When drilling, the cutting tool-drill 1 (Fig. 181, a) simultaneously receives rotation with speed v and translational motion along the axis, i.e. supply S. The workpiece 2 is fixed.

The main cutting elements when drilling are: speed v and depth of cut t, feed S, thickness a and chip width b (Fig. 181, b).

Fig. 181. The movement of the tool when drilling (a) to the cutting elements (b)

The cutting speed v is the path traveled per unit of time by the point of the cutting edge most distant from the drill axis.

The cutting speed is selected depending on the feed rate, the drill diameter, its durability, the material of the workpiece. These data are given in special directories.

The cutting speed is calculated by the formula:

where π is a constant number equal to 3, 14;

n is the specified number of revolutions of the spindle (tool) per minute;

D is the diameter of the cutting tool, mm.

The cutting tool resistance depends on the cutting speed, i.e., the time of its continuous work between two regrints. The higher the cutting speed, the more heat is generated during the formation of chips, and the faster the cutting edge becomes blunt.

The found cutting speeds calculate the number of revolutions of the spindle of the machine according to the formula:

which is adjusted according to the kinematic data of the machine.

Feed S is the amount of movement of the cutting tool or part along the axis of rotation per revolution.

Since the drill has two cutting edges, the feed per each of them,

Choosing the right feed is important for the durability of the cutting tool. It is always more profitable to work with a high feed and a lower cutting speed, in this case the drill bit wears out more slowly. However, when drilling holes of small diameters, the feed rate is limited by the strength of the drill. With an increase in the diameter of the drill its strength increases, allowing you to increase the flow; It should be noted that the increase in feed is limited by the strength of the machine.

When selecting cutting modes, first of all, the greatest flow is selected depending on the quality of the surface to be machined, the strength of the drill and the machine and other factors (according to the tables given in reference books) and is adjusted according to the kinematic data of the machine (the nearest smaller one is taken) cutting, in which the tool life between regrints will be greatest.

Modes of drilling, depending on the diameter of the hole, the material being processed, the material of the drill and other factors are given in reference books.

Preparation and adjustment of the machine

Before starting work on the drilling machine, it is first necessary to check the condition of its grounding, wipe the table, spindle hole, check the presence of fencing, check idle rotation, axial movement of the spindle and the operation of the feed mechanism, table fixing.

Preparing the machine for work consists in installing and fixing the cutting tool and part and in determining the cutting mode (speed and feed).

The drill is selected in accordance with the specified bore diameter and depending on the material being processed.

Choosing the diameter of the drill, it should be remembered that when working with a drill as a result of the beating, the hole turns out to be somewhat larger than the drill. Hole development averages:

In some cases, the accuracy of drilling can be improved by carefully adjusting the machine, by correct sharpening the drill or by using a conductor sleeve.

Depending on what the shank has a drill - cylindrical or tapered, select the drill chuck or the corresponding adapter sleeve.

Based on the shape and size of the workpiece, choose one or another device for fixing it during drilling.

Before installing the chuck or adapter sleeve, it is necessary to cleanly wipe both the shank and the spindle hole. Do not wipe the spindle during its rotation.

The drill is inserted into the hole of the spindle with a slight push of the hand. When installing the drill in the chuck it is necessary to ensure that the drill shank rests against the bottom of the chuck, otherwise the drill may move along its axis during operation. Then install the device or part on the machine table, having previously cleaned both the table surface and the stop plane of the device or the part itself.

If it is necessary to drill a through hole, then in order to avoid damage to the table, a lining is placed under the part (if the table does not have a hole).

Knowing the diameter and material of the drill, as well as the material of the workpiece, adjust the machine at a certain number of revolutions and feed.

The order of adjustment of the machine at a certain number of revolutions and feed depends on the design of the machine. In some machines, this is done by transferring the belt from one pulley stage to another, or by switching using gear handles in the gearbox and feedbox. Many machines, especially designed for drilling holes of small diameter, do not have a mechanical feed, and the movement of the drill on such machines is carried out manually.

To increase the durability of the cutting tool and to obtain a clean hole surface when drilling metals and alloys, coolants should be used.

