Unusual shapes - Just business as usual for Northfield

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Northfield customer Mascotech Sintered Components, is the second largest powdered metal automotive parts maker in the world. This is not a new technology but it is one that can provide tremendous financial savings in parts processing.

As the name implies, the process starts with metals in powdered forms. Typically, several alloys are combined to create a new material with specific properties. The powdered metals are put into a mold and compressed under several hundred tons of pressure. This causes them to fuse. The piece is released from the mold (this is called the green state) put into an oven and sintered. The result is a strong, economically produced near net to totally complete component.

In addition to doing the powdered metal work, Mascotech also performs roughing and finish machining on some of their parts. This is where Northfield comes in.

Transfer Case Component
For this automotive transmission component, Mascotech needed to finish the bore and cut two grooves that would hold a snap-ring and a wave spring.

What made this part challenging from a work-holding perspective was that putting in the grooves with a forming tool develops up to 20 horsepower. That meant that the part would have to be held very securely while the material was being removed. Yet the part has thin walls, making it difficult to grip without deforming it. And, since all the machining operations would be done at the same time, maintaining roundness was critical.

We solved the problem by outfitting our standard 8″ Model 800 3-jaw chuck with special full circle jaws that locate and grip the circumference of the part with a drive pin to pick up most of the torque.

Water Pump Component
Like many powdered metal parts, this water pump component comes out of sintering nearly complete, but still needing a few final operations. In this case that means machining the bore and flange cutting the treads and tapping the holes.

To hold this part, Northfield provided one of our standard Model 670 2-jaw chucks fitted with special jaws to grip the outside diameter of the part. Special orientation pins are used to locate the part for finish machining.

Crankshaft Sprocket
The final piece is one of a family of sprocket gears. After sintering, the material has a particle hardness of 58/63 Rockwell “c” scale. Mascotech needed to hard turn the bore.

What made this job challenging for Northfield was the keyway between the gear teeth.  It makes one section of the work piece very thin and introduces an interrupted cut during machining of the bore. Our solution employs a 4″ diaphragm chuck with six jaws to grip the major diameter of the gear teeth and three pads for axial banking. One of the jaws has a drive pin to insure no slippage while holding the part very gently. Using our chuck, Mascotech was able to achieve a roundness spec of less than 0.0002 inch when machining the bore. Mascotech utilities Northfield work holding for over 80% of their turning applications at their Ridgway, PA facility.

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