Stupid question of the week: What's "galling"?

i have wondered that to.

Galling is a heat/friction welding od SS to SS, from the quick google search I saw.
My metalurigical memory is of a work-hardened scaling as the surface becomes over-hardened, then flakes away.

But, I'm using memory, that weakest of references to cite

Google is your friend.

Galling, according to ASTM standard G40 (2006), is: “a form of surface damage arising between sliding solids, distinguished by microscopic, usually localized, roughening and creation of protrusions (i.e., lumps) above the original surface”. In other words galling is material transfer from one metallic surface to another caused by movement and plastic deformation.

From here: http://en.wikipedia.org/wiki/Galling

deformation

From my Navy nuclear days, if I recall correctly. Galling: The microscopic welding and subsequent shearing of two metals in intimate contact resulting in material transfer between them.

A quick way to look up a word, on Google type
define: whatever word you're looking up

For define: galling
Here are some that came up.

a form of wear in which seizing or tearing of the gear or bearing surface occurs.
www.noria.com/dictionary/default.asp

A severe form of adhesive wear which occurs during sliding contact of one surface relative to another. ...
www.boltscience.com/pages/glossary.htm

A condition whereby excessive friction between high spots results in localized welding with subsequent spalling and further roughening of the rubbing surfaces of one or both of the mating parts. This is a typical tool failure mode. ...
www.richterprecision.com/richter_glossary.htm

Damage to the surfaces of materials sliding in contact with each other, usually caused by the localized welding together of high spots. ...
www.tdcoating.com/td_glossary_terms3.htm

A type of wear that occurs when one surface slides against another where particles of one part stick to the other part or break away from the ...
www.emachineshop.com/machine-shop/Manufacturing-Glossary/page119.html

Basically two pieces of metal rubbing on each other with no lube in between, and the damage caused by it.

Ever remove an old bolt and it removes some of the female threads it used to be in? That's galling.

Galling looks like wear. It is a way wear happens. Often shows up as a track of parallel gouges, both formerly smooth surfaces now rough....

Some metals gall easily (titanium, aluminum, many stainless steels), others have a natural resistance to it....

Learn more: http://en.wikipedia.org/wiki/Galling

Wiki and google are your friend, used judiciously.

J

Galling can also be when your crotch gets red from riding a bicycle.

Friction induced pain or redness.

Same principal when two similiar stainless steel surfaces rub together.
It used to be a major problem with guns made of one grade of stainless steel.

Then the manufactures developed better alloys, and started using different types of stainless on mating friction surfaces. (Slide & frame are different grades of stainless for instance)

rc

Here is a pic I jacked from GB, shows heavy galling on the chamber end of a Yugoslavian Barrel pulled from its stub. Its extreme for galling, but shows you what it looks like-

Basically two pieces of metal rubbing on each other with no lube in between, and the damage caused by it.

Click to expand...

What he said.

Hmmm.... dry firing comes to mind. Acutually, some metals gall more easily than other and it depends on whether the 2 metals are the same or different... along with many other factors.

Stupid question of the week: What's "galling"?

Click to expand...

People who ask stupid questions.

Sorry, I'm kidding, I just can't resist wordplay.

I've never heard of it either. Learn something new every day.

If you want to see galling in action (though not how it relates to firearms), go to the hardware store and buy a 5/8" bolt and nut, both in 316 stainless steel. Go home, spin them together and apply 150 - 200 ft-lbs of torque. Then try to get them apart.

You will likely find that they have essentially been welded together. Heating won't help separate them either. You will either have to cut the bolt, or get a BIG impact wrench and twist the bolt until it shears.

This is easily avoided by using a bolt/nut combination of differing materials. Can't explain the reason but I've seen it happen many times, and always in some grade of stainless.

Hmmm.... dry firing comes to mind.

Click to expand...

Why?

I don't make the connection.

In the simplest terms, leading a barrel when shooting cast bullets is a form of galling. Copper jacketed bullets will gall barrels to some degree when the copper is deposited on/in the rifling and you have to scrub the barrel to remove it.
I've seen punches in a punch press used on softer aluminum, develop metal buildup (alum)on the tool steel punch to the point that the punch would stick in the metal without some form of lubrication.
I hope this clarifies the meaning for some.


NCsmitty

galling is also caused by rimfire firing pins hitting the chamber wall during dry firing correct?

chevyforlife21 said:

galling is also caused by rimfire firing pins hitting the chamber wall during dry firing correct?

Click to expand...

No, not really. That would be more like hobbing. The firing pin would displace metal on the chamber face but not fused to it. The pin being quite a bit harder than the barrel metal would make it not gall.

Galling is when the metal surfaces have fused together on the molecular level much as when welding. It occurs when the contact pressure between two metal surfaces is high enough to cause the surfaces to fuse. That can be a threaded connection, press fit connection or other metal to metal interface bearing a high load (pressure).

When two pieces of metal have galled together the pieces can only be separated by shearing the interface material. It takes a lot of force depending on how complete the galling has become. Many time the pieces are deformed, broken or otherwise destroyed before the galled surfaces are sheared apart. Most of the time you merely shear the base metal and not the interface. That's what makes the appearance of metal stuck to one piece or the other.
Prevention includes high film strength lubricants, use of dis-similar metals or metals of differing hardness.

Gall dang. Thanks for the info.

The picture in the posting is a good example of galling !
Look at the waving in the material in the picture that is galling .

most of the response are correct as well .

In the machine tool industry it is mainly caused by poor lubrication or dull tooling .

Main cause of it is friction .

Ever had a bearing of any sort go bad on a motor vehicle, particularly axle bearings! That pitting and roughness on the axle shaft is "galling"