Fillet radius on turned shaft

[mudd8]

I have been asked to review a tension rod design for a safety catcher on a press. Bascially the catcher is a rod that goes up and down through a cylindrycal braking mechanism. The vendor is looking to attach the fixed end of the rod using a collar connection. The rod will have to be turned down to receive the collar. He is asking me to specify the radius at the edges of the turned portion. I beleive that this is to reduce stress concentrations at these locations. Does anyone have any idea of how to arrive at the appropriate radius?

Thanks,
Jim

 

[Carburize]

As big as you can get without interfering with anything else like bearings or seals. In the case of radii bigger is better.

 

[arto]

Look in Peterson's "Stress Concentration Factors"
Sometimes you can undercut/relieve the shoulder to get a bigger radius or use a compound radius for lower SCF's.

 

[yates]

Whatever size you finally settle upon, it would be very useful to get the radius fillet rolled in order to get somme compressive stress into the radius. Go see your local boltmaker.

 

[metengr]

......OR shot peening the fillet radius and tangent points would achieve similar results.