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Scarf joint

Discussion in 'Tele Home Depot' started by Laren, Aug 23, 2020.

  1. Laren

    Laren Tele-Meister

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    Hey all,

    I have a piece of sapele left over from sticking the two halves together for my body blank. Unfortunately it's not long enough to get a neck out of. It is wide enough to get two length wise bits out of it. Is there any reason I can't use an angled cut to join the length wise (like a scarf joint thing) so as to use as a neck? I don't see why not but then I don't know the 'ins and outs' as it were. Any thoughts welcomed.

    Paj
     
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  2. Fretting out

    Fretting out Poster Extraordinaire

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    Is the scarf going to be in the middle?

    If so I’ve never seen it, it wouldn’t hurt to try

    It’s perfectly okay to use a scarf joint to affix a headstock, I wonder if anyone here has put one in the non traditional location

    Good question!
     
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  3. Laren

    Laren Tele-Meister

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    Yes, in the middle basically. Can't think what else to use my leftover bit for so I guess it's worth a try. Apart from the aesthetic look it should be strong enough I guess. Just asking in case I'm missing an obvious 'no you idiot because..'
     
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  4. Wallaby

    Wallaby Tele-Afflicted

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    It seems instinctively bad to rely on end-grain in the middle of the neck, but I can't explain why it's okay at the headstock.

    The headstock at least is not endgrain to the joint there.
     
  5. jvin248

    jvin248 Poster Extraordinaire

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    .

    Here's how the headstocks are done. They glue end grain to side grain. Gluing end grain to end grain increases the risk of a problem perhaps.

    Large glue surface area is how it works. Image shows 11 degrees, I think PRS uses 9 degrees for their S2 MIA guitars. "most accurate miter saw ever" or something like that they called it on the production tour I was at when they launched the S2 models. They brought the technique from their Asian factory partners back to their US factory.


    [​IMG]


    What if you cut your blank into half a dozen "inch wide" strips, so you could scarf joint them then stagger the joints throughout the neck by laminating the strips together? Look at oak flooring, siding, or shingles where none of the joints line up from strip to strip. Or you could bias the scarf joint location at say 60%-70% of the total length you need, cut one scarf joint, glue it, then strip cut the board and flip end for end or slide every other one so the joint does not line up. See how the boards in this flooring terminate randomly.

    [​IMG]

    Add in contrasting wood strips that go the whole length. Or use this board to make these contrasting strips, by scarf jointing them longer, in an otherwise all maple neck. Then you can use your exotic wood in several necks.

    [​IMG]



    .
     
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  6. guitarbuilder

    guitarbuilder Telefied Ad Free Member

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    You could probably do it and it would work. The fretboard would help support the joint. People add splines toward the ends of necks. I've scarfed the end of a peghead to make it longer. Sapele is pretty cheap though... I might just try and procure a long enough piece unless there isn't any other timber option.

    This joint is about 1/3 of the way in length of the neck:



    https://www.warmoth.com/Guitar/Necks/Arcade/WarmothPro/
     
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  7. Engraver-60

    Engraver-60 Friend of Leo's

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    https://www.rockler.com/finger-joint-router-bit

    Provides tons of glue surface, and is widely used in Asian furniture imported to USA. We have a kitchen table that is beech and maple from Unfinished Furniture, made in Vietnam, and it is all constructed with this type of joinery. I guess they were able to use all the shorts to make an 8' x 6' table top.
     
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  8. Laren

    Laren Tele-Meister

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    Very interesting. I'll have a think about this. I've got plenty of maple so that would work fine.
     
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  9. scook

    scook Tele-Meister Silver Supporter

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    I’ve seen several small scale builders reinforce necks with carbon fiber rods, something like that might help. I’d think a slab fretboard would help out too.
     
  10. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I use scarf joints on all of my heads - I think it is stronger and far less wasteful of wood. My only concern about doing it in the middle of the neck would be jigging it so the pieces don't move under clamping pressure. Any of my build threads show how I do it, including the current classical.
     
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  11. crazydave911

    crazydave911 Doctor of Teleocity

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    It WOULD work but do want it too? The overwhelming thing for me would be how it looked. I've done this a few times at the heel end of the neck where the joint would be hidden in the pocket. Your choice ;)
     
  12. rangercaster

    rangercaster Poster Extraordinaire

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    You will never know if it will work until you try ...
     
  13. Peltogyne

    Peltogyne Friend of Leo's

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    I'd worry that a scarf joint in the middle of the neck will cause areas of different stiffness in the neck making difficulties in setup.
     
  14. BelairPlayer

    BelairPlayer Tele-Afflicted

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    Isn’t the Scarf Joint where Steven Tyler buys all of his clothes?

    Hey, thanks everybody! I’ll see myself out.
     
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  15. stratisfied

    stratisfied Tele-Holic

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    The reason you never see it done that way is ... it's a bad idea.

    Most scarf joints are at or near the headstock where there is less bending and deflection. Here's a test ... lay a 2x4x8 across 2 concrete blocks at either end leaving a 6' span in the center. Cut a notch halfway through the 2x4 near the end and stand on the 2x4 mid-span ... no failure. Now do it again except cut the 2x4 at mid-span and stand on it. I think you know what the outcome will be.

    I know the "glued joint is stronger than the wood itself" crowd will argue the point but it's not going to work due to the stresses on the neck at that point (shear and tensile) being magnified (lever action) by the bending moment at mid-span.

    The closer the joint is to the headstock, the lower the bending moment and the more the stress of string tension wants to act in compression. In the 2x4 example with the cut near the concrete block, the 2x4 reacts only in compression and shear and the tensile forces pulling the wood apart are lower.

    The strings on a guitar also act like the post tensioning cables used in concrete structures to reduce deflection under load adding more strength through compression. The added compressive forces counteract the tensile forces trying to separate the joint when the joint is closer to the headstock.
     
    Last edited: Aug 25, 2020
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