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CHAPTER TWO

Solid tools for spiral bevel gear cutting

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02.1 - Solid tools for spiral bevel gear cutting The tools used in cutting the bevel gears are cutters with frontal cutting edges, which may have inserted or solid blades, or profiled stick blades of various types. Described below are the main tools used in the various technologies, developed in chronological order of market introduction. However, as this guide does not have the intent to describe exhaustively all the efforts made to realize the transmission of power between parallel axes, it was decided to begin the overview by the cutters Gleason SOFT BODY. 02.1.1 Tools with inserted blades SOFT BODY It consist of a mill cutter with inserted blades on high speed steel, with alternating internal (IB - Internal Blade) and external (OB - Outer Blade) cutting edges. The blades are mounted on a blade holder disc, through the interposition of appropriated calibrated shims, to achieve the desired tool diameter. The type of mounting of the blades on the blade holder disc does not include any adjustment possibilities: so the accuracy of the tool depends only on the construction precision of disc and blades, then it is very relative. The blades have a pre-shaped profile that is resharpen only on the cutting face, once mounted on the disk. The body of the blades to the disc has a rectangular section with a hole perpendicular to the axis of the milling cutter for screw fixing. HARDAC It is the technological evolution of SOFT BODY: the high-speed steel has evolved in terms of duration and hardness, and the blades are in greater numbers, improving the performance of the tool, as each blade bears a lower workload. HARDAC II It is introduced the possibility of fine adjustment of the radial position of each blade into the disc blades holder, by means of a wedge driven by a screw. This allows, through a long and meticulous manual operation of centering, a blade mounting with a runout extremely small. Moreover, the body of the blade to the disc also includes an inclined plane, with holes for screw fixing perpendicular to this plane. This allows a component of the clamping force of the screw to lock the blades more rigidly to the disc, further increasing the rigidity and performance tool. The version with alternate cutting edges (duplex) is used for the roughing of pinions with the five cut method. These blades are also available as unilateral version, i.e. only OB or only IB, for the finishing of the related sides of the pinions in the five cut cutting method. The blades have a pre-shaped profile, resharpen only on the cutting face, once mounted on the disk and perfectly centered. RIDG AC It consists of a mill cutter with inserted blades in high speed steel, with TRIPLEX cutting edges, that is a sequence of Inner Blade, Root diameter and Outer Blade. The blades are mounted on a disc blade holder through the interposition of appropriate calibrated shims, to achieve the desired tool diameter. The type of mounting of the blades on the disc blade holder does not include any adjustment possibilities, so the accuracy of the tool depends only to the precision construction of the disc and blades, then very relative. They are only used for the roughing of crowns with the cut five method. The blades have a pre-shaped profile, resharpen only on the cutting face, once mounted on the disk.

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The subsequent finishing is performed with the cutters HELIXFORM. HELIXFORM They are used exclusively for finishing of the crowns "Formate". They are made of alternating cutting edges, for finishing both sides in a single cycle, with variable increment, similar to a broach. The locking of the blades on the disc is similar to that of HARDAC II, but each blade has an axial increase over the previous. No shims are used. The blades have a pre-shaped profile, resharpen only on the cutting face, once mounted on the disk. In the disc the blades have a space for the realization of the division of the gear being machined, to switch quickly from one tooth to the next, without changing the position of the milling cutter relative to the work piece. HARDAC III e HARDAC III COMPLETING The number of blades per disk is growing: this opens up new possibilities for cutting, called COMPLETING, that is work of gear construction with only one tool that makes roughing and finishing. The blades have a pre-shaped profile, resharpened only on the front cutting face, once mounted on the disk. In the vertical direction they are maintained all the same height because they lean on the body of the cutter with two shoulders rectified, one of which is indicated with the arrow in the Figure N°02.1. Note on the cut method five cut Face milling of gears type Gleason. Pinion: 1) roughing with HARDAC II DUPLEX 2) drive side finishing with HARDAC II UNILATERALI 3) release side finishing with HARDAC II UNILATERALI Gear: 4) roughing with RIDG AC 5) finishing with HELIXFORM

Figure N°02.1- Blade type Hardac®.

In the types SOFT BODY, Ridg AC and HARDAC the possibility of using different shims allows some flexibility in the implementation of desired diameters.