The choice of coolants depends on the type of metal and alloy being processed:

Wrong choice of cutting mode, inaccurate sharpening of the drill, drilling without cooling cause premature drill wear and cause a defect (table 2).

table 2
  Causes of drilling problems and how to solve them

In the process of forming the hole, the drill simultaneously performs rotational and translational movements, with the cutting edges of the drill cutting off thin layers of material, forming chips. The faster the drill rotates and the greater the distance per revolution it overcomes in the direction of the axis of the hole being machined, the faster the cutting occurs.

Cutting speed dependsfrom the frequency of rotation of the drill and its diameter, movement of the drill along the axis of the workpiece per revolution affects the thickness of the material removed (chip). Compared to other cutting tools, the drill is working, t under rather difficult conditions, since during drilling it is difficult to remove chips and supply cooling lubricant.

The main elements of cutting when drilling are the speed and depth of cut, feed, thickness and width of the chip (Fig. 3.77).

Cutting speed V is the path traveled by a point on the cutting edge of the drill, furthest from the axis of its rotation. Determine the cutting speed according to the formula V = ndnl1000 (where V is the cutting speed, m / min; d is the drill diameter, mm; n is the spindle speed, rpm; n is a constant number equal to 3.14; the number 1 has been entered in the formula for converting the diameter of the drill into meters). The magnitude of the cutting speed depends on the material of the workpiece, the material of the tool and the shape of its sharpening, feed, depth of cut and the presence of cooling when machining the hole.

Feed 3 is measured in millimeters per revolution of the drill (mm / rev). The amount of feed when drilling is selected depending on the requirements for roughness of the treated surface and the accuracy of processing, the material being processed and the material being drilled.

Cutting depth t  measured in millimeters and represents the distance from the surface to be drilled to the drill axis, i.e. when drilling, the depth of cut is half the diameter of the drill, and when drilled - half the difference between the diameter of the pre-drilled hole and the diameter of the drill.

Cutting thickness  measured in the direction perpendicular to the cutting edge of the drill, and is equal to half the amount of movement of the drill relative to the axis of the hole being machined in one revolution, ie half feed rate. Since a layer of material is removed by two cutting teeth in one turn of the drill, each of these teeth removes a layer of material whose thickness is equal to half the feed rate of the drill for one revolution.

Cut width  measured along the cutting edge and equal to its length. When drilling, the cutting width is equal to the length of the cutting edge involved in cutting. The width of the cut is measured in millimeters.

Cutting conditions are set to ensure maximum productivity. It is necessary to take into account the physicomechanical properties of the material of the workpiece, the material properties of the tool and the requirements for the quality of the processed surface, specified by the drawing or technical specifications for manufacturing.

The theoretical calculation of the elements of the cutting mode perform  in the sequence below.

1. According to special reference tables, the feed rate is selected depending on the processing xapat, quality requirements of the processed surface, drill material and other technological data.

2. Calculate the speed of the tool, taking into account the technological capabilities, the cutting properties of the material of the tool and the physicomechanical properties of the workpiece.

3. Determine the estimated spindle speed in accordance with the found cutting speed. The obtained value is compared with the passport data of the machine and is assumed to be equal to the nearest lowest value of this frequency.

4. Determine the actual cutting speed at which processing will be performed.

In practice, to determine the cutting conditions using the ready data of technological maps and tables of reference books.

Cutting modes when countersinking and deploying, as well as the criteria for their selection, do not practically differ from the choice of these parameters when drilling.

Hole processing allowances

The allowance is a layer of material to be removed during processing. The size of this layer depends on the requirements for the treated surface and the type of treatment.

When drilling allowance for processing is half the diameter of the drill. When drilling, the allowance is determined depending on the requirements for the machined surface and the need for its further processing (countersinking, deployment). Reamming allowance, depending on whether it is preliminary (before deployment) or final, is from 0.5 to 1.2 mm. The size of the allowance also depends on the diameter of the hole being machined. The deployment allowance depends on the diameter of the hole to be machined and on the requirements imposed on the quality of the processed surface and ranges from 0.05 to 0.3 mm. Typical defects in the processing of holes, the causes of their occurrence and methods of warning are given in Table. 3.2.

