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String spacing for new bridge

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String spacing for new bridge

Postby Daniel Kurtz » Tue Jul 12, 2016 10:54 am

Project is an early 70s made-in-Japan Epiphone (FT-130 I believe, OtToMH). Replacing the original, adjustable semi-bolt on bridge, because the adjustable saddles suck, and because it had split across the string holes and the back part of it was pulling a hump into the top. Intend to replace with a fixed saddle type. After taking some measurements it looked like the pre-carved bridges from StewMac might be a good, if not exact fit (owner doesn't care), and so it has proven to be - almost exact in shape, string hole placement and saddle position. Where it differs is in height, which needs to be reduced about 1/16", and string spacing, which is 2 1/8" while the old bridge is closer to 2".

I think the guitar can accommodate the wider string spacing, based on the neck-width at fret 12-14 metric. I'm wondering if opinion is that it would be reasonable to plug the current holes in top and bridge plate and redrill for the premade bridge with the wider spacing, or to acquire a blank and fashion a new bridge to match the old one with the old spacing.

This is my first bridge job and I don't doubt my ability to fashion a new bridge, including string-hole placement (I have the original to give me all those measurements) but question my ability to locate and cut a saddle slot from scratch, without having to invest in a lot of expensive tools and jigs from StewMac.

I will really appreciate any input as I'm a complete noob with this particular sort of job.

thanx.

ddk

P.S. One factor that I suppose might make a difference is that, though I don't think it's broken, I think I do see evidence that the bridge place has been stressed and perhaps warped a bit, in line with the holes, where the split was in the bridge above. I don't even want to contemplate getting into a plate removal and replacement at this point, so I was thinking that I might just try and reinforce that line by using the StewMac PlateMate, which matches the 2.125" spacing of the pre-fabbed bridge but would not match the original 2" spacing.
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Re: String spacing for new bridge

Postby Peter Wilcox » Tue Jul 12, 2016 12:19 pm

Daniel, I wouldn't let making a saddle slot be a determinant in making a new bridge. I cut saddle slots with a 1/8" router bit in a drill press. Clamp a wood fence on the table, tape a wood wedge of the appropriate angle to the edge of the bridge, and route the slot in several passes to the depth you want.

Alternatively, you could route a slot first, then draw, cut and shape the bridge around that. That would avoid doing a lot of work, and then ruining it at the end. :)
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Re: String spacing for new bridge

Postby Daniel Kurtz » Sun Jul 17, 2016 2:57 am

Hi Peter; Thanks for the suggestion. I think I'm leaning towards trying to make a new bridge. I had thought of an approach for cutting the saddle slot with a drill press to drill a million holes along the line and then using a file to finish and clean up the slot. After reading your suggestion when I got home I tried out the drill bit in the press and I can see it working. I'm just unsure how you control the depth. My drill press doesn't allow me to lower the bit and then lock it at a fixed position. Do you have a suggestion on how to manage that?

ddk
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Re: String spacing for new bridge

Postby Barry Daniels » Sun Jul 17, 2016 6:44 pm

Make a depth stop out of a wood dowel with a hole down the center that just fits over the drill bit. Slide it over the bit up to where it touches the drill chuck. The amount that the drill bit sticks out of the wood will determine how deep it drills. Adjust the length of the depth stop to give you the right hole depth.

Suggestion: use a drill bit smaller than your intended saddle slot width to allow for a little alignment error during drilling.
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Re: String spacing for new bridge

Postby Peter Wilcox » Sun Jul 17, 2016 8:41 pm

daniel kurtz wrote:My drill press doesn't allow me to lower the bit and then lock it at a fixed position. Do you have a suggestion on how to manage that?
ddk

Aye, there's the rub. :) What I do is set the depth stop to make a shallow cut (1/16" to 1/8"), then get the bridge/wedge in position against the fence, turn on the drill, lower the feed against the stop, and slowly slide the bridge along the fence with the left hand as it's cutting, while holding the feed lever down against the stop with the right hand. Then reset the depth stop for a slightly deeper cut, and repeat. Continue lowering and cutting until the desired depth is reached.

It might take a little practice (it's important to keep it tight against the fence as you move it), but even with shallow cuts (which give better control) it doesn't take long.
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Re: String spacing for new bridge

Postby Keith Howell » Mon Jul 18, 2016 4:37 am

A simple mod on some drill presses which don't have a locking mechanism:

Unscrew the depth stop and add an extra nut underneath the piece of metal with the hole drilled in it that sticks out from the side of the press.

Adjusting the nut allows you to lock the press at the correct height.
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Re: String spacing for new bridge

Postby Keith Howell » Mon Jul 18, 2016 8:27 am

Here's a shot of my drill press
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IMG_20160718_133430.jpg
Drill press mod
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Re: String spacing for new bridge

Postby Peter Wilcox » Mon Jul 18, 2016 7:42 pm

Thanks, Keith, good idea. Looks like mine will take the same mod. The lower 1/4" of the rod has no threads, so the nut can just sit there loose, out of the way when not used.
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Re: String spacing for new bridge

Postby Daniel Kurtz » Fri Jul 22, 2016 1:02 am

Cool, guys! Gives me something to experiment with. Hope to spend some time over the weekend trying to make some practice bridges out of softwood... maybe one or two out of some mahogany I have that is close to the right thickness... while I wait for some rosewood blanks to come.

d
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