Shoulder and groove milling
TO category:
Milling work
Shoulder and groove milling
A ledge is a recess limited by two mutually perpendicular planes forming a step. The part may have one, two or more ledges. A groove is a recess in a part, limited by planes or shaped surfaces. Depending on the shape of the recess, the grooves are divided into rectangular, T-shaped and shaped. Grooves of any profile can be through, open or with an exit and closed.
Processing of ledges and grooves is one of the operations performed on milling machines. Milled shoulders and grooves are subject to different technical requirements depending on the purpose, serial production, dimensional accuracy, location accuracy and surface roughness. All these requirements determine the processing method.
Milling of shoulders and grooves is carried out with disk end mills, as well as a set of disk cutters. In addition, shoulders can be milled with end mills.
Milling shoulders and grooves with disc cutters. Disc cutters are designed for processing planes, shoulders and grooves. Disc cutters are distinguished between solid and inserted teeth. Solid disk cutters are divided into slotted (ST SEV 573-77), grooved backed (GOST 8543-71), three-sided with straight teeth (GOST 3755-78), three-sided with multi-directional small and normal teeth. Milling cutters with insert teeth are made three-sided (GOST 1669-78). Disc groove cutters have teeth only on the cylindrical part; they are used for milling shallow grooves. The main type of disk cutters are three-sided. They have teeth on the cylindrical surface and on both ends. They are used for processing ledges and deeper grooves. They provide a higher roughness class for the side walls of a groove or shoulder. To improve cutting conditions, three-sided disk cutters are equipped with inclined teeth with alternately alternating groove directions, i.e. one tooth has a right-hand groove direction, and the other adjacent to it has a left-hand direction. Therefore, such cutters are called multidirectional: Thanks to the alternating inclination of the teeth, the axial components of the cutting force of the right and left teeth are mutually balanced. These cutters have teeth on both ends. The main disadvantage of three-sided disk cutters is the reduction in width after the first regrinding along the end. When using adjustable cutters, consisting of two halves of the same thickness with overlapping teeth in the socket, after regrinding it is possible to restore the original size. This is achieved by using spacers of appropriate thickness made of copper or brass foil, which are placed in the socket between the cutters.
Rice. 1. Ledges
Rice. 2. Types of grooves by shape
Rice. 3. Manholes: through, with exit and closed
Disc cutters with insert knives equipped with hard alloy plates are three-sided (GOST 5348-69) and two-sided. Three-sided disk cutters are used for milling grooves, and two-sided ones are used for milling shoulders and planes. The insertion knives are fastened into the body of both types of cutters using axial corrugations and a wedge with an angle of 5°. The advantage of this method of attaching insert knives is the ability to compensate for wear and the layer removed during regrinding. Restoring the size in diameter is achieved by rearranging the knives by one or more corrugations, and in width - by correspondingly extending the knives. Three-sided cutters have knives with alternately alternating inclination with an angle of 10°, for double-sided ones - in one direction with an inclination angle of 10° (for right-cutting and left-cutting cutters).
The use of three-sided disk cutters with carbide inserts gives the highest productivity when processing grooves and shoulders. A disk cutter “holds” the size better than an end cutter.
Selecting the type and size of disk cutters. The type and size of the disk cutter are selected depending on the size of the surfaces being processed and the material of the workpiece. For given processing conditions, the type of cutter, the material of the cutting part and the main dimensions - B, D, d and z - are selected. For milling easily processed materials and materials of average processing difficulty with a large milling depth, cutters with normal large teeth are used. When processing difficult-to-cut materials and milling with small depths of cut, it is recommended to use cutters with normal and fine teeth.
The diameter of the cutter should be chosen as small as possible, since the smaller the diameter of the cutter, the higher its rigidity and vibration resistance. In addition, as the diameter increases, its durability increases.
Rice. 4. Selecting the diameter of disk cutters
In Fig. 5, a, b shows a diagram of milling two shoulders on a part. Milling of shoulders with disk cutters, as mentioned above, is usually carried out with a double-sided disk cutter. However, in our case, we should choose a three-sided disk cutter, since we need to process one shoulder on each side of the part in turn.
