Galled Stainless Steel machinist jack??

[davidpbest]

I whipped up a machinist jack the other day. I used a piece of stainless steel that I had laying around, it machines beautifully.
It came out great except it felt like there was some grit in the bore.
I placed both pieces in my ultra sonic cleaner.
When it was finished I screwed the pieces together. It got tighter and tighter. Maybe because the pieces expanded in the heat?
Now it’s ruined. I can’t budge it. It’s completely stuck. Scrap pile!!
I used a commercial tap and die to produce the threads.

What the heck happened??
Have you ever experienced this??

Don’t laugh at my knurling

For threaded fittings like this in stainless, you can largely eliminate the tendency for them to gall by using dissimilar versions of stainless on the mating parts. For example, if the male thread is 304, make the female component out of 316. Just a thought. Once stainless starts galling to itself it's nearly impossible to get them apart without doing serious damage to the threads.

 

[Ulma Doctor]

I live in a world of stainless steel machines.
One of the first lessons I learned in this business was the use of anti-seize compounds .
If you are hoping to separate galled fasteners, be ready to drill the broken stub out

When making threaded parts I’ll add a piece of shop rag to the tap to make the female threads a couple thousands larger, to resist galling from insufficient clearance.
You could instead tap drill for less engagement from say 75% to 60% where possible

 

[Dabbler]

This makes me wonder, is copper anti-seize, or silver better for stainless? Especially for the very soft 303 or 304 stainless....

 

[Ischgl99]

This makes me wonder, is copper anti-seize, or silver better for stainless? Especially for the very soft 303 or 304 stainless....

I was always told at my previous employer never to use copper based anti-sieze on the machines, but I had to look up the reason. This is from Henkel:

“However, it is important to remember that while many compounds exist for stainless steel, copper anti-seize on stainless steel will create inter-crystalline corrosion which can cause parts to crack or break when under heavy loads. “

It probably wouldn’t matter in many applications that we do here, but I won’t use copper anti-sieze on any stainless application just in case.

 

[34_40]

We've always used copper anti-seize for only high heat applications. In a pinch and you need some for a fastener or two but you don't have any? you can substitute white toothpaste. in my experience It works. I wouldn't do it unless pressed for the need, but I have seen it in some printed materials and I have used it in a pinch. Regarding Henkel's advice, the "inter-crystalline" corrosion will develop no matter what you do. imho.

 

[Jake M]

This makes me wonder, is copper anti-seize, or silver better for stainless? Especially for the very soft 303 or 304 stainless....

Nickel for stainless.

Anti-seize is not a grease, it's oil with metal (and other) components in solid form. It's use (depending on the application) is very sciencey. It can be a lot of things in chemical/physical reactions, from preventing reactions, to causing reactions, to just "who cares but it's thicker than oil...

Aluminum/graphige (regular, cheap) anti-seize isn't "evil" in a stainless joint, but it's not that beneficial, and if temperature is an issue, it's poor. Nickel is good for (among other things) stainless to stainless, and stainless to aluminum. Copper is fine for a lot of things, but it does react funny with stainless, and in most common joints (steel to steel, steel to aluminum) it messes with galvanic potentials and drives several undesirable reactions. Over some time. None of these "blow up in your face" or anything like that...

It's crazy stuff that I don't even try to keep up with any more as the chemistry, while I can understand it when it's spelled out, goes way over my head to the point that I don't even try to "figure it out" any more. But yeah.... Stainless to stainless and stainless to (almost) anything else gets nickle.

And if you happen to be torquing something where it's warranted, or in my case with the sidewalk sanders I mentioned, when playing with stuff that warrants no such thing, but you drag out the torque wrench while investigating problems and/or just to keep your click elbow in calibration... Check out the nut factors on that stuff if anything's threaded. (Reputable brands provide that, but it's probably on the website, not the bottle). It'll blow your mind how much that will adjust the desired torque to properly tension a fastener, or in the case of a machinist jack, how little force it'll take when you "snug it up", to lift a part right out of a vise... They're all a little different, but overall, generalizing, and on new fasteners- It'll be different by product, but something on the order of cutting the actual tightening force in half to achieve the correct preload. You can break stuff without even breaking a sweat if you don't adjust for it... Crazy stuff.

 

[GeneT45]

I recall seeing somewhere that some sort of mint oil was the best anti-seize for stainless. Peppermint? IIRC the advice came from someone claiming to do a lot of work on stainless vacuum lines where a 'perfect' seal was important, as was being able to disassemble the thing at some point.

GsT

 

[rwm]

@Janderso - To get back to the original part- You could machine out the screw without getting into the minor diameter of the internal thread. Then you could probably pick the thread out. At least you could save that piece and make a mate out of mild steel.

 

[Dabbler]

Nickel for stainless.

Thanks, Jake!

 

[Janderso]

You used stainless in a non stainless application.

It’s what I had laying around
The second one is low carbon steel.