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mistermikev

anyone use a radius jig?

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for anyone wondering the same thing (how far can wood bend without steam or releif cuts)... this is an interesting read regarding cold bending...

https://www.popularwoodworking.com/techniques/bending_wood_the_wright_way

summary: recommended radius/thickness

2-4" radius - 3/32"

4 - 8" radius - 1/8

8 to 12" radius - 3/16

12"+ radius - 1/4"

 

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It's very difficult to bend in a useful curve against the grain where the wood is weakest. Fender did a similar thing for pre-radiusing fingerboards in the (70s?) where the top and lower portions of the wood and the corresponding face of the neck were milled to specific radii, allowing for "veneer" fingerboards. I might be a little hazy on that one, however I don't believe that they bent the boards and actually milled them.

I love G&W's jig. It's durable and will last through many many router fitting/removals and the stuff that wears out plywood jigs. All I needed for it was a baseboard with a midsection matching the cutout in the jig base. Very happy with it. Shame the additional radii are costly investments, but they pay for themselves in the end result even if you don't build in quantities.

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8 hours ago, Prostheta said:

It's very difficult to bend in a useful curve against the grain where the wood is weakest. Fender did a similar thing for pre-radiusing fingerboards in the (70s?) where the top and lower portions of the wood and the corresponding face of the neck were milled to specific radii, allowing for "veneer" fingerboards. I might be a little hazy on that one, however I don't believe that they bent the boards and actually milled them.

I love G&W's jig. It's durable and will last through many many router fitting/removals and the stuff that wears out plywood jigs. All I needed for it was a baseboard with a midsection matching the cutout in the jig base. Very happy with it. Shame the additional radii are costly investments, but they pay for themselves in the end result even if you don't build in quantities.

good to hear from you prostheta.   that jig is very nice - hardly worth the work to build one but then the experience is worth something. 

I've seen/heard of lam fingerboards before... I think they offer it as an option at musikraft or warmoth.    to be clear... the laminate part is regarding a possible 60" radius on a radiused body using a 3/16ish top.  my thinking is to build something that could do both a 20" fretboard radius, and then be re-used for a radiused guitar top.  for now its just dreaming but I def appreciate the input!

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Thanks, I've been a little indisposed and unable to spend a lot of good time online recently.

I agree that the experience of being able to design and make a jig is invaluable. Throwing tools at a problem rarely solves it, since the understanding of how a solution is reached ends up side-stepped.

A body doesn't need to be perfect from a geometric point of view compared to a fingerboard. I'd be tempted to elect for planing facets roughly, and just using some sort of flexible plastic bent into the radius required with strengthening to keep it in the shape. Then use 80 grit sandpaper on the inside surface to get the body into the right radius. To me that seems easier than going to the lengths of making a rail and sled type system.

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1 hour ago, Prostheta said:

Thanks, I've been a little indisposed and unable to spend a lot of good time online recently.

I agree that the experience of being able to design and make a jig is invaluable. Throwing tools at a problem rarely solves it, since the understanding of how a solution is reached ends up side-stepped.

A body doesn't need to be perfect from a geometric point of view compared to a fingerboard. I'd be tempted to elect for planing facets roughly, and just using some sort of flexible plastic bent into the radius required with strengthening to keep it in the shape. Then use 80 grit sandpaper on the inside surface to get the body into the right radius. To me that seems easier than going to the lengths of making a rail and sled type system.

thanks as always for the advice. doing it by hand... I'm not sure it would be accurate enough to glue a top on to afterwards.  and the top in mind is too thin to carve the radius into.  I don't know... will have to think on this some more but i appreciate the feedback.

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It should be if the body is straight down its length. That said, there are an infinite number of ways to screw up simple procedures. Ask me how I know this.

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2 hours ago, Prostheta said:

It should be if the body is straight down its length. That said, there are an infinite number of ways to screw up simple procedures. Ask me how I know this.

hehe... my whole thought process on that is "yeah, YOU might be able to keep it straight but me - unlikely!"  I find it difficult to get a perfectly straight flat neck blank!   goes something like: sand, sand, sand... still a crack of light... sand, sand, sand... dang it it still hasn't moved... sand, sand, sand... and on and on like that!

more importantly... I feel like it is the same technology - to radius a body or a fretboard.  If I can learn how to make it work for one - the other will be a piece of cake... maybe.  Also if I can make a radius that flips I'll be able to make better fb sanding blocks.  Seems like a lot of benefit from one skill/jig.

 

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You'd be surprised at some of the obvious things you miss that suddenly improve your technique. Concentrating on where you apply pressure, whether you're bending the beam or the workpiece, uneven contact, you know.

A router jig will do it, I guess that I was pointing out that it doesn't need to be overengineered (hard for me to say this, I know) in order to be effective.

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1 hour ago, Prostheta said:

You'd be surprised at some of the obvious things you miss that suddenly improve your technique. Concentrating on where you apply pressure, whether you're bending the beam or the workpiece, uneven contact, you know.

A router jig will do it, I guess that I was pointing out that it doesn't need to be overengineered (hard for me to say this, I know) in order to be effective.

right as rain as usual.  I suppose in the end - even if I use a jig/router - I will have to sand it to get the tool marks out so... no way of escaping!  Have to get better at sanding to a dimension for sure.  I think the thing that has been holding me back there, is I was using a 3m sanding block... only 4-5" long.  I've recently picked up a harbor freight auto-body sanding block.  it's about 14" long and has a nice big handle... for $7!  working pretty good so far because this morning I sanded my neck blank and it looked pretty straight.  We'll see what happens after a few days of 'adjustment'!

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Totally. I actually think that using longer beams can be just as difficult as shorter ones, especially when it comes to ensuring even downpressure over the contact area and not to one end. It's tedious as hell, but try doing single strokes in one direction only. That upped my feel for the tool.

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Roger that... oddly enough at first I was trying to sand down the high spots... and in the end I found that full length strokes worked better.  Also trying to lighten up my pressure - both things you have advised.  so thank you for the good advice!

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For getting a true flat surface on a neck (or other part), I like a piece of granite from a counter shop.  So far, I have had excellent luck getting cast off pieces from an order.  I just go to the stone shop and ask if I can buy a chunk of left over granite.  Since I don't care what it looks like, it's easy to source the stone.  I have gotten chunks left over from sink cut outs and end cuts for free.  I use pressure sensitive adhesive backed sandpaper and run the part over the stone instead of the other way around.

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right on.  good idea.  I may have to find a local granite or solid surface shop.  As an alternative... I have been using a harbor freight auto body sanding block.  They are actually really nice for $7.  checking against my straight edge they produced straight results.

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