Official Luthiers Forum!

How do you put a uniform radius along an edge?
My router with a round over bit tears up end grain.
I’d like to have about a 1/16” radius. I want it to look consistent after finishing.

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Wah-wah-wah-wah
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they do make 1/16" round over bits...and they are really a pain to set up for various reasons (undulations in the wood resulting in some spots being perfect, others being shallow, and others the dreaded too deep)...I've found with smaller round over bits the odds of tearing stuff up goes down significantly...doing a climb cut becomes less and less necessary, but I still climb cut most everything these days just because it's "safer" as far as results on the wood...

point being, in addition to the obvious having a sharp bit, do a climb cut first and go back in a regular fashion to clean things up...the biggest problem I have with end grain is burning...and as always if doing a sharp corner do the end grain first as if there is a small blow out it will hopefully be removed when going with the grain

For a 1/16 inch radius you can skip the router and use the bit as a scraper to scrap the roundover by hand.

How about these - Veritas Cornering Tool Kit
https://www.canadiantools.co.uk/product/veritas-cornering-tool-kit/

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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 just did that on a cello. Set a compass for 1/16" and mark both sides. I used a small finger plane to cut a 45 degree chamfer that is not even a third of the space between the limes. Cut a flat at about 20? degrees on both sides of that not to the line. All cuts going going downhill. A fine file will work too, the plane didn't fit around my corners. Fold up a small piece of 320 or so sandpaper, and round it up.
It went really fast. Mark a test piece and try it.

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Why be normal?

Thanks! I’ll try these.

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wah
Wah-wah-wah-wah
Wah

For something like a Tele body top and back round-over or rounding over an unbound body edge such as a 15-Style trim package on an acoustic, using the technique typically employed when routing binding channels to minimize any opportunity for tear-out seems to work well. With a sharp bit, you really should not be seeing tear-out on radii under 1/4" or so. Another approach is to take multiple passes using the same combination of climb cuts and standard cuts used for binding channels...but as mentioned, if your router table is not dead level or you don't have a top-registered binding jig, it can be a bit inconsistent. Round-over bits seem to dull pretty quickly, and that dullness can show up as edge burn, slight chip-out, and - worst case - major blowout.

For roundover on binding, we always worked that by hand with coarse grit paper for the initial chamfer and a steel scraper and gauge combination plus fine grit paper for the finish.

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A constellation only takes shape when one maps the whole.
- Beth Brower

Please let us know how they are to use.

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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 made up a 'scratch beader' from a scraper. I drilled a 1/8" hole a half inch or so in from both edges, and cut away the corner of the scraper, making a notch of more than 90 degrees with a rounded corner. This is used as a scraper, with tape on the flats to reduce the chance of marking the top, back, or sides. It cuts in both directions, and works well, even on curly maple binding; if it starts to grab just reverse direction, and changing the angle helps too. When it gets dull you can touch it up with a jeweler's file.

I made this up originally when I was asked to give a talk about scrapers at a luthiers meeting. I'd known about these for a long time, but never made one for this purpose until then. Once I tried it I wished I'd done it a few decades sooner.

45 degree chamfering router bit with non-marring pilot bearing. I think these bearings are made for Corian, etc. After routing 45 degree facet make a few swipes with a fine file on both edges of the facet at about 22 degrees. A few final passes with 150 grit sandpaper.

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Stay with the happy people.
--Reynolds Large

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I have a set of Veritas Cornering Tools.

How are they to use? OK, not great.

If you're rounding the corner of a straight board, with reasonably consistent runout, they'll work fine. Rounding the corner of guitar binding in the real world, maybe not quite as well. But if care is taken to NEVER use them in a direction where they will turn runout into blowout, they're a decent first step in getting a consistent roundover. Sandpaper, carefully utilized, is the next step.

I also have a set of those Veritas corner round over tools. I’ve done a lot of edge round overs and beads and I find that tool very hard to control. You have to be hypersensitive to runout or you can easily lift a sliver of wood from the edge. I’ve done much better with a scraper, as Al described. The safest (tho slowest) way is to shape a notched sanding block.

I, too, have a set of the Veritas cornering tools. I tried them a few times. I don’t usually use them now. I round the corners on my bindings with hand held sandpaper—first, 120 grit, then 220 after that.

For a small radius like we use on binding I just use sandpaper on an eraser.

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Steve Smith
"Music is what feelings sound like"

Same experience here. They've been sitting in a drawer looking pretty for a long time.