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Figure N°02.2

Figure N°02.3

The main disadvantage is the fact that the blade and clamping system form a group very bulky and therefore on the body you can only mount a limited number of blades. This considerably reduces the number of cutting edges which generate the side of a tooth and then the level of finishing will be associated with the utilized progress. Additionally the steels used are historically low alloy and therefore not very high performance, also are not generally marketed uncoated; miniToolsCoating produces blades Hardac II ® III ® with last-generation High Speed Steel, combining specific PVD coatings to increase the performance of this tool. These blades also are complicated to build and therefore their cost is generally high. The blades Hardac have different dimensions in relation to the diameter of the body on which they are mounted and to the type of cutter. Figure N°02.4 shows the dimensions that characterize the body and Table N°02.1 shows the types of cutters Hardac with the corresponding number of blades and the size of the body.

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Figure N°02.4

Table N°02.1 - Types of blades Hardac. Number of blades for cutter

Φ nominal (inch)

Hardac Hardac II Hardac III Hardac III

Completing Size of the Body mm

7,5 16 16 16 18 20,62 x 17,6 9 20 20 20 22 20,62 x 17,6

10,5 -- -- -- 26 20,62 x 17,6 12 -- -- -- 30 20,62 x 17,6 12 12 12 -- -- 23,81 x 19,2 12 28 28 28 -- 23,81 x 19,2 14 -- -- -- 32 23,81 x 19,2 14 -- -- 32 -- 23,81 x 19,2 16 -- -- -- 36 23,81 x 19,2 16 24 -- -- -- 23,81 x 19,2 16 36 -- 36 -- 23,81 x 19,2 18 -- -- -- -- 23,81 x 19,2 18 24 -- -- -- 23,81 x 19,2 18 36 -- 36 -- 23,81 x 19,2

02.1.2 – Milling cutters with stick blades RSR® This type of cutters, represented in Figure N°02.5, improves under many points of view the tool described just above.

Figure N°02.5

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As can be seen, it is possible to mount many more blades which, in this case, are commonly called "Stick Blades RSR®". This allows for a better finishing and reduced cycle times. Also in this case it is possible to adjust the nominal diameter of the milling cutter with the use of shims. The locking of the blade takes place with a screw which presses the blade in the radial direction. This locking system limits a little the stability of the blade. The blades are placed in very precise sites that make the cutter body particularly expensive. The stick blades RSR®, which are shown in Figure N°02.6, have a square or rectangular body with size with very narrow tolerances (5-6 µm). On one side is formed an inclined plane which constitutes the cutting face which is never affected by the sharpening

Figure N°02.6

The sharpening is performed, with the blade removed, by profile grinding in the active part. The method of sharpening constitutes, in a way, the main drawback of this type of cutter; in fact, having to disassemble all the blades, sharpen them one by one and reassemble them, are operations that, in the first place, require CNC sharpener machines and specific equipment to control the position of the blades on the cutter body. In addition the operations are long and delicate. Also in this case on the cutter blades are mounted in alternately IB (inner blades) and OB blades (outer blades).

Figure N°02.7

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Figure N°02.8

In case of use of the center blade, the sequence of the blades is the following: OB > central blade > IB > central blade > OB > central blade > IB ... etc.. This means that 50% of all the blades are central, 25% are OB and 25% are IB. It is clear that against a possible increase of the working conditions, there is a strong reduction of the cutting edges that finish the side of the teeth and then a deterioration of the finish quality of the worked surfaces. The geometrical characteristics of the profile of these blades, as well as the blades Hardac, are summarized in Figure N°02.8. The internal and external blades overlaps for a certain distance in order to properly finish the bottom of the tooth without leaving steps. The average diameter is the nominal diameter of the milling cutter. Other important elements are: Blade Point: is the theoretical point of the extreme tip of each blade. Constitutes the

reference for determining the width of the complex of the two blades. Point Blade Width (PW): is the distance between the tips of the internal and external

blades. Radius Edge: is an element that influences the curvature radius at the bottom of the

tooth of the produced gear. Inner & outer cutting edge angles (Blade Angle): in practice corresponds to the

angle of pressure of the teeth. These angles may differ from the nominal ones. In the case of milling cutters with central blades you have the characteristics shown in Figure N°02.9. As indicated, the width between the tips of the center blade must be the theoretical one between the tips decreased by 0.020'' (about 0.5 mm), while the protrusion beyond the diameter of the two side blades will be about 0.25 mm.

