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| calculating binding purfling channel size http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=9503 |
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| Author: | letseatpaste [ Sat Nov 25, 2006 1:18 pm ] |
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When you are setting up your router or gramil or whatever to cut binding and purfling channels, do you make an allowance for the thickness of the glue? If so, how much do you figure? I'm using my luthiertool binding jig, and I tested on scrap and thought I had it adjusted just right for the width of the purfling ledge. I dry fitted some pieces to the scrap and it looked dead on. Then I routed the guitar and it still seemed fine in the dry run, so I glued it on (Titebond original) and now the purfling is sticking over the ledge. I think I'm going to rout it off and try again. (This is par for the course on this guitar, it's fought me every step, but I'm determined to defeat it). An aside... This is my first experience with the luthiertool jig. I'm developing a love-hate relationship with it. The channel is really nice and crisp with the downcut spiral bit, no fuzz or tearout. It's so nerve-wracking to use, because if it tips inward just once, it leaves a divot or a deeper channel... I'm already adding one more piece of purfling because of this. It did get a lot better when I changed my hand position on the jig making it less likely to tip inward. |
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| Author: | peterm [ Sat Nov 25, 2006 1:32 pm ] |
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Jon, its ok if the binding sticks out a bit as you can scrape it flush. But I always allow about .010 to .015 for glue and wood expansion as it absorbs some glue. Having said, its better to scrape flush than routing to deep and then having the binding not be thick enough to conform to the sides. If its only a very little amount sticking out, I would just scrape it off and don't bother re-routing it. Good luck... |
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| Author: | letseatpaste [ Sat Nov 25, 2006 1:39 pm ] |
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It's really the purfling ledge I'm a little concerned about... I wanted the purfling to just sit flush or ever-so -slightly proud of the channel, so the binding could be flat against it with no void. Right now, the purfling is hanging over by a significant amount in my estimation, I actually had trouble with it slipping off of the ledge while I was gluing and taping. I'm also trying to install two pieces of b/w/b purfling, which is sort of makes it an additional pain to get everything glued and in place. |
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| Author: | peterm [ Sat Nov 25, 2006 1:45 pm ] |
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hmmm,with that much purfling I would add about 0.015 to the ledge since you'll have a bit more glue to worry about. You can also try on a piece of scrap wood with glue first to make sure. |
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| Author: | Rod True [ Sat Nov 25, 2006 1:52 pm ] |
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So from the sounds of it Jon, your just installing the purfling first, than doing the binding? On my first, I used titebond for the purf/binding job, but glued them both on at the same time. My purfling lines were home made (zealous idiot) and I had three purfling lines and the binding. It was very messy but it all worked out fine as all the swelling from the glue happened to all of the components. I'm having a difficult time trying to figure out how doing one step at a time is easier than just doing all of them at once. Also, do you just route the purfling channel, glue in the purfling than cut the binding channel? I would think the first option is the only way to go as there would be to much squeeze out, getting into the binding channel to clean up before installing the binding. Have you tried the CA method yet Jon? I did this on #2 and I don't think I'll ever look back. You route the channel to exact size with about 0.005+/- overhang for the binding, tape it all on into the channel, get the miters just "perfect" and when your happy with the fit, wick a little bit of thin CA over the binding and purfling. remove the tape after about 30 mins and wick in a bit more where the tape was. The most important part of using the CA method is this... Seal the channels with shellac or thinned down lacquer first If you don't there can be a tendency for the CA to discolor the top wood. |
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| Author: | letseatpaste [ Sat Nov 25, 2006 2:12 pm ] |
