Fretboard Radiusing Accuracy

[Jockson]

I'm trying to radius a fretboard using a radius sanding block and I'm not getting very good results. The board ends up straight at the center but the sides are always a little uneven and "over radiused" at places (I can see that when I put the Stewmac fret pressing caul against the fretboard). I think the reason for that is my inability to keep the block perfectly aligned at all times.

How accurately do you guys do this by using this method (radius sanding blocks)? I would use a router jig but it would be hard to set it up now as the fretboard is already glued to the neck. I'm not really a fan of "close enough is good enough" approach but if I get it right within say 0.2mm across the whole board, is that good enough considering I have to level the frets later (and therefore "fix" the problem)? I don't want to keep sanding as the board could end up being too thin and the radius that I'm getting is not getting any better.

Any advice, tips or perhaps an alternative method? Is it worth the effort to set up a router jig now?

[Jon]

I would not use a router jig on a neck that has the fingerboard already glued to the neck - you would have to go to a lot of trouble to make sure it is flush if the neck is already carved.

Regarding your technique - it sounds like you're focused on small areas. You're supposed to take long strokes, not focus in 4-8 inch areas at a time. Use a straight-edge and measure frequently, it wont take too long to get a nicely radiused fingerboard.

[SwedishLuthier]

You are right about the reason to why this happens. If you angle the block slightly your edges will be over radiused. I use a simple jig that holds the fret board using double stick tape and have fences that keep the block aligned. But that is before I glue it to the neck.

A very simple tip that might help you to keep the block straight is to draw a pencil line along the centre of the block. That gives you a visual guide to keep the block aligned. That’s how I did before I made my jig.

[biliousfrog]

I'll just add to SL's response by saying that you could also draw a line down the center of the fingerboard (white chinagraph pencil is good for dark woods)...Not only does it help to keep the block straight but when the line has gone you've radiused the board.

[P90]

Jockson.. are you using just one block for a continual radius... or multiple blocks for a compound radius?

[low end fuzz]

i get a compound radius by using 1 -14" long readius block that is approx 70mm wide;

doing each side riding the taper along the edge (so its tight at the nut and still flat topped at the bottom)

then grab a 15" straight edge (1"wide)(mine is heavy ebony) and go over the same stlye of following the taper 1"at a time

do it with 60 grit your done on rosewood in 7 mins

[johnsilver]

I use a simple jig that holds the fret board using double stick tape and have fences that keep the block aligned. But that is before I glue it to the neck.

+1.

The jig works great. Make long stokes. I change position and direction from time to time keeping the number of strokes relatively the same in each direction.

[guitar2005]

I guess that one of the key things here is to radius the board BEFORE the fretboard is tapered so that you can guide the radius block along a fence. Make sure you use long strokes that span the entire length of the fretboard.

First time I radiused a board, I did it on a tapered board. It worked out allright because I used long, slow strokes but its much easier with the fretboard straight.

Another tip: Check the radius block radius against the Stew Mac fret press caul radius. You may find that they're not an exact match if you did not get your blocks from Stew Mac.

[GuitarGuy]

Another tip: Check the radius block radius against the Stew Mac fret press caul radius. You may find that they're not an exact match if you did not get your blocks from Stew Mac.

Unless the radius block is brand new it will most likely never be an exact match. Wood moves unless you have them painted and sealed and even then they fluctuate with temperature and humidity. not much you can do about it besides getting aluminum blocks. even so The difference between a 9.5 radius and a 10 radius is marginal. If you put the two beside each other you would be hard pressed to tell the difference.

The main thing that is important is that the neck is true down the length. As long as the radius is close thats all that matters.

[Supernova9]

I guess that one of the key things here is to radius the board BEFORE the fretboard is tapered so that you can guide the radius block along a fence. Make sure you use long strokes that span the entire length of the fretboard.

First time I radiused a board, I did it on a tapered board. It worked out allright because I used long, slow strokes but its much easier with the fretboard straight.

