Metal wear

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rooster
Posts: 33
Joined: Fri May 18, 2012 3:08 pm
Location: centrel louisiana

Metal wear

Post by rooster »

Hope i explain this right , here goes , if you have two metals same metals rubbing against each other how much ware occures even if its lubricated ,steel against steel or aluminum against aluminum, lets say a 3/8 inch hole with a 3/8 shaft going into is slightly smaller so it will fit inside the other maybe a few thousands smaller moveing at 1/4 inch movement back and forth, looking at this as opposed to a brass bushing which will ware after a period on time (brass being softer?). Pressure will be maybe three pounds applied to said parts. any thought anyone? Russ
hammermill
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Location: pendleton or

Re: Metal ware

Post by hammermill »

if lubrication can be maintained there will be no metal to metal contact. real wear will occur as the parts start to move up until the lubrication become a barrier between the 2 parts

when the lube fails the harder material will begin sutting thru the softer part.
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refinery mike
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Joined: Sat Jul 02, 2011 1:54 pm

Re: Metal wear

Post by refinery mike »

Look up coefficient of friction on Google, you will find charts that give the relative friction of different sets of metal on metal. Look for a chart that contains lists for lubricated and unlubed metals. The lower the coefficient the better. This only applies if you keep the parts lubed at all times. a dry bearing can go to pot in pretty short order. this will only be a general guide, i do not think that cadmium on cadmium would make a very good bearing even though it has a low coefficient. A little to soft and brittle.
hammermill
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Joined: Sun Jun 27, 2010 10:43 pm
Location: pendleton or

Re: Metal ware

Post by hammermill »

if lubrication can be maintained there will be no metal to metal contact. real wear will occur as the parts start to move up until the lubrication become a barrier between the 2 parts

when the lube fails the harder material will begin sutting thru the softer part.
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rudd
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Joined: Wed Dec 12, 2007 11:21 pm
Location: savannah ga.

Re: Metal wear

Post by rudd »

Finish pays a huge part.
Look also to what materials form good bearings against each other. Only cast iron works well with itself.
Steel works well with cast iron, bronze, and some others I can't recall at the moment.
Aluminum has few compatible metals, bronze would be one.
Steel on steel will gall, bronze on bronze will gall, aluminum on aluminum, or steel, or cast iron, will gall.
Southbend used steel spindles on cast iron bearings during WWII, the still work great, but you'd better believe that spindle is SMOOTH.
Yes, I realize that in theory, a lubrication film should not allow the two materials to touch. Nice theory, works well in auto engines where the oil is pumped at pressure into the bearings. But note that even there, the highly polished steel crank is supported on bronze bearings. And the bearings do wear, mostly at start up when oil pressure is zero.
Why the requirement for the same metal for the bearing and the shaft? I ask because this is against usual engineering practice..
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