Neck has back bow after cutting

Discussion in 'Tele Home Depot' started by 1bad914, Aug 11, 2020.

  1. 1bad914

    1bad914 Tele-Holic

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    I cut a beautiful piece of 3x4 inch QS Mahogany for an acoustic neck. As soon as I cut the main shape out the piece started moving. It has now settled, but has a back bow. It is about 1/8 Inch of bow.

    Not sure what I should do. I have not glued the fretboard on yet.
    1. Glue the FB on and hope the string pull and truss rod straighten it out?
    2. Glue the FB on with the truss rod cranked to fight the back bow?
    3. Try to straighten the neck out before gluing on the FB? How?
    4. Throw a $140 piece of wood in the burn pile.

    Thoughts??
     
  2. guitarbuilder

    guitarbuilder Telefied Ad Free Member

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    My rule of thumb is to rough cut a neck out of a billet so that is oversize. That way it can move and then be squared up. Maple is worse than mahogany in that regard. Wood has internal stresses that get released when you cut into it. Some wood that dries too fast develops what is called "case hardening" and the saw kerf starts to close as soon as you cut into it. Hopefully you can salvage it by making a two piece neck. I've found when you try to get too many necks out of a billet to save money, it usually doesn't work out, so I am more conservative and have a bit more waste.
     
  3. 1bad914

    1bad914 Tele-Holic

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    This was one solid piece, one neck only.
     
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  4. 1bad914

    1bad914 Tele-Holic

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    Here is a picture for clarity.

    85213A0C-B1BA-4768-A7E2-6AADA26371C9.jpeg
     
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  5. guitarbuilder

    guitarbuilder Telefied Ad Free Member

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    Joint it flat and then put on a thicker fretboard or add a veneer in between the neck and fretboard. I personally wouldn't want a neck that starts out warped in the beginning of the build process and then try to bend it back or rely on the truss rod to bend it straight. Wood has a mind of its own. I've added a veneer back in my early days to salvage a neck. The guy loved it as it was dyed blue and looked like a racing stripe.

    https://www.lmii.com/wood-veneers/653-black-veneer-06mm.html
     
    Last edited: Aug 11, 2020
  6. Engraver-60

    Engraver-60 Friend of Leo's

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    Is there any way to wet the top surface, and then clamp it firmly to a granite plate to make it flat? Or will it just bounce back to being bowed? I had a Martin D-35 that kept back bowing, and the luthier in Nashville (Old Time Pickin' Parlor - 1977) steamed it and bent it over his knee to straighten it. It was a 1976 that did not have adjustable truss rod.
     
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  7. G.Rotten

    G.Rotten Tele-Afflicted

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    Go with this at this point. Wood should be cut over sized, then left to settle for a bit, then squared & shaped. If you think of all the fibers of wood working together to hold the piece in one resting state, then removing some of the wood will create a new resting state.
     
  8. 1bad914

    1bad914 Tele-Holic

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    I thought about wetting it down and heating it while bending it over something with clamps. It is firewood as it is.
     
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  9. Freeman Keller

    Freeman Keller Friend of Leo's

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    So when you say it has "about 1/8 inch of (back) bow" you mean that you planed the top surface (mating with the f/b) perfectly flat on the billet before your started and when you cut the head, heel and shape of the neck it is now 1/8 higher in the middle of the f/b surface? That is a huge amount and if I'm correct you just built it. I'm afraid that neck would for ever scare me.

    However what I would do right now is plane the top flat again and put it away for a long time - a year or more. If it stays flat I would go ahead and build with it, if it doesn't I would burn it

    ps - if this is the guitar you are building for a commission then there is no way I would use that neck
     
    Last edited: Aug 11, 2020
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  10. Freeman Keller

    Freeman Keller Friend of Leo's

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    I'll add my personal feeling about truss rods. I install the truss rod neutral in a neck that is flat on top. I level the frets perfectly flat. When I string it up I expect the tension to pull a little bit of relief into the neck, usually it will be slightly too much. I use the truss rod to bring that back where I want it. I have never had a case where I had to introduce relief (I hear it happens). I deal with relief in the thousands, ten is a lot.

    If I had a neck that all by itself generated minus 0.125 inch of relief it would be out of my shop so fast.....
     
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  11. 1bad914

    1bad914 Tele-Holic

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    What I did not add to my original thread was that I have already ordered another billet from SM. I am just trying to save this one.
     
  12. 1bad914

    1bad914 Tele-Holic

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    The necks I build are usually very flat and as you stated require very little adjustment once under tension. This is sad. Sigh, oh well, we cannot control what wood will do, we can only caress and cajole it and hope it listens...if not we burn it. Lol
     
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  13. guitarbuilder

    guitarbuilder Telefied Ad Free Member

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    You may want to consider buying wood from a lumber source as opposed to stewmac. I have purchased large billets of 12/4 mahogany from various lumber sources online. I cut my own billets out of them for one piece necks. It's not cheap, but it's cheaper than stewmac.

    https://www.bellforestproducts.com/...MImr2MyLOV6wIVVtyGCh3MkQjDEAYYBiABEgK5FvD_BwE

    https://wphardwoods.com/products/regions/central-america/41/honduran-mahogany-genuine-mahogany

    I never heard of these guys before...but 12/4 is roughly 20 dollars a board foot...still cheaper than stewmac for a neck blank. a 3 x 3 x 36 is only 2.25 board feet of mahogany.

    http://www.mahoganykings.com/prelim...MIrLi4wbWV6wIVFU2GCh3G0QJuEAAYASABEgIUG_D_BwE
     
    Last edited: Aug 12, 2020
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  14. Newbcaster

    Newbcaster Tele-Holic

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    I think the granite slab idea is a great one.

    Put a slightly thicker fretboard on it thats well seasoned and won't move.

    Fat strings. God made that wood. Don't waste it.

    If you really decide to burn it, I'll pay postage. Send to me please!
     
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  15. guitarbuilder

    guitarbuilder Telefied Ad Free Member

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    What happens there is the heat softens the fretboard and neck glue joint. Then the clamp pressure allows the wood to slip back into a straighter position as the glue softens and clamps press on it. It's not always permanent. I had to do this a few times at a repair shop I worked at for a short time.

    https://sfguitarworks.com/straightening-a-warped-neck/
     
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  16. Engraver-60

    Engraver-60 Friend of Leo's

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    Can you please take picture of the side view of this neck with a good straight edge on top? That way I can understand why you are so concerned. Thank you.
     
  17. Engraver-60

    Engraver-60 Friend of Leo's

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    And if you decide to burn it - DON'T. I have 5 banjo neck cutoffs that I plan to make an end table out of some day. They'll make great legs, and musicians love this kind of stuff.
    [​IMG]
     
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  18. jimgchord

    jimgchord Tele-Afflicted

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    1/8 is a lot. Id scrap it.
     
  19. 1bad914

    1bad914 Tele-Holic

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    Here are some pics of the mess. It is safe to say that I have a hang dog face today.
    049C0F59-A67C-4577-A676-9F72159DD3DC.jpeg 78092AB9-F73F-4D90-AE20-951BD54D381D.jpeg
     
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  20. 1bad914

    1bad914 Tele-Holic

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    On my router table.
    109C264B-574E-4495-8590-DC0A93B21F44.jpeg
     
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