Cutting speed v-surge speed of the point of the blade furthest from the drill axis is determined by the formula

where D is the diameter of the drill, mm;

n is the number of revolutions of the drill per minute.

The cutting speed is a variable variable for different points of the blade. In the center of the drill speed is zero.

Cutting depth is defined as follows: when drilling in solid material (Figure 9.)

b - when drilling.

b - when drilling out "

img9_4. jpg" >

Figure 9.4 - Elements of cutting mode: a - when drilling;

b - when drilling.

where d- diameter of previously drilled holes, mm.

Innings s - the amount of movement of the drill along the axis one turn. Since the drill has two main blades, the feed falling on each blade,

Minute feed is determined by the formula:

S   _m  = s .n mm / min

The width and thickness of the slice (without taking into account the lintel) is determined by the formulas:

and
.

When determining the area of ​​cut, the jumper is not taken into account, since the calculation error will be small.

Cutting area when drilling in solid material per blade,

.

Cutting area corresponding to one turn of the drill

Feed when drilling can be determined by the formula:

where C   _s  - coefficient depending on the properties of the material being processed.

During boring, the feed rate is taken 1.5–2 times more than when drilling.

9.3 Cutting forces and drilling torque

The cutting process when drilling has much in common with the process of turning. Drilling is accompanied by the same physical phenomena: heat generation, shrinkage of chips, build-up, etc. Along with this, the drilling process has its own characteristics. So, the formation of chips occurs in more severe conditions than when turning. When drilling is difficult to exit chips and supply coolant. In addition, the angle and cutting speed are variable along the length of the blade values. This creates dissimilar working conditions for different points of the blade.

The shrinkage of the chip at the web is greater than at the periphery of the drill, as the cutting angle increases and the cutting speed decreases, which increases the deformation of the chip.

The pattern of change in shrinkage of chips, depending on the cutting speed, feed, coolant and the geometry of the cutting part of the drill is about the same as in turning.

With increasing drill diameter shrinkage decreases. This is due to the fact that with increasing diameter, the cross-sectional area of ​​the drill groove increases, which leads to looser chip formation. With increasing drilling depth, shrinkage increases. With a drilling depth l= D  shrinkage 1.7-2 times more than shrinkage at l = D. With an increase in the depth of drilling, the emergence of chips is difficult, its friction against the groove increases, which causes an increase in deformation. The shrinkage of the chips during drilling as well as during turning has an effect on the magnitude of the cutting forces.

Consider the forces acting on the drill. Suppose that the resultant forces applied to the main blades are at points BUT  (Figure 9). By decomposing these resultant in three directions (as in turning), we obtain the component forces P   _z  R   _y  R   _x.

The torque required for drilling is equal to the sum of the moments of the tangential forces acting on all the blades of the drill. It is established that 80% of the total moment is the moment of forces P   _z  12% of the moment of tangential forces of the auxiliary blades and 8% of the moment of the tangential force of the jumper blade.

img13_1.jpg" >

Figure 9.5 - Diagram of the forces acting on the drill

Feed force (axial force) is equal to the sum of the forces acting along the axis of the drill. Strength R _x   is about 40%. feed force R _n -57%, the forces of the auxiliary blades, as well as the forces of friction between the chips and the grooves of the drill, constitute 3% of the feed force.

Radial forces Р y with the correct sharpening of the drill (symmetrical), as equal in size and oppositely directed, are balanced. Torque and axial force is determined by the formulas:

Fig. Diagram of the forces acting on the drill

The magnitude of the coefficients WITH _m   and WITH ₀   depends on the properties of the material being processed, drill geometry, coolant and other cutting parameters.

