Alchool Posted June 22, 2003 Report Share Posted June 22, 2003 I glued two pieces of maple for a neck using polyurethane glue. Now that's dry and the excess glue has been scraped, the join is quite visible. Then I realized that the laminates were machine-planed and I forgot to sand them before glueing. Now, I don't mind if the join is visible, since I'll put an ebony fingerboard on it and paint the neck black, but I'm scared it could cause some problems... Should I cut some other laminates and make another neck? Quote Link to comment Share on other sites More sharing options...
Scott Rosenberger Posted June 22, 2003 Report Share Posted June 22, 2003 Nah, if you used Poly Glue that thing should stay together forever. Chances are you didnt use quite enough clamp pressure when glueing. Poly Glue expands as it cures thats probably why you're seeing the glue line Quote Link to comment Share on other sites More sharing options...
Alchool Posted June 22, 2003 Author Report Share Posted June 22, 2003 Nah, if you used Poly Glue that thing should stay together forever. Chances are you didnt use quite enough clamp pressure when glueing. Poly Glue expands as it cures thats probably why you're seeing the glue line I'm so happy to read this Quote Link to comment Share on other sites More sharing options...
westhemann Posted June 22, 2003 Report Share Posted June 22, 2003 yeah scott's right if you clamp it tightly you will not see a line.if you sand it though make sure to leave it rough so the glue will stick.i have often wondered about the possibilities of using dovetail joints for laminates. Quote Link to comment Share on other sites More sharing options...
Scott Rosenberger Posted June 22, 2003 Report Share Posted June 22, 2003 i have often wondered about the possibilities of using dovetail joints for laminates. I think it would look cool but it's probably overkill Quote Link to comment Share on other sites More sharing options...
Setch Posted June 23, 2003 Report Share Posted June 23, 2003 yeah scott's right if you clamp it tightly you will not see a line.if you sand it though make sure to leave it rough so the glue will stick.i have often wondered about the possibilities of using dovetail joints for laminates. 1. Don't clamp too tight. You risk forcing all the glue out of the joint and creating a starved joint. The role of clamps is to hold the joint whilst the glue dries, not to force a poorly fitted joint to close. If you want invisible glue joints, the only answer is getting both components totally flat - if you joined surfaces which were still only rough planed a visible glue line is inevitable. I'm pretty sure that your joint will hold fine, so if you can find a cosmetic solution go ahead and use the neck as it is. 2. Don't leave the surfaces to be joined rough - contrary to what most people believe the best glue joint with wood is created by joining totally smooth surfaces together - ie planed or scraped surfaces hold best. The common exception to this is when using epoxy, or joining disimilar materials - ie glueing plastic binding, in these cases raising a little 'tooth' helps. I'm sure I'll get a few people raising eyebrows at this, but it is accepted as fact by most experienced builders and woodworkers. 3. Dovetails for laminates would look amazing - I'm totally with you there. However, they would be totally hopeless mechanically, since the grain direction would mean there was short grain at the base of every dovetail, making the joint weaker than a standard flat lamination. Quote Link to comment Share on other sites More sharing options...
