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Home >> Technical FAQs >> pcd inserts for boring of connecting rod


pcd inserts for boring connecting rod

The connecting rod in an automobile engine is used to connect a piston to the crankshaft. Connecting rods are made of different kinds of materials including steel, aluminum, and aluminum alloys that contain titanium. Steel connecting rods are commonly used in mass produced cars while aluminum and aluminum alloys are used in high performance vehicles and racing cars. Polycrystalline cbn inserts are suitable for bolt hole boring, pin hole drilling, crank core boring, and balance weight milling, for connecting rods made of steel. For other non-ferrous materials, polycrystalline diamond pcd inserts will provide high precision machining and excellent surface finish.

Boring of Little End Hole
The little end hole joins the connecting rod to the piston. Hence, it should be carefully machined so that it fits perfectly into the piston. For more economical cutting, it is advisable to use inserts with at least 4 cutting edges. These inserts will fit into an indexable drill which produces lower cutting noise during boring. To minimize vibration and distortion during machining, use a cutting speed of about 80 m/min, and a feed rate of 0.11 mm/rev.

The boring of the little end hole is a continuous operation. So the four-sided tipped square-shaped insert will give a more efficient cut since the cutting speed is quite slow. Use the SEMT 0602 insert for roughing of the hole. Then use SDMT 0602 for semi-finishing and SCMD 0602 for finishing operations. During semi-finishing and finishing operations, the cutting speed may be increased to 150 m/min with a feed rate of 0.19 mm/rev.

Boring of Big End Hole
The big end hole is attached to the crankshaft. It transfers motion to the crankshaft and bears part of the weight of the shaft. For efficient transfer of motion, it needs to fit the shaft perfectly and prevent slipping or friction while the engine is running. To achieve this, the recommended cutting speed for roughing is 110 m/min, with a feed rate of 0.25 mm/rev and a cutting depth of 2.0 mm.

Both boring and chamfering of the big hole can be done with the same tool. The SPGT 0903 or CPGT 0903 polycrystalline diamond pcd inserts may be used for the roughing of the big hole. Semi-finishing and finishing operations should be completed using inserts such as the SCGW 0602 or CCGW 0602. During the semi-finishing and finishing stages, the cutting speed may be increased to 220 m/min but the depth of cut should be reduced to 0.15 mm.

Weight Adjustment Milling
Milling of the weight adjustment section of the connecting rod may be done with a standard face milling cutter. The milling cutter with a standard screw on mechanism will aid stable cutting and absorb vibration even during high load conditions. With a cutting speed of 180 m/min, cutting depth of 2.0 mm and a feed rate of 0.2 mm/tooth, the milling can be accomplished using a SEMT 1204 tipped pcd insert.


The connecting rod plays a vital role in the operation of the automobile engine. So it should be machined with polycrystalline diamond inserts that can withstand vibrations, provide high quality surface finish and long tool life.

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