The angle of inclination of the helical groove affects the cutting forces, as the rake angle depends on it. With increasing angle v the rake angle increases, and cutting forces decrease. The angle in terms of w affects differently the values M _cr   andP ₀ . With increasing angle w increases resistance to penetration of the drill, which leads to an increase in the force P _{0 . Simultaneously with the increase of the angle w, the width decreases and the thickness of the cut increases, which helps to reduce the force R z   and M cr .}

The elements of the cutting mode, the properties of the material being processed, coolant and other cutting conditions affect M _cr   and P ₀   the same as when turning. Effective power is determined by the formula:

9. 4 Cutting speed when drilling

Cutting speed when drilling, as well as when turning, depends on a number of factors and can be expressed by the formula:

where C _v   - constant for a specific group of the processed material; TO   _M- coefficient depending on the properties of the material being processed;

TO   _rTo   _andTo   _lK   _h  K   _sozh-coefficients that take into account the influence of the drill geometry, the material of its cutting part, the depth of drilling, drill wear and coolant. From the formula it follows that with an increase in the diameter of the drill cutting speed increases. It would seem that with an increase in the diameter of the drill the speed should decrease, since the depth of cut depends on it. With increasing D increases the depth of cut, and with it the amount of heat generated, which should lead to a decrease in speed. But with an increase in the diameter, there are other factors that prevail over the former, which have a favorable effect on the resistance of the drill. With increasing D  increases the mass of the metal, which improves the heat sink; the volume of chip grooves increases, due to which chip removal and coolant supply are improved; rigidity of a drill increases therefore its wear decreases.

The influence of the material of the cutting part of the drill is taken into account TO _and .   If for high speed steel drill to take TO _and   == 1, then the average values ​​of this coefficient for drills from other materials are as follows: for drills from tool alloyed steel TO _and   = 0.65, for drills from carbon tool steel TO _and   = 0.5, for carbide TO _and =2-3.

With an increase in the drilling depth, the cutting conditions deteriorate because it is more difficult to remove chips and supply coolant. When drilling holes with depth l > 3 D cutting speed is reduced and the correction factor K   _l< 1.

When working with a drill having a wear above the permissible norm, the cutting speed is reduced, which is taken into account by the coefficient TO _h .

The use of coolant can increase the cutting speed by 40-45%. Especially great effect can be obtained by using drills with internal cooling. The durability of such drills (at an equal cutting speed) is several times higher than the durability of conventional ones.

Machine (main) time when drilling and bleeding is calculated by the formula:

where L is the length of the passage in the feed direction, mm.

L = l + l ₁ + l ₂ .

where l is the depth of drilling, mm;

l ₁    - plunging amount, mm;

l ₂    - overrun value, mm;

Approximately for single angle drills in plan

L ₁   + l ₂ = 0.3D.

10 MILLING

Milling is a common type of machining. In most cases, milling processes flat or shaped ruled surfaces. Milling is carried out by multi-blade tools - cutters. The milling cutter is a body of rotation, in which the cutting teeth are located on a cylindrical or on the end surface. Depending on this, the milling cutters are respectively called cylindrical or face mills, and the milling work done by them is cylindrical or face milling. The main motion is attached to the cutter, the feed movement is usually attached to the workpiece, but it can also be attached to the tool - the cutter. Most often it is translational, but may be rotational or complex.

The process of milling differs from other cutting processes in that each tooth of the cutter is in operation for a relatively short period of time in one turn. Most of the turnover of the tooth cutter passes without making cutting. This has a positive effect on the durability of the cutters. Another distinctive feature of the milling process is that each tooth of the cutter cuts off chips of varying thickness.

Milling can be done in two ways: against the feed and

img10_1.jpg" >

Figure 10.1 - Types of milling: a) - against the feed, b) - by feed, c) - face milling cutter. d) - end mill.

By filing (Fig. 10.1.). The first milling is called the counter, and the second - passing. Each of these methods has its advantages and disadvantages. Counter milling is basic. Associated milling is advisable to conduct only when processing workpieces without a crust and when processing

materials prone to strong work hardening, as when milling against the feed of a tooth cutter, crashing into the material, quite a significant way goes through a very glued layer. Wear of the cutters in this case proceeds too intensively.

When working face or end mills distinguish symmetric and asymmetrical cutting. For symmetrical cutting, the axis of the cutter coincides with the plane of symmetry of the surface to be machined, and for asymmetric cutting it does not coincide.

The main elements of the cutting mode for milling are the depth of cut, feed, cutting speed and width of milling.

Cutting depth t  is the thickness of the metal layer, cut in a single pass. In case of cylindrical milling, it corresponds to the length of the arc of contact of the cutter with the workpiece and is measured in the direction perpendicular to the axis of rotation of the cutter, with the face in parallel.

