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PostPosted: Tue Feb 19, 2008 6:23 pm 
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I was kind of stalled making progress with my first guitar until I had made a couple of jigs that I wanted. These were a compound radius router jig for doing the fretboard, and a Fleischmann derivative flying router binding jig. I decided to build them into one work unit.

Here are some pictures of the jig I built for routing a compound radius on fretboards (12" radius at the nut end and 20" radius at the soundhole end). The original designer of this type of jig is Mario Proulx (of Proulx Guitars fame) who has a brief description and some photos of it on his website - kudos to Mario for thinking of it first (way back in 2003 or earlier I believe!). I found out about Mario's original after I'd started work on my version! Great minds think alike, they say (or is it "fools never differ"? :lol: ). I checked with Mario first before posting, to make sure he was okay with it, and of course, like the true gentleman he is, he had no issue with it at all. Thanks Mario [:Y:] [clap]

My version of this jig occupies the left hand end of a mobile work unit that will also have a Fleischman derivative binding routing jig on it. The work unit will also eventually have a set of 8 or 10 drawers for luthier tools and supplies. The jig works by virtue of a stainless steel shaft that runs in four spherical bearings, one pair on the sides of the work bench and the other pair on the sides of a swinging router guide. The shaft is set at an angle to the work surface such that the radius of the swing is exactly 12" (from the axis of rotation to the surface of the fretboard - assumed to be 0.25" thick before routing) at the nut end of the work piece and exactly 20" at the soundhole end of the work piece. The shaft forces the router guide to swing in a compound arc, tracing the surface of a section of a cone.

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Almost done! The swinging router guide subscribes exactly the right compound arc, per the calculations! It has plenty of free swing to route the widest fretboard I'm ever likely to want (over 4" wide!). The swinging router guide binds on the sides of the work unit at its extremes. Just need to add some aluminum angle with some sticky-backed slick material (which is clear, so you can't really see it in the photos) to set the router path straight:

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Et voila! Done!! It's incredibly smooth in operation. I think I will devise a way to lock the swinging router guide in place for each pass of the router - perhaps a set of holes with a lock-pin, or perhaps a threaded lock-knob of some kind (although I'd rather it not intrude on the drawer space...). I'll post pictures when I come up with something.

I will also post a link to the SketchUp file (that I got my son to make to prove the design) in this thread later tonight when I get home from work.

I hope this helps someone.

Cheers,
Dave F.

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PostPosted: Tue Feb 19, 2008 6:43 pm 
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Dave,

Very Nice [:Y:] I also like combining it on a workstation with the routing jig. I'm going to be looking for the Sketchup
file tonight- I intend to build one like it. I'd seen Mario's design before, but hadn't gotten around to doing anything with
it- so far I've hand planed the compound radii on my fretboards, but the router setup will be much quicker... and with
a small shop, having the two combined helps a lot.

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PostPosted: Tue Feb 19, 2008 7:03 pm 
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Dave you are a genius! Where did you get the hardware? [:Y:]

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PostPosted: Tue Feb 19, 2008 7:23 pm 
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Dave I've thought about bearings like that but couldn't locate them. Where did you get those?

Vince


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PostPosted: Tue Feb 19, 2008 7:33 pm 
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Genius? :o That's a bit strong Ricardo... :oops: Maybe "dexterous" :D

The bearings were from The Big Bearing Store ($8.78 each) and the shaft was from Mc Master Carr product number 89785K173 ($59.45). The alumin(i)um angle for the router guides was from a local metal supplier - you can find it pretty much anywhere. The work unit is plain old 3/4" A/C birch plywood glued and screwed using pocket-hole joinery courtesy of Kreg. Sturdy castors were from Woodcraft - product #141050.

The bearings and shaft I used are way over-engineered for the job really. I'm sure you could use a much smaller (1/2"?), and cheaper, shaft and bearings without any issues.

HTH,
Dave F.

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Last edited by Dave Fifield on Tue Feb 19, 2008 7:43 pm, edited 2 times in total.