Radiusing should be done after tapering - have you tried using a router to taper a radiused board? Mark the centreline of the fretboard, then set your fences apart from that centreline, so say your radius block is 4" wide, draw the centreline on the fretboard, tape the board down on a flat surface, then measure 2" from this centreline on either side, and that's where you fix the fences. Then just sand away.

[Mattia]

I radius (with a router) and then taper (with a hand plane). If I blow out an edge with the router, at least I plane it away.

[Jaden]

serious question here, if the radius block is a constant radis - which it is, why would moving it across the fingerboard make any difference ?

as long as you stroke the block along the entire length of the fingerboard, tapered or not and assuming that you make contact between fingerboard and sanding block for the entire length, why and how could the board be over-radiused ?

Jaden.

[Mattia]

serious question here, if the radius block is a constant radis - which it is, why would moving it across the fingerboard make any difference ?

as long as you stroke the block along the entire length of the fingerboard, tapered or not and assuming that you make contact between fingerboard and sanding block for the entire length, why and how could the board be over-radiused ?

Jaden.

Because your hand doesn't apply even pressure across the entire width, evenly, so things can go a little lopsided, quickly.

In theory, you're right of course. It shouldn't matter. But experience shows it does.

[Jaden]

serious question here, if the radius block is a constant radis - which it is, why would moving it across the fingerboard make any difference ?

as long as you stroke the block along the entire length of the fingerboard, tapered or not and assuming that you make contact between fingerboard and sanding block for the entire length, why and how could the board be over-radiused ?

Jaden.

Because your hand doesn't apply even pressure across the entire width, evenly, so things can go a little lopsided, quickly.

In theory, you're right of course. It shouldn't matter. But experience shows it does.

ah, of course !

to be honest, I took that aspect of the procedure as given....

Ive re-raduised two fingerboards to date - not a wealth of knowledge I know but... they have both been spot-on !

as long as even pressure is applied across the sanding block and long even strokes are taken, everything should be cool !

or am I missing something ? - I always check my work with a radius gauge and so far - no problems...

[guitar2005]

Another tip: Check the radius block radius against the Stew Mac fret press caul radius. You may find that they're not an exact match if you did not get your blocks from Stew Mac.

Unless the radius block is brand new it will most likely never be an exact match.

... Whatever... Its still a good idea to have the radius block and fret press caul to match as close as you can.

If they don't match EXACTLY, its better to have a slightly tigher radius on the board rather that the opposite. With pre-bent fretwire, it should fit snug.

Good luck

[Jockson]

Thanks for the advice guys. I'm using one block for a continual 12" radius and a matching fret pressing caul. The block is not from stewmac but it's supposed be the same radius. When I compare them now, they indeed do not match perfectly (have to look really hard to tell the difference, however). The radius on the block is tighter, so I guess at least that is a good thing

I will try the suggested method and if that doesn't work for me, I'll set up a router jig if the fretboard doesn't become too thin already. I didn't carve the back of the neck yet so it's still square. So although it will be hard to set up the jig now, it won't be impossible.

[carousel182]

this thread save my fretboard lol i almost forgot to check it

[TechArt]

If anyone is interested in having any boards radiused/slotted/cut for inlay, please let me know. I've got a CNC & would be happy to work something out.

Thanks,

Trev

[SwedishLuthier]

if the radius block is a constant radis - which it is, why would moving it across the fingerboard make any difference ?

as long as you stroke the block along the entire length of the fingerboard, tapered or not and assuming that you make contact between fingerboard and sanding block for the entire length, why and how could the board be over-radiused ?

That is not the biggest problem. The worst case is if you use the block at an angle compared to the centre line of the fret board. If you have a radius gauge, pick it up. Look how the radii changes as you slowly spin the gauge so that you at the end are looking at the edge of the gauge (can’t really explain it better but I hope that you get the picture). That is the same thing that will happen if the sanding block isn’t perfectly aligned with the fret board. But there we are not talking a thin gauge. Because the block is longer it will start to reshape the edges of the board and you will get exactly the result that Jokson describes.

I prefer to use sanding blocks for the shaping of the board. Then I make sure that the board has uniform thickness by using a long aluminium sanding stick, taking light strokes and double checking with a radii gage to make sure that I don’t change the radii by mistake.

