Official Luthiers Forum!

Here's a question about router bits. Specifically, is it better to use a spiral upcut or downcut bit when cutting ledges for bindings and purflings? And why is one better than the other if it in fact is?

Thanks,
Max

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Max Bishop
Brighton, Michigan

I prefer downcut because it doesn't leave a fuzzy edge on the top. Either way, sharper is better

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

The down cut has the cutting force coming down into the wood, as opposed to an upcut which has it lifting out of the wood. So you should be able to get a cleaner cut with the down cut. I've never tried it, but I read of some folks shellacking the area first to get a nice crisp channel.

you will get less tear out with a downcut bit and +1 on the sharpness!

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Martin Taylor
http://martintaylorguitars.com.au

down cut on open ledge work (binding) and very shallow channels (rosettes/purfling)

up cut on deeper pocketing (truss rod trenches, mortises)

sharp tools and and a helpful air stream or vacuum.

circumstances will vary, experience will decide.

Thanks to all for the excellent input.

Regards,
Max

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Max Bishop
Brighton, Michigan

Oh, and either way you go, applying a wash coat of shellac to the top seems to stiffen up the fibers leading to an even cleaner cut.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com