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PostPosted: Tue Feb 19, 2008 7:37 pm 
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Dave - Great minds do think alike! At least yours and Mario's!!!!!!!!!!!

I had seen pics of Marios and had been mulling it over in my mind and was thinking of a stationary router and a swinging device (yours inverted on a base). I think it would have been similar to the Grizzly jig for a belt sander. However, your design is inherently safer since the router bit is pointing down and confined in the slot.

I am thinking of making the radii of the cone adjustable...........

I think that, with your permission, I would like to steal your design. :D

Thanks,

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PostPosted: Tue Feb 19, 2008 7:41 pm 
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Nicely done and well thought out Dave. [clap] The pictures are self explanatory and thanks for even including the part numbers for the bearings and shaft stock. Integrating it into a work station was a great idea. Thanks for sharing !!

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PostPosted: Tue Feb 19, 2008 7:48 pm 
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Steve, go ahead...Mario said it would be okay for people to copy it.

I thought about making it adjustable too. All I'd have to do is make large slots for the bearings to run in, with T-track fixings to hold them in place either side of the slot. That, or just screw into the wood wherever you like :roll:. However, I decided not to do that at this early stage as I really don't see that I'll be needing any other profile on my fingerboards for the forseeable future. If you want to play with different f/b profiles, go for it! 8-)

Cheers all,
Dave F.

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PostPosted: Tue Feb 19, 2008 9:25 pm 
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Looks great Dave! How sturdy is it against twisting? What kind of bit are you using?

Any photos of a fretboard straight out of the jig?

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PostPosted: Tue Feb 19, 2008 9:34 pm 
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Guys, don't complicate it further <g> To cut various compounds, simply move the fretboard forward or back on the jig. Plan on it ahead of time, and make the jig longer if need be, but mine and this one will do quite a range.

But in the end, you'll find little reason to vary the compound. Even for mandolins, I find the same radii used for guitars(albeit shorter and thus stopping at maybe 14") works fine.


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PostPosted: Tue Feb 19, 2008 10:35 pm 
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Very clever design...good stuff.

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PostPosted: Tue Feb 19, 2008 11:28 pm 
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Very interesting and got me thinking (hard to this this late in the evening). I drew on auto cad the different radius (12",16" and 20") on a 2 5/16 block. The difference between a 16"R and 20"R in the 2 5/16 distance is .00704" ,not much. Mario obviously you feel having a compound radius-ed fretboard is worth the effort. My question is how do you level the frets on a compound radius-ed fretboard?
Thanks
Peter LaMorte


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PostPosted: Tue Feb 19, 2008 11:51 pm 
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how do you level the frets on a compound


I don't have to... [:Y:]

For the rest of you mortals, you simply follow the lay of the strings. In the end, that's what it's ALL about...


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PostPosted: Wed Feb 20, 2008 12:06 am 
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Great answer [clap] [clap] [clap] [clap] [clap]
:lol: :lol:
Peter


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PostPosted: Wed Feb 20, 2008 12:28 am 
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fmorelli wrote:
I was about to build a jig for using a router to radius fretboards. But then I just found out that Luthiers Supplies is about to release a jig for radiusing fretboards on a thickness sander. I think their intro price is $129. Given the supplies, several hours of work, and corresponding dust collection I have to sort out with the router, I think this is a good deal as my thickness sander dust gets effectively captured by the dust collection system.

The jig is not listed on the Luthier Supplies web site, yet - given they are a sponsor I assume they'll announce when the new stuff is available.

Filippo


Filippo,
Perfect timing! We will be releasing this jig in about 2-3 weeks. It will do compound radius, and it will come with 12", 14", 16", & 20" radius'. You can mix and match the radius too. Edward Dick, the inventor also says it can do incremental radius too, like if you wanted a 13" radius. Don't know why anyone would, but he told me it can be done. I actually haven't seen that done yet. We are still testing it, and will have updates on the website soon. In fact, I already have all the video up on the website, but it is a blind page for now.
Here is a pic of it:
Here is a link to the video showing its use. Enjoy! http://www.luthiersuppliers.com/products/videop12/vid12-5.html


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PostPosted: Wed Feb 20, 2008 3:42 am 
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First off - Mario - you are GRUMPY????!!!!!!!! :o :shock: :lol: :D 8-) I had no idea!

