Narrow grooves are processed with slotted cutters. The shape of the cutting edge of the cutter corresponds to the shape of the groove being machined. Slotted incisors can be straight or bent, which in turn are divided into right and left. The most commonly used slotted incisors are right straight and left bent. In the picture on the right: a) - straight left, b) - straight right, c) - bent left, d) - bent right

The rigidity of the part does not always allow cutting grooves of a given width in one cutter pass. When it is necessary to machine a groove wider than 5 mm in a non-rigid part, this is done in several passes of a cutter with a transverse feed (figure on the right). At the ends and along the diameter of the groove, an allowance of 0.5-1 mm is left for finishing, which is performed with the same cutter or a groove cutter with a cutting edge size equal to the specified groove size.

Workpieces and parts are cut with cutting tools. The width of the cutting edge of the cutting tool depends on the diameter of the workpiece being cut and is taken equal to 3; 4; 5; 6; 8 and 10 mm. The length L of the head of the cutting cutter should be slightly more than half the diameter D of the rod from which the workpiece is cut (L>0.5D). Cut-off cutters are manufactured in one piece or with inserts made of high-speed steel or carbide. To reduce friction between the cutter and the material being cut, the cutter head tapers towards the rod at an angle of 1-2 degrees (on each side of the cutter), angle φ=0, clearance angle α=12 degrees (figure below: d,g). In parting cutters, the auxiliary lead angle must be less than the auxiliary clearance angle. An incorrect ratio of these angles can lead to increased friction of the rear auxiliary surface of the cutter on the machined surface of the part and, as a result, to increased wear or breakage of the tool.

Cutting cutters should be installed at right angles to the axis of the workpiece, figure b) Setting the cutting edge of the cutter above the axis of the workpiece (even by 0.1-0.2 mm) can lead to its breakage, and when installing the cutting edge of the cutter below the axis of the workpiece, an unprocessed protrusion remains at the end of the part. The distance o from the end of the device for securing the bar to the machined end of the bar should be minimal and not exceed the diameter of the bar being cut (Figure a).

When cutting brittle material, the workpiece breaks off before the cutter reaches the center of the workpiece, resulting in a protrusion (boss) remaining at the end of the workpiece. To obtain a smooth end, the cutting edge of the cutter is made at an angle of 5-10 degrees, figure e). After cutting off the part, the cross feed is not turned off and the boss on the workpiece is cut off. You can cut off the part with a curved cutting cutter: “Goose” figure c), while the spindle should rotate clockwise. To reduce the surface roughness obtained after cutting, chamfers 1-2 mm wide are made on the rear auxiliary surfaces of the cutter. Transverse feed when processing grooves - 0.05-0.3 mm/rev (for steel parts with a diameter of up to 100 mm). The cutting speed when processing grooves and cutting off workpieces is 25-30 m/min (for cutters made of high-speed steels) and 125-150 m/min (for carbide cutters).

Control of external ledges, ends and grooves.

The depth of the grooves on the outer surface of the part is measured with a ruler, picture on the right a), a caliper, picture on the right b), a depth gauge, picture on the right c) and a step gauge, picture on the right d). The width of the treated area to the ledge is measured with a ruler if great measurement accuracy is not required. If there are higher requirements for measurement accuracy, it is better to use a caliper, and for mass production of parts, a step gauge. When measuring, the passing side of the template (PR) should rest against the machined cylindrical surface of the part, and the non-passing side (NOT) should rest against the outer cylindrical surface of the part.

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§ 38. Grooving and cutting. Cutters for cutting external grooves. Cutters for cutting work.

Cutters for cutting external grooves.

Narrow grooves are machined using slotted or groove cutters. The shape of the cutting edge of the cutter corresponds to the profile of the groove being machined (Fig. 77).

Rice. 77. Shapes of groove cutter heads

Slotted incisors can be straight or bent, which in turn are divided into right and left. More often, slotted incisors are used: right straight and left bent (Fig. 78).