Rice. 5. Milling a shoulder with a disk cutter
Setting up a machine for milling through rectangular grooves using disk cutters. When milling shoulders, the accuracy of the width of the shoulder does not depend on the width of the cutter. Only one condition must be met: the width of the cutter must be greater than the width of the shoulder (if possible, no more than 3-5 mm).
When milling rectangular grooves, the width of the disk cutter should be equal to the width of the groove being milled in the case when the runout of the end teeth is zero. If there is runout of the cutter teeth, the size of the groove milled by such a cutter will be accordingly larger size cutter width. This should be kept in mind, especially when machining grooves that are precise in width.
Setting the cutting depth can be carried out according to the markings. To clearly highlight the marking lines, the workpiece is pre-painted with a chalk solution and recesses (cores) are applied to the line drawn with a surface scriber using a center punch. Setting the cutting depth along the marking line is carried out with trial passes. At the same time, make sure that the cutter cuts the allowance only half of the recesses from the center punch.
When setting up a machine for processing grooves, it is very important to correctly position the cutter relative to the workpiece being processed. In the case when the workpiece is installed in a special device, its position relative to the cutter is determined by the device itself.
Precise installation of cutters to a given depth is carried out using special settings or dimensions provided in the device. In Fig. Figure 6 shows diagrams for installing cutters to size using settings. Dimension 1 is a hardened steel plate (Fig. 6, a) or a square (Fig. 6, b, c), fixed to the body of the device. A measuring probe 3-5 mm thick is placed between the set and the cutting edge of the cutter tooth to avoid contact of the cutter tooth with the hardened surface of the set. If the processing of the same surface is carried out in two passes (roughing and finishing), then probes of different thicknesses are used to install cutters of the same size.
Milling shoulders and grooves with a set of disc cutters. When processing a batch of identical parts, simultaneous milling of two shoulders, two or more grooves can be carried out by a set of cutters. To obtain the required distance between the shoulders and grooves, a corresponding set of mounting rings is placed on the mandrel between the cutters.
When processing workpieces with a set of cutters, one cutter is installed according to the dimensions, since the relative position of the set on the mandrel is achieved by selecting mounting rings. When installing cutters to a given size, they resort to using special installation templates. For precise installation of cutters, plane-parallel end blocks and indicator stops are used. In Fig. Figure 7 shows a diagram of the arrangement of indicator stops on a horizontal milling machine for precise installation of cutters during transverse and vertical movements of the table. Using such a device, you can raise and lower the table by a given amount with accelerated movement, without fear of making a mistake in the count.
The feasibility of processing shoulders and grooves with a set of cutters can be established based on the total time spent (calculation time) per part for the compared options for processing grooves.
Milling shoulders and grooves with end mills. Shoulders and grooves can be machined with end mills on vertical and horizontal milling machines. End mills (GOST 17026-71*) are designed for processing planes, shoulders and grooves. They are manufactured with cylindrical and conical shanks. End mills are manufactured with normal and large teeth. Mills with normal teeth are used for semi-finishing and finishing machining of shoulders and grooves. Mills with large teeth are used for roughing.
Roughing end mills with backed teeth (GOST 4675-71) are intended for rough processing of workpieces obtained by casting and forging.
Carbide end mills (GOST 20533-75-20539-75) are manufactured in two types: equipped with carbide crowns for diameters 10-20 mm and screw plates (for diameters 16-50 mm).
Rice. 6. Application of installations for milling cutters
Currently, tool factories produce solid carbide end mills with a diameter of 3-10 mm and end mills with a solid carbide working part soldered into a steel conical shank. The diameter of the cutters is 14-18 mm, the number of teeth is three. The use of carbide cutters is especially effective when processing grooves and shoulders in workpieces made of hardened and difficult-to-cut steels.
The accuracy of grooves in width when processing them with measuring tools, such as disk and end mills, largely depends on the accuracy of the cutters used, as well as on the accuracy, rigidity of the milling machines and on the runout of the cutter after fastening in the spindle. The disadvantage of a measuring tool is the loss of its nominal size due to wear and after regrinding. For end mills, after the first regrinding along a cylindrical surface, the diameter size is distorted, and they turn out to be unsuitable for obtaining the exact width of the groove.