[Mickguard]

This thread comes at just the right time for me...

Here's a question:

The board I need to radius to 12" is 7 mm thick. It has already been shaped to the dimensions of the neck.

I plan on placing L-shaped rails along side the board that will stand at the right height to stop the radius sander thingamajig from going any deeper. The vertical side of the rails will be used to keep the sanding block more or less in a straight line.

What I need to figure out is at what height the horizontal part of the rails needs to be set --I want to remove a minimum of the fretboard.

So, do any of you math types know the formula I'd need for calculating this?

Or maybe this isn't that important...I should just go with the thickness of the rails I find?

And do you think the idea of using the L-shape is unneccessary? I figure I'll set them just barely wider than the radius block to allow for a smooth movement. (And maybe I'll attach a handle to the back of the block).

I screwed up my first try at sanding/radiusing a board...I'd like to get it right this time!

[SwedishLuthier]

The L-shaped part might be a really good idea. You will get an uniform thickness along the centre line. The downside is that your fretboard edge will taper from slightly thicker at the nut to thinner near the body. Most guitars are made that way, but I always sand my fretboards so that I get a uniform thickness at the edge. That gives me a fretboard that is thicker (about 0,7mm on the last one, measured at the centre line) at the body end.

I have never seen a formula to calculate the thickness of the “L-part” needed, but I did a quick sketch in TurboCAD and came up with the thickest measurement possible to use with radius blocks that are 2 374 wide (stewmac). You should use a max thickness of an even 0.5mm. If you use that the fretboard will keep the 7 mm thickness at the centre. It will be 6.3mm thick at the nut (if your fretboard width is 42mm) and 5.6 mm at the body end (@55mm width).

And yeah, a handle will come handy if your fences are much higher then say 10mm

[Mickguard]

The L-shaped part might be a really good idea. You will get an uniform thickness along the centre line. The downside is that your fretboard edge will taper from slightly thicker at the nut to thinner near the body.

Why is this? I'm not sure I understand what you mean.

At any rate, I picked up a couple of L-beams today. But then I realized that the sanding block is only slightly wider than the body end of the fretboard--so the beams won't really work the way I want them to, because they're too wide. Instead what I'll end up doing is use the beams to set the depth of the fretboard edge (which should be uniform for both sides of the fretboard along the entire edge? ), and just use one of the vertical walls as a guide for the radius block.

Another option is to make my own L-beam --there are smaller, thinner flat bars availalbe, I could glue one of those to the wall of the beam.

Anything to keep me from screwing up again!

There's no rush...my telecaster is ready for wetsanding and polishing...think I'll do that this weekend instead...

[Mattia]

The L-shaped part might be a really good idea. You will get an uniform thickness along the centre line. The downside is that your fretboard edge will taper from slightly thicker at the nut to thinner near the body.

Why is this? I'm not sure I understand what you mean.

Simple, really: your radius is constant. Your fretboard gets wider as you move up the neck. If you have the same arch along the entire length, and the same thickness down the middle of the board, the edge of your board (Because you've tapered it) gets thinner as you move up the neck/as the fingerboard gets wider.

Easier thought experiment: say you radius a squared fingerboard blank. Even thickness down the centreline, even thickness down the edges. Now mark the taper. The edge thickness at the headstock end will be more than at the body end. A properly calculated compound radius board, on the other hand, will have even thickness down the centreline, and even thickness along the edges.

[Mickguard]

Okay, I get it now...thanks.

I'd be interested in tapering the last few frets, but not the whole board. So I need to find a better way...think I'll just go simple, with SL's line on the back of the radius block (and Bilious' line on the fretboard too) and just take it nice and slow. Worse comes to worse, I'll have to shop for a new board...

[Jockson]

I sanded the fretboard some more and it became even worse even though I drew a center line on the sanding block and sanded carefully. Then a friend of mine helped me to set up a router jig and it's perfect now! It took us a few hours but it was worth it

BUT, the board is now 5mm thick at the center. Is this thick enough?