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Thread: Another Siminoff Neck Joint Question

  1. #1

    Default Another Siminoff Neck Joint Question

    I am making the Siminoff jig to set and glue the neck to the body. The center of the crossmember in the position of the bridge and housing the body during glueing is 7/16". The top of the Cumberland adjustable bridge I'm using, while sitting on the instrument, is at least 7/8" high. How does this geometry work to set the correct angle for the neck and fretboard?

    [IMG]Untitled by Gary Davis, on Flickr[/IMG]

  2. #2
    Registered User
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    Default Re: Another Siminoff Neck Joint Question

    That spacer looks too thick. Several things will be happening after you glue that together. When you're gluing the neck in, there's no fingerboard (with frets) on the neck. If you want, I can measure my spacer like yours for height, but I think it's about 3/8" at the top of arch. That height thing seems to take care of itself. Years ago I erred and made one mandolin where there was a combination of a slightly underbuilt top and too high a neck angle. The bulge in front of the tailpiece showed up a few years later. Just make sure you don't make the top too fragile in front of the tail piece. The height thing should all be fine once you've got the fingerboard, frets, strings, and clearance.
    Seriously, if you want, PM me (cause I don't always log in) and I'll measure and post my spacer stuff tomorrow.

  3. #3
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    Default Re: Another Siminoff Neck Joint Question

    Just eyeballing my bridge right now, I think it's probably about 7/8" hight with action set "bluegrassy".

  4. #4

    Default Re: Another Siminoff Neck Joint Question

    Thanks Dale. I'll check tomorrow to see how close mine is to 3/8".

  5. #5
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    Default Re: Another Siminoff Neck Joint Question

    I'll check mine also.

  6. #6
    Adrian Minarovic
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    Default Re: Another Siminoff Neck Joint Question

    From memory... I use small box of mechanical pencil leads as my height gauge for neck projection (without fingerboard) laying at the center of arch and it is 11 or 12 mm high. I aim for 22-23mm final bridge height.
    I use flat 3/16" fingerboards, some folks use thicker boards and radiused, that will add to final bridge height.
    Adrian

  7. #7

    Default Re: Another Siminoff Neck Joint Question

    Thank you Dale and Adrian. I've got to dispatch some weeds this morning but maybe in the afternoon I can get to the shop.

  8. #8
    Adrian Minarovic
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    Default Re: Another Siminoff Neck Joint Question

    Quote Originally Posted by GaryDavis View Post
    Thank you Dale and Adrian. I've got to dispatch some weeds this morning but maybe in the afternoon I can get to the shop.
    Simple mathematics would be
    projection of neck = planned bridge height - thickness of fingerboard - fret height - 2x action at 12th fret.
    for me it is 22 - 5 - 1 - 2x1.5 mm= 22-9=13mm
    The box I use is 12mm (measured it) and straightedge laid on neck surface passes just above the box when it is laying on top of arch.
    You should count with some drop of neck or arch after first stringing but for me usually the difference between planned and actual bridge height after stringing is less than a mm.
    Adrian

  9. #9
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    Default Re: Another Siminoff Neck Joint Question

    Well, it looks like Adrian and I are in the same club. I just measured mine and it's 7/16", which is just just over 11 mm.

  10. #10
    Registered User j. condino's Avatar
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    Default Re: Another Siminoff Neck Joint Question

    Just make a clean, simple traditional dovetail and you won't need all of those jigs and second guessing extra stuff....

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  12. #11
    Adrian Minarovic
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    Default Re: Another Siminoff Neck Joint Question

    Quote Originally Posted by j. condino View Post
    Just make a clean, simple traditional dovetail and you won't need all of those jigs and second guessing extra stuff....
    And tapered dovetail to be even more traditional...
    Simple it is for you or me, but for first timers with no woodworking background and notion in geometry of the parts it is like solving differential equations with elementary school math knowlegde.

    I posted my method here, all you need is handsaw and chisel and a SHARP pencil:
    https://www.mandolincafe.com/forum/t...etails-by-hand
    Adrian

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  14. #12

    Default Re: Another Siminoff Neck Joint Question

    Thanks again guys. I didn't get to the shop yesterday but I will today. I cut the support to be 7/16" as instructed and its close. But I want to work on Adrian's formula just because I'm OCD, and my fretboard may wind up being a hair or so thicker than 3/16".

    It was very hot in Montana yesterday (and all week) but we had a cold front come through last night with very strong winds and a tornado or two. It feels so much better this morning. But the heat returns next week with forecasts of 100-103F for a couple of days. Yuck.

    Hope y'all enjoy the weekend - Gary

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