Ferrules in a painted body - install

I want to install vintage style ferrules in an already drilled and painted body.

The holes are currently 3/16". How could I make the holes bigger without damaging the paint? The holes need to be 3/8" wide and 3/8" deep. The holes are already deeper than that. Will there be enough wood to support the pull of the strings?

I want to install these:
http://www.allparts.com/Nickel-String-Ferrules-p/ap-0187-001.htm

Thanks for any help!

You could probably use a 3/8 in. Forstner bit without damaging the paint. The sharp edges shown here can slice through the paint without chipping.

......http://img.photobucket.com/albums/v208/jwells393/Forstner-1.jpg

Just how much deeper than 3/8 in. are the holes now. I use similar ferrules I get from StewMac. I like to drill the holes a little deeper than 3/8 in. then bevel the holes a little like this.

......http://img.photobucket.com/albums/v208/jwells393/Thinline%20Project/DSC04181.jpg

If the holes are too deep now, just glue in some 5/16 in. dowel and re-drill. If you decide to re-drill the ferrule holes, I suggest following the procedure show in posts 38 and 39 of the following thread.

http://www.tdpri.com/forum/tele-home-depot/97436-**hmmm-think-ill-build-thinline-**-4.html


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Ahhh! you may have hit on something. I may need to plug it, then re-drill it. I will need a template or way to accurately space the holes, i.e. scaling system / digital readout.

I may have to contemplate this a bit more. Nice idea with beveling though it would hurt the paint in my case.

Thanks for the spark* (of an idea)

Masking tape over the holes/paint before you drill. It will help to minimize chipping.

I will need a template or way to accurately space the holes,

The procedure I linked to at the end of my previous post accounts for the spacing.

A step drill will have a 1/4, 5/16, 3/8 inch drill bit in that order on one bit in steps . Harbor Freight has them if you have one nearby. The 1/4" drill would follow your 3/16 hole, and then just keep going until you get the 3/8 cut started some. Then I'd go down deeper with a 3/8 forstner bit.

if the holes are too deep you could always put in a small piece of dowel to make it proper depth. it would in invisible on the outside.