Second off - quel surprise - an even simpler jig to do the same thing! Fantastic! Doncha just love innovation?! [:Y:] [clap] [clap]

Dave F.

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PostPosted: Wed Feb 20, 2008 3:58 am 
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For those still interested, you can get my son's 3D Google Sketchup drawing here. It's not drawn to scale. It's just a quick and dirty drawing to see if the basic idea worked.

In order for it to "work" you will need to have the SketchyPhysics add-on loaded. You can get that free from here.

I'm not a Sketchup user, so if anyone has questions, I'll have to bounce them to my son and reply to you later.

Cheers,
Dave F.

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PostPosted: Wed Feb 20, 2008 4:32 am 
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Erik Hauri wrote:
Looks great Dave! How sturdy is it against twisting? What kind of bit are you using?

Any photos of a fretboard straight out of the jig?


Hi Erik,

It's very sturdy indeed. I don't perceive any twisting at all. The swinging router platform is stiffened by the plywood "end plate" and further by the alumin(i)um angle router guides. It doesn't need it, but if you wanted to further stiffen the jig, you could add metal angle to the vertical sections of the swinging router platform.....really though, it doesn't need it.

I used a 1/4" diameter flat bottomed router bit and ran about 10 positions when I did a 2" wide test piece (scrap wood) on it last night. Perhaps Mario will tell us what bit he uses also. I have yet to do my first real fretboard (the one you can see in the photos) in it - I'll do that this coming weekend and post pictures then.

BTW, I set up the height from the top of the work unit to the underside of the swinging router platform to be exactly 3/4". This made set up (getting the platform exactly parallel with the work surface) easy - all you need to do is slide a 3/4" thick board into the jig, then tighten down the bearing screws. Also, it allows you to use a simple piece of 3/4" plywood to stop the platform from falling all over the place when you're not using it - you can see the simple L-shaped plywood "stop" that I made for this in the last few photos above. This holds it in the dead straight up position when not in use.

Cheers,
Dave F.

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PostPosted: Wed Feb 20, 2008 9:02 am 
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1/4" bit here also...

Tracy, I've seen a few of those jigs, but i don't think they'll do a true compound, unless yo can make it skew, also. Can you put a 10" and 18" caul in it and show us what it looks like at their travel limits?


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PostPosted: Wed Feb 20, 2008 9:33 am 
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LuthierSupplier wrote:
fmorelli wrote:
I was about to build a jig for using a router to radius fretboards. But then I just found out that Luthiers Supplies is about to release a jig for radiusing fretboards on a thickness sander. I think their intro price is $129. Given the supplies, several hours of work, and corresponding dust collection I have to sort out with the router, I think this is a good deal as my thickness sander dust gets effectively captured by the dust collection system.

The jig is not listed on the Luthier Supplies web site, yet - given they are a sponsor I assume they'll announce when the new stuff is available.

Filippo


Filippo,
Perfect timing! We will be releasing this jig in about 2-3 weeks. It will do compound radius, and it will come with 12", 14", 16", & 20" radius'. You can mix and match the radius too. Edward Dick, the inventor also says it can do incremental radius too, like if you wanted a 13" radius. Don't know why anyone would, but he told me it can be done. I actually haven't seen that done yet. We are still testing it, and will have updates on the website soon. In fact, I already have all the video up on the website, but it is a blind page for now.
Here is a pic of it:
Here is a link to the video showing its use. Enjoy! http://www.luthiersuppliers.com/products/videop12/vid12-5.html


Tracy,

I like your design quite a bit. I was curious as to whether the reference lines at the ends are even, or fanned out to simulate the spread of the strings. If it can stay stiff and stable in sanding it would get a slightly truer plane under each fret than a conventional compound radius.

