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Fillet radius of Stepped-down shaft

Fillet radius of Stepped-down shaft

Fillet radius of Stepped-down shaft

(OP)
Hello,

I was wondering if anyone out there knew where I could find good design rules / practises defining the proper radius at the point in a machined shaft where the diameter changes abruptly (such as at a bearing shoulder).   

I know it is a function of the larger diameter, D, and the smaller diameter, d, as well as the type of stress the shaft receives (torsion, or bending, or both).    I was wondering if there was any set of "rules" for minimum radius, r, based on this D/d ratio to acheive acceptable stress concentration in this area?

Thanks very much

D

RE: Fillet radius of Stepped-down shaft

the stress concentration of a fillet radius on a stepped shaft is a very typical solution, one source is ...
http://www.fatiguecalculator.com/constamp/index.htm

the design guide-line is to make the stress concentration either as low as you need to meet the fatigue life requirements of your part, or as low as you can reasonably afford.

RE: Fillet radius of Stepped-down shaft

Looking at the situation from the aspect of the lathe operator the minimum inside corner radius would be the smallest radius on the carbide cutter insert that is available.  

RE: Fillet radius of Stepped-down shaft


 You could also look at the equivalent radius on a ball bearing inner race which has to fit snug against the shoulder.

Offshore Engineering&Design

RE: Fillet radius of Stepped-down shaft

All steps on our shafts are specified to have a 3mm fillet radius unless otherwise specified.  Sometimes the radii have to be to suit proprietary parts mounted on them.

RE: Fillet radius of Stepped-down shaft

The largest radius you can use is the best. But as already other people said:
One limitation is the corner radius on the bearing's internal ring. Any bearing catalog has the chart with the recommended radii.
And yes - select the size using the standard insert tip radius. The manufcturing people will appreciate it.

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