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bertbass

FRET SLOT CUTTING JIG

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Posted (edited)

When I've made basses before, to cut the fret slots, I've used squares and various blocks of wood to try and get the slots square and vertical.  This worked OK but was time consuming.  Now I have the urge to make a couple more I got to thinking, is there a better way?

I could perhaps buy a mitre jig but they are a tad expensive or perhaps I could make or buy a tiny table saw with a 1mm blade and then use a slotted rule for fret positions.  That could take quite a while to design and build.  So what to do?

 

NCJ 1.jpg

 

Having a laser cutter / engraver the obvious solution for me was to make one from 6mm thick acrylic.  I calculated the fret spacing for a 30" scale and then designed the fret slot cutting jig this was transferred to the laser cut and cut out.

 

NCJ 2.jpg

 

The individual pieces were then glued together. Once the glue had dried, a quick pass through the band saw saw the jig nearly finished.  The edges were sanded and polished to make it a little more professional looking and the finished jig looks like this.

Just a quick buff needed to get rid of the excess glue marks.

NCJ 3.jpg

The jig sits over the fretboard blank.  The fret cutting saw just fits in the slots and the acrylic being 6mm thick should hold the saw square.  I'll let you know how well it works after I've tried it. 

Edited by bertbass
Place photos properly
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Good luck.  I'm interested to see how durable this jig will be.

57 minutes ago, bertbass said:

I could perhaps buy a mitre jig but they are a tad expensive or perhaps I could make or buy a tiny table saw with a 1mm blade and then use a slotted rule for fret positions.  That could take quite a while to design and build.  So what to do?

Then you said:

57 minutes ago, bertbass said:

Having a laser cutter / engraver the obvious solution for me was to make one from 6mm thick acrylic.

Why didn't I think of that before?  I'll just go and find mine.

Heeheehee

More seriously, is there a reason you can't use the cutter engraver directly on a fretboard?  Is it just going to cut right the way through or what?

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4 hours ago, bertbass said:

Just a quick buff needed to get rid of the excess glue marks.

NCJ 3.jpg

The jig sits over the fretboard blank.  The fret cutting saw just fits in the slots and the acrylic being 6mm thick should hold the saw square.  I'll let you know how well it works after I've tried it. 

I love the template!  But I can't quite work out what shape this is and where the fret saw goes??

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I’m guessing there are two strips top and bottom running horizontally that the vertical pieces are glued to and the fretboard sits between these (if that makes sense!!)

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Posted (edited)

Sorry for the tardy reply but I've been a bit busy.  In my enthusiasm to post I'd assumed that what was in my head would have been easily understood by all, however, what is is in my head is quite often not understood by even me so my apologies for not explaining properly.

 

To answer your questions,

On 08/10/2020 at 17:06, SpondonBassed said:

Good luck.  I'm interested to see how durable this jig will be.

Then you said:

Why didn't I think of that before?  I'll just go and find mine.

Heeheehee

More seriously, is there a reason you can't use the cutter engraver directly on a fretboard?  Is it just going to cut right the way through or what?

A couple of reasons really.  The laser only cuts a slot 0.1mm wide so although the slots would be perfectly spaced they'd still need opening up with a saw, also, although the laser in a precision machine in operation, setting the work pieces in place isn't, so a great deal of trial and error is involved getting things square.  This isn't a problem normally but if I wanted to cut fret slots square to a fret board, I'd only know if I'd got it right after it's finished cutting.

 

Secondly, The varying density of the wood being cut effects the cut which means that it is not uniformly consistent over the whole piece of wood, so a hard bit of wood in the middle of a fretboard would result in a slot being less deep than the others and could even end up burnt.  I have used the laser to cut a fretboard for the long term P bass that I'm making and here's a photo of the results.  When I say P bass, I don't mean precision I mean Pallet, as in made from pallets.  If I eventually finish it I'll post its construction.

 

NCJ 5.jpg

 

To answer the other questions, here's a photo that hopefully illustrates the principle behind my thinking.  That's not actually a fretboard, it's just a bit of wood that I had laying around.

 

NCJ4 .jpg

Edited by bertbass
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Ah - I see now.  Thanks. 

That said, I'm still not sure how you cut the fret depth...is the bottom strip half cut?

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How does this work if you have a tight radius, say like a Jazz.  Will the saw " curve " over the radius so that the fret cut is the same depth all across the fretboard ?

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5 hours ago, fleabag said:

How does this work if you have a tight radius, say like a Jazz.  Will the saw " curve " over the radius so that the fret cut is the same depth all across the fretboard ?

In relation to this question and not really the build, sorry @bertbass.

Does it matter if the bottom of a fret slot doesn't follow the radius of the board? Is just cutting them flat and then tapping/glueing the fret in so that middle is hollow underneath OK, or is that a big no no. I assume it's better if the slot base is radius'd but is it vital? 

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Thats my reasoning for asking.   If the saw goes across a tight radius, say a Jazz, in a straight cut, then the middle bit of the cut will be lower than the edges, and as you say Maude, there will be a slight hollow under the middle of the fret.

I dont know either if its ok or not.  Never built a neck   :)

 

Edited by fleabag

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Just my opinion.......

If you buy a pre-slotted fretboard, the board is generally not radiused and the fret slots will be a uniform depth. Many luthiers will use a specialist, thin circular saw to cut the slots and home builders often use the StewMac fret slotting jig, again both of these cut a slot parallel to the bottom of the fretboard and therefore when the frets are fitted, there will be a small gap behind the fret when fitted. You can get a guide that fits to a fretsaw to control the depth of cut. If you were slotting a radiused board then this would give you a slot that follows the radius.

Does it make any difference? I have seen a website for a boutique builder (can't remember who) that claims these voids cold be heard but I tend to be a little sceptical and wonder if it did, could the vast majority of us notice and why do we always assume things like this have a negative impact. When a fret is fitted it is the bottom of the fret that is the contact area with the fretboard, the tang with it barbs is there to prevent the fret from coming out. Some folk will glue frets in that might fill this void, some don't. I think getting the slots in the right place as not to affect intonation is probably the most important thing and what we would notice if it wasn't correct. That's where accurate jigs like this come in.

As  say, just my opinion!!!

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4 hours ago, fleabag said:

Thats my reasoning for asking.   If the saw goes across a tight radius, say a Jazz, in a straight cut, then the middle bit of the cut will be lower than the edges, and as you say Maude, there will be a slight hollow under the middle of the fret.

I dont know either if its ok or not.  Never built a neck   :)

 

Most fret slots are flat bottomed.

The critical thing is that the slot has to be deeper than the fret tang across the whole length - even after radiusing the board - otherwise the fret won't seat.

The fret is wider than its tang and so seats on the surface of the board and therefore follows any radius the board happens to be.

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The simple answer is no, it won't follow the radius of the neck.  All the fret slot cutting videos I've seen show a cut straight across the fretboard whether it's radiused or not and it would seem from the replies above that the jury is out on this one.  All the fret cutting jigs that I've seen, that are available to buy, only cut a flat slot.

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