You can get the exact size of the groove width by processing it in two passes: roughing and finishing. During finishing, the cutter will only calibrate the groove in width, maintaining its size for a long period of time.
IN Lately chucks for securing end mills have appeared, allowing the installation of a cutter with adjustable eccentricity, i.e., adjustable runout. In Fig. 8 shows a collet chuck used at the Leningrad Machine Tool Association named after. Y. M. Sverdlova. The hole in the chuck body is bored eccentrically by 0.3 mm relative to its shank. A sleeve for collets is inserted into this hole with the same eccentricity relative to the inner diameter. The bushing is attached to the body with two bolts. When the sleeve is turned with a nut and the bolts are slightly loosened, a conditional increase in the diameter of the cutter occurs (one division per limbg corresponds to an increase in the diameter of the cutter by 0.04 mm).
When machining grooves with an end mill, the chips must be directed upward along the helical groove so that they do not spoil the machined surface or cause breakage of the cutter tooth. This is possible in the case when the direction of the helical groove coincides with the direction of rotation of the cutter, i.e., when they are in the same direction. However, the axial component of the cutting force Px will be directed downward to push the cutter out of the spindle socket. Therefore, when machining grooves, the cutter must be fastened more securely than when machining an open plane with an end mill. The direction of rotation of the cutter and helical groove, as in the case of machining with face and cylindrical cutters, should be opposite, since in this case the axial component of the cutting force will be directed towards the spindle socket and tend to tighten the mandrel with the cutter into the spindle socket.
Rice. 8. Chuck for milling measuring grooves with standard cutters
Rice. 9. Milling an inclined plane in a vice
Rice. 10. Milling the recess of the body part
Other types of work performed by end mills. In addition to processing shoulders and grooves, end mills are used to perform other work on vertical and horizontal milling machines.
End mills are used for processing open planes: vertical, horizontal and inclined. In Fig. Figure 9 shows milling of an inclined plane in a universal vice. The techniques for processing planes with end mills are no different from the techniques for processing shoulders and grooves. End mills can be used to process various recesses (sockets). In Fig. Figure 10 shows the milling of a cavity using an end mill. Milling of recesses in the workpiece is carried out according to the markings. It is more convenient to first make preliminary milling of the recess contour (without reaching the marking lines), and then final milling of the contour.
In cases where it is necessary to mill a window rather than a recess, it is necessary to place an appropriate backing under the workpiece so as not to damage the vice when the end mill comes out.
Milling shoulders with an end mill. Shoulders can be milled on both vertical and horizontal milling machines. Machining of parts with symmetrically located ledges can be carried out by securing the workpieces in two-position rotary tables. After milling the first shoulder, the fixture is rotated 180° and placed in the second position to mill the second shoulder.
Often found in mechanical engineering flat parts having 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.
A ledge closed on both sides is called a groove. The grooves may have 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. Released for these cutters state standard(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 groove being milled.
Since three-sided disk cutters are made with pointed teeth, after subsequent regrinding of the end teeth, the width of the cutter 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 composite 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 from high-speed steel P9 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 using 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.
A ledge is a recess limited by two mutually perpendicular planes forming a step. The part may have one, two, three or more ledges (Fig. 72). A groove is a recess in a part, limited by planes or shaped surfaces. Depending on the shape of the recess, the grooves are divided into rectangular, triangular, trapezoidal, T-shaped and shaped (Fig. 73, a, b, c, d, e, f). Grooves of any profile can be through (Fig. 74, a), open or with an exit (Fig. 74, b) and closed (Fig. 74, c).
Processing of shoulders and grooves is one of the operations performed on milling machines.
Milled shoulders and grooves are subject to different technical requirements depending on the purpose, serial production, dimensional accuracy, location accuracy and surface roughness. All these requirements influence the choice of processing method.
Milling of shoulders and grooves is carried out with disk end mills, as well as a set of disk cutters. In addition, shoulders can be milled with end mills.
Solidity when processing grooves and ledges. A disk cutter “holds” the size better than an end cutter.
