Making bridges for vintage guitars using minimal tools
– a layman’s approach (Part 2).
I’ve approached this subject in 4 separate posts. It’s necessary to read the Introduction Post, Part 1, first or the other posts (Parts 2, 3 and 4) may not make much sense.
Part 1. Introduction, tools and a jig.
Part 2. 20th Century pyramid style bridge.
Part 3. Truncated pyramid style (or Chicago) bridge.
Part 4. 19th Century pyramid style bridge.
Part 2. 20th Century Pyramid Style Bridge.
I believe this style came into use about 1910 but I am open for correction. I really like this style of pyramid bridge. It was used by many manufacturers including Oscar Schmidt. By the 1930’s most manufacturers had phased out using this style (most likely to save on costs) replacing it with a simpler made bridge.
I’m starting with this style pyramid bridge because it’s probably what most people think of as a pyramid bridge.
Marking out the bridge design:
These are fairly standard measurements for a replacement bridge, the length slightly over the 6 inches and the width slightly over 1 inch to cover any ‘shadow’ on the soundboard left from the old bridge.
Positioning the bridge blank on the jig:
(See PART 1. INTRODUCTION for more detail about this jig).
The blank is positioned in the center of the jig with one of the ‘valleys’ under the line of the rod that is guided by the end blocks. It’s good to run the rod with sandpaper wrapped around it back and forth a few times to check that it falls in the center of where the valley needs to be. If the scrape marks from the sandpaper are not in the center it’s just a matter of repositioning the blank slightly.
Sanding the Valleys
After the blank is set-up on the jig, the jig can be screwed to a workbench. Then it is just a matter of starting with the roughest grit (80grit) sandpaper wrapped around the center of the rod and running this back and forth over the blank:
To achieve a result like this:
With 80 grit paper this only takes a few minutes work. I like to stop the bottom of the valley about 1/8” (3.5mm) from the base of the bridge. When it is getting close to that I step down to a finer grit sandpaper until that 1/8” mark is almost reached, then finer again until I am using 1000+ grit that sands almost to a polished finish. Then the blank can be reversed, and the other valley cut:
Filing and Sanding the Pyramids
Once these valleys are on the blank I like to take off about 2mm off the top of the proposed ‘pyramid’ ends of the blank. This is so that it does not stick up above the main body of the bridge when finished. I use a disc sander for this but could just as easily be filed off:
Then because I’ve sanded off my white guide lines I need to redo those. Then I either file or machine sand the end taper:
Using a file, I then taper the other 2 sides to the pyramid. Emery ‘buffer’ sticks are great to finish and smooth off the file marks:
Then it’s time to file and sand the other 2 sides of the pyramids:
Shaping the bridge body
After sanding the pyramids with 800 grit it’s time to shape the main body of the bridge. Lately I’ve just started painting on the profile I want to achieve, makes for less mistakes:I shape the main body of the bridge with both the disc sander and by filing it in a vice until I get close to the shape I want. While still in the vice I use sandpaper strips to sand back and forth to achieve a smooth curve. I use 400grit and then 800 grit for this. (Below photo is working this with the 19th century bridge (forgot to take a photo using this sandpaper with the 20th Century bridge):
Once I am happy with the shaping I take it out of the vice and sand with 1000 or 1500 grit and finish off with a micro-mesh 6000 polishing cloth (see tips at the end of this post):
Finished bridge, no coating, just polished:
End of Part 2; Links to the other posts about this subject:
Part 1. Introduction.
Part 2. How to make a 20th century pyramid style bridge.
Part 3. How to make a Truncated (Chicago) style bridge.
Part 4. How to make a 19th century pyramid style bridge.