Best way to radius the fingerboard?

[Mark McLean]

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"Originally Posted on: Mon Jun 14, 2010 10:59 pm

How do you all get a good radius on the fingerboard if the fret slots are already cut? I have a sanding block with a 16' radius concave surface which is good for finishing the job, but what is the best way to rapidly remove the 1mm or so from the outside of the fingerboard to get about the right curve? I have tried doing it with a block plane but when the fret slots are already cut I find the plane tends to catch the top of the slots and widen them a bit. But taking that much down by sanding is slow work. Got a good tip?

[Nick]

I usually 'roughout' some flats on the belt sander Mark then go in with the radius block. But I have done it with just the radius block & the 3M stickit paper that Stewmac sell. I double sided taped the fingerboard (with it going longitudinally away from you) to some MDF which was clamped to a worktop, this stops it trying to go anywhere while you lay into it. You can hold the radius block with both hands to get some good elbow grease into it.

[jeffhigh]

I use a tilted sled throught the drum sander to take off the bulk.
I cut slots afterwards anyhow cause I am using a handsaw.

[Allen]

Sillvan Wells does a very good explanation of the way I do mine. So here is the link.


Jigs to Crown the Fretboard

[jeffhigh]

Mine is similar but I put a fence along the lower side and at the end of the sled to give me consistent positioning.

[christian]

yip Allen thats the way i do it too,
although a more industrial way of radiusing them which i'm gonna action shortly is using your thicknesser as a profile shaper, remove the blades and get some radiused blades made up make sure they are long enough to cover at least two sets of nuts . line them up and tighten them in place
mark on your feed table where centre of the blades are and then lets say 30mm either side for your fretboard width,you can make a whole jig to place on the feedtable or just clamp a thin straight edge on the outsides of the lines to keep the fretboard on track, adjust your height feed your fretboard through hey presto one radiused fretboard.

Christian.

[Kim]

I made one of these jig and it works well, a light hand sand to remove some machine marks and the board is perfect.

6_radiusing_1.jpg (56.22 KiB) Viewed 18156 times

Plans are available from luthier cool tools:

http://www.luthierscooltools.com/Dwgs.htm

It is suggested that these will cut a compound radius but they won't, it just can't work like that, but for a straight radius they are real good and I do not see the need for compound especially on an acoustic. All done and dusted, if this one were somehow destroyed, I would take the time to build another.

Cheers

Kim

[Peter T]

I came up with a slightly different take on the router sled.

photoez.jpg (97.51 KiB) Viewed 18156 times

The upright piece of ply that you can see in the middle of the box is the same length as the radius and is hinged at the bottom. A fingerboard blank is stuck on with double sided tape. The turn screw system is from a cheapy vise that i picked up for about 10 bucks. I find this a very accurate system as the blank holder works as a large compass.
Some advise if you are trying to use a plane on a fingerboard with fret slots - First use a square edged file on an angle to chamfer the top edges of the slots slightly.- Use a longer plane.
Good luck, Pete.

[Dennis Leahy]

Very clever, Pete!

[Mark McLean]

OK, lots of ideas there. Thanks. I've just finished doing a board by hand with a radius block and lots of (cheap) sandpaper and elbow grease. Got a fair result but it is the last time that I will do it that way! I will be building a sled for the next one. cheers gents.

[J.F. Custom]

Not much more to be said here Mark but for what it is worth...

With respect to your exact question on a board that has already been slotted, sandpaper is the safest bet. So the quickest option, also that which I use, is as has been mentioned - the tilted sled through the drum sander.

Kim and Petes method would have less risk of chip out than a hand plane on a pre-slotted board, but still more than a drum sander due to the aggressive action of the cutter. Possibly most at risk would be the edges of the board in the direction of the travel. So if it were already profiled to the right taper too - it may prove too risky. At least if it were still rectangular and chipped along the edge you could plane that out when tapering. The use of a triangle needle file to bevel the edges of the slots would help lessen risk too. I have not tried this router method though so it is purely speculation on my part.

Finally Christians comment on the Planer/Moulder is a great option, one which I am in the throes of setting up. Bear in mind not all thicknessers have this capability - the set up is slightly different. I intend its use for raw fingerboards though - not for a slotted board. Ordinarily the safest cut through a thicknesser is when you feed at an angle to the cutters. In this case, that is not possible so the cut will be somewhat aggressive. Small passes required, particularly for figured material. I wouldn't like to try it on a slotted board though. Some timbers may be ok but I doubt something such as figured gidgee would surface scar free.

Anyway, my thoughts thrown in.

Jeremy.

[Kim]

J.F. Custom wrote:

Kim and Petes method would have less risk of chip out than a hand plane on a pre-slotted board, but still more than a drum sander due to the aggressive action of the cutter.
Jeremy.

