# Press fit and powder coat

Hello all, I need some help with a sheet metal part I am going to produce. The part consists of 12ga A572 grade 50 sheet metal and a 1020 or 1018 steel spacer that will be press fitted into a laser cut hole in the sheet metal. After assembly the part will be powder coated where I know temperatures in the oven are normally 300~400 degrees. Will there be a problem powder coating parts that are pressed together? More specifically I am concerned with there being a difference in expansion rates between the different materials causing the press fit to fail when exposed to those temperatures. I think it should be fine since both materials are low carbon steel and should have similar expansion rates but I wanted to post here for some input/assurance.

Thank you!
- Eric

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You can estimate the stress developed as follows:

stress = E * [ alpha(A572) - alpha(1020) ] * (Tf - Ti)

E = modulus of elasticity (should be about the same for both)

alpha = coefficient of linear expansion for your two steels

Tf, Ti = final and initial temperatures.

Try to limit your stress to 60% of the yield stress of the weaker of the two.

I would have greater concern if the sheet metal were of thinner gage, but your combination will probably be okay. Run a test piece through the process to be sure.

I would have greater concern if the sheet metal were of thinner gage, but your combination will probably be okay. Run a test piece through the process to be sure.
Thick or thin material can still develop thermal stress. Notice the thickness does not appear in the formula I listed.

Thick or thin material can still develop thermal stress. Notice the thickness does not appear in the formula I listed.
I should have been more clear -- I wasn't thinking about stress, I just meant that thinner gage steel would absorb heat more quickly than the spacer, which may allow the hole to expand faster than the thicker section of the pressed-in piece.
(I know, that's not phrased in the best technical verbiage, but I'm tired, and I think you'll understand my intent.)

Hello all, I need some help with a sheet metal part I am going to produce. The part consists of 12ga A572 grade 50 sheet metal and a 1020 or 1018 steel spacer that will be press fitted into a laser cut hole in the sheet metal. After assembly the part will be powder coated where I know temperatures in the oven are normally 300~400 degrees. Will there be a problem powder coating parts that are pressed together? More specifically I am concerned with there being a difference in expansion rates between the different materials causing the press fit to fail when exposed to those temperatures. I think it should be fine since both materials are low carbon steel and should have similar expansion rates but I wanted to post here for some input/assurance.

Thank you!
- Eric
I don't think the expansion will be so much a difference as to allow your spacer to fall out, not at that temp.

Thank you all for the help! I think I am going to just run a couple samples through different processes and see what works best =)