Shrink Fit Question

[CodeRed7]

Quick Question:

I am currently designing an assembly where I need to use shrink fitting to fit a square shaft into a square hole. I know shrink fitting is most commonly used with circular holes, and was wondering is it possible using a square shape? The material will be 360 Brass Alloy.

Any help would be greatly appreciated.

 

[MikeHalloran]

It's theoretically possible, but it isn't done much, probably because the corner location tolerances have to be on the order of the press fit tolerances, e.g. about ten times tighter than normal. ... else you shave off a lot of material at assembly.


Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

The proper way to do a shrink fit on a square shaft is to drill holes at each corner and then machine the square hole, so that there is no contact at the corners but only on the flats. This reduces the stress concentration in the corners of the hole which is prone to crack. I have seen this happen.

 

[MikeHalloran]

Another option along the same lines is to use a round shaft with four flats, pressed into a square broached hole. ... and it would be good practice to also radius the broached corners of the square hole to reduce the stress concentration and to extend the broach life.



Mike Halloran
Pembroke Pines, FL, USA