Hambone help!! Stainless steel threaded inserts

Discussion in 'Hardware, Setup & Repair [BG]' started by BFunk, Aug 8, 2002.

  1. BFunk

    BFunk Supporting Member

    I would like to use stainless steel threaded inserts for my Warmoth deluxe 5 bass project. Where can I get these? What size should I use? How many should I use? How should they be arrainged?
  2. I don't know of a source anywhere for stainless inserts. I use steel but they aren't stainless. I also use stainless bolts with them so they don't get locked together with rust or oxidation from plating. I use ¼-20 threads for my basses. The arrangement can be the same as the original holes but I fill them with maple dowels and redrill even if they are in the same place. It's sometimes hard to center an already cut hole with a bit so this helps make a perfectly aligned hole. Use a brad pointed bit so that you cut a flat bottom hole. Some bits will have so much point to them that they intrude into reinforcement channels. Be very careful to use the right sized bit because these inserts can split a neck if inserted into a too small hole. Also measure the depth of the insert and make sure that you can use it with the heel thickness of the neck. I will drill the holes and then use carpenters (yellow) glue as a lubricant and lock-in sealer to thread them in. The steel inserts use a hex head wrench for insertion while the brass use a slotted tool for insertion. Either way, you should chuck your tool into a drill press and hand turn the inserts into the neck. A drill press helps align them vertically. Make sure the inserts don't rise above the surface of the heel so that it has 100% contact with the neck pocket floor.

    Gee, that's about it...Go fer it!!
  3. BFunk

    BFunk Supporting Member

    Someone also recommended aircraft aluminum inserts and bolts. Any experiance with these?
  4. I don't know who did but IMO they are talking through their hat. Aluminum is rarely used as a threaded fastener and when it is, it's never in a longitudinal stress situation. Though hard, even aircraft grade alloys (like 5052 or 6000 with T6 hardness) will pull apart with very little effort. Either the bolt or the threads would let go inevitibly. Besides, I know of no place that one could purchase such items if one were to want them. If the argument is weight savings, it holds little water. At most you might save a couple of ounces over a stainless steel/steel/brass combination. If your bass is that unbalanced, you should probably look for a chainsaw.

    Just thought of another problem with that suggestion. Assuming such a thing were available, the contact points between the two components would eventually oxidize and be difficult to seperate. Then you've got a bolt and an insert with a powdery oxidized coating. And remember, especially with aluminum, oxidation will consume the aluminum until the components are very weak and unable to hold torque.
  5. BFunk

    BFunk Supporting Member

    I got that from a 'reputable' luthier. Ok, so now I question his reputation!!
  6. Cool. Hambone nailed it.

    I'd not suggest Stainless/Stainless inserts and bolts. They tend to become one, then you have to rip the threads out of your insert and hopefully be able to chase them clean again. Most likely you'll have to replace it or heli-coil it. Black oxide fasteners will do perfectly fine, and you can find them at local hardware stores. Besides, the fasteners will be about 10x stronger than any adhesive (Epoxy) that you use to hold the inserts in with.

    Carbon steel with an anti-seize or a thread lube (non sealing) used on it should give a great service life. It'll keep the threads from oxidizing and locking up. Always a good idea, especially in something that's gonna be coming apart on a semi-regular basis.

    And in case you were wondering. A 1/4-20 has a area under the threads of about 0.034 in^2. Assume 50000 in^2 as a yield strength (don't have my books at home...doh). So a 1/4-20 can hold 1700lbs roughly. Assume 75% bolt preload to yield for bolt stretch (I think 11ft-lbs is right..), and your bolts can hold 425lbs a piece in tension. Safely. Could prolly hold 600lbs and be okay for life. Bolts in shear have about...oh...230x's the strength. Basically...shear good, tension bad. TENSION BAAAAD

    Me? I'd machine some little cups that would give me room to put a AN washer under the socket head, and allow greater area of wood under the bolt head..in effect another washer to spread the load. Plus I'd use 10-32's. Small fasteners rule. I've used 4-40's w/ some 4-40 nuts epoxied in the P/U route to hold the pickup down. So adjusting the P/U will never wear out the wood holding it down. Plus it looks cool lol.

    But....listen to hambone. He doesn't talk in a freaky language heh.
  7. BFunk

    BFunk Supporting Member

    Tufnuts, hearing your explanation reminds me of the conversation I had with Bill Lawrence, the pickup guru, the other day. I didn't understand most of it, but hey it sounded really good. :)

    So Tufnuts and Hambone -

    Is it really worth the extra hassle on the Warmoth Deluxe 5 I am trying to put together to go with inserts over standard 4 neck screws and a neck plate?
  8. I would. The fact the neck has to come off for truss rod adjustments means the wood will someday fail. Steel lasts longer.

    That reminds me...I gotta build a bass again.
  9. Exactly why I prefer to use necks with truss nuts at the head, not the heel.
  10. Tufnuts explanation has all the evidence built right in. What you lose in inconvenience, you gain in gobs of strength and that's for the life of the bass. Look at it this way - A single #10 wood screw has how much tension strength in maple? - maybe 100 lbs? Multiplied by 4 that's 400 lbs. total tension strength maximum applied to your neck. Using Tuf's figures, that would be covered and then some with only 1 bolt using inserts. But you'll have 3 others that will add to that. That combination will pull the neck to the body with enough force to where you won't be able to tell the difference between it and a set-neck arrangement. That's my opinion. You've got a wider neck, more neck mass, more string tension, and a neck that will require removal for trussrod adjustment. That's plenty of reason to use inserts. Then in 5 years, while the others are having to use oversize screws or fill and re-tap the holes, you'll be crankin' 'em down tighter than they can with 8 neck bolts.

    And besides, you would doubt a guy named Tufnuts?
  11. Yes. I don't usually take myself seriously lol.
  12. Unless you have a set-up where you have a heel adjustment and you don't have to remove the neck, like on many other basses.

    Oh, and I prefer neck inserts, though I haven't seen a case where a neck joint has failed due the screws being set into wood. I am using 6 on my 7 string, probably a little overkill.

    I suppose it is similar to the argument against using headstock end adjustments on truss rods. The channel weakens the headstock. But I haven't seen alot of basses/guitars damaged in this way.

  13. BFunk

    BFunk Supporting Member

    I am getting the warmoth 3+2 tiltback headstock which has the trussrod nut at the head end. Still, it looks like it has great advantages long term.
  14. Suburban


    Jan 15, 2001
    lower mid Sweden
    I'm not sure, but I assume you're talking neck attachment. Right?

    If you are:
    The best way to fasten a neck is - with inserts and "machine screws". Wood is soft, and does not allow taking off and resinserting - in the same threads! Hence, you ruin the wood rather fast.

    The best thread insert for a neck is the kind you knock is from the opposite side. This allows for a lonng screw, from the heel washer to the first thread in use. This allows for more initial tension, which is good. BTW, tufnuts, machine screws are designed to carry longitudinal loads, not shear. It actually carries 3-4 times more longitude, when the joint is properly designed.
    That nut insert is to be put in before placing the fretboard.

    The second best is an ordinary "screw-in" insert. This is OK, though set it in deep, through all the neck except anything of the fretboard.

    Material? Well, some say that the nut should be of higher strength than the screw, so that if the thread is ripped, yo just install a new screw. It's not all that easy, you have to clean the thread, which means you need to have access to the nut.
    But normally, for a neck seat, you'll be OK with whatever steel you get. Because the most important part of a neck joint is:
    the seat routing.

    The screws are there, just to keep the neck from rotating out of the heel.