I much prefer to drill the holes from the rose side. I don't care as much about the rear end of the bridge, only that the holes line up somewhat tidily. It's quite often the case that the drill can wander off it's course. This is why I prefer the rose side. I like to design the distance between the hole and the top of the bridge to enable a clear indication of how high the string's action will be. The lute string will ultimately like to lie somewhere in the middle of that distance using the classic loop tie. Also, I can make slight deviations from the original hole, left or right, which is usually the case.
With all of this in mind, I have been using a somewhat simple method and what I will describe as a bow drill. Instead of twisting the drill bit between my fingers, the bow drill will do the work in a fraction of the time. Like with many lute repair operations, you need to be extremely careful. Here is the apparatus.
I am somewhat embarrassed with it's simpleness and lack of refinement. I could likely spend a bit more time and design the tool rather than finding the bits and pieces around the shop. However, at first, I wasn't convinced that it would work.
The drill bit is easily acquired from a jewelry supply house. You can find the proper diameters and the business end is just barely long enough to get through the bridge. The shank of the drill is thicker than the drilling diameter which allows the drill to follow the direction you give it a bit more than a long spindly bit would.
The block of wood holds the blunt end of the bit securely and at the correct height from the soundboard. To make them slightly different as you progress towards the bass, I will shim the block with masking tape as required. Hold the block securely from the back and forth motion of the bow. This unfortunately, is the spot where pressure might be applied to the soundboard, likely between the two soundboard braces. You do have to hold it somewhat securely. Only apply as much pressure as necessary to keep the drill straight. Watch out for the end of the bow you're not holding! Don't drive it into the edge of the soundboard.
You are using the soundboard as a table at this point and extreme caution needs to be observed so as not to put too much pressure on it's delicate areas, which is anything other than the extreme edges. It can be tricky to a hold the lute in this position, as it wants to rock on it's back and this just has to be dealt with one way or another. I lightly rest my arm around the edge where the binding is, if I need to.
The bow is merely a length of hardwood notched to accept an old string. Wrap the string around the bit several times to provide enough surface area to allow friction to grab the bit. If you are pressing too hard into the bridge the bit will grab, overcoming the friction of the bowing string and you'll have to back it out and try again. This is a nuisance because you'll likely have to re-twist the string around the bit.
To drill the hole, you need to measure and prick your points with a sharpened metal rod to give the drill point somewhere to begin, as is standard drilling practice. Don't push into the bridge, only light forward momentum is needed if any at all. Let the drill work. I concentrate all my efforts on protecting the lute from inadvertent damage by the bow and to keeping the drill straight. The height is already set by your block of wood holding the other end of the drill.
Leave it to a lutemaker, to derive pleasure from a tool like this. I'm sure with time and money that I could find a machine tool to do the job. The last time I did this was 2007, so I will likely grab this tool the next time I need it and marvel at simple physics, while doing a mundane task. The jewelers Archimedes push drill didn't work for me. It's diameter was too thick and mine gave up only after a few practice holes were drilled.
This operation is somewhat quirky, demanding your attention. It does have the benefit of using technology that our highly skilled ancient lutemakers might have used. The only point to this being most of the parts can be obtained rather quickly and likely just lying around. I would certainly try gluing a bit in the end of a dowel and try that before. However, if accuracy suffers here may be an alternative.
