Torsion bar design help

[coppersmith]

Hi I am new to this group. I am looking for assistance on a torsion bar I need to manufacture. It is a replacement part on equipment I service. This bar is small (15mm long and about 3mm in diameter). This spring rotates a very small amount at a rate between 3 and 8 KHZ. The most important characteristic is it's ability to return to the starting position after energy is released. I had the metal analized. I was told it is similar to 4150. My plan is to but 4150 stock and grind the shape. My questions are, will this be the best way. Should this be heat treated after grinding. (I currently don't know the parts hardness). Any suggestions on this manufacture, the material selection would be appreciated.

Mark

 

[israelkk]

No, you should heat treat it and then grind it. Heat treatment distorts the part. I assume that the part failed due to fatigue. Therefore, you have to request a non destructive tests to make sure that the grinding process does not causes cracks on the surface. You can consult MIL-STD-866B avaiable at

http://assist.daps.dla.mil/quicksearch/