Threaded Bushing Torque Setting

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Joel Nowland
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Threaded Bushing Torque Setting

Post by Joel Nowland »

Has anyone discovered an ideal torque setting for tightening threaded tuning machine bushings so they are tight enough but not so tight as to damage/crack the finish?

I have acquired a precision torque screwdriver and would like to employ it.

Joel
Rodger Knox
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Re: Threaded Bushing Torque Setting

Post by Rodger Knox »

The answer from my motorcycle mechanic days is "Tighten it till it cracks, then back off a quarter turn."
I'd be suprised if anybody has an in/lb number, so you may be stuck with finishing up some scrap and measuring how much torque it take to crack.
A man hears what he wants to hear, and disreguards the rest. Paul Simon
Joel Nowland
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Re: Threaded Bushing Torque Setting

Post by Joel Nowland »

Rodger

I imagined the same that there would be no answer.

This morning I received an e-mail from one of the best know custom guitar builders in the US who said to start at 10 inch pounds and work up a bit from there.

Joel
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Barry Daniels
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Re: Threaded Bushing Torque Setting

Post by Barry Daniels »

I did not answer because I don't think you should be using a torque wrench at all. You should just snug the bushings up. Any setting that would even register on a regular torque wrench scale would probably be too much. Tighten the bushings to 10 inch pounds at your own risk.
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Rodger Knox
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Re: Threaded Bushing Torque Setting

Post by Rodger Knox »

I'm with Barry on this. I tighten the bushings as tight as I can possibly get them with bare fingers. If they come loose, I repeat the process.
A man hears what he wants to hear, and disreguards the rest. Paul Simon
Joel Nowland
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Re: Threaded Bushing Torque Setting

Post by Joel Nowland »

Roger & Barry

I have built nearly 200 guitars now and have got along fine but I have always wondered if there is a way to know that I am getting them just the right tightness every time.

These torque screwdrivers like the one I have are extremely sensitive and range from 5 to 35 inch pounds some go a bit higher. They are used for assembling very sensitive electronic devices and cost from about $250.00 to over $400.00. I just happen to find a slightly used one for a great price.

These torque screwdrivers are a long long way from a "regular" torque wrench.

Joel
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Barry Daniels
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Re: Threaded Bushing Torque Setting

Post by Barry Daniels »

OK, I did not know the difference. Never mind.
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Clay Schaeffer
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Re: Threaded Bushing Torque Setting

Post by Clay Schaeffer »

I've used a torque screwdriver for the past several months working on gas meters. For bushings I would try a setting of 6 to 8 inch lbs if the bushing uses a washer under it to help spread the force.
At what point the finish cracks will be determined somewhat by the wood under it. A denser, harder wood will be less likely to compress and allow the finish to crack than a softer wood would.
Randy Cordle
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Re: Threaded Bushing Torque Setting

Post by Randy Cordle »

I kind of like the guitars I've seen with a counterbore for the tuner bushing washer. I think one of the advantages is greatly reducing the chance for damaging the head stock finish.
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Michael Lewis
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Re: Threaded Bushing Torque Setting

Post by Michael Lewis »

The point to remember is you are working with wood (headstock) not metal, so gentle is the rule. Goes for screws too. Those collars can get loose when the wood shrinks, but if you tighten them so they don't come loose when the wood shrinks then you will be crushing the wood and probably causing finish adhesion problems in the immediate area.
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