Can anyone help me with a method for drilling a small hole into the center of a quarter without having the burr/bump/rough mess on the other side?

There must be some way to do this that some of you are aware of...?

Any help would be greatly appreciated...

Steven

There needs to be something backing the coin to avoid this. The backing should fit as tight as possible to the coin and preferably be the same material as the coin. I'm guessing that simply using a wood backing will not prevent the "blow-out".

Perhaps pressing the coin into liquid steel and then allowing that substance to harden would help. The coin could then be recessed into a wooden scrap that had been prepared with a hole via spade or forestner bit of appropriate size. I would certainly test this on a cheap coin first. You'll also want to clamp the coin because drilling circular objects tends to induce spinning of said object.

Lastly, have some oil on hand as you don't want to overheat the coin. If there is a small amount of "blow out" you could always just file & sand it away.

As I haven't actually drilled a coin, I'm just thowing out an idea. Please be careful, use the right type of bit and test on scraps first! Sorry about all the warnings...I was a woodworking teacher for a while, so I'm cursed.

Chad

Hello.

I have had much experience with drilling into steel and I would suggest a TITANIUM drill bit. Do not use a coolant or an oil. This may cause the metal to temper if it gets to hot. Run the drill at a slow speed. I had to drill 92 1/2" holes to build my Chinese Water Torture Cell and I think I finally got it right.

Good luck!

Richard

If you aren't already using one, you will have better luck with a drill press than a hand-held drill. Be sure to clamp the coin in place to prevent it from spinning. Do not try to hold it by hand.

Drill slowly until the tip of the bit just breaks the surface on the other side, turn the coin over, centering the bit with the pilot hole, and finish drilling. If you take care to line it up for the second drilling phase, you will end up with a smooth hole, as both sides are entrance points, and neither is an exit.

Be sure to use the sharpest bit you can get. Copper is a soft metal and it will be easy for a dull bit to grab and dig in.

~michael

If you first drill a shallow hole to hold the quarter in a piece of wood, this will automatically center the quarter (assuming you don't move the block, or you could set up a stop so that it will be positioned in EXACTLY the same position every time), and then you could just lightly drill one side, then turn it over and finish the other side (I believe that a 1" hole will work for a quarter). You could also try using a tapered reamer, and you could also touch up the edges with a countersink. Good luck -
Bill

PS - You will still need to clamp the quarter to keep it from spinning.

I'm not a metal worker, but a woodworker. You might drill a smaller pilot hole all the way through. It will leave a burr, but then use the above methods of drilling halfway through from both sides. The pilot hole makes sure the two drillings line up. And by all means use a drill press.

A pilot hole then useing a Uni-bit will clean up the holes. B