Installing the Full Circle

[ethnotime]

After fretting about which size of the full circle I should get, I finally decided that it had to be 1/4-20". Then after weeks of fretting about installing it without the soundpost falling, I finally get to the job and low and behold: I did indeed buy the right size but now the blunt end won't fit!!!! At least the soundpost didn't fall!

It's a really nice bridge actually and my luthier put in threads on the feet of the bridge so I have no choice but threads down but unfortunately the non-threaded side won't fit! Anybody have any tips on what I can do to widen the hole? Is this a common issue? I'm sorry if this has been brought up in the past but I did a search and not much came up.

Thanks in advance

[Mark Carlsen]

I use reamers here to open a hole up, but if you are careful a drill bit [ hopefully brad-point ] will also work. You do need to keep it square or you will be refitting the the feet a bit. Also a handle for what ever tool you use is helpful.... a drill press and just lining things up and not using the power but turning by hand has helped me w. this very problem before.

[Greg Clinkingbeard]

There is a risk of splitting the bridge if the bit grabs and bites in too fast. The hole can be reamed by reversing a portable drill. Probably not the best way but there's little risk of ruining the bridge.

[robobass]

If you can get use of a vise and floor drill press, you can do this accurately. First lock the drill chuck in the down position, find a piece of blank shaft which fits snug in the hole, chuck in the protruding part of the shaft with the bridge sticking down off of it, then carefully position the bridge and lock it into the vise using shims so that the shaft can move smoothly in and out of the bridge leg. Remove the shaft and replace it with the proper size drill bit (1/4"?), and drill out the hole. Otherwise, this would be quick work for a machinist with a horizontal mill.

Edit. If you have a machinist buddy, he could quickly turn down the diameter of the non-threaded side of the pickup, but this might be a bit risky.

[ethnotime]

Thanks for the replies. I have a small screwdriver bit that worked but it's not long enough. I'll look for a reamer, seems to be the safest item to use.