Under milling width AT  it is necessary to understand the width of the surface being machined, measured in a direction parallel to the axis of rotation of a cylindrical or end mill, and when milling with an end mill, in a perpendicular direction.

Cutting speed v is the circumferential speed of the milling cutter blades

where: D  - diameter of mill, mm;

n - cutter rotation frequency, rpm.

Feed is the movement of the workpiece relative to the cutter. When milling there are three types of innings:

feed per tooth (s _z   , mm / tooth) - the amount of movement of the workpiece over time

turning the cutter on one tooth;

feed per revolution s _about , mm / rev) - the amount of movement of the workpiece during one revolution of the cutter;

feed per minute (or feed per minute, s   _m, mm / min) - the amount of movement of the workpiece per minute. These feeds are related by dependency:

s   _about= s   _z.z;

s _m = s _o . n;

_{s m} = s _z . . z. n ,

where: z - the number of teeth of the cutter, n - rotational speed, rpm

The smoothness of the cutter depends on the depth of cut, the diameter of the cutter and the number of teeth. It is determined by the angle of contact of the cutter with the workpiece. The contact angle d is the central angle corresponding to the length of the arc of contact of the cutter with the workpiece-part (Figure 10.2).

  _max .

  max . "

img10_2.jpg" >

Figure 10.2 - calculation scheme: a) - contact angle of the cutter ; and b) - maximum chip thickness a   _max .

To ensure smooth operation of the cutter, the number of simultaneously working teeth should be at least two.

The thickness of the slice during milling is variable, its value depends on the feed per tooth and the contact angle of the cutter:

When calculating the cutting mode, the cutting depth t  appointed as possible under the terms of the rigidity of the technological system, the width of the milling AT  determined by the size of the treated surface. Feed per tooth s is selected according to the tables of reference books, depending on the type and size of the tool used, the power of the machine and the properties of the material being processed.

The cutting speed v is calculated taking into account the size of the selected elements of the cutting mode by the formula:

where: WITH _V - constant depending on the properties of the processed material;

D- diameter of cutter, mm;

T  - the resistance of the cutter, which is assigned in the range from 60 to 400 minutes depending on the type and size of the cutters, min;

z - the number of teeth of the cutter; S _z   - feed per tooth, mm / tooth.

After calculating the cutting mode, the main component of the cutting force is determined. P _z , torque M _cr   and power consumption per cutting N:

.

.

Figure 10.3 Calculation scheme of the main technological time during milling

Main technological time T o  calculated by the formula:

L = l 1 + l 0 + l 2;

The amount of penetration l 1 depends on the diameter of the cutter and the depth of cut. The figure shows that:

The magnitude of the overrun l 2 assigned depending on the size of the workpiece and the diameter of the cutter.

11 PROTRONEDE

Lab number 6

Calculation of cutting modes when drilling

Objective:  learn how to calculate the most optimal cutting conditions when drilling using analytical formulas.

1. Cutting deptht mmWhen drilling depth of cut t = 0,5 Dwhen drilling out, reaming and deploying t = 0,5 (D – d) ,

where d  - the initial diameter of the hole;

D  - hole diameter after processing.

2. Filings mm / rev When drilling holes without limited factors, choose the maximum allowable for the strength of the drill feed (Table 24). When drilling holes, the feed recommended for drilling can be increased up to 2 times. If there are limiting factors, the feeds are equal when drilling and reaming. They are determined by multiplying the tabulated feed value by the corresponding correction factor given in the note to the table. The obtained values ​​are adjusted according to the passport of the machine  (Appendix 3). Serving at countersinking are given in table. 25, and during deployment - in Table 26.

3. Cutting speedv r m / minCutting speed when drilling

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Coefficient values WITHv  and exponents m, x, y, q  are given for drilling in table 27, for reaming, reaming and deployment - in table. 28, and the period of resistance T  - tab. thirty.

General correction factor for cutting speed, taking into account the actual cutting conditions,

Kv = Kmv Kiv Kv,

where Kmv  - coefficient on the processed material (see tab. 1, 3, 7, 8);

Kiv- coefficient of instrumental material (see table. 4);

Kv,  - coefficient taking into account the depth of drilling (Table 29). When drilling and reaming cast or stamped holes, an additional correction factor is introduced CPv  (see tab. 2).