Selecting the type and size of disk cutters. The type and size of the disk cutter are selected depending on the size of the surfaces being processed and the material of the workpiece. For given processing conditions, the type of cutter, the material of the cutting part and the main dimensions are selected - D, B, d and Z. For milling easily processed materials and materials of average processing difficulty with a large milling depth, cutters with normal and large teeth are used. When processing difficult-to-cut materials and when milling with small depths of cut, it is recommended to use cutters with normal and fine teeth.
The diameter of the cutter should be chosen as small as possible, since the smaller the diameter of the cutter, the higher its rigidity and vibration resistance. In addition, as the diameter of the cutter increases, its cost increases.
As can be seen in Fig. 78, with a milling depth t and a guaranteed gap between the setting ring and the workpiece within (6-8) mm, the condition must be met 
from where we get the expression for selection minimum diameter cutter 
Where d1 is the diameter of the cutter hub (installation ring).
In table Figure 5 shows the dependence of the cutter hub diameter d1 on the hole diameter d for disk cutters. 
We will explain the setup and adjustment of the machine for milling shoulders with disk cutters using the example of processing the shoulders of a prism (Fig. 79, a, b). The choice of the standard size of a disk cutter depends on the size of the shoulder, the type of material being processed, the power of the machine’s electric motor and other conditions.
Milling shoulders with disk cutters, as mentioned above, is usually done with a double-sided disk cutter. However, in our case, we should choose a three-sided cutter, since it is necessary to alternately process one shoulder on each side of the prism (Fig. 80, a, b). We choose a three-sided cutter with insert knives in accordance with GOST 5348 - 69, equipped with T15K6 hard alloy plates. The diameter of the cutter is D = 100 mm, width B = 18 mm, number of teeth z = 8. When milling grooves and shoulders, the vice must be aligned using a surface planer or an indicator with a stand and secured. We install and secure the workpiece in a machine vice with a liner. The disk cutter is secured to the mandrel in the same way as a cylindrical cutter. Milling modes are selected either from reference books, if they are not listed in operational cards, or directly from operational or instruction cards.
Milling mode for our case: B = 13 mm, t = 4 mm, sz = = 0.06 mm/tooth, v = 335 m/min. According to the graph (see Fig. 48), we determine the number of revolutions of the machine spindle - 1000 rpm.
According to the graph (see Fig. 49), we determine the minute feed - sM = 500 mm/min. Then the machine is adjusted to the required number of machine spindle revolutions and the required minute feed.
Milling each shoulder consists of the following basic techniques:
1. By pressing the “Start” button, turn on the electric motor and the machine spindle in the direction opposite direction helical flute of the cutter. 
2. Bring the workpiece by manually moving the table with the handles of longitudinal, transverse and vertical movements under the rotating cutter until the side cutting edges lightly touch the workpiece. Then, by rotating the vertical feed handle, lower the table until the cutter extends beyond the dimensions of the workpiece being processed. Next, by rotating the cross-feed handle, move the workpiece in the direction of the cutter by 13 mm, using the cross-feed dial. Raise the table until the rotating cutter lightly touches the top plane of the workpiece. By rotating the longitudinal feed handle, remove the workpiece from under the cutter, turn off the machine and raise the table by 4 mm, using the vertical feed dial. Lock the vertical and cross slides.
3. Set the cams for mechanically switching off the longitudinal feed of the table to the milling length. Turn on the spindle rotation again, manually feed the workpiece by rotating the table longitudinal feed handle towards the rotating cutter, turn on the mechanical longitudinal feed and mill the first shoulder (see Fig. 80, a). Turn off the machine without moving the table.
Check the width and depth of the machined shoulder using a caliper. If the size is not accurate, it should be corrected
processing defects.
4. The order of installing the cutter relative to the workpiece when processing the second shoulder (see Fig. 80, b) depends on which of the dimensions must be maintained exactly (size 13 mm or the size of the protrusion between the shoulders 89 mm). Since in our example the size is set to 13 mm, the procedure for processing the second shoulder will be exactly the same as the first. If it were necessary to maintain the size of the protrusion along the length, then after processing the first shoulder, the processing of the second shoulder can be carried out according to one of two options, depending on the length of the protrusion. If the protrusion length is relatively short, the table should be returned to its original position before the cutter leaves the dimensions of the workpiece being processed. Then move the table transversely a distance equal to the width of the shoulder plus the width of the cutter, and rout the second shoulder.
