Cut Outs

Make an aluminum clamping fixture to hold the coin blank by clamping the circumference, i.e. pocket out the hole to size, do a horizontal hole for a clamping bolt and cut a relief slot so you can tighten it. Cut the blanks via another method, like sizing and parting on a lathe. Then drop a blank into your fixture, clamp, engrave one side, unclamp, flip, reclamp and engrave the other side.

Don't forget to include a couple access notches in the fixture to allow the coin to be removed easily.

You might try making the base plate into a vacuum table, cutting and drilling a vacuum manifold under the parts to hold them down. Or glue them to a substrate with a glue that can later be cut or heated, or dissolved away. Wood turners often glue a thin piece of paper between the material they are turning and a faceplate, then split the paper when they are done to free the work.

Stuart

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I like the vacuum table idea. How much would it take to work? Would, say, a hand operated brake bleeder pump be enough? Might be if only one item was being held? phil

Unlikely. A vacuum table has leaks even at best. You'll need a pump which can keep ahead of the leaks. You might work with a shop vac, or even a house vacuum cleaner, if you don't need the maximum hold.

Good Luck, DoN.

I would do it as a sandwich. A bottom plate that is solid, A middle layer that has an x-y grid cut into the interior and all connected to a port for the nozzle of a shop vac, (1.25"), and a sacrificial top layer, that you change for each new design, which has holes drilled to intersect the x-y grid under the parts in strategic places.

Use MDF or something else quite flat and smooth surfaced for the top layer.

Good luck.

Stuart

Two classic solutions: jeweler's wax (black hot-melt adhesive) can hold a sheet firmly, but let go with gentle heating (like, on a hot plate). Coolant is required, of course.

Also, electrochemical machining (i.e. make a stencil, use it to apply a mask, then etch in appropriate reagent). Copper and stainless etch well with FeCl, and a little electric current and salt water made washers from stainless shim stock last time I needed those.

That is interesting. I could never get FeCl work on stainless steel. Mild steel, copper, brass, yes. Stainless steel, never. Do you have more details?

I was using KPR photoresist, there was some adhesion difficulty (HNO3 acid wash before applying the resist?), and it etched rather slowly, but I was only going through 2 mils. The photoresist mal-adhesion just put a few pits into the field, didn't bother my application.