When using the luthier cool tools jig I pre slot the board and it is tapered after the radius has been cut. I have not experienced any tear out whatsoever as the cutter used in this jig is a CMT bowl/tray cutting bit which, because of it's curvature, offers gradual increments of entry into the cut. With this in mind the word "aggressive" does not describe the process very accurately.

851.001.11_tn-01.jpg (8.15 KiB) Viewed 18156 times

Cheers

Kim

[J.F. Custom]

Nice Kim

As stated, it was purely speculation on my part having not tried it personally. It would seem there is no such concern after all. The use of a rounded bottom bowl cutter is good thinking for that too - I'm sure that helps your cause. Thanks for the feedback.

Cheers,

Jeremy.

[Allen]

Good point about the cutter Kim. I had made a similar set up to yours a few years ago now, but used a flat bottom cutter. Got hellish chipout on the edges of some wood.

[vandenboom]

I made up the jig described in the following post to OLF a couple of years ago.
Fingerboard radius jig-OLF Post: http://www.luthiersforum.com/forum/view ... 01&t=20318

It is just an inverted version of 'Peter T' design above.
I laugh at it now because it's just so big and rediculous, even though it does the job well. I slot, taper and bind fb first. There are a couple of other potential ideas/approach in the OLF post as well.
One thing I found I had to watch was binding - point of entry was fairly crucial. First time I tried it, the router ripped the binding of the side!!!

I like Kim's sled approach as it offers the accuracy and has about 10% of the storage space requirement.

Frank

[Lillian]

Kim, couple of questions for you sir, if I may.

How hard/difficult/time consuming/expensive was it to build the jig?

Was it worth the time/money/energy you put into it for you? Would you build another one if something happened to this one?

[Kim]

Hi Lil,

Yeah I would take the time to build another if this one were somehow destroyed, its a pretty useful jig.

It is not overly difficult to build but like all jigs, you do need to take your time and get it right as any mistakes you make will be reflected in the output making the whole concept of repeatability pointless.

The jig has a relatively small footprint and can be hung up out of the way. This point gives some indication of the amount of ply used, and other than a few of bolts, screws, bearings, washers, springs, wood and aluminum angle there really is nothing else to it.

The jig operates by allowing a carriage, to which the FB is secured by double side tape, to ride upon matching pairs of radius cams. These cams are cut from a printed template and range from 24"down to 12" with singular cams incrementing down to 7.5".

It is maintained that the jig can accurately cut a "compound" radius. That is to say that by placing a 22" cam at one end of the carriage and a 9" cam at the other you can achieve a compound. This simply cannot work as the rigidity of the carriage board to which the fret board has been secured, demands that the bearing follow one radii or the other, it simply cannot follow both without the carriage twisting and if the material the carriage was made from were supple enough to allow that to happen, it would hardly be suitable choice as a bed to support the FB whilst it is being cut.

This point aside, the jig is really good for cutting a singular radius and that is what makes it worth while. Using it and may table saw, I can take a bit of stock and have it accurately slotted with a radius cut and finish with a tapered fretboard in no time at all. Best of all, turning out another exactly the same is no challenge at all so for a 'standard' like ebony in a 25.4 scale, you can set up and run as many off as you like, throw them in stock and hang the jig out the way.

Cheers

Kim

[Lillian]

Thanks Kim. That's just what I wanted to know.

Now to find time.

[tim mullin]

Peter T wrote:
I came up with a slightly different take on the router sled.
The upright piece of ply that you can see in the middle of the box is the same length as the radius and is hinged at the bottom. A fingerboard blank is stuck on with double sided tape. The turn screw system is from a cheapy vise that i picked up for about 10 bucks. I find this a very accurate system as the blank holder works as a large compass.

Hey Peter, I think that is rather clever, and perhaps easy to redesign for multi-radius by simply putting moveable pivot points at each end of your upright piece, rather than a fixed hinge at the bottom.
Personally, I never radius more than 2 fingerboards in a given day, so radius sanding blocks get the job done and give me some exercise. But I'm intrigued with the possibilities to develop Peter's design further.

[Peter T]

Thanks for the comments Tim. You are spot on with your suggestion of the movable pivots. My original sketches that I prepared had multiple pivot points with a slot system in the end of the box. I never followed through with this as I decided that I only ever use 1 radius (16") and took the short cut. I actually came up with this idea after seeing the eBay add for the plans for kims jig. Being a cheaparse I decided I didn't want to part with my hard earned and set about solveing the problem my own way. The jig was quicker to build than to hand plane and sand the fretboard on my first build. Next improvement on the wish list would have to be a vacuum system to hold the blank in place. It takes just as long to scrape the double sided tape off as it does to do the routing.
Cheers, Pete.

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