Rice. 78. Slotted cutters:

a - straight left, b - straight right, c - bent left, d - bent right

The rigidity of the part does not always allow cutting grooves of a given width in one cutter pass. When it is necessary to machine a groove wider than 5 mm in a non-rigid part, this groove is machined with several passes of a groove cutter with a transverse feed. In this case, an allowance of 0.5-1.0 mm is left at the ends and along the diameter for finishing. The final processing is performed with the same cutter or a groove cutter with a cutting edge equal to the specified groove size.

Cutters for cutting work.

Blanks and parts are cut with cutting tools (Fig. 79). The width of the cutting edge of the cutting tool depends on the diameter of the workpiece being cut. The width of the cutting edge is taken equal to 3, 4, 5, 6, 8 and 10 mm. The head of the cutting cutter is made slightly larger than half the diameter of the rod from which the workpiece is cut, L>0.5D of the rod.

Rice. 79. Cutting cutters of various designs: a, d - to reduce friction between the cutter and the material being cut, b - to obtain a smooth end of the cut part, c - to reduce the roughness of the surface obtained after cutting

Cutting cutters are made solid, as well as with plates made of high-speed steel or carbide. To reduce friction between the cutter and the material being cut, the cutter head is narrowed towards the rod by 1-2° on each side of the cutter, angle λ=0, clearance angle α=12° (Fig. 79, a, d).

Grooving and parting cutters should be installed at right angles to the axis of the workpiece. Setting the cutter with its cutting edge even 0.1-0.2 mm above the axis of the workpiece can lead to its breakage. When installing the cutter below the axis of the workpiece, an unprocessed protrusion remains at the end of the part. The distance from the end of the device for securing the bar to the end after cutting should be minimal and not greater than the diameter of the bar being cut.

When cutting brittle material, the workpiece breaks off before the cutter reaches the center of the workpiece. As a result, a protrusion (boss) remains at the end of the workpiece. To obtain a smooth end of the part being cut, the cutting edge of the cutter is made at an angle of 5-10° (Fig. 79, b). After cutting off the part, the cross feed is not turned off and the boss on the workpiece is cut off. To reduce the roughness of the surface obtained after cutting, chamfers (Fig. 79, c) 1-2 mm wide are made on the rear auxiliary surfaces of the cutter. Cross feed when cutting grooves - from 0.05 to 0.3 mm/rev for steel parts with a diameter of up to 100 mm.

The cutting speed when cutting grooves and when cutting off is calculated according to the initial diameter of the workpiece being processed and is taken within the range of 25-30 m/min, and when using carbide cutters - 125-150 m/min.

Elements and cutting modes

Before talking about processing methods, let's briefly get acquainted with the elements and cutting mode.

Here we will encounter new concepts: depth of cut, feed, cutting speed.

They are all interconnected, and their magnitude depends on various reasons.

The depth of cut is the thickness of the metal layer removed in one cutter pass. It is designated by the letter t and ranges from 0.5 to 3 or more millimeters during roughing to tenths of a millimeter during finishing turning.

Feed is the movement of the cutter along the machined surface. Numerically, it is expressed in millimeters, denoted by the letter S and indicates the amount of displacement of the cutter per revolution of the part. Depending on the strength of the material being processed, the rigidity of the machine and cutter components, the feed rate can vary from 0.1-0.15 mm/rev to 2-3 mm/rev at high-speed cutting conditions. The harder the metal, the less the feed should be.

The cutting speed depends on the spindle speed and the diameter of the part and is calculated using the formula.

When choosing a particular cutting speed, you need to take into account the hardness of the material being processed and the durability of the cutter, which is measured by the time of its continuous operation before dulling in minutes. It depends on the shape of the cutter, its dimensions, the material from which the cutter is made, and on turning with or without a cooling emulsion.

Cutters with plates made of hard alloys have the greatest durability, while cutters made of carbon steel have the least resistance.

Here, for example, are the cutting speeds that can be recommended when turning various materials with a high-speed steel cutter. Its durability without cooling is 60 minutes.

Approximate data on metal cutting speed:

Turning smooth cylindrical surfaces

Smooth cylindrical surfaces of parts are ground with passing cutters in two steps. First, a rough grinding is performed with a rough cutter, quickly removing the bulk of excess metal. The figure shows a straight cutter for roughing:

Rough cutters: a - straight; b - bent; c - Chekalin's designs.

