1937 Kay M4 Neck reset

Discussion in 'Luthier's Corner [DB]' started by Dennis Ramsey, Nov 10, 2021.


  1. My first post on talkbass ….

    I bought this old Kay bass at a yard sale last week without any knowledge of Kay Bases. The evaluation was a decent instrument that needed a neck reset.

    I build Ukuleles so this intrigued me as to figuring I could do a repair similar to the way I build Ukuleles….I do bolt on necks.
    I didn’t spend much for it so no big loss if it doesn’t work out …..

    After getting it home I began to do a little research …. I found the Kay bass registry and began a conversation with Steven Ayers about this instrument ….

    Steven sent Pictures of the neck joint which allowed me to go ahead forward and remove the neck from the body
    I had talked about the idea of a bolt on neck repair and Steve being a nice diplomat he gently encouraged me to get it repaired with the intention of restoring as a historical instrument …. It was a pleasure to talk with Steve and gain some insight into this Bass and I instantly gained more respect for this Bass.

    So I took it over to an old build instructor that I built a 12 string acoustic guitar with years ago in a one on one class … George Leach at the Phoenix Guitar Company. George has done dovetail joints throughout his career and a mentor that I worked with concerning a dovetail joint in the past.

    With this being a 1937 first year M4
    George was excited about the idea of doing it right. So …. Off to Stewmac website to order some Hide Glue! George is going to help guide me and put his hands on the actual repair as to make sure it’s done correctly

    I’ll have a few questions as I get going as to doing things right….

    neck angle?
    Have a Slight bow in ebony fingerboard… is relief normally built in or should it be straight ?


    Dennis Ramsey
    Brothers Ukes

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    AGCurry, marcox and Steven Ayres like this.
  2. eh_train

    eh_train Supporting Member Commercial User

    Jan 12, 2004
    Toronto
    Owner, Stand Up Guy Basses (Repair/Sell/Buy upright basses)
    My .02 cents:

    1) Clean everything up, thoroughly. By this I mean remove any glue and loose bits that are only in the way. Hopefully it's just water soluble hide glue to deal with.
    2) Rebuild the dovetail joint so that it becomes a mortise and tenon.
    3) Fit the new neck joint so you have about 1.5" of neck projecting above the body. This is referred to as overstand, and some old Kays had as little as .5" of it. You'll likely need to glue on a piece at the back of the neck to accomplish this (* see below)
    4) While doing steps 2, 3, and 4, adjust the angle where the mortise and tenon join so that the bridge height is now in the 6-6.5" range. Some old Kays had a bridge height as low as 5".
    5) Repair the button at the same time. A patch glued onto the back of the neck isn't the same as a proper join between the back and the neck.

    There is a lot of calculating and measuring involved in the above. Fortunately you have some luthier skills already. Good luck, and please keep us posted!

    * re. losing the dovetail, this joint was pretty much the worst thing about Kay basses. The joints usually have gaps filled with glue and/or wood shims. You can restore the bass while giving it a much simpler and stronger joint, and the work will be invisible (i.e., nobody sees it until they have to take it apart. And btw, with a dovetail joint that's usually when they break the cheeks of the upper block and let loose a flurry of unprintables). If the neck is out, as in your case, it's a perfect time to make it a much more functional instrument!
     
    Last edited: Nov 10, 2021
    AGCurry likes this.
  3. eh_train

    eh_train Supporting Member Commercial User

    Jan 12, 2004
    Toronto
    Owner, Stand Up Guy Basses (Repair/Sell/Buy upright basses)
    Forgot to mention:

    1) Welcome to Talkbass!

    2) Please let me know, by private message, where this garage sale was and how many more of these they have lying around!
     
    Dennis Ramsey likes this.
  4. Thanks Eh_train for both cents :)

    Yes, I've been looking around at old threads here and began to consider the mortise tenon conversion.
    Thanks for the input and dimensions to work within.

    What is the best way for a button repair?
     
  5. Steven Ayres

    Steven Ayres Supporting Member

    Mar 11, 2007
    Northern Arizona
    The pro luthiers here will have advice from a lot more experience, I'll just help get the discussion going.

    If you're just putting it back together, the angle is already set; if rebuilding the joint entirely, you have choices.

    Raising the neck angle raises the bridge and creates a more acute break angle over it, increasing tension on the sound table.

