Gear-cutting Tool

Gear-cutting Tool

 

a metal-cutting tool for machining gears, worms and ratchets, splined shafts, and other toothed parts. Depending on the method of cutting, face-and-side cutters or end mills and gear-cutting heads are used in the forming method, and gear-cutting dies, hob cutters, slotter rams, tooth planers, and cutter heads are used in the generating method.

A face-and-side cutter is a forming cutter and has a formed tooth whose profile in the radial plane corresponds to the profile of the depression of the gear being cut. Face-and-side gear cutters are made up of assemblies of 8, 15, and 26 pieces. Each cutter in the assembly is used to cut gears with specific moduli and number of teeth that can be used only in unstressed low-speed drives.

An end mill is a gear cutter with a formed tooth, used mainly to cut helical and spur gears with ITKK ‘ali of more than 20 mm. When cutting cylindrical spur gears the profile of the cutter in the axial section corresponds to the profile of the depression in the gear. Cutters for double-helical or helical gears have more complicated profiles.

A gear-cutting head is used for simultaneous cutting of all of the depressions of a gear in several strokes. The profile of the working part of each cutter is a copy of the depression between the teeth. Such heads are made for machining gears with moduli of 2-6 mm and are used in mass production.

A gear-cutting die is a toothed rack whose operation is similar to that of a planer tool. Spur-gear racks (Figure l,a) are used to cut cylindrical gears; helical racks (Figure 1 ,b) are used for cutting double-helical gears. Spur-gear racks are made in two types: racks without a front top rake angle, which are mounted for operation at an angle of 6°30’; and with a cutting angle of 4°, which are mounted perpendicular to the direction of the cut. Helical racks have inclined teeth (at an inclination of 30°) with the cutting surface parallel to the butt of the gear being cut. The teeth are cut by two racks: the left rack planes the left-hand teeth, and the right rack planes the right-hand teeth. The gear-cutting dies are made in one piece or are welded together (the cutting part, from R-9 or R-18 high-speed steel; the mount, from no. 45 steel).

Figure 1. Gear-cutting dies: (a) spur-gear, (b) helical

A hob cutter is used for rough cutting and finishing of gears. A distinction is made among cutters for cylindrical gears with spur or helical teeth, worm gears (Figure 2), conical

Figure 2. Hob cutter for cutting worm gears

gears with curvilinear teeth, and globoid gears. The most common hob cutters for cutting cylindrical gears with spur or helical teeth are those with rectilinear profile in the normal section, as well as Archimedean hob cutters, with a rectilinear profile in the axial section. Single-thread unit-construction cutters are made of R-18 high-speed steel; there are also cutters that are made in sections. Gears with moduli of 5-15 mm are cut on cutters made in sections with an external diameter of less than 120 mm and with inserted racks, and gears with moduli of more than 15 mm are cut on cutters with an external diameter of more than 120 mm and with inserted teeth. Hob cutters with hard-alloy plates are used to cut gears with moduli of less than 5 mm.

Slotter rams are used to cut the teeth of gears with external and internal gearing. A slotter ram is a cutting tool shaped like a gear with cutting elements.

Tooth planers are used to cut conical gears for external gearing (Figure 3) and are made of R-9 or R-18 high-speed

Figure 3. Tooth planer: (a) rake of tool, (b) external view

steel. According to their purpose, they are classified as grooving tools (for rough cutting and finishing). Grooving tools are used for preliminary (rough) machining of the depressions between the teeth of conical gears with large moduli (more than 10 mm); finishing tools are made for final machining of conical gears with moduli of 0.3-20 mm.

Tooth-planing cutting heads are used to cut conical gears for external gearing with teeth outlined along the arc of the circumference. Such cutting heads are made in the form of disks into which individual cutters (Figure 4) are set along the edge. The cutting heads are made in ten types and sizes with different diameters (whole or in welded sections). The bits used are welded (the cutting part is made of R-18 steel and the mount is made of no. 45 steel).

Figure 4. (1) Tooth-planing cutting head, (2) gear being cut

V. V. DANILEVSKII

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