A bent cutter is convenient for grinding the surface of a part near the chuck jaws and for trimming ends. Typically, cutters have a working stroke only in one direction, most often from right to left. A double-sided cutter designed by the innovative turner N. Chekalin allows eliminating the reverse idle stroke of the cutter, reducing processing time.

After turning with a rough cutter, large marks remain on the surface of the part and the quality of the machined surface is therefore low. Finishing cutters are used for final processing:

Finishing incisors: a - normal; b - with a wide cutting edge; c - bent, designed by A.V. Kolesov.

The normal type of finishing cutter is used for turning with a small depth of cut and low feed. A finishing tool with a wide cutting edge allows for high feed rates and produces a clean, smooth surface.

Trimming ends and ledges

Scoring cutters are usually used to trim ends and shoulders on a lathe. Such a cutter is shown in the following figure:

Trimming in the centers: a - scoring cutter; b - cutting the end with a half-center.

It is better to use it when turning parts on centers. In order for the end to be processed entirely, a so-called half-center is inserted into the tailstock.

If the part is fixed at only one end - when processing in a chuck - then a bent cutter can be used to groove the end. For the same purpose and for turning ledges, special scoring thrust cutters are used, which work with transverse and longitudinal feed.

Trimming the ends: a - trimming with a bent cutter, b - trimming persistent cutter and its work.

When cutting ends and ledges, the young master must ensure that the tip of the cutter is always set strictly at the level of the centers. A cutter set above or below the centers will leave an uncut lip in the middle of the solid end.

Grooving

Slotted cutters are used for turning grooves. Their cutting edge accurately reproduces the shape of the groove. Since the width of the grooves is usually small, the cutting edge of the slotting tool has to be made narrow, so it turns out to be quite brittle. To increase the strength of such a cutter, the height of its head is made several times greater than the width.

For the same reason, the head has a small rake angle.

Parting cutters are very similar to slotting cutters, but have a longer head. A narrower head is made in order to reduce material consumption when cutting.

The length of the head should be selected according to the dimensions of the part and be slightly more than half of its diameter.

When installing slotting and parting cutters, you also need to be very careful and precise. Careless installation of the cutter, for example, its slight misalignment, will cause friction of the cutter against the groove walls, defective work, and tool breakage.

Turning of narrow grooves is carried out in one pass of the cutter, which is selected according to the width of the future groove. Wide grooves are machined in several passes.

The procedure is as follows: use a ruler or other measuring tools to mark the boundary of the right wall of the groove. Having installed the cutter, they grind a narrow groove, not bringing the cutter 0.5 mm to the required depth - the remainder is for the finishing pass. Then the cutter is shifted to the right by the width of its cutting edge and a new groove is made. Having thus chosen a groove of the intended width, they make the final, finishing pass of the cutter, moving it along the part.

The workpiece installed in the centers should not be cut to the end: the broken part can damage the tool. A short part clamped in a chuck can be cut clean using a special bevel cutter.

The feed rate and cutting speed when turning grooves and cutting should be less than when machining cylinders, because the rigidity of the cutting and cutting tools is not high.

Turning cones

In the practice of a young turner, turning cones will be less common than other work. The simplest method is to turn small cones (no more than 20 mm) with a special wide cutter.

When making an outer or inner cone on a part fixed in a chuck, a different technique is used. Having turned the upper part of the caliper at an angle equal to half the angle of the cone at its apex, they grind the part, moving the cutter using the upper slide of the caliper. This is how relatively short cones are sharpened.

To make long and flat cones, you need to shift the rear center, move the tailstock a certain distance towards you or away from you.

If the part is fixed in the centers in such a way that the wide part of the cone will be at the headstock, then the tailstock should be moved towards you, and vice versa, when moving the tailstock away from the working one, the wide part of the cone will be on the left - at the tailstock.

This method of turning cones has a serious drawback: due to the displacement of the part, rapid and uneven wear of the centers and center holes occurs.