4. Speedn , rpmcalculated by the formula

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5. TorqueM cr , N · m, and axial force RoH  calculated by the formulas:

when drilling

Md = 10 cmDqsyCr;

P0 = 10 WedDqsyCr;

reaming and countersinking

Md = 10 cmDq tx syCr;

P0 = 10 Wedtx syCr;

Meanings Cm  and Wedand exponents q, x, y  are given in table. 31.

Coefficient Kp, taking into account the actual processing conditions, in this case depends only on the material of the workpiece and is determined by the expression

Cr = Kmr.

Coefficient values Kmr  are given for steel and cast iron in table. 11, and for copper and aluminum alloys - in Table. ten.

To determine the torque when deploying each tooth tool can be considered as a boring tool. Then when the tool diameter D  torque, H · m,

;

here sz  - feed, mm per tooth tooth, equal to s / z,

where s- feed, mm / r, z  - the number of teeth sweep. The values ​​of the coefficients and exponents, see table. 22

6. Cutting powerNe kWdetermined by the formula:

where netc  - the frequency of rotation of the tool or workpiece, rpm,

Cutting power should not exceed the effective power of the main drive of the machine Ne< Nuh  (where Ntwo- engine power, h  - machine efficiency). If the condition is not met and Ne> Nuh, reduce the cutting speed. Determine the overload coefficient, calculate the new lower cutting speed value https://pandia.ru/text/80/138/images/image011_47.gif "width =" 75 "height =" 25 src = "\u003e, where Growth  - axial force of the machine.

7. Basic time Thatsmincalculated by the formula

where L –   length of the tool stroke, mm;

The length of the working stroke, mm, is equal to L= l+ l1 + l2 ,

where l  - length of the treated surface, mm;

l1   and l2   - values ​​of penetration and overrun of the tool, mm (see Appendix 4).

Table 1

Correction factor TOmv, taking into account the influence of physico-mechanical properties of the material being processed on the cutting speed.

table 2

Correction factor CPv  , taking into account the effect of the state of the surface of the workpiece on the cutting speed.

Table 3

Correction factor Kmv  , taking into account the influence of physico-mechanical properties of copper and aluminum alloys on cutting speed.

Table 4

Correction factor Kiv  , taking into account the influence of tool material on cutting speed.

Distinguish two drilling patterns:

First:  the main cutting motion (rotational) is given to the tool. He also reported the forward movement of the filing. This scheme is typical for drilling machines.

Second:  the main cutting movement is reported to the workpiece, the feed movement to the tool. This scheme is implemented on the lathe group.

Cutting depth  when drilling

when reaming

Cutting speed  when drilling is the peripheral speed of the point of the cutting edge furthest from the drill axis.

Analyzing the last formula, it is clear that for a given period of durability, an increase in feed requires a reduction in cutting speed. Drilling speed

Main (technological or machine) time  is defined as the quotient of dividing the calculated path by the speed of the relative movement of the tool and the workpiece

L p = l + y + Δ - the length of the estimated tool path

n - the number of revolutions of the spindle

S o - feed per revolution.

When drilling resultant resistance forces  on the cutting edges can be distinguished into 3 components:

P 1 is the vertical component parallel to the axis. Together with the axial component Р о acting on the transverse edge, it determines the axial force during drilling, which counteracts the feed movement. According to its value, they count on the strength of the detail of the drilling machine feed unit.

P 2 - the horizontal component passing through the axis of the drill.

P 3 is a component directed tangentially to the circle on which this cutting edge point is located. The tangent component is determining not only the moments, but also the processing speed. Forces R 3 acting on both cutting edges are directed towards each other and theoretically should be balanced, however, due to the inaccuracy of sharpening the drill, differences in edge lengths and j values, they are not equal. Therefore, in real conditions, there is always some resultant DP 3 directed toward the larger component. Under the action of this component is a breakdown of the hole, that is, its increase compared with the diameter of the drill. The breakdown of the hole leads to another error - withdrawal drill. The axis of the hole is shifted relative to the feed direction. This is due to the fact that with an increase in the diameter of the hole due to the breaking of the ribbon, they cease to perform their centering functions. Breaking a hole and dropping the drill is always in varying degrees inherent in the processing of holes with a double-blade tool, which is the drill.