The processing sequence for the second option will be given only in general view.
Since in our case the width of the projection is 89 mm, and the width of the cutter is 18 mm, then to move the table in the transverse direction a distance equal to the width of the projection plus the width of the cutter, i.e. 89+18 = 107 mm, it would be required make more than 17 revolutions of the cross-feed dial (with a pitch of the cross-feed screw t = 6 mm). Therefore, in such cases, obtaining the exact size of the protrusion can be achieved by milling in two passes - preliminary and final. Preliminary milling can be done according to the markings, leaving an allowance along the length of the protrusion for final milling within 1 - 2 mm.
After preliminary milling, measure the length of the shoulder and, in accordance with the resulting size, determine the number of divisions by which the cross-feed dial should be turned without disturbing the height settings, and perform final milling of the second shoulder. The second option for processing ledges in single and small-scale production is preferable.
Setting up a machine for milling through rectangular grooves using disk cutters. When milling shoulders, the accuracy of the width of the shoulder does not depend on the width of the cutter. Only one condition must be met: the width of the cutter must be greater than the width of the shoulder (if possible, no more than 3 - 5 mm).
When milling rectangular grooves, the width of the disk cutter should be equal to the width of the groove being milled if the runout of the end teeth of the cutter is zero. If there is runout of the cutter teeth, the size of the groove milled by such a cutter will be correspondingly larger than the width of the cutter. This should be kept in mind, especially when machining precise groove widths.
Setting the cutting depth can be carried out according to the markings. To clearly highlight the marking lines, the workpiece is pre-painted with a chalk solution and recesses (cores) are applied to the line drawn by a thicknesser with a center punch. Setting the cutting depth along the marking line is carried out with trial passes. At the same time, make sure that the cutter cuts the allowance only half of the recesses from the center punch.
When setting up a machine for processing grooves, it is very important to correctly position the cutter relative to the workpiece being processed. In the case when the workpiece is installed in a special device, its position relative to the cutter is determined by the device itself. 
In the case when processing is carried out without a special device, the task becomes more complicated and its solution depends primarily on what dimensions must be maintained when processing the groove. Let's explain this with an example. Let's say you need to mill a rectangular groove of width b with dimensions a and h, which determine its position on the part. In Fig. 81 dimension h is measured from the top plane of the workpiece, and in Fig. 82 dimension h is set from the lower supporting surface of the workpiece. 
The procedure for installing a disk cutter in the first case (see Fig. 81) is as follows. Bring the rotating cutter to the side surface of the workpiece until it touches in the form of a mark (position I). Then lower the table so that the cutter is above the top surface 
workpiece and move it with the cross feed handle to dimension a. Then raise the table to a height at which the cutter will leave a light mark on the top surface of the part. Next, you need to move the table in the longitudinal direction, move the cutter beyond the dimensions of the workpiece and, raising the table to size h, turn on the longitudinal feed and mill the groove (position II).
The order of installation is to size h, specified from the base of the part (see Fig. 82). Raise the table until the cutter touches the table surface if the part is installed directly on the table, or until it touches the support if the part is installed in a fixture (position I). Then lower the table to dimension h (position II). After this, turn on the rotation of the cutter and move the table until the cutter comes into contact with the workpiece being processed and a slight mark from the cutter is formed (position III). Now move the table in the longitudinal direction, move the cutter beyond the dimensions of the workpiece and move the table with the cross-feed handle to dimension a (position IV). Turn on the longitudinal feed and mill the groove. 
If instead of size a in both cases size c was specified, then the table would be moved in the transverse direction by the amount c + B, where B is the width of the cutter.
Precise installation of cutters to a given depth is carried out using special settings or dimensions provided in the device. In Fig. 83 shows diagrams for installing cutters to size using settings. Dimension 1 is a hardened steel plate (Fig. 83, a) or a square (Fig. 83, b, c), fixed to the body of the device. Between the setting and the cutting edge of the cutter tooth, a measuring probe 2 with a thickness of 3 - 5 mm is placed, in order to avoid contact of the cutter tooth 3 with the hardened surface of the setting. 
