How to slot a bridge

[Bob Schmidt]

What is the best way to slot a bridge. Should I use guaged nut files or a V file?
Should the angle be half the angle from the bridge to the tail piece?

[Ivan Kelsall]

I fitted a brand new Cumberland Acoustic bridge to 'once owned' mandolin ten years back. My mandolin had a radiussed fingerboard but the only bridge the store had was a straight topped one. I had to sand the top to a contour to suit the fingerboard (template made from the old bridge) & cut new nut slots.

Realistically,you don't have to do much in the way of making new slots to fit the strings 'perfectly'. The A & E strings simply need narrow 'vee' cuts sloping down towards the tailpiece by a small amount,just to keep them in place. I used a scalpel to do the job. The A & E slots were hardly wider than the thickness of the scalpel blade & they were fine.

For the G & D strings,i just cut a slightly wider & deeper vee cut,but it was still very small. Under pressure,the strings will soon bed in & make their own 'shape'.
The beauty of making vee cuts,is that as long as the strings touch the side of the vee,they won't buzz. The 'vee' cradles the string & provides 2 points of contact = no buzzing. It worked for me perfectly.

There are specialised files for doing the job ( as i now know),but using any type of file,you're in danger of removing ''too much''. Using a sharp blade removes just enough & it really doesn't need much of a slot to keep the strings on the bridge. You could use a 'vee' bladed Swiss file VERY carefully,but the above scenario still applies,
Ivan

[Bob Schmidt]

Thanks Ivan, that makes sense. I tried using a nut file and wound up with a buzz on the A string so I posted this. I probably should have posted it first. If we learn by our mistakes I am working on being a genius.http://www.mandolincafe.com/forum/im...ilies/grin.gif

[Ivan Kelsall]

If you can,sand the top of the saddle to remove the slots & start again using a sharp blade. If your first cut doesn't do the job,a tiny 'bit by bit' strategy will work - take your time. Usually the A & E strings need almost nothing to keep them in place. As soon as they touch the slots they'll begin the process of bedding themselves in & forming their own 'shaped' slot as they exert a lot of pressure on that spot.

The G & D strings will only need a tiny bit more than the treble slots - again,try a small cut,take it bit by bit,keep the 'vee' shape & adjust the depth rather than the width. Strings buzz from side to side not usually up & down,
Ivan

[Stephen Perry]

http://www.stewmac.com/Luthier_Tools...Y_UaAoZa8P8HAQ

Fun stuff, nobody notices the differential spacing, just comment on how much better it feels!

[Ivan Kelsall]

Thanks for that info. Stephen. It certainly is important,especially as the article says,with the thicker strings. The D & G strings do need proportionally wider spacing. Going off the string centre line for all 4 courses will result in the G & D stings being too close for comfort. It's the space 'between the string sides' that's important. I was fortunate when i fitted my first & only bridge,the bridge was already slotted correctly & i simply copied the original spacing via a template onto the sanded bridge top.

Very well pointed out,
Ivan

[Stephen Perry]

Of course, Ivan. I assume people will figure out all those pesky details. On the ruler, one marks the outer E and inner G, then where the inner E and outer G give a nice spacing, and then select the slots that make that work. Looks good, too! Of course, can start compensating the nut (works nicely) and doing other things. A nice sticky web of "Oh, I could also . . . . . "