Drill making

Part of the process of manufacturing drills is performed according to standards, and some - according to specifications

Manufacturing methods: carved grinding (from solid blanks 0.5-13 mm), as well as longitudinal-helical rolling.

Material:

High-speed steels P6, P5

Drills with a conic shank are made of pressed materials (sintered) by milling.

Wear-resistant TiNO 3 coating is applied

Hole drilling

Zenkering  called the process of processing holes, obtained by casting, stamping or machining in order to improve accuracy and reduce roughness.

Countersinking occurs when using a working tool - countersinker.

This tool has from three to six blades. As with the drill, the working part of the countersinker includes cutting and calibrating parts. Cutting depth is calculated in the same way as when drilling (half-difference between the countersink diameter and the hole to be machined).

The countersink has the same angles as the drill, with the exception of the inclination angle of the transverse edge: it is absent from the countersink, the inclination angle of the grooves is ≈10 ° -20 °.

The countersink is stronger than the drill. When machining holes of 13-11 quality, countersinking can be the final operation.

Crushing with cylindrical or conical grooves (for screw heads, jacks, for valves, etc.), mating cylindrical and conical, end and other surfaces, through and blind holes.

This method is considered productive - it improves the accuracy of pre-machined holes, partially corrects the axis curvature after drilling. To improve the accuracy of processing using devices with conductor sleeves.

In practice, besides reaming, they apply counting. Work tool - tsekovka. Regrinding, when necessary, to obtain grooves, for example for seals, end planes, which are the supporting surfaces for bolts, screws or nuts.

Deployment

Deployed handle holes with a diameter of from 3 to 120 mm. Thanks to the clean deployment, the surface roughness characteristic of the 7th grade is obtained.

Work tool - scan. Development designed to remove a small allowance. They differ from countersinks in a large number (6-14) of teeth. To obtain holes of increased accuracy, as well as in the processing of holes with longitudinal grooves, screw reamers are used.

Distinguish the working part of the scan (I) and the shank (II) with a foot for embossing.

For small-diameter reamers, the shank is cylindrical, large-diameter reamers are performed with a tapered shank.

The working part of the scan is divided into cutting (A) and calibrating (B) parts.

Inside the cutting part distinguish

1 - lead-in cone

2 - cutting cone

The calibration part consists of

3 - cylindrical gage part

4 - calibrating part with reverse taper

The difference in the diameters of this taper is from 0.03 to 0.05 mm. Reverse taper is performed to reduce friction and prevent an increase in the diameter of the hole being machined due to the sweep beating. This increase can be from 0.005 to 0.08 mm. To reduce the hole breakdown, floating self-centering chucks (mandrels) are used to compensate for the deviation of the scanning axis from the spindle axis.

The sweep front angle is close to 0. On the cutting teeth, the posterior angle is about 10 °, the teeth of the calibrating part have a ground and the posterior angle on them is 0.

Depending on the specified accuracy of the hole being machined, the following processing schemes are used:

All tools are dimensional, in mass production they use a combined tool - a drill and a reamer.

Pulling

When pulling use the tool - broach.

Pulling  - the process of processing internal surfaces of various shapes and flat external surfaces. The method is applied in large-scale and mass production. The advantage of the method is its high performance when processing complex surfaces with a high degree of accuracy.

The fundamental difference in pulling is the lack of feed movement. The cutting motion is always straight forward. The removal of material in the process of cutting (in the absence of feed movement) occurs due to the fact that each subsequent tooth of the broach has dimensions larger by some value t than the previous one.

In broach distinguish

1 - front gripping part

5 - rear gripping part

3 - cutting part

4 - calibrating part

The tooth pitch should ensure a uniform cutting process, but it is necessary to strive so that the length of the broach is as short as possible, in order to avoid difficulties during heat treatment.

