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| vtsteam:
--- Quote from: Fergus OMore on July 15, 2018, 04:11:46 AM ---Simon 'Chinese metal' appears regularly in such things as vehicle carburetors and in model engineering, the feed nuts on Myfords are a zinc alloy. One fault is that it does corrode until after a certain point it will be nothing more than white fluff! Chemically, it is somewhat worse than cheap brass. However, it is easy to cast and I have rather a nice Unimat clone lathe made from -- lots of it. Probably 'metal' for typesetting is something similar. I hope that I haven't stolen the original post-- but Simon did ask Norman --- End quote --- No problem adding to the conversation Fergus. I would qualify the statement "it does corrode until after a certain point it will be nothing more than white fluff!" by saying that iron and steel will corrode until after a certain point they will be nothing more than red dust. You are speaking of unprotected metal exposed to outdoor or saltwater environments, or road salt, which is true of both metals. Bronze and some aluminum, and corten steel alloys are the only answer for corrosion. With regard to cheapening metal parts by use of die cast zinc alloys, the cheapening is mainly due to the ease of die casting these alloys allowing absolute minimum parts thicknesses and the very high strength of the material -- everything of that sort is hollow and usually 1/16" thick -- car door handles and such. It's a whole different ballgame in a 1/2" or 3/4" thick part, painted, except for wear surfaces and used in a lathe. As an example, my own unpainted lathe, which has both steel and zamak parts, sat for a couple years in an unheated cinder block shop, with ice on the floor all winter. When I returned to it this summer, the zinc parts had dulled to a nice evn gray, not white fluff, but a gray patina, looking very much like plain anodized aluminum. Quite servicable, as is. On the other hand the carefully scraped and oiled steel ways had spots of surface rust which had to be removed. My drill press table was orange with surface rust, as was my iron vise, and just about everything else ferrous. So, yes in certain applications -- chromed auto hardware, for instance, zinc alloys have been used to cheapen products, and corrosion may be a problem. But that doesn't have to be the way they are used. I think they have great advantages if used with a different approach, and I certainly wouldn't have gone to the trouble of putting them into my own lathe if they weren't ideal (from my perspective) for certain parts. After all I can cast Iron, brass, bronze, aluminum, and obtain and machine steel easily. And have, where I thought appropriate. I used zinc alloys by choice for purpose not cost reductions, and not for ease of machining (ugh!) |
| vtsteam:
Of course, I do enjoy running against conventional wisdom. So far: welded steel lathe beds will warp, firebrick can't be used for melting iron, plaster of Paris won't make a suitable foundry furnace lining, and zinc alloys in a lathe will turn to powder. Outside of this forum I've been told hundreds of times I can't do things I've managed to achieve, so I guess it's just a normal situation for me. I don't mind, just hope people widen their knowledge base. My firm belief is generalizations are true, except when it comes to specific cases. And even that belief has exceptions! :lol: |
| awemawson:
You're like me Steve - you rise to the challenge. If someone says to me that something can't be mended it's like waving a red rag at a bull and I dig my heels in and charge! |
| Neubert1975:
sounds like a person i have been arround since birth :) When people tell me that things cant be done, i often answer, in that case i must be a magician. and if i havent done it, it is like awemawson says, like waving a red rag at a bull :thumbup: |
| vtsteam:
btw, sorry just one more a humorous thought, I have a 20 year old garbage can (dustbin, Br.) that lives by the road, outdoors in all Vermont weather. It is hot dip galvanized steel (zinc coated). It's in fine shape -- no deterioration, despite its rough use, exposure to rain, corrosive contents, and proximity to road salt. If it had been plain steel of the same thickness, treated this way for twenty years, it would indeed now be a small pile of rust flakes. My 20 year old house roof is also made of galvanized steel sheeting. In fact the very roof that protects my ferrous machine tools from the elements is also zinc coated. I know some rake is going to point out the galvanic series now, and trot out old saws about anodic protection, but I would ask that he or she then consider all-zinc roofs. No steel couple. Why in the world choose a metal that will turn to white fluff to protect against the elements? Tell me when my zinc headstock will be powder, so I can switch off the lathe in time, boys! :lol: |
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