stainless steel?

Question

nuts and bollts stick and strip threads, what causes it and how can i avoid it. Iv tried general greese and copper slip??.

Answer 1

A few times each year we receive calls from fastener suppliers who are in conflict with their customer over the quality of stainless steel bolts and nuts. The customer's complaint is that during installation the bolts are twisting off and/or the bolt's threads are seizing to the nut's thread. The frustration of the supplier is that all required inspections of the fasteners indicate they are acceptable, but the fact remains that they are not working.

This problem is called "thread galling." According to the Industrial Fastener Institute's 6th Edition Standards Book (page B-28),

Thread galling seems to be the most prevalent with fasteners made of stainless steel, aluminum, titanium, and other alloys which self-generate an oxide surface film for corrosion protection. During fastener tightening, as pressure builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out.

Carpenter Technologies, the fastener industry's largest supplier of stainless steel raw material, refers to this type of galling in their technical guide as "cold welding." Anyone who has seen a bolt and nut with this problem understands the graphic nature of this description.

The IFI and Carpenter Technologies give three suggestions for dealing with the problem of thread galling in the use of stainless steel fasteners:

1. Slowing down the installation RPM speed will frequently reduce, or sometimes solve completely, the problem. As the installation RPM increases, the heat generated during tightening increases. As the heat increases, so does the tendency for the occurrence of thread galling.
2. Lubricating the internal and/or external threads frequently eliminates thread galling. The suggested lubricants should contain substantial amounts of molybdenum disulfide (moly), graphite, mica, or talc. Some proprietary, extreme pressure waxes may also be effective. You must be aware of the end use of the fasteners before settling on a lubricant. Stainless steel is frequently used in food related applications, which may make some lubricants unacceptable. Lubricants can be applied at the point of assembly or pre-applied as a batch process similar to plating. Several chemical companies offer anti-galling lubricants. One such source, EM Corporation, suggests their Permaslik¨ RAC product for use at the point of assembly. They suggest Everlube¨ 620C for batch, pre-applying to stainless steel fasteners.
3. Using different stainless alloy grades for the bolt and the nut reduces galling. The key here is the mating of materials having different hardnesses. If one of the components is 316 and the other is 304 they're less likely to gall than if they're both of the same alloy grade. This is because different alloys work-harden at different rates.

From: http://www.estainlesssteel.com/gallingofstainless.html

Answer 2

Worth very little as far as I'm concerned. It has a very poor co efficient of heat, is hard to lubricate to keep the food from sticking and will develop a hot spot easily. My preference is a good quality cast iron, it is heavy but conducts heat well and spreads it evenly. Stainless with copper bottoms is marginal for boiling water but it does clean easily. There are several alloys on the market that are usable as cook ware. Aluminum is worse than stainless. Of the pure metals, copper is the best conductor of heat, cast iron is my choice, spun steel does work. Hope this helps. Never wash cast iron cookware with soap and water.

Answer 3

You have two passable problems:

1/ The threads in the nut do not match the threads on the bolt.

2/ Over torquing,

Stainless should not need lubricating.

Answer 4

You'll have to use anti-seize. Stainless steel naturally forms a chrome oxide film on its surface which gives it resistance to corrosion. However, in putting on a nut rubs off this film and the stainless parts will actually fuse together. Sorry I don't have the link for this. But the last time I found it I was searching on stress corrosion cracking of austenitic stainless steels. If you want to see the why it happens you'll have to look that up.

We use anti-seize mentioned by one of the other folks here and it works pretty good. But it is messy.

Answer 5

Graphite is a good lube for stainless steel threads.

Answer 6

Have you got the right threads for the nuts and bolts. If they don't match you will strip the threads trying to tighten them down.

Answer 7

This is a common problem with stainless. This is called gall. It happens when the stainless is over torqued.

Answer 8

Either the thread spacing or the size match is wrong.

Answer 9

Pick some up at your local auto parts store
"antiseize".