Tolerances for a Force Fit on a profile

[rhmeng]

I have a part that is made of steel that I want to press fit into a part that is made of anodized aluminum. The shape of the press is shown in the attached image and the dimensions are roughly 0.5" x 1.5". My question is on how to tolerance each part. Should I simply use the machinery's handbook for an FN1 or FN2 force fit even though it is not a cylinder? I am also worried about how to keep the anodization on the Aluminum tight enough that the press works.. Any advice is appreciated. Also the thickness is a little over a mm.

 

[3DDave]

Cylinders in press fits can have uniform surface pressures applied. That won't happen in this case so you need to decide what amount of surface pressure you want and then use that to determine the amount of deflection you will get in the parts you have. By varying the surface pressure in the analysis you can determine the tolerances for fabrication. I expect you will need to use FEA methods.

 

[SnTMan]

I don't know this for certain, but I expect the normal interference fit calculations ignore any "edge effects". At about 1 mm thick, likely it is ALL edge effects.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[rhmeng]

hey guys, thanks for the response. I believe there is a formula for surface pressure in the machinerys handbook, although it was for steel on steel.. I am not sure I know how to go from surface pressure to deformation. Or is it simply figuring out how much surface pressure that I want, then applying that to the profile via FEA to see the deformation in the mating parts?

 

[3DDave]

The latter is what I'm thinking.

 

[GregLocock]

If the parts are axisymmetric then you could use Excel to figure it out. I did once for a spike and cone termination for a cable. FEA is certainly quicker and probably better.

Cheers

Greg Locock


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