Treatment of internal surfaces

Hole processing can be done with various tools, depending on the required surface shape and processing accuracy. In production, there are blanks with holes made during casting, forging or stamping. A young metal worker will encounter ready-made holes mainly in castings. When processing holes in solid workpieces that do not have prepared holes, you will always have to start with drilling.

Drilling and reaming

Shallow holes are drilled on a lathe using feather and twist (cylindrical) drills.

The feather drill has a flat blade with two cutting edges that turns into a rod. The angle at the tip of the drill is usually 116-118°, but it can be, depending on the hardness of the material, from 90 to 140° - the harder the metal, the larger the angle. The accuracy of the hole when processing with a feather drill is small, so it is used when great accuracy is not required.

Twist drills are the main tool for drilling. The machining accuracy of these drills is quite high. A twist drill consists of a working part and a part of a conical or cylindrical shank, with which the drill is attached to the tailstock quill or chuck.

Spiral drills: a - with a conical shank; b - with a cylindrical shank

The working part of the drill is a cylinder with two helical grooves that form the cutting edges of the drill. The same grooves lead the chips out.

The drill head has a front and back surface and two cutting edges connected by a bridge. The chamfers running along the helical grooves guide and center the drill. The angle at the tip of a twist drill is the same as a feather drill and can vary within the same limits. Drills are made from alloy or high-speed steel. Sometimes alloy steel drills are equipped with carbide inserts.

The drill is secured in two ways, depending on the shape of the shank. Drills with a cylindrical shank are fixed in the tailstock quill using a special chuck, drills with a conical shank are inserted directly into the hole in the quill.

It may happen that the tapered shank is small in size and does not fit the hole. Then you will have to use an adapter sleeve, which, together with the drill, is inserted into the quill.

Adapter sleeve for drills with conical shanks: 1 - drill shank; 2 - bushing.

To push the drill out of the quill, you need to rotate the handwheel to tighten it into the tailstock housing. The screw will press against the shank of the drill and push it out. Using a special holder, you can secure the drill in the tool holder.

When drilling, you need to carefully ensure that the drill does not move to the side, otherwise the hole will be incorrect and the tool may break. The drill is fed by slow and uniform rotation of the tailstock handwheel or by moving the caliper if the drill with the holder is fixed in the tool holder.

When drilling deep holes, you need to remove the drill from the hole from time to time and remove chips from the groove.

The depth of the hole should not exceed the length of the working part of the drill, otherwise the chips will not be removed from the hole and the drill will break. When drilling blind holes to a given depth, you can check the drilling depth using the divisions on the quills. If they are not there, then a mark is placed with chalk on the drill itself. When a characteristic squeal is heard while drilling, this means that either the drill is skewed or it has become dull. Drilling must be stopped immediately by removing the drill from the hole. After this, you can stop the machine, find out and eliminate the cause of the squealing.

Reaming is the same drilling, but with a larger diameter drill in an existing hole. Therefore, all drilling rules apply to reaming.

Other methods of treating internal surfaces

In the practice of a young turner, there may also be a case when the diameter of the required hole is much larger than the diameter of the largest drill in his set, when a groove needs to be turned into the hole or made conical. For each of these cases there is a different processing method.

Boring of holes is carried out with special boring cutters - roughing and finishing, depending on the required cleanliness and accuracy of processing. Roughing cutters for turning blind holes are different from roughing cutters for turning through holes. Finishing of through and blind holes is carried out with the same finishing cutter.

Boring cutters: a - roughing cutter for through holes; b - rough for blind holes; c - finishing

Boring has its own difficulties compared to external turning. Boring cutters have low rigidity; they have to be significantly moved out of the tool holder. Therefore, the cutter can spring and bend, which, of course, negatively affects the quality of processing. In addition, it is difficult to observe the operation of the cutter. The cutting speed and feed rate of the cutter should therefore be 10-20% less than during external processing.

Particularly difficult is the processing of thin-walled parts. By clamping such a part in the chuck, it is easy to deform, and the cutter will select thicker chips on the depressed parts. The hole will not be strictly cylindrical.

