Last year I did a sample for a customer. This is a government fella who needs 100 boomerangs engraved and also to have a coin flush-mounted with the face. The sample I did before was easy. I simply engraved it, made a hole part of the way through with a Forstner bit, and glued the coin in. Now, that was nearly a year ago. Today he came back in with almost the same type of boomerang, but this one, along with the other 99 I have to do, are much thinner than the original boomerang.

So now I have a dilemma. I need to be able to recess this coin into the boomerang without any hole coming through the back side and a regular Forstner bit will no longer work due to the "spike" in the middle. I've tried to find a Forstner with a totally flat face, but have been unsuccessful.

I need to make a hole 1.75" in diameter and roughly an eighth of an inch deep into this thing. Can anyone suggest a bit I could use which has a completely flat face? My last resort would be attempting to modify the Forstner bit I have, but I'd like to avoid this, if possible.

Thank you.