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A question, probably for Bob Holo.

Hello there,
Could you please tell me how one routs the oval rebate for the rosette on a 'petit bouche'?

I'm keeping my fingers crossed that it's sufficiently complicated for me not to have to hang my head in shame and embarrassment for not having been able to work it out.

Many thanks.

Comments

  • Bob HoloBob Holo Moderator
    Posts: 1,240
    It's not like routing a standard rosette. IE: you can't drill a hole in the center and use a jig to scribe the holes and rebates. Oval jigs with center pinions, for reasons of geometry, are only good for holes that are more "oval" than the blunted design of selmer soundholes.

    So you have two options. The more difficult and inaccurate is to secure the soundboard to a flat surface and then secure a small oval shaped block to it and then use increasingly large pattern cowls attached to the router base to progressively work outward. The reason this is inaccurate is that errors in the small center block get magnified as you work outward and also - it is more difficult to hold a router tight to the outside of a small solid pattern than it is to hold a router to the inside of large cutout patern.

    The other option is to start with a large oval shaped cutout and secure it to the soundboard (and the flat work surface) and use progressively larger pattern cowls attached to the router base to work progressively inward. The reason that this is more accurate is that errors in the cutout get minimized as you work inward. The challenge is getting the soudboard secured properly and getting the pattern secured properly without damaging or putting holes in the soundboard. My current technique needs improvement so I'm going to stop short of giving specific recommendations. Bottom line, you secure everything well and do it all at once... the whole rebate for the rosette... if you try moving the pattern... there is no way you'll be accurate enough. If you really pay attention - you can re-attach the pattern to the soundboard later to cut the soundhole because if the consistency of the strip of wood between the rosette and soundhole is off by a few thousandths - the world won't come to an end. But if the rosette channel is inconsistent in width by a few thousanths of an inch it looks like hell. One way to get very accurate on the consistency in width of the rosette channel is to cut it in one swath with a half-inch fluted cutting bit... but it is also a good way to really mess up if you slip :) With the good there is always bad, right? It's good to cut the soundhole after doing the rosette because expansion of the rosette material can chip off material on the inside if you've not left much space between the soundhole and the inside of the rosette. In fact, it's good to have the rosette go in "not too snug" because when you glue the rosette inlay it will expand and you might not get it in to the channel and/or it will expand and pop out before you can get it weighted or damage the wood around it (bend / tear fibers)

    When you get the rosette in - cover it with wax paper covered wood or non-stick baking paper covered wood or HDPE covered wood and gently weight or clamp it till it drys. Alternately you can soak the rosette with thinned cyanoacrylate and spray it with hardener as you hold the rosette in with a HDPE mallet or similar... sort of the "Charles Fox" method.

    One more thing - I've heard some people say: "pre-cut the rosette channel freehand with a razor knife to reduce fuzz and tear out" and that is not good advice. The best advice is to get a really sharp high quality router bit to use only for rosettes - treat it gently - clean it often - only use it for cutting binding and rosettes in soundboards. Never use it on harder wood or for other utilitarian tasks. CMT makes great router bits. Concentrate on getting the cut right. If you get a little fuzz - gently brush it out of the way so it doesn't spoil the fit of your joint and keep working. It will sand away later. Fuzz is not the enemy... what people do to avoid and remove fuzz is the enemy. Spruce is very stringy and will produce fuzz no matter how it is worked.

    Party on.

    Best yet, get Collins' book (if he ever publishes it... Hi Michael :)
    You get one chance to enjoy this day, but if you're doing it right, that's enough.
  • DiggerDigger New
    Posts: 77
    Thanks for your helpful reply, Bob. It was more or less as I suspected. As you quite rightly point out, the problems stem from the geometry.

    Oh well, I shall make up some templates and get stuck in. It'll be a long process but I'll post a few photos from time to time if any of you'd be interested.

    Thanks again, Bob, and cheers for now.


    P.S. I dream about the Collins book. :lol:
  • Josh HeggJosh Hegg Tacoma, WAModerator
    Posts: 622
    I have taken a short break from my guitar building project in hopes that that book would come out. I'm getting to the point where I think I'm just going to move on without it. I'm ready to attach the back to the sides. So I guess I'm just going to jump right along and hope that I don't have to start over due to any huge mistakes.

    Cheers,
    Josh
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