# Idea: conical sanding drum for making compound radius fretboards



## russmuller (Jan 5, 2015)

I saw another thread about making a drum sander (with a link to this page) so I figured it would be worthwhile to throw this out there for feedback/advice. I'm interested in making guitars with compound radius fretboards, but I don't have a clue how to accurately or consistently make them. Then I had a crazy idea (one I'm sure others have had at some point) that seems like it could yield consistent results without having to program a CNC. I'm not really familiar with the techniques used to execute a compound radius otherwise, so this was what popped into my head.

I know that the risk of tearout is higher when using powered blades on figured wood, so sanding is typically the best option. Couldn't one make a large conical sanding drum where the sanding surface is on the inside of the cone? Imagine a section of a cone long enough that the fretboard can fit inside, with an interior radius of 16" at one end and a radius of 20" at the other. Line the inside with sandpaper, spin it on a belt, and voila!

There's a drum company near me that specializes in stave drums, and I thought it probably wouldn't be too hard to make a cone using that method. I imagine it would be pretty big (at least 40" diameter at the big end), and probably difficult to true the inside of it to a perfectly conical surface. What do you guys think? Has this been done? Am I nuts? There are probably simpler solutions than this, but I thought it was a neat idea.


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## DistinguishedPapyrus (Jan 5, 2015)

I had an idea one time to make a compound radius sanding jig with a long straight rail, and two different radiused guide pieces at each end just past the fretboard ends... if that makes any sense. 

I see where you're going with your idea, I have thought of something similar myself. I thought about the exact same thing you're saying but instead of an entire rotating drum, just about a 12" wide section of the cone sitting stationary on a bench top, and you manually slide the neck side-to-side inside the jig. 

Like a compound radiused sanding beam, but 12" wide and 20" or so long, sitting flat on a bench, radiused side up, lined with sand paper on the inside. Lay the neck face down on top of it and sand side to side. The problem is you'd have to slide it very precisely. A jig of some knd would be ideal for the movement of the neck across the radius.


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## russmuller (Jan 5, 2015)

Making a stationary sanding beam and moving the wood is probably an easier solution (provided there's a jig to keep the sanding motion radially back and forth like you said).

You could probably also design it such that it wouldn't allow you to sand the wood to shallower than 1/4" so you don't accidentally sand it too thin when using coarse paper.


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## Pikka Bird (Jan 5, 2015)

^The advantage with the adjustable arms swinging over a sanding surface (a long belt sander, for instance) is that you can adjust both the nut-end radius and the rate at which the radius gets larger towards the end.


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## russmuller (Jan 5, 2015)

Excellent point! What I'm envisioning now is actually a flat sanding surface laying flat and the fretboard swinging like a pendulum but with adjustable arms to set the radius at either end of its arc. MUCH more flexible than my idea as the sled that mounts the fingerboard can be adjustable in length to accommodate any scale length.


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## TonyFlyingSquirrel (Jan 5, 2015)

I used to work at Warmoth, and the Compound Radius jig is a "one off" piece that swings without any way of altering the radius. 

Their other Jig on another machine is adjustable from fixed radii up to 16".

A good pic is on their website under "Factory Tour" and you can also see another example on Grizzly's website as they have a rediculously overpriced machine that does this.


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## russmuller (Jan 5, 2015)

TonyFlyingSquirrel said:


> I used to work at Warmoth, and the Compound Radius jig is a "one off" piece that swings without any way of altering the radius.
> 
> Their other Jig on another machine is adjustable from fixed radii up to 16".
> 
> A good pic is on their website under "Factory Tour" and you can also see another example on Grizzly's website as they have a rediculously overpriced machine that does this.



Warmoth Custom Guitar Parts - Shop Tour


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## DistinguishedPapyrus (Jan 5, 2015)

yep... basically that, but something I can put in my garage without a multi thousand dollar price tag.


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## TonyFlyingSquirrel (Jan 5, 2015)

Those images are basically.
#1, fixed radius jig, part 1
#2, Compound radius jig
#3, fixed radius jig, part 2

That guy's name is Boon & he's been there for nearly 30 years, not long after Ken & Paul Warmoth started under the Warmoth brand after working for their dad doing Boogie Bodies.


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## immortalx (Jan 6, 2015)

Just throwing ideas here, but please don't laugh at my drawing skills 






It's basically a compound radius sanding beam (steel or some kind of exotic plastic material?) mounted on 4 actuators (hydraulic or mechanical, i guess) inside an edge sander. The beam moves vertically in small increments while the belt is running and the fretboard is secured to the table underneath.
I doubt I could ever build such a high precision machine  but I believe it should work as an idea.


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## GXPO (Jan 6, 2015)

If you just had a conical radius template sitting under the belt sander, couldn't you basically accomplish the same thing? I think that's basically what Warmouth are doing but with a fancier setup for standardisation purposes..

Once the shape is roughed in you'd be completing the finer sanding with a straight block anyway I assume. I may be under thinking this.


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## immortalx (Jan 6, 2015)

Warmoth's jig (the middle one as Tony described) seem to have no template under the belt sander, just a flat surface. It's the swinging arms with different radii of rotation that do the job. The other Warmoth jig works with the same principle but both the arms have the same radius.


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## Manton Customs (Jan 7, 2015)

If you're careful a router jig will work just as well and possibly require less fine sanding (sanding belts are generally very coarse). Here is a jig which you can make compound radii on, we use a very similar version. It's much simpler to make than a sanding jig and wont cost much to make. Fingerboard Radius Jig for Router | TalkBass.com


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## immortalx (Jan 7, 2015)

Manton that's a very nice and well constructed jig!
Talking about jigs here's mine that I posted some time ago here :





Just like a sanding belt, it has coarse sandpaper but requires minimal sanding afterwards.


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## Cpt_Adama (Oct 26, 2020)

I know this is an old post, but for reference for the future, the Grizzly G0574 - Guitar Fretboard Radiusing Sander is the same kind of tool as the Warmoth for a reasonable price $1,050 + $129 Freight, if you are doing more than a one of a kind.


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## KR250 (Oct 26, 2020)

I keep meaning to build a jig like this one for neck shaping: 

Simple and cheap, though for a fretboard might be a challenge to get the radius wide enough with this style of design.


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## pondman (Oct 31, 2020)

I had a thread for one I made a few years ago but I cant find it now.
This is how I made mine.


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## pondman (Oct 31, 2020)

I had a thread for one I made a few years ago but it seems to have gone.
This is how I made it in pics. It didn't take a great deal of time to knock up.
I loaded the pics up in the wrong sequence so look from the last pic upwards.


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## Cpt_Adama (Oct 31, 2020)

pondman, thanks for those pics, awesome. Looks like it is only one radius size though. I might suggest instead of angle iron for the verticals you could use square tubing and have another tube inside the outer that could rise and lower so to change the radius as needed.


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## pondman (Oct 31, 2020)

If you look carefully you'"ll see that the top can be raised or lowered for any radius.


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## Cpt_Adama (Oct 31, 2020)

pondman said:


> If you look carefully you'"ll see that the top can be raised or lowered for any radius.



Doh, I just assumed that was for attaching it to the crossbar, now I see what the longer threaded shaft and nuts are for, brilliantly simple. good job.


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