Allen key design examples

[engsign]

Hello,

Is there any software (or clearly worked example) out there for determining the torque vs material stress when an allen (hex) key is placed in a hole and twisted.

It sounds simple, but the size of the gap is going to matter along with assumptions of friction between the key and the hole.

Thx

 

[drawoh]

engsign,

I am positive I have seen an example somewhere of an FEA problem based on a key in a hex socket. I cannot remember where.

Your hex key will not engage your socket in a perfect surface to surface contact. The hex key will have a radius at each corner, which will engage the flat face of the socket. The theoretical contact face will have an area of zero.

You could look up literature on roller bearings, which cause a similar analysis problem. Is your cap screw hardened, or is it soft and ductile like 303[ ]stainless?

I do not see friction as an issue unless you have stripped something.

JHG