I was told by someone who was in the precision group that the bolts should be changed every three months if being used daily. I had one of the copper nuts strip the threads out on me.
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You’d have to lubricate them, because stainless steel will scratch stainless steel. The silicone bronze does actually have higher tensile strength than stainless steel (as it should, since the nut is the “fastener”). I question the quality of a lot of the silicone bronze nuts I’ve used. Why do they strip so easily? Sometimes on the first use? I sometimes like to hand-tighten a second nut for safety measures. Dunno how much it would actually help in case of emergency.
There’s a really good video I’ll have to dig for that shows why clamping force on the gasket is actually more important than the torque on the nut. Measuring torque with a torque wrench gives us a good idea of clamping force, but is probably more and more inaccurate the more that the nut wears down.
For torquing, I used to do 20 ft•lbs, as per manufacturer ratings for. I noticed 20 ft•lbs easily deformed gaskets, both PTFE and Viton (not as bad with Viton). Now, I typically start at 10 ft•lbs and use the minimum torque required to create a good seal. I usually find that this is 12 ft•lbs, but can go up to 15 ft•lbs without deforming gaskets. This only goes for silicone bronze nuts with stainless steel bolts. This is why I think we should be measuring clamping force.
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Plz only use brass…if u use another metal u could generate sparks which could ignite your rig…ppl be careful and change ur nuts every so often they’re super cheap plus u can recycle the old ones…once u hear the nut squeak you’re shaving brass off at that point…tighten evenly on both sides not one at a time
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You need a torque wrench
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Brass is used because stainless on stainless will cause galling. Stainless can make sparks just like its low chromium brethern. Read more about galling here Bolt Depot - About Thread Galling
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Like materials under pressure gall…steel, stainless, nickel copper will all gall.
I never thought about the spark factor. We’ve actually manufactured special nickel aluminum bronze wedges for separating components in an environment that requires zero spark. Never gave that application a second thought to the fasteners on my extractor though…good point
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Brass has lower tensile strength than stainless steel. Can anyone here give me a logical explanation why the actual “fastener” (aka the piece that your seal relies on the most) would be weaker than the clamp/nuts?
I didn’t find the video I was looking for, but these cover some of the torque issues:
Torque vs Clamp - YouTube
Torque vs Clamp Force - YouTube
Applied Bolting - Torque isn't Tension - YouTube
If I have hear one more extract artists talk about “once you hear the squeak . . .” 
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Brass is a soft metal which reduces the chances of spark…have u ever smacked a brass piece with another metal and seen a spark?
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yeah keep tightening until the clamps touch. i hear thats the best way to stop leaks.
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I’ve never seen Kevlar spark either, but I sure wouldn’t try to fasten a high pressure clamp with it…
Spark resistance is only one characteristic needed. By nature of fasteners and clamps, the nut should be the strongest piece involved. Convince me otherwise - I’m all ears.
Hahah one of the videos I posted a link to above shows how less torque can actually give more clamping force (aka tension on the bolt)
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Yea I’ve personally seen overtightning lead to leakage. Too tight an gaskets fail
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Thanks for this! Exactly what I was looking for.
I like the idea of going by clamping Force you got something there I think…
Don’t lie you hit that shit with a hammer! Jkjkjk
Holy cow! I’m glad mine wasn’t that bad!
Galling mostly
Yeah, a hammer drill.
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where do you guys get you replacement nuts and bolts
LMAO that’s me
What’s your preferred torque? Does it vary per size of tri clamp?
Me too lmao
haven’t had any issues so far.