Tooth pitch

Number of teeth

Allowance z = 0.5 ÷ 1.5 mm

Sewing speed V pr = 1 ÷ 15 m / min

L - the length of the hole

Teeth differ angles of sharpening. The rear cutting angle of the cutting teeth of the broach is 24 °, the front one is 10 ÷ 20 ° when roughing and about 5 ° when finishing.

Depending on the complexity of the contour of the treated surface, various pulling patterns:

1) Profile scheme. Each tooth removes shavings along the entire contour with thin parallel layers. This scheme is used when pulling simple contours, when on each tooth it is enough just to provide a fully stretched contour.

2) Generator circuit. It provides for the division of the contour into areas where the cutting teeth remove chips also in parallel layers, and only the last teeth carry out the processing of the entire profile.

3) Progressive scheme. It is also called group. This scheme implies a breakdown of the entire contour into narrow sections from which material is removed for the entire amount of the allowance.

For crushing chips on the teeth make grooves in a checkerboard pattern. Pulling is carried out both vertically and horizontally.

Stitching call a similar pulling processing shorter tool - firmware. When flashing, the tool experiences compressive stresses, and when pulling, stretches, so the firmware is made of a relatively short length (250-500 mm).

Also used in mass production. Preferably assembled broach - from the replacement of teeth, etc.

Milling

Milling  - This is a high-performance material processing method. During milling, flat and shaped surfaces are machined. The processing contour in the latter case is determined by the tool - frezoy.

Among all blade tools, cutters are the most diverse. They are distinguished

According to the location of the teeth on the source cylinder:

Butt end

Cylindrical

By way of fixing on the machine:

Tail

Mounted

By the method of arrangement of the teeth on the cylinder:

Spur

With helical tines;

By the nature of the work

Corner;

Shaped;

Slot;

Keyways;

Cutting;

Gear cutting;

Tooth size:

Fine teeth;

Large tooth cutters

Milling cutter  - this is a multi-tooth tool, which is the initial cylinder on which the cutting teeth are placed.

The screw arrangement of the teeth ensures the uniformity of the cutting process, eliminating the impact of each tooth on the workpiece, therefore, it is used more often (part of the cutting edge is constantly in contact with the surface to be processed).

The number of pointed teeth of the cutter depends on its diameter and is determined by the formula Z = mÖD

m - coefficient, the value of which depends on the working conditions and design of the cutter, and 0.8

D is the diameter of the cutter.

Cutting speed V when milling is determined by the spindle speed

Depth of cut t - the shortest distance between the treated and the treated surface

With this method of processing often use the parameter, called the width of the mill B. The width of the mill is determined in a direction parallel to the axis of the cutter.

Feed (S) during milling is defined as the amount of movement of the cutter relative to the machined surface per revolution. Since displacement is measured in mm, the main dimension [mm / r].

Feed per tooth: S z [mm / tooth]

Feed per revolution: S 0 = S z × z [mm / r]

z is the number of teeth

Minute feed S m = S 0 × n = S z × z × n [mm / min]

Machine time is as a quotient from dividing the tool path by the minute feed.

The amount of penetration y depends on the depth of cut and the diameter of the cutter, the overrun is 1 ÷ 5 mm.

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Milling patterns

When milling, the cutting movement is reported to the mill, and the feed movement is reported to the workpiece. In this case, with the same rectilinear movement of the workpiece, the direction of movement of the tool can, with the movement of the feed, can be directed oppositely.

Associated milling  - is a type of milling, in which the cutting direction and feed movement coincide. The disadvantages of this scheme include the fact that when the cutter's tooth touches the workpiece at the maximum chip thickness a max, a blow occurs. Milling conditions can be complicated if the workpiece has a casting crust. The advantages of co-milling include the fact that the resultant cutting force P presses the workpiece to the device, which does not require additional efforts to secure it. Changing the chip thickness from the maximum value to zero provides a high quality of the surface being processed, that is, a low roughness.

With counter milling  the thickness of the layer being cut varies from zero to a max, so at the initial cutting moment the cutter may slip relative to the surface being processed, which does not allow for high quality of the latter. In addition, the resulting cutting effort P tends to tear the workpiece from the tool, which requires additional efforts to secure the workpiece. The advantage of the method is the ability to work from under the peel.

Milling is carried out on horizontal or vertical milling machines.