Tuesday, May 27, 2014

Tenor Guitar Fret Board

 This tenor guitar has a 23" scale length.

To determine the spacing between the frets and from the nut to each fret bar you have to do some math.

Who doesn't love a good math equation =)

The magic number to figure this out was derived from the Greek Philosopher/Mathematician Pythagoras and refined over the years to 17.817.

A good article to read about calculating fret positions can be found here. If you want to totally geek out, click here.

To find the fret spacing on any stringed instrument, you divide your scale length by this magic number to get your first fret position from the nut.

Next, subtract your first fret position from the nut from the total scale length, then divide by the magic number, 17.817.

Repeat until you reach the total number of frets you plan to cut. I used Excel to create this sheet and a conversion chart of decimal inches to find the closest fractional inch.

The first fret should be 1-9/32" from the base of the nut slot, the 12th fret should be at 11-1/2", and the 14th fret should be at 12-3/4".....

Side note: When I checked where the neck meets the body I noticed my drawing was 3/8" off, so I'll have to redraw my plans for my next tenor guitar build.

Once I drew all the lines with a straight edge and 90° square, I made a few photo copies at a local drafting shop and cut out my fret board template.

Prefab 23" fret board templates can be found at Stew Mac or LMII, but I chose to do it from scratch so I could, theoretically, reproduce any scale length going forward.

I cut out a little over 2" wide plexiglass and taped my template over the top and used scarp pieces of wood on the top and bottom so I could clamp to my work surface.
I notched the plexiglass with a hack saw and another small scrap piece to line up with my fret line. I tried to line up the saw blade with the middle of my line as close as possible.

Note: I had to re-cut this template because I cut the middle of the nut line at the top of the fret board instead of using the inner most width of nut line as the end point.

If I didn't re-cut the nut line to make a new template, I would have been 1/64th off at the 1st fret, then it would've thrown out the spacing and, most likely, the intonation across my entire fret board :(

Using a cross cut jig with a razor blade as my marker, I methodically slotted a couple fret boards using the Stew Mac fret table saw blade.
Next up..... attach top and neck...

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