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Figure N°02.9

The profile may make provision for protuberance toward the head of the blade, which takes the name "toprem". This variant of the profile is used to to widen the base of tooth at the bottom of the tooth of the gear with the purpose to avoid interference between the root fillet during the meshing, and to form a step after the operation of lapping or grinding of the tooth side. The shape of the toprem is, basically, the decreasing of the inclination angle of the cutting edge, in a section next to the head of the blade, as shown in Figure N°02.10. The size of the toprem are depending on the height of the tooth of the gear and each dimension is identified by a pair of letters, as shown in Table N°02.2.

Figure N°02.10

Table N°02.2 Height of the pinion teeth Toprem letters Toprem height DT Angle modification

Up to 0,270’’ FH 0,050’’ 2° 24’

0,270 – 0,360’’ EH 0,065’’ 2° 24’

0,361 – 0,490’’ CH 0,080’’ 2° 24’

0,491 – 0,600’’ BH 0,100’’ 2° 24’

0,601 – 0,690’’ AH 0,120’’ 2° 24’

0,691 – 0,850’’ ZH 0,150’’ 2° 24’

0,851 – 1,060’’ WH 0,190’’ 2° 24’

1,061 – 1,260’’ MH 0,230’’ 2° 24’

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The codes AY, BY, CY, EY, FY indicate the same changes but with an angle modification of 3 ° 30. It has already been mentioned that the angles of the inner and outer cutting edges may be different from the theoretical ones. The modification of these angles pressure is indicated by the following rule:

Either you specify the correct values of the angles or you specify the number of correction.

The number of correction, multiplied by 10 gives the value of a degree which must be reduced the pressure angle of the OB (outdoor knife) and increased the value of the same pressure angle of the IB (inner blade).

Example: if you have a theoretical pressure angle of 20° and the number of correction is 30, we must reduce the angle of the blade outer (OB) than 300 degree, ie 5°, and correspondingly increase the angle of the blade inside (IB). The angles will then become respectively 15° and 25°. A further advantage of the stick blade RSR® is given by the fact that the user can shape the blades within his factory. In fact, to use these blades, the user must be equipped with a CN sharpener which is capable to produce the profile. This sharpener will also be able to derive the profile from a raw bar, meaning with the term "raw" a stick blade rectified grossly on the sides but not molded according the profile, as shown in Figure N°02.11.

Figure N°02.11

In the companies that produce in large quantities, the stick blades to be sharpened are a lot and, because the CNC precision grinding machine is expensive, is not convenient to keep it busy for long time just for roughing the stick blades. It's more convenient to assign this task to specialized external vendors, better equipped for roughing at a lower cost. One of these companies is miniToolsCoating (Padova - Italy) which is able to rough at high precision the profiles, providing the stick blades with minimum machining allowance, so that the user can finish them with a time comparable to a normal sharpening. The allowance which is left by the roughing for the next finishing is 0,1 - 0,3 mm. For each sharpening the stick is shortened by 0.4 - 0.5 mm. Both for the operations of roughing and sharpening, miniToolsCoating builds a pair of stick blade masters, certified by the user, with the purpose to reproduce, even in later times, always the same profiles. In addition, after the roughing, miniToolsCoating normally perform also the coating with the most suitable products for each individual operations.

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Advantages and disadvantages: Compared to the miller cutter Hardac the RSR® system is more performing but, because of the re-composition after each sharpening of the tool, only one user very well structured and with high production can secure a financial return while maintaining the correct levels of quality. The RSR® system has been replaced by the system Pentac®. 02.1.3 - Milling cutters and blades Pentac® The blades Pentac® differ from blades RSR® because they have a base formed by two inclined faces which rest on a "V" of the cutter body. The cross section of the stick blade has a pentagonal shape with two supporting surfaces, at 30° and 60° In this way, it improves the accuracy of positioning and the stability of the blades. The stick blade Pentac® are therefore a refinement of the blade RSR®.

Figure N°02.12

The milling system Pentac® is used both in the dentition in continuous (Face Hobbing) and dentition in a single compartment (Face Milling). Even in this case are valid the considerations made on the system RSR®, because the blades, whether HSS or Carbide, must be disassembled in order to be re-sharpened on two or three sides. So, only users well structured in terms of sharpening and replacement processes with significant volumes needs can fully exploit the productivity features that are expressed by the system Pentac® The re-sharpening on three faces, which build a perfect cutting edge and therefore provide the maximum performances, requires however a coating treatment, especially on the Carbide blades. miniToolsCoating expressly developed this processes, leading to the highest levels of the performance of the stick blades Pentac®. 02.1.4 - Solid cutters

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In many cases it is convenient to use HSS solid cutters instead of cutters with inserted blades, and, in some cases, you can only perform the toothing with solid milling cutters (for example in the case of cutters with small diameters). But even with larger diameters, and in some special cases (for example up to 9 ") there are considerable advantages. In general we can say that the solid milling cutters are conveniently used when the cutter has a diameter less than 6": in this case it becomes very important the possibility of having more cutting edge and a limited procurement and management costs. The Company specialized in the production of this type of cutters is miniToolsCoating (Padova – Italy), which is capable of providing cutters from 1.1 "(28 mm) to 9" (230 mm) diameter.