If the processing of the same surface is carried out in two transitions (roughing and finishing), then probes of different thicknesses are used to install cutters of the same size. 
To fully work with manual router In addition to the tool itself, the material and the corresponding set of cutters, you must have one more component - fixtures. In order for the cutter to be able to shape the workpiece in accordance with the master's plan - cutting the material exactly where it is required - it must be in a strictly defined position relative to the workpiece at each moment of time. Numerous accessories for a hand router are used to ensure this. Some of them - the most necessary ones - are included in the scope of delivery of the tool. Other devices for milling can be purchased or made by yourself. Wherein homemade devices so simple that to make them you can do without drawings, using only their drawings.
Parallel stop for a manual router: 1 - stop, 2 - rod, 3 - base of the router, 4 - rod locking screw, 5 - fine adjustment screw, 6 - movable carriage, 7 - movable carriage locking screw, 8 - pads, 9 - screw stop locking.
To install the device in the working position, it is necessary to slide the rods 2 into the holes of the frame 3, ensuring the required distance between the supporting surface of the stop and the axis of the cutter, and fix them with the locking screw 4. To accurately position the cutter, you need to release the locking screw 9 and rotate the fine adjustment screw 5 set the cutter to the desired position. For some stop models, the dimensions of the supporting surface can be changed by moving or spreading the support pads 8.
If you add one simple part to the rip fence, then you can use it to mill not only straight, but also curved grooves, for example, to process a round workpiece. Moreover inner surface The bar located between the stop and the workpiece does not necessarily have to have a rounded shape that follows the edge of the workpiece. It can be given more simple form(Figure "a"). In this case, the trajectory of the cutter will not change.
Of course, a regular rip fence, thanks to the notch in the center, will allow you to orient the router along a rounded edge, but the position of the router may not be stable enough.
The function of the guide bar is similar to that of a rip fence. Like the latter, it ensures strictly linear movement of the router. The main difference between them is that the tire can be installed at any angle to the edge of the part or table, thereby ensuring any direction of movement of the router in the horizontal plane. In addition, the tire may have elements that simplify certain operations, for example, milling holes located at the same distance from each other (with a certain pitch), etc.
The guide rail is attached to the table or workpiece using clamps or special clamps. The tire can be equipped with an adapter (shoe), which is connected to the base of the router by two rods. Sliding along the profile of the tire, the adapter sets the linear movement of the cutter.
Sometimes (if the distance of the tire from the router is too close), the supporting surfaces of the tire and the router may appear in different planes in height. To level them, some routers are equipped with retractable support legs, which change the position of the router in height.
Such a device is easy to make with your own hands. The simplest option is a long block secured to the workpiece with clamps. The design can be supplemented with side supports.
By placing a block on two or more aligned workpieces at once, grooves can be made in them in one pass.
When using a block as a stop, it is inconvenient to place the block at a certain distance from the line of the future groove. The following two devices do not have this inconvenience. The first is made from boards and plywood fastened together. In this case, the distance from the edge of the stop (board) to the edge of the base (plywood) is equal to the distance from the cutter to the edge of the router base. But this condition is met only for a cutter of the same diameter. Thanks to this, the device quickly aligns along the edge of the future groove.
The following device can be used with cutters of different diameters, plus when milling, the router rests on its entire sole, and not half, as in the previous device.
The stop is aligned along the edge of the hinged board and the center line of the groove. After fixing the stop, the folding board folds back, making room for the router. The width of the folding board, together with the gap between it and the stop (if there is one), should be equal to the distance from the center of the cutter to the edge of the router base. If you focus on the edge of the cutter and the edge of the future groove, then the device will only work with one diameter of the cutter.
When milling grooves across the grain, at the exit from the workpiece, when milling an open groove, cases of wood scuffing are not uncommon. The following devices will help to minimize scuffing: I press the fibers where the cutter exits, preventing them from splitting off from the workpiece.