westhemann Posted June 24, 2003 Report Share Posted June 24, 2003 yeah scott's right if you clamp it tightly you will not see a line.if you sand it though make sure to leave it rough so the glue will stick.i have often wondered about the possibilities of using dovetail joints for laminates. 1. Don't clamp too tight. You risk forcing all the glue out of the joint and creating a starved joint. The role of clamps is to hold the joint whilst the glue dries, not to force a poorly fitted joint to close. If you want invisible glue joints, the only answer is getting both components totally flat - if you joined surfaces which were still only rough planed a visible glue line is inevitable. I'm pretty sure that your joint will hold fine, so if you can find a cosmetic solution go ahead and use the neck as it is. 2. Don't leave the surfaces to be joined rough - contrary to what most people believe the best glue joint with wood is created by joining totally smooth surfaces together - ie planed or scraped surfaces hold best. The common exception to this is when using epoxy, or joining disimilar materials - ie glueing plastic binding, in these cases raising a little 'tooth' helps. I'm sure I'll get a few people raising eyebrows at this, but it is accepted as fact by most experienced builders and woodworkers. 3. Dovetails for laminates would look amazing - I'm totally with you there. However, they would be totally hopeless mechanically, since the grain direction would mean there was short grain at the base of every dovetail, making the joint weaker than a standard flat lamination. i am with you but i actually meant a dovetail running the length of the body for strictly mechanical purposes.i just have seen some dropped guitars which were broken at the glue joint and am looking to avoid that.but i think you could get around the short grain problem and dovetail it as you and scott are talking about by running the grain crossways.instead of the length of the guitar run the grain from the upper horn sloped down about where the jack is.see what i mean?might make for an interesting look also. and of course you are right about the joint.what i meant to say was not to sand it finer than about 220 if he didn't have a joiner or planer.i buy all my wood with one edge already planed so i don't have to mess with it. i have found the correct clamping pressure to be right at the point where the two pieces of wood almost meet.i clean up the glue that is forced out and clamp until i see a fine line of yellow,about 1/64" thick.then when the glue dries it is clear and you cannot see it at all.it takes me about 10 minutes to clamp a piece where i am happy with it.then i ussually check it every 2 minutes or so to make sure it doesn't walk.but that's just me being paranoid but you sound like you have more experience in this area than me.how about a walk through of your procedure? Quote Link to comment Share on other sites More sharing options...
Setch Posted June 24, 2003 Report Share Posted June 24, 2003 i am with you but i actually meant a dovetail running the length of the body for strictly mechanical purposes.i just have seen some dropped guitars which were broken at the glue joint and am looking to avoid that.but i think you could get around the short grain problem and dovetail it as you and scott are talking about by running the grain crossways.instead of the length of the guitar run the grain from the upper horn sloped down about where the jack is.see what i mean?might make for an interesting look also. Hmmm. I think you'd still have grain trouble if you ran the dovetail joint at less than 45 degrees off the grain direction. Hope that line makes sense... It would certainly look pretty cool, but I doubt even with the grain angled it would add much strength. If you've seen a guitar break along the glue join I would attribute that to a poor joint, if the joint was executed correctly it should be stringer than the original wood. For once an ad slogan is actually true! and of course you are right about the joint.what i meant to say was not to sand it finer than about 220 if he didn't have a joiner or planer.i buy all my wood with one edge already planed so i don't have to mess with it. Cool. I buy most of my wood thicknessed but unplaned, so I have to prepare it. I usually run timber through my DIY router table to square and straighten edges, then sand with 80 grit paper on a slab of plate glass to get then dead flat. Finally, I scrape with a cabinet scraper or plane iron to remove the sanding 'fuzz'. i have found the correct clamping pressure to be right at the point where the two pieces of wood almost meet.i clean up the glue that is forced out and clamp until i see a fine line of yellow,about 1/64" thick.then when the glue dries it is clear and you cannot see it at all.it takes me about 10 minutes to clamp a piece where i am happy with it.then i ussually check it every 2 minutes or so to make sure it doesn't walk.but that's just me being paranoid but you sound like you have more experience in this area than me.how about a walk through of your procedure? Not that much experience - I'm building guitar number 3 at present After the procedure above, I find that most of my neck laminates, or body joints will lie together so the line is virtually invisible using just finger pressure. I also hold then upto the sun to ensure they are light tight, no light should be visible through a good joint. If they fit that well dry, I lay them together, drill a 2mm hole in scrap at each end, then glue them up using a cocktail stock through the hole to prevent them slipping around like a burger with too much mayo! I whack a whole load of clamps along the length, but only apply enough pressure to get squeeze out along the length of the joint. I don't have a pic of the neck clamped up, but here's one of the body. Quote Link to comment Share on other sites More sharing options...
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