Figure N°02.13

The advantages provided by the solid milling cutters can be summarized as: Easy sharpening Greater precision Milling cutters always ready in stock Perfect stability

These cutters can be sharpened with the same sharpener used for the mill cutter Hardac. Compared to Hardac®, the solid milling cutters have the advantage of having many more teeth and, therefore, to allow most demanding working conditions, with reduced production times and much more precise gear. However, it is clear that for cutter of large diameter , over 6', the solid cutters are not convenient. miniToolsCoating has responded to this need by starting, in parallel to the solid milling cutter, the production of cutters "Crown": these cutters (see Figure N°02.13) considerably reduce the demand for high quality steel for the cutter body, re-proposing then the solid milling cutters for diameters up to 9'. Compared to the cutters and blades RSR®, the Pentac® have the great advantage of not having to remove anything for sharpening and it does not require the sharpeners to reproduce the profile or the need of special equipment for accurate reassembly of the blades on the cutter body. There is not, therefore, the need for expensive equipment to maintain a good constant quality in small and repetitive batches, where the cost factor is not the only production driver. The milling cutter with inserted blades utilize very expensive cutter bodies, and for every single operation is not sufficient to use only one of it: it will takes at least two or three cutter bodies to avoid stop production during sharpening and also to have a safe replacement in the case of machine accidents that may ruin the cutter body. In general, so if you want to switch from Hardac cutters to RSR® cutters, the investments would be significant: something that does not exist if you opt for solid cutters.

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They are always ready in stock and the investment is very modest, not to mention that an accident which deteriorates the body of the cutter blade produces considerable damage. Finally, we must consider that in the solid milling cutter there are no errors in the blades positioning which, small or big, are always present in the inserted blades. Of course, also these tools have the profile of the teeth with the geometric characteristics described for the stick blades. They have alternating teeth, OB and IB and may even have the central roughing tooth, if it is really necessary, but given the high number of teeth with which they can be built, the central tooth is almost never necessary. The rake angle of the head can be 12 °, 6 ° or 3 °, according to the angle of pressure (the smaller the pressure angle the greater must be the rake angle of the head). On the drills Face-Milling the standard cutting angle is 20°. Soft materials can be sharpened with angle of 25-30°, while hard materials are sharpened even with 10-15°.

Figure N°02.14

The subsequent re-sharpening with an angle of 20° does not change the profile, provided that the cutting edge always corresponds to the ideal cone distance of which the tooth side is part. Normally the teeth have a top rake of 12°; is all the tooth that is tilted at this angle. It is a helix portion which would wrap on the lateral surface of a cylinder having the diameter corresponding to the nominal diameter of the cutter. The most obvious comparison is the helix of a cylindrical spring: each section with a radial plane, or with another defined angle, always keeps the same profile. Table N°02.3 shows the dimensional characteristics of standard mill cutters built by miniToolsCoating. Table N°02.3

Type Nominal diameter Number of teeth Type of steel

Solid milling cutter

1,1” 8

ASP23 or

S390

1,5” 12

2” 16

2,5” 16

2,75” 20

3,5” 20

4,5 20 (24)

5” 20 (24)

6” 20 (24)

Crown cutter

6” 24 (28 – 30)

7,5” 32 (36)

9” 40

The crown cutters are typical for large diameters (4.5" - 5"- 6'' - 7.5'' - 9'').

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They require a mounting flange which is an interface between the tool and the spindle of the machine.

