OT - threaded inserts for guitar necks

[Doc B.]

I snuck out a little early today and spent the afternoon working on the Bottlecaster. There have been a couple of things I've been wanting to do to the Squire Mini Strat short scale neck I used. One was to fix the slightly stripped neck screw holes, by installing threaded inserts. I had used threaded inserts on my spalted maple Tele project a few years ago and really liked the sustain that guitar has. So I went to the local Coast to Coast and picked up some #8 brass threaded inserts and 2" long stainless oval head 8-32 machine screws.

Now putting these inserts into the maple Mini Strat neck is a PITA. The type I used are the ones that have a screwdriver slot for installing them. There is another type that has an Aallen head - much better head for installation, but the threads on those inserts are no where near as stout or sharp. Kind of a paradox...the 8-32 insert of the insert I chose is supposed to require a 1/4" hole. Fuggedaboudit - after struggling for a while I upped the hole size a couple drill sizes to 9/32", done on a drill press set to 14mm depth.

A bigass slotted screwdriver would start the insert but then even with wax on the threads the insert would get so tight that the brass would break away from the slot. On top of that the inserts were canting over at an angle and trying to chip out the maple of the neck - a disaster in the making. I tried a method suggested on the web, of putting a slotted bit in a drill press and turning it by hand while pressing down, but it did no better. So I stopped what I was doing, went to Ace hardware to get a couple more inserts and put on my thinking cap.

Came back with more inserts, an #8-32 x 1/2" machine screw with Allen head, and a 5/16" - 18 tap to match the outside thread of the insert (which I figured out a when I got home that I already had one of - sigh). Ran the tap into the 9/32" holes with no problem, then put the #8-32 screw into the insert. This allowed me to use an Allen wrench torquing in steel rather than a slotted screwdriver in brass (!?!?!?) to run the insert into the threads until the top was just below the surface of the wood. They went in nice and straight. Backed the screw out and I was ready to install the neck on the body.

Next I ran a couple drills through the neck holes in the body to increase their diameter slightly, as I needed just a bit of wiggle room to take a slight cant out of the neck. I used a bolt cutter to cut the stainless screws down to 1-3/4" ( you can get these, and steel inserts from McMaster Carr and save some hassle - but I was impatient). Cleaned up the ends of the chopped screws on a grinder and ran them through an 8-32 die.

The screws clamp into the inserts really well. The inserts were ever so slightly out of alignment with the holes in the body, but my sizing those body holes solved any misalignment and the screws snugged down nice and tight in the backing plate. The end result was much better alignment of the neck, curing a slight misalignment of the strings, and giving gonzo sustain.

While I had the neck off I pulled off the inexpensive tuners, opened them up, lubed them with Teflon lube and snugged the little clamping screw a touch. Makes them take and hold tune quite well. Last thing I need to do on this neck is to replace the plastic nut with a bone one. I think I will save that for a time when I am fresh and my old hands aren't aching...

[kgoss]

Very creative solution Doc!  I never considered running a tap into wood before, but maple is certainly dense enough to make it work well.

Ken

[Laudanum]

   ... Tap the maple was the first thing that came to my mind before reading that you tried it.   Must be one of those rare smart days for me   
Glad it worked out.   

If those stock tuning machines are the real cheap box style or similiar ...  http://www.ebay.com/itm/RMS-6-INLINE-MINI-CHROME-ECONOMY-GUITAR-TUNERS-RGTM40-/330746909743?pt=Guitar_Accessories&hash=item4d020d542f  ...  and if you really like the guitar, it may be worth an upgrade.  Gotohs and Schallers (some) arent bad and can be found pretty inexpensive on ebay frequently enough (overstock, slight blems).    Even some of the inexpesive no-name look-alikes of the Grovers, Schallers etc. arent bad.  I have a set of "Grovers" on one guitar that I bought from asia for under 20 bucks.  Have to be counterfeits but you would never know it (maybe I got lucky).    It's not hard to improve on those real cheap ones.  Ive never been able to do anything to make those cheapies (like those in the link) acceptable enough.    Only thing is you may have to enlarge the thru-hole in the headstock and do some fill and finish on the small mounting screw holes.  Generally not a problem for me because anything I have had that came with those machines was either a project or a beater.   YMMV and you probably know all this stuff already, in which case ... nevermind   

[Pfenning]

Hey Doc. At my shop we have to install thread inserts quite often. The easiest way we have found to run them in is to use a shoulder bolt. The shoulder bolt threads into the insert and the shoulder bottoms out on the face of the insert holding it square and solid. Our shoulder bolts have allen sockets, so like you said, they are easier to run in because they grip more positive than a slot or phillips. Most of the guys in the shop have a set of shoulder bolts with the heads cut off, and the clamp them in a drill chuck and run them in with the drill press like you mentioned. Once the insert is inserted to the correct depth, you just back out the shoulder bolt. Hopefully it works as good for you as it does for us.

Pfenning 

[Doc B.]

I was typing too fast when I wrote the initial post and said that I used a #8 Phillips screw to install the inserts. I did try one at first, but actually I did pick up a #8 Allen head cap screw to put in the inserts instead. I have corrected that in my post. With the threaded hole in the maple I didn't need the pressure of the drill press. The inserts threaded in nice and straight and very snug with an Allen wrench, and the neck now attaches really tight and straight. In fact the whole guitar has come together quite nicely for a Frankenstein. I just wish I had slowed down when I drilled the holes for the string thrus. I knew very well that the drill would wander but i was under a time constraint. I try to keep people from looking at the back of the body, as the holes are all over the place!

And in the interest of full disclosure, I must admit that one of the inserts I picked up was a #6 of the same outside diameter. Didn't realize it until it was in the wood. A drill bit and a #8-32 tap took care of the problem. Be careful to check the thread size if you are picking these inserts out of those scrambled bins at Ace or Coast to Coast.

Re the tuners, I have nice ones on a Tele I built (Kluson Vintage) and a Gibson (stock), and generic Asian ones on a kit Tele I built. Once these Squire tuners were worked over they seem to work about as well as the others. I think getting the little tensioning screw tightened down just right is the trick.

[Jim R.]

Dan,

Next time you might want to give one of these goodies a try:

http://www.mcfeelys.com/product/3603-PD/Driver-Bit-for-8-32-Threaded-Insert

These are wonderful things, save lots of time and can, with just a bit of practice, do a perfect job every time.

Also, I'm sure you're aware of this, but a little super glue or gorilla glue on threads cut directly into wood or mdf, and then retapped when dry, makes them significantly stronger.  The CA glue is easier and more convenient to use IMO.

HTH,

Jim

[Doc B.]

Thanks Jim, I'll keep that driver in mind. Luckily the Allen head cap screw worked just fine without backing out the inserts when it was withdrawn.

[Laudanum]

Thanks Jim, I'll keep that driver in mind. Luckily the Allen head cap screw worked just fine without backing out the inserts when it was withdrawn.

I think you may have been better off anyway tapping that hard wood first rather than just driving them in.  Or maybe I should say, safer.  Im no Luthier, wood artisan, beaver or woodchuck,  but I have split hard wood just driving small screws in. Pilot hole probably too small.  Probably why tapping came to mind as soon as I read about the difficulty you had with the inserts.   I would have tapped first