Two boards, strictly perpendicular, are connected with screws. WITH different sides For the stop, different cutters are used so that the width of the groove in the fixture matches the width of the groove of the part being milled.
Another tool for routing open slots can be pressed harder against the workpiece, which further minimizes scuffing, but it only fits one diameter cutter. It consists of two L-shaped parts connected to the workpiece with clamps.
The diameter of the copy ring should be as close to the diameter of the cutter as possible, but the ring should not touch its cutting parts. If the diameter of the ring is larger than the diameter of the cutter, then the template should be smaller than finished parts to compensate for the difference between the cutter diameter and the copy ring diameter.
The template is secured to the workpiece with double-sided tape, then both parts are pressed with clamps to the workbench. Once you have finished routing, check that the ring is pressed against the edge of the template throughout the entire operation.
You can make a template for processing not the entire edge, but only for rounding the corners. In this case, using the template shown below, you can make roundings of four different radii.
In the figure above, a cutter with a bearing is used, but the template can also be used with a ring, only either the ring must exactly match the diameter of the cutter, or the stops must make it possible to move the template away from the edge by the difference in the radius of the cutter and the ring. This also applies to more simple option pictured below.
Templates are used not only for milling edges, but also grooves on the face.
The template can be adjustable.
Template routing is a great method for cutting out hinge grooves.
It is better, of course, for the compass to be made of two rods.
In general, compasses are a very common device. Exists a large number of branded and homemade devices for circumferential milling, varying in size and ease of use. As a rule, compasses have a mechanism that ensures a change in the radius of the circle. It is usually made in the form of a screw with a pin at the end, moving along the groove of the device. The pin is inserted into the central hole of the part.
When it is necessary to mill a circle of small diameter, the pin must be located under the router base, and for such cases, other devices are used that are attached to the bottom of the router base.
Ensuring the movement of the cutter in a circle using a compass is quite simple. However, one often has to deal with the need to make elliptical contours - when inserting oval-shaped mirrors or glass, installing arched windows or doors, etc. The PE60 WEGOMA device (Germany) is designed for milling ellipses and circles.
It is a base in the form of a plate, attached to the surface using vacuum suction cups 1 or with screws if the nature of the surface does not allow it to be fixed using suction cups. Two shoes 2, moving along intersecting guides, ensure the movement of the milling cutter along an elliptical path. When milling a circle, only one shoe is used. The device kit includes two mounting rods and bracket 3, with the help of which the router is connected to the slab. The grooves on the bracket allow you to install the router so that its supporting surface and the base of the slab are in the same plane.
As can be seen from the photographs above, a router was used instead of a jigsaw or band saw, at the same time, due to the high speed of the cutter, the quality of the processed surface is much higher. Also, if you don’t have a hand-held circular saw, a router can replace it.
To make grooves at the end, you can make a simple device in the form flat base, attached to the milling cutter base. Its shape can be not only round (according to the shape of the base of the router), but also rectangular. On both sides you need to secure guide pins that will ensure the straight movement of the router. The main condition for their installation is that their axes are in line with the center of the cutter. If this condition is ensured, the groove will be located exactly in the center of the workpiece, regardless of its thickness. If you need to move the groove to one side or another from the center, you need to put a bushing with a certain wall thickness on one of the pins, as a result of which the groove will move to the side on which the pin with the bushing is located. When using a router with such a device, it must be guided in such a way that the pins are pressed on both sides to the side surfaces of the part.
If you attach a second rip fence to the router, you will also get a device for milling grooves in the edge.
But you can do without special devices. To ensure stability of the router on a narrow surface, boards are secured on both sides of the part, the surface of which should form a single plane with the surface being processed. When milling, the router is positioned using a rip fence.
You can make an improved version that increases the support area for the router.
Sometimes there is a need to mill various grooves in rotating bodies. In this case, the device shown below may be useful.
The device is used for milling longitudinal grooves (flutes) on balusters, posts, etc. It consists of a body 2, a movable carriage with an installed milling cutter 1, a disk for setting the angle of rotation 3. The device operates as follows. The baluster is placed in the body and secured there with screws 4. Rotation to the desired angle and fixation of the workpiece in a strictly defined position is ensured by disk 3 and locking screw 5. After fixing the part, the carriage with the router is set in motion (along the guide bars of the body), and the milling a groove along the length of the workpiece. Then the product is unlocked, rotated to the required angle, locked, and the next groove is made.