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[QUOTE=Hesh1956] Jon that was my fear about this jig and why I am changing jigs before the next guitar.[/QUOTE] I'm still hanging in there with it for now... I'm just sort of surprised because I heard nothing but rave reviews from the people that had it, and I know lots of people use this style of jig. I wonder if a different shaped base would make it less prone to this. I've considered the thin superglue method, I remember reading about it in the GAL quarterly. It seems like a really slick method. The fumes bother me a bit, and I'm trying to limit my exposure to that sort of thing. I may keep that as a last resort. Thanks for the ideas and advice. I think I'm going to go rout off the purfling and go a little deeper with the channel. Mostly the reason I'm installing the purfling first and then the binding is because that's how I did it in Harry Fleishman's class. Also, it seems like that would allow you to fuss around and get better miters and joints. I'm also going to have a side purfling mitered at the tail wedge, and I'll glue those in at the same time as the binding. I remember someone here suggesting that (not gluing side purfling to binding before bending) as it allowed for better miters. It just seems like it'd be a mess trying to do it all at once. I've only bound one guitar before. I'm in learning mode, though, I'll rout it off and redo it till it's right. |
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| Author: | Serge Poirier [ Sat Nov 25, 2006 5:03 pm ] |
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Jon, i don't have the tool you're using but a home made one and i routed both the purfling and the binding channels , i then glued and taped separately so i could scrape it all flush at once, if that could be of any help. Serge |
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| Author: | Colin S [ Sat Nov 25, 2006 8:38 pm ] |
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The nice thing about using a laminate trimmer with the guide wheels attached to the trimmer rather than the bit is that if you do make a bog up of routing the purfling channel and end up with gaps it is easy to put in a smaller downcut bit and either cut the purfling out, leaving the binding, or make another 1mm or so cut and add another strip of narrow purfling. Don't ask how I know about this! I have in fact installed the binding, then cut a channel for the top purfling afterwards (changed my mind on the design!). It ended up the neatest purfling job I've ever done. I do always use a gramil first to define the channel. For a laminate trimmer with the guide wheels used in a Fleishmann/Williams jig the modification designed by Dave White using a second lazy Susan on the trimmer mount is needed. Colin |
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| Author: | Tom Armstrong [ Sun Nov 26, 2006 12:03 am ] |
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John, This won't answer your question directly but I would suggest you go to this link and watch how a pro installs the purf and bindings. I'm sorta new at this, having only six builds under my belt but when I recently discovered this site it was a real eye opener for me. It gave me some ideas and validated many that I had come upon through trial and error (mostly error). http://www.taylorguitars.com/video/factory-fridays/ good luck and keep on keeping on, Tom Armstrong |
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| Author: | Cocephus [ Sun Nov 26, 2006 12:20 am ] |
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Rod, I`m intigued by the CA method. Does the CA wick in far enough to hold things in place reliably? I`d hate to see purflings and/or bindings work themselves loose later on. BTW, a buddy of mine had the herringbone on his Martin (D-28, I believe) come loose last year. Kinda surprised me as he take care of his gitter. |
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| Author: | TonyKarol [ Sun Nov 26, 2006 1:24 am ] |
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I route the purf ledge dead on or a hair shy ... then the binding ledge is 85 thou (I have a dedicated 7310 an 1/4 downcut router set up only for this, homemade jig just like the luthiertool one), and I use about 90 thou binding. You want the binding to really sandwich the purf on its ledge tight, I leave no allowance for glue. I also use the CA method, with a quick french polish on the top only, not into the ledges, and maybe I am just lucky, but I never get dicoloration at the binding with this method - I also give everything a good sand though afterwards too. |
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| Author: | Rod True [ Sun Nov 26, 2006 2:54 am ] |
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Coce... Tony would probably be a better person to ask regarding the CA method, or anyone else with more experience than me. I have 3 guitars built with the CA method and they are all holding up just fine. |
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| Author: | TonyKarol [ Sun Nov 26, 2006 3:00 am ] |
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None of mine have ever come apart ... yet. Not sure what glue martin uses, but remember in a lot of areas, you are gluing to the end grain of the top on the vertical ledge - titebond provides a lousy joint into end grain. Who is to say they got any glue in there at all as well ??? |
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