Please note: I've edited this post to reflect v2.0 of this tool V1.0 did not perform up to my expectations. See below for new text and photos.
I've been using the "popsickle stick" method Cumpiano illustrated in his book for cutting the edges of my classicals' rosette channels for far too long.
I'm still using ready-made rosettes. (I know, I know, I should design and make my own -- all in good time) But one of the problems with ready-made classical rosettes, less so with steel-string acoustics, is each rosette has a slightly different OD and ID, even if they're all the same design. I got tired of punching new holes in my stick (which was actually a piece of spruce soundboard offcut), so I decided it was time to get serious about this and make a decent adjustable cutter.
I did a bit of brainstorming and, being a cheap bastid, I rummaged around in my shop, seeing what sort of materials I had on-hand that I could put to good use. I decided all I'd need would be a small piece of closet rod, small sections of 1/2" and 1/4" dowels, a couple of threaded inserts, and a couple of thumbscrews. Oh, and after thinking about it a bit more, I decided to include some EIR from a piece of back offcut I had lying around.
I needed to start with a longish piece of closet rod so that it would sit in the hole-drilling jig pictured above. I then drilled a hole for the 1/2" dowel piece. Once the hole was drilled, I trimmed the closet rod piece to the length I needed. Then I drilled a 5/16" hole in the top all the way through to the cross-drilled hole, and threaded in the insert for a 1/4"-20 screw. Next, I drilled a 1/4" hole in the bottom of the piece and matched it up with the EIR offcut, which already had a 1/4" hole, thanks to the circle cutter I used to cut it out. Inserted a small piece of 1/4" dowel, and glued the three pieces together.
I machined a flat edge in the dowel so the top screw would keep it from turning, and so that it would have more material to bite against. Then I drilled a 1/4" hole in the 1/2" dowel piece about 3/4" deep, and attempted to thread in the insert for a 10-24 screw. It didn't work so well. In fact, the original design didn't work that well at all really. Originally, I cut a slot in the dowel for an X-acto blade. The problem with this design was, when I tightened the thumbscrew on the end, the wood spread apart at the slot, forcing the blade out an an unacceptable angle, plus I could never really get it snug. Not only that, but an X-acto blade is fairly flexible, and it was sitting high enough above the top so that, when cutting and transitioning from cutting perpendicular to the grain to with the grain, the blade flexed and wandered. Really not acceptable. So I redid the design. The following photo shows the new one. As before, I drilled out the dowel for the threaded insert and superglued it in place, because otherwise if I tried to thread it into the dowel, it just wanted to split. Next, I superglued a fender washer on the end of the dowel. I decided I would try holding the blade in place with two fender washers, clamped down with a socket-hex screw. Finally, I replaced the X-acto blade with an old jigsaw blade. I honed a nice edge onto the jigsaw blade and tried it out on some cedar. It cut well. Nice thing about the jigsaw blade is it is much less likely to flex. That, and the wide fender washers adding additional support have pretty much ended the flexing issue.
A shot of the finished cutter. I'm not concerned about lining the 1/2" dowel with metal to reduce the chance of the wood getting chewed up from the screws, since the pressure needed is just barely finger-tight.
I had the wood components lying around the shop. The thumbscrew, socket screw, and inserts cost me $2.52 at my local around-the-corner hardware store. Time to build and assemble (not including glue drying time) was less than an hour. A nice little project for a lazy Sunday afternoon.
Best,
Michael
Michael McBroom38838.7629282407
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