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| How much play in dovetail neck joint? http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=9941 |
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| Author: | Michael Lloyd [ Thu Dec 21, 2006 2:56 pm ] |
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Hi, I'm new here and would like your opinion on the dovetail joint for the neck. Should there be any play in the joint when dry before applying glue? I have noticed that when I apply the glue I get some swelling and I am not always happy with the fit. Usually it ends up being too tight a fit and I really have to apply excessive force to seat the joint to my liking. Your thoughts on improving the fit would be greatly appreciated. My hide glue beads of the brush and is at 140 dg. F. |
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| Author: | Anthony Z [ Thu Dec 21, 2006 3:30 pm ] |
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There shouldn't be any play in the joint. The most critical part of the joint is the bottom of the heel. Due to string forces the neck will tend to want to pull away from the body at the bottom of the heel. When you dry fit the neck, it should be snug enough such that you aren't relying on the glue to hold the bottom of the heel tight to the body. To test that -- push on the underside of the neck near the headstock -- there should be no gap between the cheeks of the neck and the side of the body. When you disassemble the neck it should slide out with a small rap on the bottom of the heel. [EDIT: I place a hardwood block on the heel cap and give it a rap with another block of wood or with a small hammer if one is handy. Besides its fun -- I love the sound of the "BOING" made when the body resonates.] What I have been doing is making the fit so that the neck easily slides in and out then adding a small almost paper thin veneer shim at the bottom of the dovetail tenon. It's a fiddly joint isn't it - last thing you want to do is make it so tight with the glue swell that you crack the neck block. I hope that helps |
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| Author: | Tom Morici [ Thu Dec 21, 2006 8:33 pm ] |
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Anthonys post is good info. Is it possible your HHG is too thick. It should be like thin syrup. I always have to add water as I use up my current batch. Just a thought. Tom |
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| Author: | Kevin Gallagher [ Thu Dec 21, 2006 11:22 pm ] |
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Your dovetail joint should need to be pushed in to its final set position with moderate pressure and your neck should stay in place fairly securely with no glue present. You glue application in the joint should be minimal. If it stops the neck from being completely set, the glue is either too thick or there's just too much of it. When you mix your hide glue, it's thinner than you'd expect it to be. We're so used to the thickness of Titebond and other glues that we can tend to think our hide glue should be the same which is way too thick. Regards, Kevin Gallagher/Omega Guitars |
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| Author: | Michael Lloyd [ Sun Dec 24, 2006 2:01 pm ] |
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Thank you gentlemen. When dry the dovetail joint is a good fix with no play in any direction. My glue is thick similar to the Titebond so I will thin and give it a go. You suggestions are greatly appreciated. Happy Holidays. |
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| Author: | tippie53 [ Mon Dec 25, 2006 12:17 am ] |
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Here is a trick I learned that serves me well to this day. As Kevin pointed out the Dovetail should be a tight fitting joint. This is actually a mechanical joint in that it is interlocked to the mating surface. Using Chalk , you mark up the neck block , then press the neck into the joint. As you will see chalk will stick to the touching faces and tell you where you are high. If you can twist the neck at all you are too loose. I have found that when you look at the neck , your critcal area is the lower 2/3rds of that are deepest into the block. You do want to clear all mating edges so they don't hold the joint off. You also want to have at dry fit the fretboard high about the thickness of a business card .008 to .010 off the top to assure a good mechanical bite. then when you do glue up you are forcing the joint together. This not only gives the joint strength but will pull the heel into the body. Keep the lower heel celar to about .010 of the body so that you don't pop it off. Those that have gotten to tour Martin may have seen the neck setters setting a shim behind this part of the heel. I asked them ,thinking this was a finish clearance and was told they do this so they know the heel is just off the body so when the set is complet they don't have to repair a broken heel. MERRY CHRISTMAS TO ALL |
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| Author: | Martin Turner [ Mon Dec 25, 2006 10:50 am ] |
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Chalk works but I find carbon paper leaves a more visible mark. I wrap the carbon paper around the tenon with carbon facing the tenon and then slip the tenon into the mortise. Works for me. Getting an M and T joint right is a challenge but its a great feeling when you do finally get it right. |
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| Author: | tippie53 [ Mon Dec 25, 2006 1:15 pm ] |
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Careful to be sure to clean out all the carbon paper. The oils in the ink can work against your glue. Chalk will acccept glue and not cause a problem if you miss some. |
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| Author: | Martin Turner [ Mon Dec 25, 2006 2:06 pm ] |
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Good point Tippie. |
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| Author: | tippie53 [ Mon Dec 25, 2006 11:17 pm ] |
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The most important point here is that the joint be firm and stable when dry fitted. Most people tend to "overdo" this joint. If you use Carbon paper chalk or pencil lead , any one of these will help you see where you are making contact and where you are not. |
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