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Hello,

Currently I use a jig to put the radius on braces. I basically use the jig described in the Gore book for 15’ and 30’ radius. I use a pattern bit in the router. I also have been hitting the radiused side with 180 on a wood block to clean up the bit of wave from the router bit.

I started thinking that maybe I should move the whole operation to a sander instead so there is just one step.

I have a 12” Delta disc sander I use for putting the radius on neck and tail blocks, but the grit is too rough (I hit the blocks with 180 as well after putting the radius on). I also have a Rikon 6x48 combo and one of the Rigid oscillating belt / spindle sanders.

For the Rigid sander I have 180 and 220 belts so I’m thinking that might be a good choice.

Anyone using a sander based jig for putting the radius on braces? Care to share any pics?

Or does everyone just rub the braces in a dish?

Thanks!
Brad


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Mark, cut on a band saw, sand on a sanding batten. Less than 2 minutes each?

Ed

Same here except I sand them on a radius dish. Pretty fast.

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My dish has 60 grit. Do you go straight from 60 grit to glueup?

I’ll take a few pics of what I’m doing now with the router to help with where I’m coming from. I’ve been working for months on a build system using jigs and locating pins. This is one piece of the puzzle.


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This is the concept Charles Fox taught in his course. He used it on a horizontal edge sander but it should work on the Rigid.

Make an auxiliary table that has a piece of thin aluminum attached as a buttress your radius template pushes against. Attach the part to be sanded to the template on a sliding cradle so it can be moved into the belt at the proper thickness.

The picture is this concept being used for radiusing end blocks.



I still use a router table and template bit using climb cuts. Comes out pretty smooth. When I tried to sand in the dish I inevitably rocked it a little or used uneven pressure or a varying angle resulting in a less than perfect mating surface.

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Awesome. Thanks, Terence.

Out of curiosity - do you use any special bits? I’m using a two flute pattern bit, maybe I need to do three flute or take the passes differently? What I found is just a bit of wave in the cut and was trying to clean it up with 180 paper. It’s possible I’ve talked myself into the routed surface not being “good enough”. Wouldn’t be the first time I guess.



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My dishes have 60 or 80 grit, I don't remember which. After the initial sanding to the radius, I place a long strip of adhesive-backed 220 grit across the diameter of the dish and sand the braces to remove the 60/80 grit scratches. That step is fast. Right before gluing the braces, I scrape the brace bottoms with a fresh razor blade. Also, I sand the inside surface of the top and back to 220.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Sanding? Dishes?
I swiped this idea and pics from Bruce Sexauer, infinitely adjustable, and your gluing surface is just off a sharp (hopefully) plane
I use my Veritas Shoot Board plane it works pretty good

Clinchriver just beat me to it, why not just use a plane?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Just to be clear. I personally use a different system, similar to yours Brad.
I have 60 grit in 12' and 28' radius dishes, and I shape my braces with a router trim cutter and radius template.
I also made 2 each radius blocks, 12' and 28' radius, about 2" square x 2', double sided, with 100/150/180/240 grit abrasives.
These radius blocks are used both to sand the rims (after initially shaping and "driving the bus") and to sand the braces to the higher grits.
240 grit is saved for final touch up just before gluing.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I just mark it and use a block plane. Too many jigs clutters up my small workshop. This guy uses a jig and can probably do it in about a minute. Takes me a bit longer but saving a minute or so is hardly a big deal for me.

https://www.youtube.com/watch?v=qrO6ZEECmFY

Drive the bus. [MAN]????‍[AIRPLANE]️


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I have been just using a two flute template bit doing climb cuts and finishing with a regular cut. I do go over it with a hard sanding block just prior to gluing to freshen things.

As usual many paths to a good outcome. I think a sanding jig on the Rigid with around 120G would work great.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Thanks, Terence. I think I will use your idea to make a plate for the jig I already have and use the rigid. The nice thing about the Rigid is I can go down to really close with 120 or so and then hit it once last hit with 180 and the belt swap out is really easy.

Thanks everyone else for the ideas. Of course there are lots of ways to do this, but I’m specifically looking for a jig approach that uses a sander and can keep things square for me. Even hand sanding off the router with a hard block I tend to nip the edges sometimes which ruins the fit. The jig will help with this. I’ll post some pics of what I come up with.




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With the plate in the radius dish, scribe the brace to the plate.
Block plane to the scribe line, test fit, maybe touch up once more.

B

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My memory is so good, sometimes I remember things that never happened.

Rotate the assembled rims and end blocks (clamped in the mould) on radius dishes with PSA abrasive to achieve desired spherical rim shape.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

For odd radii, bench hook and block plane. For 15', 28' and 60', we use the Luthier (Oops...Suppliers!!!) tablesaw brace radiusing jig finished with a jack plane while the brace is still presenting a flat surface to the tool. We are typically doing 3-4 brace kits at one time, so jigs do save a significant amount of time.

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Scribe to your radius on the bottom of your brace. Use a 12 in disc sander on a combo sander, finish sand to 180 , or a suitable radius dish . Have the LMI radius jig costs $$ but one can easily make a copy of them for your final sanding

Stanley used to offer this tool, and L-N still does. Bamboo rod makers use it in their aluminum or steel jigs for planing the long hexagonal lengths of material for assembly into rod section. You set the blade so that it is not lower than the bed but just cuts inside the groove, and you can run the bed over your jig without planing the jig. Would be simple to alter a garage sale #4 or #5 like this, making the groove as wide as you wanted. I keep a special plane for a shoot board, why not for jigs?

https://www.highlandwoodworking.com/lie ... plane.aspx


Ed

^^^Agreed!

Woodie, I can’t seem to find this jig online. Is it from Chris at luthiertool.com?

Brad


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Perhaps Woody means this from Luthier Suppliers:

http://www.luthiersuppliers.com/products/p6.html

I was not in the shop today, so was working with what appears to be a very faulty memory! Luthier Suppliers, indeed. For shops that are less tablesaw-centric, the jig works with a bandsaw as well, assuming a fence and accurately tracked blade. A pass with a plane clean s up or sanding in the appropriate dish (the plane is much faster).

_________________
For the times they are a changin'

- Bob Dylan

You can also tack glue 3 or 4 braces together then shape them all at the same time, assuming they are all at the same radius. I've done that when I'm after super speed.

I make the back braces start to finish with no jigs in about 6 minutes....

First I take a piece of spruce the length of my longest brace and 5/8" high by about 1-1/4" wide.

Then I sand a radius (by eye) on one side with my 6 X 89 sander with the table at 90 degrees to the platen.

I then compare it to my radius dish-I am usually right on or close-I adjust if necessary.

then I slice that up into four 1/4" (or 5/16") braces

Then I cut them to length and scallop the ends (roughed out on the bandsaw first) on the wheel end of the belt sander
and bevel the length on the platen -Done!

I leave a little flat on the top of the braces for the go bars to have some purchase.

So I am gluing on a 95% finished brace to the back.