For proper processing when boring, the cutter is installed at the level of the centers. Then you need to bore the hole 2-3 mm in length and measure the diameter.

If the size is correct, you can bore the hole to its full length. When boring blind holes or holes with ledges, as well as when drilling, a chalk mark is made on the cutter indicating the boring depth.

Trimming of the internal ends is carried out with scoring cutters, and turning of internal grooves with special slotted groove cutters, in which the width of the cutting edge exactly corresponds to the width of the groove. The cutter is set to the appropriate depth along the chalk mark on the cutter body.

Measuring the inner groove: ruler, caliper and template

In addition to boring cutters, countersinks are used for boring cylindrical holes. They are similar to twist drills, but have three or four cutting edges and are not suitable for making holes in solid material.

Spiral tail countersinks: a - made of high-speed steel; b - with hard alloy plates

Very clean and precise cylindrical holes are made using reamers. Both of these tools are used not to widen the hole, but to adjust it to the exact size and shape.

Reamers: a - tail; b - back

Making tapered holes

Turning the inner cones is perhaps the most difficult part. Processing is carried out in several ways. Often, conical holes are made by boring with a cutter and turning the upper part of the caliper.

A hole must first be drilled in solid material. To make boring easier, you can drill a stepped hole. It should be remembered that the diameter of the drill must be selected in such a way that there is an allowance of 1.5-2 mm on the side, which is then removed with a cutter. After turning, you can use a conical countersink and a reamer. If the cone slope is small, immediately after drilling, use a set of conical reamers.

The last of the main operations performed on a lathe is thread cutting.

Mechanical thread production is possible only on special screw-cutting machines. On simple machines this operation is performed manually. The techniques for manually making external and internal threads are described above.

Measuring tool

In turning, the same tools are used as in metalworking: a steel ruler, calipers, calipers and others. They have already been mentioned before. New here may be various templates that the young master will make himself. They are especially convenient when making several identical parts.

Remember that all measurements can only be made after the machine has completely stopped. Be careful! Do not measure a rotating part!

Precautionary measures

When working on a lathe, you must follow the following rules:

1) you can start working on the machine only after a detailed familiarization with the machine and processing methods;

2) do not work on a faulty machine or with an unusable (dull) tool;

3) securely fasten the part and monitor the serviceability of the fencing devices;

4) do not work in loose clothing: tie sleeves at the wrists, hide long hair under a hat;

5) remove shavings in a timely manner and maintain order in the workplace;

6) do not stop the rotating cartridge with your hands;

7) in case of malfunction, immediately turn off the machine.

Machine care

The more carefully you care for the machine, the better and longer it will work. This simple rule should be firmly remembered and followed carefully. Caring for a lathe comes down to the following.

The main thing is to lubricate all rubbing parts. Before starting work, it is necessary to inspect the machine and check whether there is enough lubrication. You need to pay close attention to the lubrication of the bearings by filling the oil nipples and lubrication holes with machine oil. The machine must be stopped at this time to avoid an accident.

After work, you need to clean the machine, remove the chips, wipe the guides of the frame and calipers, and lubricate them with a thin layer of oil.

The conical holes of the spindle and tailstock quill must be absolutely clean. The accuracy of the machine will depend on their good condition.

Before starting work, you should also check the condition of the drive belt. It must be protected from oil splashes and drops, since an oily belt slips and quickly works. The belt tension should not be too strong, but not too weak: a weakly tensioned belt will slip, and if it is too tensioned, the bearings will heat up and wear out quickly. The drive belt guard should also be in order.

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• Basic work performed on a lathe

When turning grooves and cutting, the following rules must be observed:

the cutter is installed as accurately as possible relative to the axis of the centers of the machine: if the cutting edge is below the axis of the centers, then when the cutter approaches the axis, a rod is formed on the part being cut; when installed above the center axis

the cutter, approaching the axis of the workpiece, can rest its back surface against the remaining rod;

the holder of the straight cutting cutter is installed strictly perpendicular to the axis of the workpiece so that the side surface of the cutter head does not rub against the walls of the groove being cut;

cutting is performed at a distance of 3-5 mm from the chuck jaws;

when cutting large-diameter workpieces, the cutter is not brought to the axis of the workpiece by 2-3 mm and, stopping the machine, breaks off the part to be cut off.

