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I have a sneaky suspicion my donut is the cause of some of my binding channel inconsistencies.

Could some of you please post a few pics of what the donut on a binding cutter should look like?

Thanks,
dl

I don't use a donut, just a smooth wedge riding very close to the edge...

I can't say this is what it should look like, but this is what it could look like. The donut that came on my binding cutting tower was an awful small-diameter Delrin-looking ring that looked like a binding accident waiting to happen. I cut it off flush to the plate and then made a donut with a 6" radius dome shape from a piece of scrap 2 x 4 fir and double stick taped it to the router plate on the tower. It's been on there for about 7 years and does the job no problem. If I did again, I would make it all nice and spiffy to look at, but there's been no need so there you have it.

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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

My 3rd iteration, don't know if this is what one "should look like", but works for me.
UHMWP, glued and screwed.
Very close to the cutter, steepish slope, sharpish edge, but rounded off lightly.
My tower jig is counterbalanced to reduce weight on the donut, to around 440 g IIRC (15 oz)

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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.

I’ve always wondered why my stewmac jig has such a small one?!?!
I agree .... a wider one would out my mind at ease


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The router isn't mounted, but there are the base screws I was looking for the other day.

UHMW, I double stick taped it to a face plate on my wood lathe.

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

This is what I am using but I'm always looking for something better. It works but I just threw it together too. I don't really have the tools and or perhaps the skills to make one so I keep thinking what's already out there in the wild that can be repurposed. This is the collar of a door knob, or whatever it's called. I had since filed that little edge flush.

Off the topic, but Colin is that also some tape round the bearing to give you a different cut thickness?

Dave

Yup, 6mm copper shielding tape IIRC, sticks like ****, and works a treat.

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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.

You all are some creative folks!


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Looks like Jay and Colin don't have any flat area, am I seeing that right? What are the ideas for and against if any?

I think both of mine do, one more than the other, but I'm not at home this week.

New username, same Pat Mac

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Pat

Pat, not much at all in my case, as I said just slightly rounded off.
My idea is to keep the binding ledge height variation to a minimum, especially at the neck end of the back, and for wedged guutars.
Same reason for the minimum clearance to the cutter.
The further away the contact point of the donut on the guitar is from the cutter, the greater any height variations will be.

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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.

Crude, but works perfectly.
I have been using it for over 20 years...


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Here is my reasoning, and I am curious to hear other opinions. It seems like you would want a flat section at least as wide as your binding. Because if you slip off and down the cutter would not start traveling down until the flat ring clears The Binding.

It seems like if you had a zero clearance Donut with no flat spot it would be hard to keep it riding on the top and as soon as you accidentally moved away from the guitar the cutter would immediately start going down deeper than you want.

Brad, you are going to put donut makers out of business! LOL

New username, same Pat Mac

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Pat

I really dont find it hard to keep the donut riding on the top, but if you're going to accidentally move away from the guitar by your reasoning I think you would want the flat section of the donut PLUS the clearance from the cutter from the donut to be greater than your binding OR purfling width.

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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.

Here are a couple of donuts I have used hand held to cut binding and purfling channels. The first one I made from plexiglas and it has a larger diameter circle. For fairly flat work it worked O.K. With more strongly arched plates I found the smaller diameter corian donut rode closer to the edge and gave a better result. I have thought about making a binding rig like some of those I have seen on the forum, but thinking about it is as far as I've gotten.

Sorry. Couldn't resist... Somebody had to do it...

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Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

Those donuts that are small in diameter and flat are the type of donut I was referring to above as looking like a binding accident waiting to happen. I know that people use them successfully, but that's the way they look to me. That's why I cut the original donut off my tower and replaced it with the domed one.

My Dome Donut™ has a 6" radius so it's a fairly flat dome and it's 3" across. With the dome shape, there is no way for the cutter to slip and suddenly drop off an edge like on a small diameter flat donut short of pulling the body more than 1 inch away from the cutter and then you would be dropping the whole router off the edge of the body. Some major inattention would be needed for that to happen. The gradual and wide dome shape also makes for controlled and smooth introduction of the body to the cutter without having to negotiate a lip to get onto the donut. In my case, the donut isn't zero clearance. There is a 1/8" gap between the cutter and the edge of the donut hole.

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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

I was having trouble seeing out the rear view on my old truck so I took this off and got to thinking that it might work for a donut on the binding cutter jig. I already have one I made out of plastic but don't see why these won't work. I drilled a hole through it and it seems pretty rigid even though it's semi hollow.

I don't have a picture, but I made a donut. This is how I did it.

- Took an old worn high density plastic cutting board and cut a piece out of it with the band saw.

- Drilled a hole in the center and put a bolt through it. I attached a nut to hold the plastic tight.

- Put the bolt in my drill press and used a chisel like a lathe and turned the piece into a donut shape.

- Took the bolt out and used a Forstner bit to drill a 1 inch hole to accommodate the router bit and bearing.

- Mounted the donut with screws on the bottom of my router mount.

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Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com