Brass-Bronze ID

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John Evans
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Joined: Tue Jan 20, 2009 9:33 pm
Location: Phoenix ,AZ

Brass-Bronze ID

Post by John Evans »

Is there any good/easy way to tell apart ? Got a odd bunch of rems that I'm not sure what they are. I keep my bearing bronze stock that I know what it is separate. I do have some stock that I know is brass rod and 1/2 hex, but some of this other ????
Thanks for any enlightenment.
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pete
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Re: Brass-Bronze ID

Post by pete »

For bar stock I don't know of any guaranteed method other than maybe having access to a XRF analyzer. Depending on the alloy, the free machining brass I've used seems to be mostly a pretty consistent yellow color, some of the known to be bronze scrap I have has a more reddish tinge to it. And I have one large plate of what I think is what's called aluminum bronze, maybe C95500? It machines a lot more like mild steel than any other bronze I've used. And it's even a lot harder and slower to band saw than mild steel. Afaik the harder variety's of bronze are more tarnish resistant because of that addition of aluminum and get used in marine or more corrosive environments. It's still no guarantee, but anything that does tarnish fairly quick is more likely to be brass. In a home shop a few drops of vinegar left over night on the surface or testing with a file might help narrow it down a bit?
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BadDog
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Re: Brass-Bronze ID

Post by BadDog »

Small world. I'm currently trying to reverse engineer a locking hub that uses a [red-metal] bearing/bushing that sometimes gets trashed. It's a little red for typical brass I have to compare it to, but too yellow for most bronze I would think appropriate for that application. Thinking maybe silicone bronze or SAE 64, IF it's intended as a wear surface. But I'm not sure that it is a wear/bearing surface. 2 examples checked show between 0.020 and 0.030 clearance, and it runs in grease, not oil. I'm starting to think it's just a (roughly) centralizing bushing not intended to act as a bearing for wear, and something is wrong behind it that is causing it to take wear it should never see. Just started poling at it, and only mention it because I was just asking the same question as John (who is right down the street)
Russ
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pete
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Re: Brass-Bronze ID

Post by pete »

I don't know it this is of any use, but it seems to be rarely mentioned and lots with home shops don't seem to have run across the details. I went a few decades before I found out free machining brass is soft enough to be used as a bearing surface with unhardened but polished steel pins. The recommendations I've seen in print for more durablity are that most bronze bushings or sleeve bearings require hardened steel. So it's not something you can guess at.In most cases with mining equipment that use grease, bronze bushings get used with I'd assume hard turned pre hardened steel pins and the bushings are meant to wear first. New pins are pretty smooth but definitely not ground. With lack of or poor lubrication both parts always wear the most on the side with the highest loads. If or when the pin starts to gall it then wears more than the bushing. But that .030" clearance seems pretty high even with grease. I'm sure no expert, but I've seen a few posts recommending .001" per inch of shaft diameter. That might be at the absolute minimum though and specific to what type of grease is being used.

Too tight is just as bad. The last mine I worked at had to replace the pin and sleeve bearings on the booms point sheaves for a P&H 2800. At the time they could get the bearings, but the shaft was out of stock so the mines machine shop made one. I found out later from the machinist that his own recommended clearance got ignored and the shop superintendent decided to go a lot tighter with .005" for a 10"-12" shaft diameter. That shaft and the sleeve bearing on those shovels are lubricated with a black semi liquid grease on a timed grease pump and support well over 100 tons with every loaded bucket. Those bearings lasted around 36 hrs before they started to smoke from the friction and lack of lube. So another set of bearings flown in and a new shaft with a bit more than double the clearance. Probably $20k + and even more downtime.
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BadDog
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Re: Brass-Bronze ID

Post by BadDog »

Yeah, I don't want to derail the brass or bronze OP question, but I agree on the excessive clearance. BTW, the piece OD of the one (mystery red metal) I have in hand is 1.989 and the new part it mates (or matches) with is 2.012 ID. The other no longer here had about 0.007 more clearance. Very loose tolerances it would seem, and one of the reasons I decided I don't think it's actually meant to be a wear/bearing surface, and thus the failure mode indicates something wonky elsewhere.
Russ
Master Floor Sweeper
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