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drilling indexed bridge pin holes
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=17790
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Author:  Ken Mitchell [ Sat Jun 28, 2008 4:47 pm ]
Post subject:  drilling indexed bridge pin holes

I've sent Bob Garrish a PM, but maybe someone can push me in the right direction in the meantime...

The bridges he did for the group order some time back came with small indexed bridge pin holes that were not drilled all the way through the bottom of the bridges. How should one go about drilling them to the full diameter and depth? Not with a brad point bit, I'd assume, but with a regular bit that will center itself in the indexed point?

TIA,
Ken

Author:  Hesh [ Sat Jun 28, 2008 5:35 pm ]
Post subject:  Re: drilling indexed bridge pin holes

That is what I would do Ken my friend and what I do when I make a bridge from scratch. It's probably over kill but I sneak up on the final hole size using a number of consecutively larger, non-brad-point bits so they can self center as you indicated. I also hold the bridge firmly but so that it can move slightly as the bit contacts the pilot hole to permit the self centering to happen.

I do the same thing for tuner holes and I also place masking tape in the exit area of the holes to help discourage tear-out.

Author:  Ken Mitchell [ Sat Jun 28, 2008 5:41 pm ]
Post subject:  Re: drilling indexed bridge pin holes

Thanks, Hesh! I thought that I was probably on the right track.

Author:  Bob Garrish [ Sun Jun 29, 2008 7:13 pm ]
Post subject:  Re: drilling indexed bridge pin holes

I messaged Ken when I got back in today, but if anyone else has an issue here's the response:

The holes on the bridges are 1/8" and drilled just shy of the bottom surface of the bridge. A 1/8" drill bit will square itself up in the hole (they're around 1/4" deep IIRC) and drill a straight hole through, a larger bit will use the 1/8" hole as a guide and should self-center if you hold the drill straight. You should put a piece of scrap underneath to avoid chipping out the back. From there, you need to ream them to fit the bridge pins you use.

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