Nartker - Posted - 11/17/2013:  06:08:03

I need to slot a bridge to accept  some medium weight Thornburg gut strings.  Any suggestions other than a pocket knife?

lightgauge - Posted - 11/17/2013:  06:12:42

I slot with files.

kmwaters - Posted - 11/17/2013:  06:19:46

StewMac files for the job.

steve davis - Posted - 11/17/2013:  06:36:21

I swear by my Stewmac sized slotting saws.

If you want a good working slot without buying the Stewmacs,notch vee slots with a razor knife.
Don't draw the blade toward yourself/support the bridge on a cutting board.

As you near the height line that you drew on the neck side of the ebony,stop using the razor knife and finish the bottom of the slots with the appropriate size welding torch tip cleaner for a rounded bottom that fits the shape of the string.
Slant all cuts down toward the tailpiece.

chickenpickin - Posted - 11/17/2013:  07:07:46

If you're going to use medium gut strings I would suggest making the first cut with a small triangle file to establish the slot and then using torch tip cleaners to finish them out.  I use Stew Mac files and I like them but when I slot for Nylgut strings (which are usually much larger gauge than your typical 5 string bluegrass banjo string) I use tip cleaners because they come in a set that ranges from .006 to .045. That will cover any size string. They are inexpensive to buy as well.

Tim

rudy - Posted - 11/17/2013:  07:51:26

This diagram is from my website:

Actual "slots" are one of the easiest ways to ensure that you'll have a good chance of introducing the infamous "bridge buzz".

B0bIII - Posted - 11/17/2013:  08:18:47

I've been using a metal, grit type fingernail file similar to the one in the picture to slot nuts and bridges for the fishing line string I've been using. I start with a knife and follow with the file used like a saw. It has a little grit on the edges, and works pretty good.

--edit-- I just wanted to add, if your buying one make sure you run your finger down the edge and feel for the grit. I think the grit at the edge has more to do with sloppy manufacturing than intention or design...

Edited by - B0bIII on 11/17/2013 08:32:51

sunburst - Posted - 11/17/2013:  09:17:06

I use my Stewmac nut files, but I build and repair instruments for as living. Those files are ridiculously expensive even for pros, and if you just want to slot your own bridge there are plenty of other tools that are up to the job. A small triangular file, a pocket knife, nearly anything that will make a relatively clean notch in a piece of ebony. It doesn't really matter whether it is a round bottomed slot or a V notch to start with because the pressure of a steel string in the wood (ebony) will mash the string into the top of the bridge and form it's own burnished, round-bottomed slot. Softer strings will not mash into the bridge so quickly, but will eventually form their own little pocket in the bottom of a V-notch. Bridge slots are not like nut slots, where the strings must slip through the slot for tuning, so the strings can anchor themselves into the bridge top and all is well. Placing the peak of the notch in the center, as in Rudy's illustration makes a durable, secure notch with a definite departure point for the string, and it is the standard way to proceed, but I prefer the peak more toward the front of the bridge with a longer "ramp" back toward the tailpiece, more like a nut slot. I set banjo bridges up leaning back toward the tailpiece a little, and that moves the bridge feet toward the center of the head. The forward notch counteracts that a little, and I think most banjos sound better with the bridge not so close to the center of the head.

The notches shouldn't be right to the front edge of the bridge however, because that can cause chipping of the edge of the slot.

Now, after all that, don't over-think the situation. Just measure out your string spacing and cut your shallow string notches with whatever tool you have. If you get a clean, buzz-free sound from each string, your done. If any strings buzz, clean up the notches until the buzz goes away and then you're done.

Edited by - sunburst on 11/17/2013 09:24:22

lazyarcher - Posted - 11/17/2013:  10:27:21

I made these up using jigsaw blades. I ground them down to the exact widths on a grinder.

wrangler - Posted - 11/17/2013:  11:06:24

I use torch cleaner files.  They are sized and cheap (A couple of bucks) from any welding supply.

rendesvous1840 - Posted - 11/23/2013:  20:55:21

I have some sizes of the Stew-Mac tools, but also use welding torch tip cleaners. They don't come down to the smallest string sizes, though. For nylon/gut strings the tip cleaners are probably all you'll ever need. For steel, you may find something smaller is helpful.