Press fit metal inlay?

Today I found myself with a cut brass coin and a stainless steel blank in my pocket. They were stacked upon removal and inspiration struck, the two metals are beautiful together.

This got me thinking, could i mill an inlayed challenge coin and press fit it with an arbor press?

The answer is obviously yes… but I’m wondering if there are any “gotchas” or common pitfalls i should look out for. I’d rather learn from your mistakes than my own :wink:

Let me know what you think!

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I’ve a friend that works in a gear shop and they press fit bearings onto shafts all the time. Cool one of the pieces and heat the other. They EDIT: do this with an oven and and cryogenic bath, but I would think on your scale you wouldn’t need those extremes?

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That only works when the part geometry allows for it — the design in question would have the outer elements getting trapped/interfering w/ the fit.

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Remember your cutter diameter. Corners will have to rounded to the radius of your tool.

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All great points so far.

I’ve got a small electric kiln and access to dry ice so I’ll keep the temp difference in mind for future projects!

I definitely would have tried the temp technique and failed miserably so i appreciate the shout for certain geometries not working. That would have been a time consuming lesson to learn.

I also would have absolutely cut both pieces before realizing one had sharp corners and the other did not… Which would have resulted in trying to reclamp the part and screwing it up anyway :sweat_smile:
That one certainly saved me some material!

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@WillAdams Correct! They purposely machine for an interference fit and once the parts are assembled this way, they will not come apart without complete destruction. I’ve had the good fortune to watch both the assembly and disassembly and wow! You only get one chance putting things like this together, stand back and watch the pros!
BTW - I think the largest mill in that shop has a 30’ X 6’ (yes, foot) bed and amazingly, to me is they say it’s good for about .001" over that distance!

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Finally got around to getting this out. I figure a soft copper inlay in a hard brass outer would be most forgiving. It worked out pretty ok.

I cut the inlay to exact size, with a full depth of cut contour as a finishing pass.

For the outer brass I did my finishing pass at full doc with a .002" radial stock to leave.

I should probably sand both sides to really make it flush and fix some of the “squished” edges… I’m assuming this is because i used a hammer instead of a press :sweat_smile:




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