The diameter of the machined groove can be measured with a caliper if the groove is wider than its legs. Often, it is not the diameter of the groove that is determined, but its depth, using a template. The width of the groove is measured with a ruler, caliper or template.

6.2 Drilling and reaming holes on a lathe

Holes are processed on a lathe using various cutting tools depending on the type of workpiece, the required accuracy and surface roughness. The most common method of producing a hole in solid material is drilling.

Sometimes drilling is carried out in several stages, i.e. the hole is drilled out.

Reaming allows you to obtain more accurate holes and reduce the drift of the drill from the surface. A twist drill consists of a working part, a neck and a shank (Fig. 27). The end of the working part, on which two cutting edges are located, is called the cutting part of the drill. The angle between the cutting edges 2f (apex angle) when processing steel and cast iron should be 118-120°.

On the working part of the drill there are two spiral feathers connected by a jumper. Narrow guide strips are sanded along the outer surface of the feathers. Between the feathers there are two spiral grooves: one of the walls of the groove forms the front surface of the cutting wedge of the drill. Coolant is supplied through the grooves to the cutting edges, and chips are removed from the hole.

The drill shank is used to secure it in the tailstock quill or in a special caliper holder. The shank can be conical or cylindrical. Tapered shanks are made according to the standard (Morse taper No. 1, 2, 3, 4, 5). The shank cone ensures reliable centering of the drill and keeps it from turning. If the cone of the drill shank differs in size (number) from the conical hole of the tailstock quill or holder, then adapter bushings are used. Drills with cylindrical shanks are secured in the quill using a drill chuck.

Twist drills are sharpened on special sharpening machines. However, a turner often has to sharpen drills by hand on a conventional sharpening machine. When sharpening, it should be remembered that the cutting edges of the drill must be symmetrical (i.e., located at certain equal angles to the drill axis and have the same length), the transverse edge (jumper) must be located at an angle of 55° to the cutting edge.

Fig. 27 Parts and elements of a twist drill: 2 - angle at the tip of the cutter;  - angle of inclination of the helical groove;  - angle of inclination of the transverse edge.

The rear surfaces of the drill are given a curved shape, which ensures that the rear angles are obtained on the cutting wedges. To do this, the drill to be sharpened is pressed against the grinding wheel and rotated at the same time. With the same length of cutting edges, the diameter of the hole will be equal to the diameter of the drill; if one edge is longer than the other, then the diameter of the hole will be larger than the diameter of the drill, which can lead to defects and failure of the drill due to uneven load on the cutting edges. During the sharpening process, the angle 2ср, the angle 60° on the cutting wedge, the angle of inclination of the transverse edge 55° and the length of the cutting edges are subject to control.

When drilling on a lathe, the drill installed in the tailstock quill is fed to the part manually - by rotating the flywheel (Fig. 28). The use of any additional levers is not permitted. The workpiece must be firmly secured in the chuck, otherwise it will vibrate or move during drilling, which can lead to breakage of the drill.

The maximum diameter of holes produced on machines 1K62 and 16K20 is 25 mm for parts made of steel and 28 mm for parts made of cast iron.

Drilling with a manual drill feed is unproductive and tiring for the turner (especially for large-diameter and deep holes). Some lathes (for example, 1K62) have a device for connecting the tailstock to the support carriage, with the help of which drilling is performed by mechanical feed.

To drill blind holes of a given length, it is convenient to use the divisions marked on the tailstock quills. By rotating the flywheel, the drill is fed until its tip touches the end of the part, and the corresponding division into quills is noted. Then, by rotating the tailstock flywheel, move the quill until it moves the required number of divisions.

Before bringing the drill to the workpiece, you must turn on the machine. The drill should be brought in smoothly, without impact, otherwise its cutting edges may become dull and even crumble. When drilling, it is necessary to use cutting fluid (coolant).

