previously discussed fixture is suitable for processing ledges and grooves through and open. It is important here to ensure that the cutting tool is correctly positioned on the arbor. Installation should be done so that the runout of the cutter at the end is as small as possible. The workpiece is fixed in a vice with pads (brass, copper) on the jaws.

The accuracy of the installation of the cutter is checked with a caliper and a square. The process looks like this:

the tool is placed transversely from the end of the shaft, which protrudes from the vise, at a predetermined distance;
using a vernier caliper, check the correctness of the set distance;
a square is installed from the other end of the shaft and again a check is performed.

The coincidence of the measurement results indicates that the cutter is mounted correctly.

We add that the segment keys are machined with special cutters (shell or tail). The double radius of the grooves of these keys determines the diameter of the tool that can be used for milling. When performing such work, the feed is performed vertically (relative to the shaft axis - in the perpendicular direction).

6 Key milling units for shafts

If the grooves are to be as precise as possible, they should be machined using special keyway machines. They work with a keyed two-toothed cutting tool, and the feed on such units is performed according to a pendulum scheme.

Keyway-milling machine equipment provides processing of the groove along its entire length when cutting the working tool to a depth of 0.2 to 0.4 millimeters. Moreover, milling is carried out twice (plunge and feed in one direction, then - the same operations in the opposite direction).

The described machines are optimal for mass and serial production of key shafts. They work in automatic mode - after processing the product, the feed of the headstock in the longitudinal direction is turned off automatically and the spindle unit moves to the initial position.

In addition, these units guarantee high accuracy of the resulting groove, and the cutter on the periphery is almost not worn out at all, since the milling is carried out by its end parts. The disadvantage of using this technology is its duration. Standard grooving in two or one pass is several times faster.

The dimensions of the grooves when using key-milling equipment are controlled either by gauges or by a measuring bar-tool. Round plugs are used as calibers. Measurements using a vernier depth gauge and a caliper are performed as standard (the section, width, length, groove thickness are set).

At modern enterprises, two keyway machines are actively used: 6D92 - for machining closed grooves with an end-to-measure tool, and MA-57 - for milling open grooves with a three-sided tool. These units are usually integrated into automated production lines.