Figure N°02.15 - Crown cutters manufactured by miniToolsCoating

The adoption of the cutter into two pieces serves to reduce the amount of HSS steel and therefore have lower costs. Inevitably, however, we have small assembly errors due to the union of two pieces in comparison to the classical solid cutters. These eccentricity errors are of the order of a few micrometers and not have a decisive effect on the precision of the finished gear, also because these cutters of relatively large diameter perform gears of large diameter which are typically subjected to a heat treatment, which in turn produces distortions. They are therefore gears that in any case require a finishing operation, lapping or grinding or regrinding with carbide cutter. However the errors mentioned above are not repeated at each re-sharpening, but remains constant throughout the tool life and this, combined with better stiffness of the solid tool, means that the quality of the cut piece is definitely higher and more stable than any other piece obtained with cutters with inserted blades. For the building of the solid cutters miniToolsCoating uses CNC machines of the latest generation, with dimensional controls at each stage of processing. After the normal turning and the preparation of the blank, the teeth are milled on a machining center that uses, as well as all the other machines, specific proprietary software of miniToolsCoating

Figure N°02.16 – Teeth milling with CNC machine

The accuracy of this operation is essential to minimize the stock removal for subsequent finishing operations with grinding, obtaining two important results: less stress of the

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grinding wheels (... with less heating of the surfaces) and less danger of structural steel modifications (...with a reduced grinding time), with benefits on the final costs. The operating software installed on the various machines allow the user to follow all the stages of the operation and intervene easily to any changes in dimensions or angles. Figure N°02.17 shows a screen of the NC operating machine, where you can see that the input and management of the geometric data of the cutter is running in a Windows environment.

Figure N°02.17

After the heat treatment, carried out by specialized external firms, first we proceed to the grinding of the supporting surface and the hole and then the grinding of the profile, always using numerical control machines. Normally are used CBN grinding wheels which provide excellent dimensional stability on various teeth of the cutter and allow surface finishing with Ra = from 0.1 to 0.2 µm, ie similar to those obtained in the lapping. The grind of the profile is not the only sensitive operation that is performed on these cutters. It is indeed true that from it depends the precision of the inclination angles, the correct head sizing, with vertex and cutting edges radius in the exact position, with the size of the toprem within prescribed tolerances, but it is of great importance as well the correct sharpening of the teeth, an operation that takes place immediately after the grinding of the profile.

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Figure N°02.18– Profile grinding of the solid milling cutter

The sharpening of the cutting face of the tooth, is normally carried out with an inclination of 20° and must maintain the cutting edge of the inner and outer blades perfectly coincident with the ideal of the cone distance formed respectively from the inner or outer surface of the tooth.

Figure N°02.19 - Sharpening of a solid milling cutter

You should also ensure that all the teeth are on the same circumference, what is guaranteed if is removed the same amount of material from each tooth. The grinding wheels must have a grit enough fine to generate a surface with a low roughness, otherwise the cutting edge would be a little jagged, with consequent reduction of the efficiency of the tool. You realize therefore that the construction and sharpening of these cutters require precise, flexible and easily programmable machines. It is for this reason that many users prefer to delegate these operations to specialized service centers. miniToolsCoating executes the checks within the machine during the sharpening, as shown in Figure N°02.20: this ensures the accuracy and allows a reduction of the execution time.

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Figure N°02.20

After coating with TiN or with other types of layers, a final check is performed which generates a quality certificate that highlights the deviations from the theoretical quota of the profile, the eccentricity, the division, the exact position and shape of the cutting edge etc...

Figure N°02.21 – Final check

Tolerances miniToolsCoating adopted an internal standard that sets the tolerances for the construction of solid cutters. The quality service is based on these tables to deliberate on the quality of milling cutters. In case of errors on just one parameter , the cutter is discarded and, before being shipped to the customer, it is reworked to go back within the established tolerances. Table N°02.4 shows the tolerances of the most important elements of the solid cutter but, in addition to these parameters, many others are considered. The maximum allowable roughness on the teeth surfaces is Ra = 0.15 microns.

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Table N°02.4 - Construction tolerances adopted by miniToolsCoating for solid milling cutters

Values in mm Diameter of the cutter

1,1”-1,5”-2”

Diameter of the cutter

2,5”-2,75”-3,5”

Diameter of the cutter 4”- 4,5”

Diameter of the cutter

5”-6”

Diameter of crown cutter

6”-7,5”

Diameter of crown

cutter 9”

Point width (PW) +0,01 -0,02

+0,01 -0,02

+0,01 -0,02

+0,01 -0,03

+0,01 -0,03

+0,01 -0,04

Toprem height -- +0,15 -0,05

+0,15 -0,05

+0,15 -0,05

+0,15 -0,05

+0,15 -0,05

Toprem angle -- +5’ -5’

+5’ -5’

+5’ -5’

+5’ -5’

+5’ -5’

Edge radius +0

-0,20 +0

-0,20 +0

-0,20 +0

-0,20 +0

-0,20 +0

-0,20

Outer blade angle (OB) +5’ -5’

