bolt-on neck - helicoil inserts

I only got to skim your post...can you let me/us know where you picked them up and did that place have matching bolts included? I've considered the inserts, but didn't know where to start. Thanks Rodent!

 

Do you have any pictures left from that installation. Was it placed in the same spot as the original screws? What depth and width size threads / bolts did you use?

Cheers

 

The problem I've encountered the most is once you drill the holes in the neck, it's hard to screw in the thread at a precise 90 degree angle and not to ruin that angle. How do you go about using a press drill to screw in the thread very precisely?

Cheers

 

Rod, I might be able to save you the trouble and expense of testing the 1/4-20's - They work well as you might expect - they'll hold about 500 lbs per bolt but they are too large in scale for the smaller area of in the back of the neck pocket on Fender style basses. The heads of the ovals won't fit the neckplates and they are about twice the circumference of the 10-24's. You also won't find suitable ferrules for these bolts. I suppose you could use cap screws for a smaller look but they are fairly thick so you'll lose some depth under the neck. I used the 1/4-20's on my first build and this is what I found.

 

PM thisNSucks and ask about his Steve Harris P replica. I installed inserts for the BAII bridge on that one and he swears by it. It has an alder body with a maple neck so it should be a good empirical candidate.

 

I have used helicoils before, into metal with mixed results,most good machine shops will not use them, especially in aluminium.
I would think they would be the worst choice for a screw to timber interface.
What you end up with on the outside is a fine thread with a rounded outer edge with no interference fit to the wood.
There is a reason wood threads are coarse and sharp, it works.
try it on some scrap first if you must.
Jeff

 

Good points, this is what I was thinking, but then again, I have not tried them:

I think the friction-fit principle behind them was really made to work with hard materials. I used these pretty extensively to repair radios in the military, when an aluminum screw broke off in the chassis, we would drill out the whole shebang and put a coil in it. I think they would have significantly less holding power than a wood screw, they have much smaller threads, and remember, the screw to coil bond may be invincible, but the coils will pull out of the wood before a properly driven wood screw.

Besides, I cannot imagine wood screws being a problem unless you routinely loosen and tighten the screw. Most guitars probably only ever have the neck removed one or two times in their lifetime, most likely for repair, which should be done by someone qualified anyway.

 

Ok, it's been a long while since I used them, don't remember the profile. Havent done chevys, but when I was into air cooled VWs helicoils were frowned on and I think Time-serts were the go. Perhaps due to the crappy metal used for VW engines
Regardless, the fine threads into wood is the major concern, It may be adequate but will probably fail well before the screw.Would suggest a pull out test with the fastener through a plate blocked out from the surface.
regards
Jeff

 

No problems rodent, we have obviously had different experiences with helicoils.
My main concern with what you are proposing is the insert to wood interface.
Do you have a width restriction that prevents you using an insert designed for wood?

Jeff

 

Rodent,
Please keep us posted on how it turns out. I'm very interested in hearing how it will turn out. A couple of questions for you. Which threaded steel inserts did you use for those fender basses? And where can you get them? I'm thinking of trying some out on a bass I plan on building.

Thanks
james

 

love to see some details of what you intend ( I used to be a structural engineer)
Jeff

 

And the real answer IMO as to why wood inserts use knife threads is twofold. First, it's to create strength when connecting pieces of soft wood with machine bolts - the exact application that wood inserts are designed for. Second, it's to make installation easier because they cut into the material quickly and with less force. It's my opinion that we bassists are using them for a tangential purpose - to increase the clamping force beyond the perfectly servicable levels offered by wood screws and to allow multiple neck removals without the concern of eventually wallowing out the mounting holes.

Hate to interject some backyard engineering here but let's play devil's advocate and say there's a possibility of the HC failing under stress in the wood. What prevents one from applying a couple of drops of water thin CA along the HC and running with it? I don't for a minute think they won't work. The rhomboid shape and depth of the insert are plenty to maintain the force x 4 needed for a bass neck. I've only got anecdotal evidence to support that idea and that would be the successful use of NO insert or helicoil and just using a machine screw by some high end builders. Would using a helicoil be a gain or a loss over that method? Common sense answers that one. I can also state with some degree of certainty that top quality machine shops do indeed use helicoils in the right applications as I have discussed their use with some top notch builders during my racing operations back when.

I'm not defending the use of a helicoil in this application. What I AM saying is that there's ample evidence - both empirical and anecdotal - to support the hypothesis that not only would it work, it might work really well. There's also plenty of evidence to warrant completion of the testing without regarding unsupported "scientific" opinion.

 

Hi There,

How has the helicoil fixing come out,im a toolmaker by trade and I use helicoils quite a bit for fixings into aluminimum when there is a need for constant un-bolting.Due to the thread form on the helicoil,there could be problems with the helicoils pulling out of wood.Ive used standard thread inserts of wood cabinet and had good results.