    Increasing the overstand while maintaining the neck angle will also raise the bridge, but with less added tension. Doing this with an existing neck reduces its footing in the joint.

    A higher bridge is especially practical for bowing. Its effect on the volume and tone of a Kay will depend on other setup factors and the specific response of that pile of plywood.

    Big strings need room to move, so yes the relief is important to good setup. The specific relief you need depends on the weight and tension of the strings you choose and your style of play.

    The integrity of the button helps stabilize the joint, but while it's important to a good look, I don't think it's super-critical to keeping the neck in place. For me, rebuilding one that's been sawn off is an exercise in reengineering the plywood — removing the back, cutting back the inner plies down past the block in steps and replacing them so each new ply is well attached to an old one, alternating grain to create a solid block, then feathering in a new outer ply.
     
  6. You’re getting good advice so far. I’ll go too far, like I usually do.

    Priority one is rebuilding the back button. I’d pick up a sheet of tulip poplar from a craft store, steam the broken button off the neck heel, separate the ebony plies with steam and graft it to the back, feathering in the overlaid plies. Take a week off, swear a lot, and drink some beer.

    Then you get to reset the neck. I wouldn’t rethink projection. Too much pressure on that top and the bass bar might pop, or the top might start to cave in. Rebuild the mortise with spruce and hot hide glue until you achieve a fit you can’t slip a sheet of paper into.

    Kay mortises were cut with machines and always have dead air in the joint, which, coupled with their flatsawn necks, is why the heels always break. Fix that. Set, glue, clamp, rest.

    That tailgut has to go. Braided aircraft cable and an adjustable clamp is the way to go.

    If you set the neck right, if the old bridge was fitted properly it should work again. Probably.

    Install edge bumpers to prevent further edge degradation outside the purfling. Finding appropriate veneer and finish touchup can be a longer-term project.

    It’ll want gut or other low-tension strings. Nice find there. Feel free to gift it to me.
     
  7. Yes being new to this Instrument I'm looking at the existing integrity of the Neck Block and Dovetail on the neck looks pretty good so I think just putting it back together is best.

    Think I'm not ready for that much work as far as reengineering the plywood — removing the back,

    Now I am capable of designing a clete to bridge across the heel cap and onto the neck bloc that will look real nice and since the plywood is already butchered I might remove a bit more over the neck block for a decent amount of real estate to get a good glue bond. Also I could even make it decorative using my laser to maybe put a Kay logo on to it. .... i figure if someone one day has to rebuild the button with Ply layers it really won't be any more difficult than it is now.
     
  8. Nice to meet ya Mr Kungfu
    LOL already you got me looking up words trying to figure out what these parts are .... "That tailgut has to go. Braided aircraft cable and an adjustable clamp is the way to go."

    "Edge Bumpers" , is that kind of like adding linings on the outside? I'll have to look up and see some examples

    Are you saying that it is best to add a shim between the neck block and the flat surface end of the Dovetail thus filling the gap between them?
     
    KUNGfuSHERIFF likes this.
  9. eh_train

    eh_train Supporting Member Commercial User

    Jan 12, 2004
    Toronto
    Owner, Stand Up Guy Basses (Repair/Sell/Buy upright basses)
    [QUOTE="Steven Ayres, post: 25839782, member: 89663”]...an exercise in reengineering the plywood — removing the back, cutting back the inner plies down past the block...[/QUOTE]

    From experience, there’s no need to take the back off, or even fully remove it from the block. A jewellers saw will take out a couple of individual plys, at varying depths, so that new material can be let in. It may not be be returned to new condition, but it will function as a button should.
     
    Last edited: Nov 11, 2021
  10. Greg Clinkingbeard

    Greg Clinkingbeard Commercial User

    Apr 4, 2005
    Kansas City area
    Black Dog Bass Works
    You are getting some good advice. Consider moving the neck out some. Most Kays have a projection of around 130mm but standard overstand is 150mm and they will sound better there. If you can work with the standard mortise and prefer to, that’s your call. Add a piece to the back of the heel to bring it out.
    For reinforcement, I often mortise out the back for a piece of maple similar to a very thick popsicle stick which goes into a mortise in the back of the block. Chalk fit it as well as you can and use thick hide glue.
     
  11. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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