+5’ -5’

+5’ -5’

+5’ -5’

+5’ -5’

+5’ -5’

Inner blade angle (IB) +5’ -5’

+5’ -5’

+5’ -5’

+5’ -5’

+5’ -5’

+5’ -5’

Outer blade runout 0,005 0,008 0,010 0,010 0,012 0,014 Inner blade runout 0,005 0,008 0,010 0,010 0,012 0,014

Drow 0,05÷0,08 0,05÷0,08 0,05÷0,08 0,10÷0,12 0,10÷0,12 0,10÷0,1

2 Importance of the accuracy of the tapered hole for assembly

The solid milling cutters have a centering hole slightly conical, in order to make precise clamping the cutter on the spindle of the machine. The centering hole must then be rectified with precision both as taper as well as diameter. In Figure N°02.22 is indicated a proper assembly while in Figure N°02.23 are shown the possible inconveniences in case of errors on taper and diameter. The hole must have a diameter such that when you mount the cutter on the spindle, by hand pressing and before blocking the cutter with the screws, between the supporting surface of the spindle and the front of the cutter there must be a gap of 0.05 - 0.08 mm for cutters with diameter up to 4.5 " and 0.10 - 0.12" for cutters with a greater diameter (drow), so that when you lock the cutter with the screws, you force the cutter to go to the reference surface of the spindle. In this position the cutter is centered and stable.

Then: The machine spindle and the hole of the milling cutter are tapered The taper is used for accurate centering The surfaces A and B must be in contact to provide stability to the cutter.

They are in contact after the closure with the locking screws

Figure N°02.22 - Proper mounting of the milling cutter on the spindle

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Figure N°02.23 - Possible mounting defects caused by incorrect dimensions of the milling cutter hole

Main areas of application of solid cutters for bevel gears In addition to the application areas below, the solid cutters are used in the automotive industry, in the manufacture of speed reducer, in the bevel gears for agricultural machinery and so on.

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Data required for definition of milling cutters In case of quotation or order request, the customer must notify the manufacturer with the essential data for the cutter definition. In absence of constructive drawing can be use the Table N°02.5 integrated, if necessary, with notes, where special modifications of the profile is required. Table N°02.5

Main characteristics for the definition of solid cutters for Gleason spiral bevel gears

Useful characteristics for the cutter definition (not strictly necessary)

Nominal diameter Tool material Point width (PW) Type of coating Outer blade angle Material to be cut Inner blade angle Summary of cut Edge radius Machine to be used Toprem Direction (RH or LH) Height (standard or special)

So far we have shown the types of mill cutters and stick blades typical of Gleason; below we give some information on the stick blades for the cutting of the Oerlikon bevel gears type.

Special application and spare parts

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In general, however, the methods of cutting are always the same: Face Milling or Face Hobbing. 02.1.5 – Oerlikon Arcon® stick blades They are made of HSS or, more frequently, Carbide. They are worked exclusively with the system Face Milling, with left and right blades.

Figure N°02.24 – Raw and profiled carbide stick blade Arcon® type

The peculiarity of these stick blades, is that they are sharpened on three sides, that is also on the front face. They replace in a much more productive way the stick blades RSR and compete with the stick blades Pentac. Figure N°02.24 shows a stick blade type Arcon TWIN BLADE, a special kind of sharpening that, in practice, cut almost simultaneously the PA side and the Clearance side.

Figure N°2.25 – Re-sharpening phase of a stick blade Arcon®

Figure N°02.25 shows that, in addition to the surface that the grinding wheel is rectifying, must sharpened also the surfaces A and C. The sharpening are made with grinding wheels which work in contour. The assembly of these blades in the disk blade holder is particularly rigid and allows to center the blades with extreme precision. This makes the method particularly suitable for the use of carbide stick blades.

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02.1.6 - Oerlikon FS® Stick blades They are stick blades of rectangular section with sharpening on three faces, but for the processing in Face Hobbing. In this case, working with groups of three blades: one internal, one external and one central. 02.1.7 – Oerlikon Spiron® Stick blades It is an evolution of the stick blades FS, that is for processing in Face Hobbing, but only with two blades: one external and one internal. This allows a greater number of cutting edges and enable a greater productivity. In this case, since these stick blades are in carbide, the rake angle is 0°, which makes unnecessary the central blade. All the stick blades sharpened on three sides allow the optimal application of PVD coatings, because the cutting edge is perfectly regenerated at each sharpening.