Official Luthiers Forum!

1. When designing a guitar that uses a tunomatic style bridge, how is the scale length measured if the bridge is compensated?
A: Is it measured from the nut to the center of the bridge, in-between the two mounting posts?
B: Is it measured from the nut to the bridges furthest mounting post?
C: Is it measured from the nut to the bridges nearest mounting post?

2. What angle should the bridge be after compensation?

Have several builders books, neither specifies.

I did mine by measuring from the fret board edge of the nut to the actual length of the scale, in my case 25". Then I drew a line perpendicular to the neck and marked off the width of the TOM bridge. On the Bass side I then went past this line towards where the pickups would be 3 millimeters, and one millimeter past the initial line on the treble side. I didn't measure the actual angle of it because it didn't seem necessary at that point.

Use the StewMac scale calculator thing on their site. You can specify a Tune-O-Matic & it will tell you where to put each post in relation to the nut.

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Well, that was easy. Thanks
Also found these numbers online that approximate how much compensation to add to each string. It may be accurate enough.

If the theoretical Scale Length = 24 9/16”
Low E = + 1/8
A = + 3/32
D = + 1/16
G = + 5/64
B = + 3/64
High E = +1/32

If the theoretical Scale Length = 623.887mm
Low E = + 3.175mm
A = + 2.381mm
D = + 1.587mm
G = + 1.984mm
B = + 1.190mm
High E = + .793mm

...you could make life a LOT easier if you learn to measure in metric(mm)!

Actually inches work much better for precision woodwork. The smallest dimension you can read by eye in metric is 1mm, the next division is way too fine to see with the naked eye, or even with a pair of magnifying glasses like most of us use. Where as in fractions of inches I can see and mark 1/64th of an inch very easily and estimate 1/128th with good accuracy. 1mm = 0.039 inches while 1/64th inch = 0.016 inch, easily more than double the resolution and at the 128th I mark by eye that's an incredible 0.008 inch. While the mathematics may be much easier, the accuracy of fractional inches is far superior to the Metric system and this is a game of accuracy.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

i respectfully disagree. i can easily eyeball and mark a half mm, and quite easily 3rds of a mm, and thats how i cut my fret slots. works fine.

So, 1/2 a mm.....1/3 a mm...both works I reckon.

one half and one third are intuitive, base simplicity that require no thought or math to imagine. 3/32", 3/64", 5/64"....? different story IMHO


...when i was a boy in the '70s, there was a move to get the USA with the program, and start teaching kids the metric system. for a couple years they did, then we regressed back into the ridiculous and archaic "ounce, pint, gallon, cup, teaspoon, pound, inch, mile, foot, the 'gauge system' for wire and sheet metal" and so on. even as a little kid i recognized the logic and elimination of error that metric offered.
they even taught us two letter abbreviations for states, which is easy and makes sense, and we reverted back, in large part, to "Ill, Ark, Ore" now, instead of the concise "IL, AR, OR".....
america does not like progress, and it is reflected on many fronts. but i digress.

If you are trying to locate a TOM bridge on the body, I'd suggest stringing it up and move the bridge for the best intonation with the saddles in the mid positions. Then mark the bridge drill holes. This should ensure you still have a little wiggle room to fine tune the saddles.
By the way, American units still rule!

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Wah-wah-wah-wah
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Back in the 80's there was a push to get American cabinet shops on the metric system, mostly brought about by a European cabinet craze. We started getting panels and other raw materials in metric dimensions. As long as we were building typical Euro frameless cabs in standard ( metric) dimensions it all worked pretty well. When we tried to build more traditional stuff, especially higher end with inset doors it became a nightmare real quick. All of a sudden the margin between the door and frame started showing a great deal of variance. We actually had to make the doors over size and custom fit each one at times. Switched back to inches and we had our fit and tolerance back. The reason? We are used to making these doors to the nearest 64th of an inch. Something we could do by eye with a standard rule, it just wasn't possible with a rule marked in mm's. On the other hand I do all my mixing of coatings etc, whether by weight or measure in metric because the math is so much easier.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Decimal inches. That must be American metric!
I've never understood dividing a foot into 12 inches, but I guess that makes sense if you're an architect.
Dividing an inch into 16 or 32 parts doesn't make much sense to me either, but 100 rocks.
I went to engineering school in the 70's, and we had to do everything in both systems.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon