Which Inserts For Neck?

[GoodWood]

http://www.rtlfasteners.com/RC/q.html

What size would the standard stock Martin dreadnought (kit) take? Anyone know??

[Mattia]

1/4-20 internal thread.

[GoodWood]

1/4-20 internal thread.

[jaycee]

Mat told me the same thing a while back albeit metric sizes, and the 1/4 or 6mm in my case looks plenty

I did get the 8mm sent out at the same time and not only do the inserts look to big but the bolts are as well. Fortunately it was a freebie so I thought I may as well take advantage of it

[Mattia]

My first two had M6 bolts, then I ordered a bunch of US hardware from Lee Valley because it was prettier than what I could find locally. Yes, I'm really that shallow.

[jaycee]

My first two had M6 bolts, then I ordered a bunch of US hardware from Lee Valley because it was prettier than what I could find locally. Yes, I'm really that shallow.

You say that mat but I have seen M6 bolts in Halfords which have chromed Allen key ends, much better looking than your bog standard bolt. And the worrying thing is even though they won't be seen I am actually contemplating getting them.

Edited September 4, 2008 by jaycee

[Mattia]

My first two had M6 bolts, then I ordered a bunch of US hardware from Lee Valley because it was prettier than what I could find locally. Yes, I'm really that shallow.

You say that mat but I have seen M6 bolts in Halfords which have chromed Allen key ends, much better looking than your bog standard bolt. And the worrying thing is even though they won't be seen I am actually contemplating getting them.

Heh. Lee Valley's are nice Steel bolts with a wide, flat head, hex/allen keys, and a classy bronze finish. Nothing else inside the box is that shiny, so chrome just seems a bit wrong. And not pretty enough :-P

[jaycee]

Yes |I just checked them out, I do like the wide flat head on them. I have seen them somewhere else but cannot remember where.

[GoodWood]

Ok, can you link to the lee valley stuff?

Mattia, hate to ask, but what screw to go with the brass inserts? I don't see 1/4 20 anything for screws.

[Mattia]

1/4-20 machine screws. Look under the fasteners section at the Lee Valley site, under hardware. This stuff's used for knockdown furniture a lot. And/or check out McFeely's for both bolts/screws and fasteners.

[jmrentis]

I believe those are the same style bolts I get from my local Rockler. Allen Bolts. They don't use a real picture, but they look identical to the bolts from Lee Valley. And these are the inserts I used, same size as Mattia suggested. Threaded Inserts. Rockler has those same inserts in steel, which I might try next time as I found the brass ones actually tore on me, ended up having to replace one or two, but its likely because I had them a tad snug, plus I have no idea if those others would actually hold up any better. I'm using this setup on my bolt on solid body and they look nice and offer a very solid attachment. Rockler sells some inserts with a greater gripping thread, but I couldn't imagine using anymore than these had, it seemed plenty enough, unless you were using them in something super soft like drywall or something.

[davee5]

I can't speak to the standard martin stuff, but I can add a bit of mechanical engineering / manufacturing experience to the discussion and say that 1/4-20 is going to be very, very strong. I used 10-32's on my electric bolt-on build for a few reasons.

1. #10 machine screws are strong enough for any load-bearing applications that a guitar will ever see.

2. 32 threads per inch will yield much greater adjustability, force of engagement, and holding power than 20 threads per inch.

3. Slightly smaller head sizes seemed more visually balanced.

As for threaded inserts I have used 2 versions in wood: the ones typically mentioned here with external threads which are driven into place by screwdrivers or allen keys and the ones which are press-fit in place and then expand for a tight fit when bolts are threaded into them (sometimes called finserts). I have to say I have developed a very strong preference for the finsert variety. \

The ones you screw in place, particularly those with flat-head slots are exceptionally easy to strip out, slip out of (hurting your work), are very tiring on your forearms to get in place, and they do not always end up very well aligned with the original hole you drilled (and they are super hard to correct the axial alignment of). The threaded ones are far more common, and they may be a bit stronger, but I no longer believe they are worth the effort and hassle.

By contrast finserts are a breeze. Basically they are split down the center and compress into a pilot hole for easy insertion. When you insert a machine screw/bolt the compressed body expands, cutting into the wood walls and holding tightly via barbs and pressure. Thus they are super simple to install, easy to align with the holes (just make sure your bolt goes in at the angle you want it to) and have a holding strength that does not seem to be any weaker than the threaded sort. In fact it often seems like they hold tighter and the wood you are putting the inserts into does not get as damaged upon installation. I cannot speak to their actual holding power in contrast to the ones most people are used to, but I've never had any issues with my other non-guitar projects.

So if I were to throw out what inserts I would (will) buy for my next project, I'd go with McMaster-Carr part number 90363A029.

Here's a page on how they work, crazy simple: http://www.ezlok.com/InsertsWood/woodPlastic.html

My two cents.

-Dave

[Mattia]

Keep in mind inserts for electrics are a completely different ballgame from inserts for acoustics; on an electric, the load is almost entirely lateral, while on acoustics it's in the same axis as the bolt holding the neck in place. I wouldn't trust press-fit inserts in an acoustic heel, where added pressure might split it. Rather have hex driven inserts superglued in place. You also tend to only have 2 inserts taking signficantly more tension (usually 12-54 or 13-56 string sets) than an electric with four inserts. Experience shows holding power and adjsutability isn't a problem at all.

[GoodWood]

Keep in mind inserts for electrics are a completely different ballgame from inserts for acoustics; on an electric, the load is almost entirely lateral, while on acoustics it's in the same axis as the bolt holding the neck in place. I wouldn't trust press-fit inserts in an acoustic heel, where added pressure might split it. Rather have hex driven inserts superglued in place. You also tend to only have 2 inserts taking signficantly more tension (usually 12-54 or 13-56 string sets) than an electric with four inserts. Experience shows holding power and adjsutability isn't a problem at all.

On the Stewi mac Herringbone Drednaught design (martin), he uses two 1/4 x 20 BOLTS coming out of the neck, so I may just go that way.

[Mattia]

Keep in mind inserts for electrics are a completely different ballgame from inserts for acoustics; on an electric, the load is almost entirely lateral, while on acoustics it's in the same axis as the bolt holding the neck in place. I wouldn't trust press-fit inserts in an acoustic heel, where added pressure might split it. Rather have hex driven inserts superglued in place. You also tend to only have 2 inserts taking signficantly more tension (usually 12-54 or 13-56 string sets) than an electric with four inserts. Experience shows holding power and adjsutability isn't a problem at all.

On the Stewi mac Herringbone Drednaught design (martin), he uses two 1/4 x 20 BOLTS coming out of the neck, so I may just go that way.

I know a number of builders (one in particular who I have the utmost respect for, Mario Proulx) who use hanger bolts - screw thread simply screwed into the heel, with the bolt end extending into the body to be fastened by a simple nut and washer setup. Works great, I'm sure, but I don't find the inserts difficult, and I have enough to last me at least a decade right now...