threaded neck bolt inserts?

Discussion in 'Luthier's Corner' started by L-1329, Jul 23, 2005.

  1. L-1329


    Aug 8, 2004
    Anyone know if it is a good idea to use neck inserts for a bolt on neck? I have a Warmoth neck / body project underway and have been thinking about tis idea. Would it be as stable as simply using the neck wood screws? Part of this is that I really want to incorporate a strap botton/lock on one of the neck screws, as the bass will have no upper horn, and it seems like I could find a machined screw of the right length, and get an even torque on it with the other three. Think this would be a good idea? Also, anyone know where I might find some kind of insert?
  2. The inserts can be gotten at most hardware stores or home improvements store with a good selection of fasteners. I got a set of them from Home Depot a few years back. I had a Warmoth padauk neck that the neck screws started stripping out of. This was due to the neck being removed many times to adjust the truss rod.

    Make sure you get the machine screws that are long enough to reach through the neck down an adequate distance into the inserts to hold together securely.

    Also, make sure you get the smallest inserts possible. They come in a number of sizes. Get the ones that have a screwdriver slot so they can be threaded in far enough to be flush with the wood on the neck heel.

    You drill a pilot hole into the neck heel that is slightly smaller in diameter than the insert, and then screw the insert into place.

    A final caveat: be sure the inserts are going into the wood straight. It's easy to get them going in at a bit of an angle. A bit of an angle is not the end of the world, but it's much better to get them screwed in straight down, if you can.

    If you do it right, the inserts are far superior to wood screws. You can tighten the neck screws much more. It feels very solid. Plus, you can remove the neck for truss rod adjustments with no problems - if your bass requires it.

    Didn't we have a thread on this last month or so? :)
  3. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Owner: FBB Bass Works
    If I might add to the above post....

    Look on Moses' web page for instructions on how they recommend threaded insert installations on their necks. It's not easy to find the page, but the nut-and-screw method of threading the inserts into the pilot holes is much better than using the slot-head brass inserts. Alternatively, you could use the steel hex-drive inserts. The brass ones have a tendency to rip at the slightest resistance.

    Also, I recommend 8/32 or larger inserts to use with 8/32 or larger machine screws. 6/32 are available, but I think you want a little more heavy-duty screws if you can get them.
  4. L-1329


    Aug 8, 2004
    Thanks for the info, I was hoping to hear some positive things! I will most likely use them, and hopefully I can find a way to put a strap lock or button on one of the bolts. Sounds like that will just be a matter of finding a bolt of the right length and size, that will fit the insert as well as fit through the button. Can't be that hard, right? ;)

    And Hambone, thanks for the info. I still have 8 - 10 weeks left, according to Warmoth, so I will keep that in mind as the time draws near. :cool:

  5. While Michaels advice touches the surface of the issue, there is much more depth to the subject. Let me elaborate...

    - First, I haven't see any inserts coming from the Home improvement stores that are full billet metal unless they are brass. Brass is OK for smaller screws but I've moved away from it for neck inserts because I use steel machine screws and brass, being softer, can and does fatigue easily under the torque that gets applied to the steel bolt. Brass on brass is fine but should you need to remove an insert that has stripped, it's a boogerbear, especially if you've dropped a little CA in with them, like you should. The other inserts I've seen at the commercial outlets have been "pressed" metal or "white" metal. These are very low grade, soft pieces that don't have the strength for this critical joint at all. In fact, most are so weak that insertion can be a problem because they can break simply with the force of turning them into the wood. Now, let me add that all Home Depot's aren't the same and they all carry different items. You might find what you need but be careful to check them out thoroughly before assuming you've got machined inserts.

    Matching the length of the screw and insert is important but it's done by planning how far into the neck the insert is installed. My approach is to use the insert not as a holder for a "peg", being the neck bolt but as a compression element by putting it deeper into the neck. Then when you torque down on the neck bolt, the insert compresses the material between the insert and bottom of the neck towards the neck pocket. This is the only way to increase the sonic coupling of the neck and body. Putting the insert in shallow will hold the neck in place but it doesn't pull the neck towards the body which is what you want to do.