To ensure that the drill does not move relative to the axis of the hole, at the beginning of drilling the workpiece is centered with a short spiral drill of large diameter or a special centering drill. It is important that before drilling the end of the workpiece is trimmed to ensure that it is perpendicular to the axis.

Sometimes a characteristic metallic squeal is heard when drilling. This is usually a sign that the hole is skewed or the drill is dull. In this case, you must immediately stop feeding, remove the drill, stop the machine and find out the reason for the violation. It is impossible to stop the machine while the drill is in the hole: this can lead to jamming of the drill and its breakage.

Rice. 28. Drilling on a lathe using manual feed.

Cylindrical holes can be smooth, stepped or grooved, through or blind. Holes are subject to various requirements in terms of accuracy, axis straightness, correct geometric shape, and surface roughness. The diameters of the holes are controlled with a caliper. The main types of defects when drilling holes, their causes and methods of elimination are given in Table 7.

Table 7.

The main types of defects when drilling holes, their causes and solutions

Reason for marriage	Remedy
Deviation of the hole axis from a given direction
Incorrect drill sharpening	Resharpen the drill, controlling the sharpening according to the template
Non-perpendicularity of the axis of the end surface of the workpiece	Ensure that the end is perpendicular to the axis by trimming
Working with a long drill	Perform preliminary centering with a short drill
Presence of shells or solid inclusions in the workpiece	Drill with reduced feed
"Breakdown" of hole diameter
Incorrect sharpening of the drill: one cutting edge is larger than the other, unequal angles 2f	Resharpen the drill, controlling the point according to the template
Machine spindle runout	Adjust spindle bearings
Installing a drill with a bias relative to the hole axis:
a) the tailstock quill axis does not coincide with the spindle axis;	Achieve alignment of the tailstock quill and spindle
b) the quill seat cone or drill shank is dirty	Wipe the quill cone and drill shank
Deviation of hole depth from specified
Error when controlling drilling depth during processing	Carefully control the drilling depth; when drilling with automatic drill feed, install a stop
Exceeding the permissible roughness of the machined surface
Blunt drill	Sharpen the drill
Chips getting on the drill blades	Periodically remove the drill from the hole and clean it with a brush
Insufficient cooling	Increase cooling intensity
Feed too high	Reduce feed

Due to the peculiarities of their design, groove cutters (also called slotting cutters) are considered multifunctional tools that can be used to form grooves on workpieces of cylindrical and conical configurations. Such technological operations (especially those associated with radial grooving) are characterized by significant loads, which are successfully carried by a cutter of this type, characterized by high structural rigidity. Moreover, groove cutters are successfully used for axial grooving and facing, making them versatile turning tools.

Grooving cutters for internal and external grooves with mechanical fastening of replaceable cutting inserts

It is advisable to use grooved ones to obtain parts with complex configurations. The versatility of cutters of this type in such cases allows us to minimize the number of tools used and reduce the time for equipment changeover. It is also noteworthy that the use of a groove cutter when performing many technological operations makes it possible to form surfaces with higher quality characteristics than when using a conventional turning tool.

Particularly successful is the use of a groove cutter when creating wide grooves on the surface of workpieces. When performing this technological operation, such a tool demonstrates exceptional durability; wear of its cutting plate occurs evenly even when performing a large number of passes. What is also important is that when using a groove cutter, the chip separation process is well controlled.

Requirements for groove-type cutters, which are produced in a wide variety of standard sizes, are specified by the provisions of GOST 18874-73.

GOST 18885-73 and 18874-73 regarding groove cutters

The contents of GOST 18874-73 “Slotting and cutting lathe cutters from” and GOST 18885-73 “Threaded lathe cutters with hard alloy plates” can be found below:

GOST 18874-7

GOST 18885-73

Types of groove cutters

Turning tools for forming grooves include cutters for internal and external machining. Both the first and second can be made entirely of carbide materials or have a replaceable cutting part. Carbide cutters are a fairly expensive tool, so their use must be economically feasible. When performing external work, products with replaceable inserts are usually used; using carbide groove cutters in such cases does not make sense.

