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boring transmission case bearing holes with pcd inserts

The transmission case houses the transmission system which consists of various complex systems that control the motion and speed of a car. It protects the gear train and circulates the lubricants for the transmission system. Transmission cases are usually produced with aluminium alloys. Due to their complex designs, machining of a freshly cast aluminium case requires the use of different kinds of polycrystalline diamond pcd inserts. These inserts provide a strong resistance to wear and dissipate heat rapidly to give high productivity and long tool life. Here are some important facts about boring of holes in transmission cases.

Boring of Reduction Hole
Boring of the weight reduction holes in the transmission case may be done on a CNC machining center or on a specially designed boring machine. Roughing of these holes should be done with a combination boring cutter that can also handle facing and chamfering. During roughing, it is advisable to set the cutting speed at 580 m/min, with a feed rate of 0.03 mm/rev, and a feeding speed of 80 mm/min.

The recommended pcd inserts for this operation include: the TPGT, TPGM, TPGH 110304 series, and the SPGT, SPGM, SPGH 090304 series. These tool inserts can be used to accomplish boring, facing and chamfering without changing the insert, thereby achieving effective process consolidation which will save cost and time during large scale machining. For the finishing operation, use a boring cutter that has been designed for high precision finishing operations. This cutter should be used with the TCMW 060204 and DCMW 070204 inserts.

Machining of Shaft Holes
Roughing of shaft holes can done on a machining center or on a machine designed specifically for boring of transmission cases. On a machining center, use a combination boring cutter which will do boring, facing and chamfering in a single pass. With a recommended cutting speed of 350 m/min, a feed rate of 0.1 mm/tooth, and a feeding speed of 200 mm/min, the diamond shaped pcd inserts: CPGT, CPGM and CPGH series will deliver the desired results. Also, the triangular shaped inserts: TPGT, and TPGM may also be used for roughing of the shaft holes.

On machines designed specially for boring, the cutting speed may be raised to 600 m/min, while the feed rate and feeding speed are also increased to 0.2 mm/rev and 382 mm/min respectively. The TPGM 110304 and the SPGM 090304 inserts will provide a good roughing cut with this kind of machine. Finishing of the shaft holes may also be done on a general purpose machining center or on a special purpose boring machine. This should be done with the toughest grade of polycrystalline diamond inserts.

Several cartridges may be used to combine facing and chamfering with the boring operation to improve production efficiency. This will reduce the impact of the slower cutting speed required for the finishing process. To achieve a perfect surface finish, use the DCMW 070204 and TPGW 110304 inserts and then set: the cutting speed to 130 m/min, the feed rate to 0.2 mm/rev and the feeding speed to 51 mm/min.

Conclusion
Boring of the transmission casing holes is a very important operation because these holes must provide a perfect fit for shafts or bearings without any unnecessary friction, vibration, or misalignment. Therefore these operations should be done using the most suitable pcd inserts that can provide high speed machining and excellent surface finish.

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