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Where is my math wrong? I use a .76" bearing expecting a .12" slot, I get .13". I test a .78" expecting .11", I get .12.

Mike

Did it not come with a chart? Here's ours. Bearing size above, cut size below...

I did not get a chart, but my calculations match yours. I'm saying when I measure depth of cut, I'm deeper by a hundredth than I should be. Fir my 0.8, I'm getting 0.11 for example

Are you mixing and matching stew mac stuff wth LMII? Are you sure your cutter is 1" across?

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

Lol. No, not mixing vendor bearings or cutters. I measured both the bearings and the cutter. Cutter is 0.999" on my calipers, 0.8" bearing measures 0.799". With that combo, I get a 0.11" cut. I use a precise bits collet. Router is pre-2011. I am using the long shank cutter. If I'm reading this correctly, I've got a 0.01" wobble. Maybe I should test with the short shank bit? I do seat the bit deep however.

This really is not an issue. I can just use the next size up. But I am confused why this is happening. Btw, I do not own Stew Mac bearings or cutters

Mike

Possibly lack of concentricity between the bearing mounting and the cutter itself? This would mean that one blade on the cutter does most of the work and you may be able to see witness marks on the blades to that effect.

I use the LMII cutter and would say that it isn't the smoothest cutter I've got, but workable. I have just one router that is actually zero run-out, and even in that router it is fairly rough running, so either eccentric, out of balance or both.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Probably, I don't think I've ever actually measured cuts before. Just do quick estimates, then pick bearings that get desired results. I suppose I'm not surprised at this.

I use the SM cutters and bearings, very smooth cut. I get about 6-7 guitars out of a new cutter before the end grain cut gets too fuzzy. Here's a trick I learned from John Hall: Get some adhesive backed copper tape from Hobby Lobby, its in the stained glass supplies. Very thin, about .002, and you can wrap it around bearings to dial in an exact fit for your bindings or purflings.

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It will probably be alright.