The situation is completely different with the processing of internal grooves. Here it is necessary to take into account the diameter of the hole into which the cutter is to be inserted, as well as the rigidity of the tool. The requirements for a cutter to have a minimum size of its holder and sufficient rigidity to perform metal processing are met only by carbide groove tools.

Naturally, when the processing conditions and geometric parameters of the workpiece allow it, it is more advisable to use an inexpensive tool with replaceable inserts to form external and internal grooves.

Geometry and dimensions of groove type cutters

Since groove-type cutters experience significant load during processing, which determines increased requirements for their rigidity, they are manufactured with soldered carbide plates, the characteristics of which are specified in GOST 2209-82. The requirements for the cutter itself, as stated above, are given in GOST 18874-73.

The main feature of the geometry of groove-type cutters is that the shape of their cutting part must exactly match the shape of the groove that is planned to be obtained with their help. The grooves created on the surface of the workpiece are usually small in width. Accordingly, the cutting part of the tool with which they are formed is also quite narrow, which makes it very vulnerable to mechanical damage. In addition, the working head on each side has a narrowing towards the holder (by 1–2 degrees). Such a narrowing of the sides of the cutting part is necessary in order to reduce their friction against the walls of the groove being formed.

To increase the strength of the cutting head of a groove turning tool, its height is made significantly larger than its width. This also requires a small rake angle and a sharpening of the cutting edge with a small radius (curvilinear). The optimal cutting angles for groove-type cutters are 15–25 0 (front), 8–12 0 (rear).

The width of the working part of the groove tool, which, according to the requirements of GOST 18874-73, can vary over a wide range, is selected depending on the width of the groove that needs to be formed on the outer or inner surface of the workpiece.

Selection rules

The first thing you should focus on when choosing a groove turning tool is a drawing of the finished product, which indicates both the dimensions and shape of the grooves, as well as the tolerances for the accuracy of their geometric parameters. Naturally, the choice of cutter and its geometric parameters is influenced by the material from which the workpiece is made.

When forming grooves on small parts, it is especially important to maintain a low cutting force, which minimizes the distortion that occurs during processing. Compliance with this requirement is ensured by the sharp sharpening of the groove tool, which, however, can lead to its breakage if the carbide plate material and cutting conditions are selected incorrectly - the rotation speed of the workpiece and the feed rate.

When choosing a groove cutter, you should also take into account the shape of its cutting edge, which can be straight and sharpened with a small radius. Naturally, you should not choose a product with a curved sharpening of the cutting edge if the bottom of the groove, according to the provided drawing, should be straight.

Features of turning using a groove cutter

The cutting modes when using groove-type cutters have some differences from the modes of processing the workpiece with other types of turning tools. Thus, the depth of cut is taken to be a value equal to the width of the groove being formed, and the tool feed per revolution of the part is measured in the direction perpendicular to its axis. The feed rate, depending on the material from which the cutting part of the groove tool is made, is selected in the range of 0.07–0.2 mm/rev, and the cutting speed is 15–180 m/min.

Several types of grooves can be obtained on the surface of the workpiece.

• Narrow grooves, the width of which corresponds to the width of the cutting part of the tool, are made in one pass of the cutter, which is fed manually. Before this, the exact location of the groove is determined on the surface of the part, and then the cutter is placed opposite this place and fed.
• The grooves on the ledges and ends of the part are made according to the same principle; their diameter is set using the transverse feed dial, and their depth is set using the longitudinal movement dial of the caliper.
• Wide grooves are made in several passes according to the following scheme. First, determine the location of the right edge of the groove and place the cutter opposite this location. Using a transverse feed, the cutter is cut into the part to a depth that is 0.5 mm less than the depth of the groove being cut (this allowance is left for finishing). Then, using a longitudinal feed, the groove tool begins to move to the left edge of the groove being cut, the boundary of which has been previously marked. After the rough groove is formed, its bottom is processed cleanly - to the required depth, carrying out the longitudinal feed of the cutter from left to right. In the event that it is necessary to form a groove with a very precise location of its left and right edges, allowances can also be left on them during roughing, which are then removed using the transverse feed of a groove or scoring cutter.