    It isn't important to get the smallest size insert possible. Besides, just what does "smallest" mean? Smallest diameter of insert or smallest diameter of bolt that you can get an insert for? I use 10-24 machine screws and these match the diameter of most of the wood screws used by the manufacturers. For these bolts, there are at least 2 diameters of insert available in machined steel. One is a narrow version with knife threads and a slotted top. This is easier to thread in but more difficult to keep contact with the drive tool because of the single slot. I use these in cases where clearance of the trussrod is a concern OR where I'm not certain of the space I have available and want to make sure I miss the hard stuff. The other insert available is a hex drive. These are much larger in diameter, have blunt threads but a hex drive and are easier to sink straight into hard neck wood. They are also a little taller so that has to be taken into consideration when calculating clearances. I like these for their mass and ease of installation. Each has their uses and will do fine. Both require large pilot holes based on the size of the barrel of the insert - not the thread size - and I like to chamfer the hole opening to aid in starting the insert into the hole.

    To aid in driving the inserts, I can offer two bits of advice. First, use a drill press as the power behind the insert to push while you twist the chuck. By mounting the neck firm, you can easily insert the pieces very precisely in about 30 seconds without breaking a sweat. Try this by hand and you risk a crooked insert or something worse. It CAN be done but much more care is required to do it right by hand. The second tip is to wipe some beeswax on the threads before insertion. It will make them go much easier.

    Hope this helps
  6. Fasoldt Basses

    Fasoldt Basses

    Mar 22, 2005
    Stevens Point, WI
    Karl Thompson, Builder (Formerly Fat Karl)
  7. Marcus Willett

    Marcus Willett Supporting Member

    Feb 8, 2005
    Palm Bay, FL
    Endorsing Artist: Bag End - Dean Markley - Thunderfunk
    Posted this on another thread; just playin' the odds...better to revive an old thread than start a new one.

    A question for the luthiers out there...

    I understand the mechanical arguments for threaded inserts. I have a bass neck I'm thinking of having it done to (it's a softer wood, so it makes sense). What I have never seen addressed is the sonic/tonal impact (if any) that using threaded inserts has, as opposed to wood screws.

    It's probably not significant, but there has to be some sort of effect on the tone of the instrument...?
  8. Linas


    Jan 6, 2005
    From what i have read in the threads, some swear by them as fixing any deadspots you might have on your bass. As for it being true, i am going to find out as soon as my inserts i ordered from hambone come in the mail. I have several really bad deadspots on my bass.
  9. Trevorus


    Oct 18, 2002
    Urbana, IL
    I have them in a late 80's peavey foundation s. It suprised me to find them there. But they are fantastic. They hold very well, screw in smoothly, and make it really easy to use the neck's micro-tilt adjuster.
  10. Greenman


    Dec 17, 2005
    Ontario Canada
    Mr. mcdade did a nice insert install. This neck will be tight before the inserts bottom out.
  11. Linas


    Jan 6, 2005
    Rather than start a new thread i will contribute to this with a couple questions. First off, since the fingerboard is radiused, how do i know when the drill bit is actually going into the neck strait. do i put a level on it, then clamp it when its level? Also should i dowell and re-drill the holes on the bass or keep them as is. Im not 100% sure that they were drilled strait. I plan on accomplishing this on friday.
  12. Rodent

    Rodent Supporting Member Commercial User

    Dec 20, 2004
    Upper Left Corner (Seattle)
    Player-Builder-Founder: Regenerate Guitar Works
  13. Suburban


    Jan 15, 2001
    lower mid Sweden
    A remark re. screw dimensions (complement to Hambones post above):

    Bigger is not better!
    If you compare the result from using an M6 with using an M3, you will soon find that the stiffer screw will add torque, but not contact force. The slimmer screw will stretch easier, which means that the clamping force is higher in a short joint!

    In short: few (like 3 or 4) slim screws will make a better joint than few or many (like 7 or 8) thick screws.

    The thing is to have a long screw that stretches well.