A similar device can be used instead lathe. The workpiece should be rotated slowly by an assistant or a simple drive, for example, from a drill or screwdriver, and excess material should be removed by a milling cutter moving along the guides.
The figure below shows an industrial sample of a tenon-cutting device for making three types of joints - a dovetail (blind and through version) and a through joint with a straight tenon. The two mating parts are installed in the fixture with a certain shift relative to each other, controlled by pins 1 and 2, then they are processed. The exact trajectory of the cutter is determined by the shape of the groove in the template and the copying ring of the router, which slides along the edge of the template, repeating its shape.
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Shoulder milling operations:
Shoulder milling processes two surfaces simultaneously, requiring peripheral milling combined with face milling. One of the most important requirements is the formation of a ledge with an angle of ninety degrees. Shoulders can be milled with traditional square shoulder cutters, as well as end, long-edge and three-sided disc cutters. Because of these numerous options, it is necessary to carefully consider the operational requirements to make the optimal choice.
End mills conventional design for shoulder processing, they are often capable of milling strictly rectangular shallow shoulders. Many shoulder milling cutters are versatile and can be used effectively to make holes. They are a good alternative to conventional face mills when machining axially deviating surfaces and when milling close to vertical surfaces.
Indexable and Solid Carbide End Mills – good solutions for milling benches where geometric cross-country ability is required.
Long edge cutters are used for milling deeper shoulders.
This common operation is typically performed with shoulder mills and end mills. With a small shoulder height, machining with a large radial depth of cut is possible. Often, such cutters can replace a traditional end mill, especially in conditions where it is necessary to reduce the cutting forces on the part in the axial direction, and also if access to the workpiece is difficult due to the peculiarities of the fastening device. Shoulder cutters with a larger cutting diameter provide optimal clearance when milling deep, small shoulders.
Performed in multiple passes using shoulder cutters and end mills. Minimizing surface imperfections such as scallops and transition edges between passes requires a high-precision cutter that produces perfectly square shoulders. If the shoulder depth is less than 75% of the cutting edge length, the vertical surface quality level usually does not require additional finishing.
Long edge cutters are suitable for machining taller, longer shoulders that require large amounts of metal to be removed. They have a high metal removal rate and are typically used for rough milling because the insert row marks appear on the machined surface.
Important for these cutters:
The radial forces are significant, which makes shoulder milling difficult.
Shorter long edge cutters are suitable for:
Longer versions are intended for:
Oversized shoulder cutters provide optimal clearance when milling deep, small shoulders. For even deeper benches, use extensions with a Coromant Capto connection. Long edge cutters are also available in larger sizes for deep, large shoulders. However, the cutting width is more limited here.
Three-sided disc cutters are also used for processing shoulders, especially if the shape is narrow and also long. Typically, these cutters provide the only possible machining of undercuts on closed shoulders.
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Edge milling is actually shoulder milling done using the contouring method. Face milling and contour milling are types of milling with the peripheral part of a cutter.
In the absence of cutter runout, the height of the scallop h
will be the same and can be calculated using the formula:
Profile depth/scallop height
If there is cutter runout, feed per tooth f z
and, accordingly, the height of the scallop h will vary depending on the TIR.
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f z | f z runout |
As mentioned earlier, the resulting surface roughness can limit the feed rate, especially at low radial depths of cut.
When working with the cylindrical part of the end mill, a series of ‘scallops’ are formed on the profile. The height of the scallop h is determined by the following parameters:
Indexable cutters will always have a higher TIR value than solid carbide cutters. In addition, the larger the cutter diameter, the more quantity teeth, which increases the height of the combs.
For getting optimal quality treated surface:
Note: The worst surface quality is obtained when, due to strong runout of the cutter, the surface is created by only one cutting edge.
To process ledges:
Passes should be made in a zigzag pattern.
Finishing allowance
Processing thin substrates:
If this requires milling a surface whose opposite side has already been machined:
If the part has a hole in the center of the base:
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