In his video (https://www.finewoodworking.com/subscription/workshop/workshoparticle.aspx?id=29166), Guido Henn recommends using a spiral bit to avoid tear out. The bits shown appear to be spiral upcuts (Z-twist). He starts cutting at about 3:00, and the cuts are very clean.
I am using a new spiral bit, but not having much success. The edges are nice and clean where the bit cuts in, but not so good where it exits the wood.
Any recommendations?
Janet
Replies
Back-up
I always use a back up board when doing box joints. If you are going square, run "five" sides at a time. If rectangular run "three" sides at a time. clamping them together and running all at one time.
Could you explain about the five and three sides?
Janet
Back-ups
The "extra" side is just a piece of scrap that is used on the outfeed side of your good lumber to prevent tearout.
Pretty simple, but effective.
When doing square , you can cut all the pieces at once if you off-set two of the real sides the width of one finger. four sides + scrap backup = 5
When doing rectangular, you can only do two long and two short at seperate times. but still off-setting the L&S sides by one finger width. two sides + scrap backup = 3 But REMEMBER to offset them correctly
Hope that helps.
"For the cleanest cuts, use
"For the cleanest cuts, use an up-cut spiral for solid wood; a down-cut spiral for plywood and veneers." --Router Tips, Jigs & Techniques
Does this make sense?
Janet
cutting preference
Actually, I prefer cutting box joints with the Freud box joint saw blade. It will cut 1/4" & 3/8" fingers perfectly and stay sharp much much much longer than a router bit. But if your going to use a router bit and cut multipal pieces at a time, or individually for that matter, I would stick with a spiral up cut, (which will actually be a down cut when in a router table) You want to get the chips out of there and not force them up into the "dado" you are cutting, especially important if doing multiple boards in a single pass.
Another tip, I like to cut the fingers 1/32"-1/16" longer than needed and hand sand to give the box a "log cabin" look or orbit sand with fine paper till the fingers are flush. That's determined by the final look I'm after at the moment, variety is the spice of life.
But they only describe the look of the bit, not the way it works.
Up/Down use
I use the two bits as follows. Up cut, if I'm only using it to make a plough or dado( something that has a bottom) Down cut, if the cut will be going completely through the material.
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