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I was trimming off the overhang on two new builds and the binding channel cutter left the edges of the spruce quite fuzzy, particularly the end grain. The top had a coat of shellac to stiffen the wood fibres, but that didn't seem to help. The only thing I can think of is that the bit is dull, but these are only the fifth and sixth bodies I've done with it.

I don't want to cut the binding/purfling channels till I've got this straightened out.

Any thoughts?

As always, thanks in advance

Steve

I use a downcut spiral router bit, no fuzzies ever.

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Old growth, shmold growth!

what cutter you using? I used both the LMI and Stew mac and find the LMI is a bit better. Use a sharp bit and if it down or up sharp is sharp. Not all carbide cutters are the same.
The you can use climb and route cuts.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Hey John, I'm using the LMI bit. Is there any likelihood that it could have dulled after only 6 bodies?

Thanks

Steve

BTW, you probably don't remember, but we talked at ASIA about how to clean up hide glue. You suggested I wait till it "boogerized", then just scrape it off. Works brilliantly. Thanks.

If you are feeding it the same as always I'd say it is dull. It doesn't take much.
When i get a new or freshly sharpend bit i always remind myself what a sharp bit is by running my fingernail against the edge.
MM

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Mike McNerney

Steve: Not sure of the steel in your bit,but HSS will dull from Titebond or related cousins.Carbide bits stand up much better.
Tom

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A person who has never made a mistake has never made anything!!!

That should be good , I get about 40 guitars off a bit. Some spruces are more fibrous than others. I find that climb cuts can give you a neater cut. My trick for this is to put tape on the bearing or on the guitar , make a pass then pull the tape and make it a finish cut with a climb cut.
Also like Todd points out a light rub with 220 should knock the fibers right off.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

If the bit gets hot it dulls a lot faster.

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Old growth, shmold growth!

When my straight SM carbide bit dulled I just touched it up on an extra fine diamond sharpening card, same as my other cutters (even my 3mm bridge slotting cutter). It also helps to clean the bit after every use - it's more easily done immediately.
Doesn't seem to have changed the cut depth noticeably, but even new it produced little "fuzzies", easily sanded off.
Thanks for the tip about the tape John, I'll have to give that a try.
Next bit will be a downcut.

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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.

After quite a few uses I was beginning to worry about getting bad cuts or tear outs in the spruce tops with my LMI cutter so I decided to get a second cutter and use it only for top purfling cuts. I figure that after a while I will replace that cutter and use it for cutting into the hardwoods of the sides and retire my original cutter. I was shocked at the better quality of the cuts with the new cutter the original had only done 12 guitars but was already loosing its edge, the cut on the sides with it is still excellent but the new one did a better job on the top.

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Lately, I have been cutting the ledge .010" smaller on the first pass, before going to the full depth. On the final cut, I go around ridiculously slowly, especially in those areas where the bit wants to tear the grain.
A five minute soak in lacquer thinners will clean off any accumulated gum on the bit.
& as Colin said, a couple of passes with a fine diamond stone helps a lot.

Or, you could use a gramil or Sloane style cutter first,
to score before routing.