Official Luthiers Forum!

Hi all,
I was at Lee Valley picking up some threaded inserts and bolts to do a bolt-on neck, I think these are commenly used for this purpose The sales clerk mentioned that he has a friend who builds violins and would never use aluminum and thought I should be using brass inserts due to their superior sound transfer. I realize most of the sound transfer will occur through the edge of the neck, but imagine some could also come though the bolts. Thought this was interesting and wondering if others had any opinions - would this make any difference ?. Of course the next challenge would be finding brass inserts, Lee Vlalley does sell some but they seem a little big.
Thanks,Eric

The aluminum ones are not worth using .. if anything, you want the bolt to strip, not the insert, as replacing a bolt is far easier. Seeing as the bolts are steel, I only use steel inserts - get them at Rona, they are half the price of the same ones at Home Depot. Bolts however, are cheapest at LV.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Brass are a million time better than the white metal ones. Are these with the larger thin threade to bite into the heel ? That is the style CF Martin uses. They are very reliable.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I'd be nervous about aluminum too, but for fatigue, not sound. I guess I never really paid attention, but I'm pretty sure mine are steel.

Mike

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Mike Lindstrom

Agree with Karol. Steel bolts, steel inserts.

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Francis Richer, Montréal
Les Guitares F&M Guitars

The real problem with aluminum isn't musical quality of the metal - it's the reactive qualities of the metal. Aluminum corrodes quite easily, and it galls pretty easily (unless it's aircraft quality T6). Best to use brass IMO. Steel on steel is OK, too - it is cheaper, but is not as musical a metal. Small differences, I know - but we luthiers are hair splitters as a rule.

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"Act your age, not your shoe size" - Prince

Thanks for all the replies, I was wrong about the aluminum it's acatully zinc alloy, not sure how that compares.

The sales clerk's friend would appear to have a somewhat unconventional approach to violin making ...

Don't use those; they are cheap pot metal and not suitable. Deep thread steel is good. Not likely to be at your local hardware store. You can get them from McFeeley's or McMaster-Carr.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

+1 for the deep thread steel.
I get mine from Mcfeelys.They also sell a hex driver bit to install them-much better than the slot in the brass ones

http://www.google.com/products/catalog? ... ABEPMCMAQ#
this is same kind CF Martin uses . I have used them without a failure . They also come in handy in making jigs.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Far be it from me to contradict my elders and betters( me who hasn't even finished my first acoustic build yet, although getting there slowly) but no way on earth would I use one of these inserts , zinc alloy, brass or steel, in the end grain of a tenon, whether or not Martin or anybody else uses them. Thirty odd years of wood working screams "NO!"

I will be using a threaded cross dowel, like this ...

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John Mayes
http://www.mayesluthier.com

http://www.cumpiano.com/Home/Articles/S ... block.html

Here's the system I learned from William Cumpiano, there's also links to some suppliers of the cross dowels and bolts somewhere in the article. For those who have an aversion to screwing brass or steel inserts into end grain, here's a good alternative.

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Old growth, shmold growth!

Just to throw a wrench into the works...

Seems to me it could be better to sacrifice a stripped insert, or even one that pulls out, than to have the neck break or a neck block pulled loose (but then who would want to test for that?). Could be fodder for another discussion.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

the brass threaded inserts work well . Barrel nuts also work but I still prefer dovetails .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

+1 I agree!

Also a good method!
My Stew-Mac luthiers bench is assembled the same way.

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"Act your age, not your shoe size" - Prince

I LOVE these threads...lots of advise but not much based on too much! I sell the exact same inserts as the Lee Valley ones and pride myself on only offering quality products so when I read a thread like this I start to get a bit concerned but rather than make a comment I go and check out my facts first. So I drilled a hole in a piece of birch, threaded an insert in. Grabbed a bolt and a washer and a piece of pine (I had it laying around). The I grabbed an Allen stub, a socket and a ratchet. My goal was to torque to failure and see where that was. Well, I tightened the unit up enough to crush the surface fibres of the pine enough to completely bury the 3/4" diametre washer. Then the steel bolt Allen head stripped. Unless you are using a true hex head bolt I am convinced that you can never get enough torque to ever stress these inserts. Often we are not concerned enough about how good is good enough, I mean we could just have the entire neck joint made of steel (like many adjustable necks are these days) and just weld the sucker on! If we are truly concerned about collecting every bit of sound energy then maybe we should be employing good woodworking joinery and stick with a dovetail or Spanish heel and keep steel out of this joint!.

Anyway Eric, you will not strip out those inserts when used in the application of fastening a neck to a guitar body. These inserts are also designed for endgrain application as well, that is what a wide thread path is for. But then I only have 35 years of woodworking experience using every type of fasting system out there at one time or another. I sell these inserts and make no judgments about their use but I use and will continue to use (until convinced otherwise) the traditional dovetail joint, the only metal will be the strings, tuners and truss rod (maybe a pickup).

Here is the test piece:



Shane

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Canada

Good stuff Shane ! to be honnest I never had concerns on the strength of these inserts - well at least not until I started reading the responses - so good to hear they are still a valid option. My question was never around the mechanical properties of these, what I was interested is if the superior sound properties of brass would make a difference in the sound transfer if used for inserts.
Eric

So then to your point Eric, there are so many variables in construction that effect sound that in the early stages I would not worry about the difference in "acoustic properties" of a fastener. Once you get that dialed in then you can play with the fine details and see what changes they make.

Shane

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Canada

After breaking two of those flaky installation tools that Woodcraft sells, I bought a short socket head allen screw that fit my inerts & drove them in with a T-handle allen wrench.

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Kind of a devil's advocate observation here: Unless you're using one of those "cross" style barrel ones, why use any insert? Seems redundant when a standard stairway type stud would work probably better, screwing directly into the wood. But what do I know?

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"Preoccupation with an effect gives it power and enhances the error"
from "Your Owner's Manual" by Burt Hotchkiss.

Thanks for that demonstration, Shane. You convinced me. So, what are they? I'm assuming something other than aluminum, but maybe I'm totally off.

Also, when you reply to a thread about loving threads and reading threads and installing threads, I get very confused.

Mike

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Mike Lindstrom

It's good we aren't talking about screws then!!

The inserts are zinc alloy and are plenty strong enough. If I was doing a bolt on neck I would prefer these to hanger bolts (the threaded studs) as I would not like the look of nut on the end of a bolt when looking inside the guitar, these do look clean.

Shane

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Canada