Half lap joint?

Discussion in 'Carpenters' Talk' started by dvddvd, May 12, 2023.

  1. dvddvd

    dvddvd Well-Known Member

    I want to take a piece of timber 25mm x 45mm x 700mm and cut it in half. But I'd like to join it back up with a lap joint.
    Would be easy if starting from scratch, but this is a finished guitar neck!
    I know I'd lose the thickness of the saw blade, so would have to take that into account.

    Any ideas how to cut a half lap joint?
  2. robertpstubbs

    robertpstubbs Screwfix Select


    Maybe use a fret saw.
  3. arrow

    arrow Screwfix Select

    Mark out half the thickness on both pieces of timber and cut it with a tenon saw.
    Alan22 and billfromarran like this.
  4. The Happy Builder

    The Happy Builder Screwfix Select

    Pay the extra postage, cutting it in half literally sounds like a way of destroying it.
    billfromarran likes this.
  5. billfromarran

    billfromarran Active Member

    Pity it isn't a violin, you could use a bow saw.
    Roys and robertpstubbs like this.
  6. dvddvd

    dvddvd Well-Known Member

    I want to build a travel guitar.
    You can buy them but they are small bodied guitars with a full size neck. Which if your traveling economy is to long.
    So want to build one that the neck comes apart into 2.

    I built a mock up, with a guitar neck and just cut it in half.
    Then inserted 2 x 60mm x 6mm stainless Steel dowels in one end.
    In the other piece had 2 x 6mm nylon bushings that the steel dowels slid into.
    Then a 2 piece truss rod held both halves together.

    It worked!

    But thought a half lap joint would be stronger? Still use the truss rod etc.

    It's for another mock up.

    If it works better I can make both halves separately and the lap joint would be straight forward.

    But at the moment using pre finished necks to experiment..
  7. robertpstubbs

    robertpstubbs Screwfix Select

    I think you mean what I would call a straight lap joint. You could do cuts 1 and 2 with a tenon saw. I think you would need a fret saw to do cut 3.

  8. dvddvd

    dvddvd Well-Known Member

    Thanks, yes it's the number 3 cut, which would be hard
  9. stevie22

    stevie22 Screwfix Select

    I think you'll need 2 necks to make one.

    The kerf (cuts 1 & 2)will mean that the neck will wind up a touch shorter which I doubt will matter but there will be a small lateral step due to cut 3 which I would have thought would make playing weird.

    If I get a chance I'll quiz my son who spends a lot of his time messing about with guitars.
  10. CGN

    CGN Screwfix Select

    joints 1 and 2 would be better at 45 degrees so they lock in and the string tension won’t try and ‘hinge’ the joint.
    robertpstubbs and Resmond like this.
  11. Resmond

    Resmond Active Member

    Think cuts 1/2 might actually mess with the tuning or at least the intonation, not sure by how much tho
    CGN likes this.
  12. CGN

    CGN Screwfix Select

    missed the bit about using a ready made neck, but def will effect the intonation.
    Resmond likes this.
  13. dvddvd

    dvddvd Well-Known Member

    Hi thanks,
    I would make adjustments for whatever is removed by cutting.

    So I wouldn't just cut everything and then butt up so it's 1mm shorter etc. Same with the number 3 cut.
    I'd make sure the fret board is flat afterwards.
    So intonation would be the same as before
    Resmond likes this.
  14. dvddvd

    dvddvd Well-Known Member

    Thanks I was going to make the overlap around 100mm.

    If it works I'd design one to be cut with my CNC machine which is 3 axis so a basic lap joint would be easier, but yes it would be stronger, I'll look into it.

    Last edited: May 12, 2023
    CGN likes this.
  15. Alan22

    Alan22 Screwfix Select

    Cut it in half, make two female bridle joint sides, and fit one with a tongue.

    If you want to get fancy cut the shoulders at opposing angles and it locks.
  16. CGN

    CGN Screwfix Select

    curious how small a travel guitar needs to be when dismantled? A standard neck removed is not too long
  17. dvddvd

    dvddvd Well-Known Member

    Ryan air carry on max size is 40cms a Fender Telecaster neck is 64 cms long. Or pay £50 each way to carry a full size guitar
    CGN likes this.
  18. CGN

    CGN Screwfix Select

    Yes it’s a pain. Travelled internationally with twangers, but always gone in the hold. Cling filmed multiple instruments ‘as one’ to save on excess baggage
  19. dvddvd

    dvddvd Well-Known Member

    I'm trying to build it so it's no longer than 300mm.
    Going to redesign the headstock and make it shorter.
    The main body will be 150mm wide and then outriggers with a knee rest section and a top section. So it will feel like a skeleton full size to play.
    So total size would be packed away 300mm x 300mm x 25mm
    CGN likes this.
  20. 2shortplanks

    2shortplanks Active Member

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