It can be tough to picture in your mind, but if you are making a compound radius in the conventional way (as a section of a true cone), you would not end up with the board straight under each string. In fact, if you were to reference the center of the board as straight, the edges would be in slight back bow. The only way you could end up straight all across with this conventional cone would be to ensure the change in radius stayed directly proportional to the length of the arch as the string spacing widened. Actually a consistent radius suffers the same probem to a degree, but a 12" to 14"ish compound I think would end up just right. Either that, or the string spacing would have to widen dramatically as it moved up a board to stay on a straight line on a 12" to 20" compound, leaving you with bridge spacing around 3_1/2" :o .

What that thickness sander radius jig would actually create wouldn't be the cone section that people usually think of in a compound radius. I'm not going to try to do the math again right now but I'll throw in some approximates, but let's say you were making a 10" to 20" board. The 15" radius would not end up half way from 10" to 20", but more likely around 2/3 the length. It would be even more accurate to getting a straight shot in plane with each string if the reference lines at the ends represented the spread the string spacing from nut to end, though this may be really splitting hairs.

I think most people end up leveling in this ideal and slightly uneven curve as the level the frets anyway whether they realize the geometry of what they're doing or not, as If you cut a straight line under the plane of each string this will be taken care of automatically. A board when cut on the traditional swinging arm however, while the lines being cut are certainly straight, are less in line with the strings as you spread toward the edges, resulting in a slight parabolic hump along the length at the edges.

The inconsistencies of the normal compound radius are probably tiny, a couple of thousandths perhaps, but it's something to keep in mind when leveling frets. If the thickness sander jig can remain stiff enough not to flex under the load though, it may even be a bit truer from the beginning.

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PostPosted: Wed Feb 20, 2008 9:51 am 
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nd up leveling in this ideal and slightly uneven curve as the level the frets anyway whether they realize the geometry of what they're doing or not

The closer to ideal we can get the fretboard, the less leveling we need to do. I wasn't kidding when I said i don't have to level frets...


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PostPosted: Wed Feb 20, 2008 10:17 am 
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I know Mario, Grumpy as you are, I'm getting better day by day at telling when you are saying something tongue-in-cheek. Picking up on sarcasm from some people is an acquired skill, and you could probably take that as a compliment . ;)

The reason I actually posted this was in hopes that there was a calculus major with some spare time here on the forum. I'd like to hear someone describe the actual ideal shapes and maybe put some numbers to it. I've spent a lot of time in deep though about this, usually at the bar on a napkin with no calculator or reference books around though.

Any takers???

I know what variables need to be considered, and have an abstract idea of the end shapes, but am still curious. Are the differences three places right of the decimal in inches, or four? Does each shape between the start and end radius (and beyond it considering the saddle) end up as parabolic in theory, rather than a radius? I know we're talking splitting differences of less than a hair here, but I'm curious, and while I may think I can do the math I always seem to hit a different dead end when trying to work out formulas.

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PostPosted: Wed Feb 20, 2008 10:19 am 
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As usual, the Grumpmiester has come upon the simple, yet elegant, solution! Longer jig + move FB towards one end = Non-adjustable, simple jig! Now, Why didn't I think of that????

And then.... I should be sure to read the entire thread before responding.............. [headinwall]

Thanks Grump!

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Last edited by Steve Walden on Wed Feb 20, 2008 10:32 am, edited 1 time in total.

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PostPosted: Wed Feb 20, 2008 10:26 am 
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David, Bob Garrish should be along any time now to give you the math. He made me some awesome cauls.....


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PostPosted: Wed Feb 20, 2008 11:48 am 
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Here's the math:

http://en.wikipedia.org/wiki/Cone_%28geometry%29

The relevant cone is a right-angle circular cone. The surface radius is a linear function of distance along the rotation axis. The difference between nut & bridge radii are directly a function of the r/h ratio; some of these jigs are locked into a single r/h ratio, others permit it to vary....others do not quite reproduce a conical section.

From this it is straightforward to figure out the radii for the bottoms of the nut slots and the bridge saddle, depending on what kind of action you want (not taking into account things like mid-neck relief and upper-fret fallaway that aren't conical anyway....).

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