Galled Stainless Steel machinist jack??

Janderso said:
Somewhere along the way I read or heard it's a good idea to have different materials to avoid galling.
Is this true?
I have some stress proof.
Click to expand...
Yes, the galling problem with stainless comes from the steel being relatively soft and gummy. With two parts of similar properties, they weld together due to the heat from friction, or debris in the threads can cause it too. By using a different type of steel for the two parts in contact, you don’t get that because the properties are different. If you want to use stainless for this, if one part is a 300 series grade, make the other part out of a 400 series and it will be less likely to gall. You can even harden the 400 series piece to make it more resistant to galling. The stress proof should work too.

Just a guess, but wondering if the ultrasonic cleaner removed the chromium oxide layer and exposed fresh steel on steel and caused the galling. Did you assemble it right after coming out of the cleaner? If so, it might not have had time to build up the oxide layer.

When I worked for the centrifuge company, the disk stack centrifuges had a lock ring that kept the bowl top on the bowl bottom and was under a lot of pressure since it was also compressing the disk stack. These parts were made from a duplex steel, so had some properties similar to austenitic stainless (300 series). The threads and mating surfaces would gall easily, so we needed to make sure all the surfaces were in good condition and well lubricated. This never happened to me, but I heard stories that the lock rings (that could be up to about 3 feet diameter) had to be cut off on a few machines because it was galled so bad. We also had problems with a different type of centrifuge that had a lot of stainless bolts holding everything together. If you detected any damage to the threads, we threw the bolts out and replaced with new, it was very easy to get a bolt stuck in the stainless components.
 
Janderso said:
Somewhere along the way I read or heard it's a good idea to have different materials to avoid galling.
Is this true?
I have some stress proof.
Click to expand...
It would be better to make one part out of stressproof although it would be even better to make the whole thing from stressproof. I would think 12L14 would be a good choice too since it has a little lead in it. I know it is very nice stuff
to machine giving nice smooth surfaces although I don't think I have ever tried it.
 
Milk of magnesia is an excellent anti-seize on stainless. Yes, the stuff you get from a pharmacy... It's particularly good in high-temp environments, too.
 
Stainless does that.
The only way to slow it down is to use anti seize compound on the threads.
Once galled the parts are not just effectively welded together they are actually welded together.
On the SS equipment that we build at work there are notes all over the drawings to use anti seize compound and ONLY hand tools, even a ratchet spun by hand can be fast enough to generate the heat to weld the threads, especially if there is any pressure on the thread. Once Galled there is no saving it. No penetrating oil or temperature fluctuation will break a weld.

Although less likely carbon steel can still gall with stainless. Making the thread fit really sloppy also helps some. Anti seize before assembly is your only hope.
 
cathead said:
It's probably best to set it aside and make one out of mild steel or stressproof. Some of the
stainless material is very prone to galling which looks to be the case here. Look at it as a
learning opportunity and move on with your new knowledge.:encourage:
Click to expand...
I took your advice. This one is just your basic hot rolled low carbon steel with a 5/8-18 thread.
Smooth as glass.
 

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Flyinfool said:
Stainless does that.
The only way to slow it down is to use anti seize compound on the threads.
Once galled the parts are not just effectively welded together they are actually welded together.
On the SS equipment that we build at work there are notes all over the drawings to use anti seize compound and ONLY hand tools, even a ratchet spun by hand can be fast enough to generate the heat to weld the threads, especially if there is any pressure on the thread. Once Galled there is no saving it. No penetrating oil or temperature fluctuation will break a weld.

Although less likely carbon steel can still gall with stainless. Making the thread fit really sloppy also helps some. Anti seize before assembly is your only hope.
Click to expand...
Hmm, interesting. Lesson learned.
 
This is all good to know. I also use too much stainless!
So ya'lll don't think that freezing the screw with dry ice and heating the base with a torch would yield any result? Is galling really welding?
Full disclosure...here is my ill-conceived stainless machinist jack!

1706389991116.png

Followup question: Does passivation help prevent galling?
 
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