Fret position saw width compensation

Jonathandj

I use digital vernier to measure from the nut end to a position where I clamp an engineering square, against which I cut using a .58mm saw. The measurement I use is the calculated distance according to the scale length tables PLUS half the width of the saw. This means, according to my reckoning, that the middle of the cut will be exactly on the correct position which in turn means that the centre of the fret crown will be precisely correct. I cannot find any opinion on this and most literature is silent on what could be a .29mm error if not done. Does anyone have an opinion. My first solid body using this method sounds awesome and I wish to confirm this issue as I am about to cut for my LPS replica.

AlanRatcliffe

That'll work fine. Or just move your nut by the same amount. ? Don't forget that with many guitars the slots are cut (and often fretted) before the fingerboard is fitted, so that method works fine as long as you fit the fingerboard and bridge correctly.

Plus wood varies with temperature, equal temperament is an approximation, blah, blah, etc. So the tightest recommended tolerance you'll find is .25mm.

Shibbibilybob

And it's damn awesome that you're building your own ?

Wizard

We could do the maths and translate measurement tolerance into cents of pitch.
A given error would affect the higher frets more than the lower ones.

General wisdom is that people have a pitch tolerance of 5c.
I wouldn't be surprised though if our resident forum Chuck Norris could improve on that
?

AlanRatcliffe

Wizard wrote: General wisdom is that people have a pitch tolerance of 5c.
I wouldn't be surprised though if our resident forum Chuck Norris could improve on that
?

Many players have a 2-3c tolerance in my experience. And that's relative pitch, so if one note in an interval is flat by 1c and another sharp by 1c, they'll hear it. Although as I've said before (in another way), the advent of digital tuners has created a generation of lazy ears.

The poor buggers with perfect pitch... well, they rarely play guitar...

lapdawg

Measuring accurately and cutting accurately are different things.
I suggest you get / make a good mitre box. There are printable templates online. I have a few pdf's & can send you them if you need accurate scales. Gibson used the Rule-of-18 scale for a long time & the older LP's use that scale. I am not sure when they dropped it, but I think it was some time in the 70's. Its not completely mathematical, but sounds "musical" - at least that's what I read.
In terms of measuring up ascale, you won't find a better account than this:
http://www.mylespaul.com/forums/luthiers-corner/171960-24-625-scale-24-562-scale.html#post3300766

Please tell us more about your build - I had to double check to that I was on page 1 ofthe thread. Have you built any other parts?

Also, to make a fingerboard have you worked out

Radiusing the board and bending the frets to the radius
Getting the depth of cut correct
Getting the width of cut correct - if too narrow your board will "curl" etc. etc.

kholmes

There is an in depth article on this subject, on the internet, - of course I now can't remember the guy's name !, - where he has done a whole shipload of research and has come up with moving the nut as much as 0.75mm closer to the first fret, the rest of the frets are spaced as calculated for your string length. And then shaping the saddle break point for each string (as you see done on top-end guitars) by chamfering the saddle either forward or back, - different for each string. Sorry I didn't keep the url, but keep googling the topic and I'm sure you'll find it. For individual fret spacing positions, I use a scalpel to score the fret positions and then saw freehand (carefully!) and using a digital tuner find I can fine tune and re-crown any frets that are not quite right. Remember that as the guitar ages and the frets wear, the fret crowns flatten altering "fret position" by as much as the width of the fret!and may need re-crowning/replacing. It all comes back to how much of a perfectionist you are and if you're such a maestro that a few c's can be blamed on fret positioning and not your own attack or slightly high action.!

Jonathandj

Thanks to all for the wise replies. On my first SB electric I cut the slots, using the method of saw width compensation, while the fret board was still perfectly square. Once done, to a depth of two mm I then cut the taper and sanded a 12 inch radius, after putting on the markers. I then glued it to the neck with Gorilla glue and then shaped the neck to design. All worked out great. The intonation was easily set from fret 12 which probably confirms the accuracy. I have been using maple for the neck, African mahogany for the body and Madagascan rosewood for the fret board on the semi hollow Les Paul special I am busy with. My first SB was a maple body with a Kiaat top and although my blues maestro son likes the sound, the instrument is very heavy. I will get back to modifying it one day. I have found that the rosewood must be quarter saw as flat sawn bends unrepentingly after it has been planed. I have a pile of scrap to prove that.

lapdawg

OK - sounds good.

Some general advice I have followed:
- Don't use gorilla glue. Use hide glue. Its not easy, especially for gluing finger boards. My current thread will attest. Make sure your surfaces are VERY flush before gluing. The main reason for not using conventional wood glue is that it places a rubbery film in the joint. Hide glue sets very hard, this stops muffling and damping of your sound. The closer you are to the vibrating string, the more this holds true. So, use hide glue or fish glue bind your frets in place. Fish glue is easier because it sets slowly. Titebond liquid hide glue is a good option to get around the difficulty of learning to use conventional hide glue. Unfortunately, I don't think you can find these glues in SA.
- Do you have a radius sanding block? It is a really import tool. If you have a long one, you can also clamp against it when setting the fingerboard to the neck - it really helps keep things straight.

Also, rule of thumb on the forum - give us some pics!

Jonathandj

Thanks for the advice! I have made a radius sanding block using thin veneer layers attached to a large block with edge shims which works well. As for glues - I live in Zululand where hardware supplies other than mainstream stuff are unobtainable. Hence my glue options are limited to Gorilla (got down from Jhb for another ww project), off the shelf wood glues, or good old GP epoxy. Is hide glue obtainable from Cape town or Jhb? If so I would be grateful for the details. I am also intending to use a spray reaction lacquer on my current project. I have never used the stuff before and look forward to a steep learning experience - any tips? I am still trying to figure out how to attach pics to my posts?

lapdawg

For pic posting:
http://www.guitarforum.co.za/how-to/how-to-post-pictures-t4055/

You can make your own hide glue - but its a fair amount of work. See my current thread - I made my own & it work well. You can otherwise buy it from www.stewmac.com or on eBay.

I have no experience with finishing - I haven't got there yet. there is a wealth of advice on this forum re lacquer though. I'm sure someone will advise.