New Chinese mill vs old high quality mill
I'm looking at machines for a home shop where I work on a wide variety
of projects. I can't decide which way to go: 1. Get a new Chinese mill (such as grizzly, harbor freight, etc...) 2. Get an old high-end mill (Bridgeport, etc...) Assume the machines have very similar specs (in fact, the Chinese machine may be a copy of the Bridgeport!). Assume also, that I wouldn't be able to afford the better used machines out there. Compare, for example: http://www.grizzly.com/products/item...emNumber=G6760 http://cgi.ebay.com/ws/eBayISAPI.dll...m=3823642 872 These two machines both cost about $2,500. In both cases, I would expect to spend a fair amount of work to get the machine into good shape. The Chinese machine will come with a variety of small problems and generally poor fit & finish -- it will need a comprehensive overhaul out of the box. A low-price used Bridgeport will probably also need a fair amount of work, maybe some new parts, etc... and may be somewhat the worse for wear. Are old mills on the market for $2,500 likely to be worn out? How much is it going to cost to get them into good running shape? Once it's tuned up, will the Chinese mill perform as well as the older Bridgeport? Thanks! -Bill |
New Chinese mill vs old high quality mill
On 3 Jul 2004 17:18:00 -0700, (Bill Ross) wrote:
I'm looking at machines for a home shop where I work on a wide variety of projects. I can't decide which way to go: 1. Get a new Chinese mill (such as grizzly, harbor freight, etc...) 2. Get an old high-end mill (Bridgeport, etc...) Assume the machines have very similar specs (in fact, the Chinese machine may be a copy of the Bridgeport!). Assume also, that I wouldn't be able to afford the better used machines out there. Compare, for example: http://www.grizzly.com/products/item...emNumber=G6760 http://cgi.ebay.com/ws/eBayISAPI.dll...m=3823642 872 These two machines both cost about $2,500. The Griz has a power feed, the Bridgie doesn't. Of course you can add a power feed to the Bridgie, but that's extra $$$. The Bridgie has a vari-speed head, the Griz doesn't. Old vari-speeds can be trouble, and expensive to repair, OTOH being limited to 5 speeds tends to suck, especially since the Griz doesn't have back gears. (That'd make boring and face milling problematic.) The Bridgie requires 3 ph power, the Griz runs on household AC. This has both pluses and minuses. You won't need a rotary converter or VFD to run the Griz. OTOH, you can't use a VFD to give the Griz vari-speed. You will need to budget for a rotary converter or VFD to run the Bridgie in a home shop. That need not be very expensive, but you have to have it. The Bridgie has obvious rust, hopefully the Griz doesn't. (Harold would have a fit, but the rust doesn't look too bad in the pictures. It'd probably clean up ok.) Between those two particular machines, I'd probably gamble on the Bridgeport. However, you're really comparing apples and oranges. The Griz you selected is a lightweight. A closer Griz match to the Bridgie would be http://www.grizzly.com/products/item...emNumber=G9903 Now you're closer to comparing apples with apples. Mass is critical in a mill, more is better. No way a light mill can equal a heavier one in terms of rigidity. Rigidity is the primary thing, other than wear, that controls the ultimate precision and quality of cut a mill is capable of producing. (Yes, now we're talking about a $4,000 machine, but a Bridgeport was an $18,000 machine when it was new.) In both cases, I would expect to spend a fair amount of work to get the machine into good shape. The Chinese machine will come with a variety of small problems and generally poor fit & finish -- it will need a comprehensive overhaul out of the box. A low-price used Bridgeport will probably also need a fair amount of work, maybe some new parts, etc... and may be somewhat the worse for wear. I wouldn't say the Chinese machine would require a comprehensive overhaul. You will need to clean off the shipping grease, check for casting sand, change the lubricant, maybe deburr a few edges, do normal adjustments and setup, etc, but you shouldn't need to fabricate, modify, or replace any parts. I have an ENCO mill similar to the larger of the 2 Grizzly mills listed above. It took about 4 hours to get it ready to work. You know you're going to have to derust the Bridgie, maybe work on the vari-speed ($$$), and if there is significant wear in critical areas, returning it to like new precision is almost certainly going to cost more than it is worth. (Not saying that's the case with the particular machine you listed, but it could be.) Are old mills on the market for $2,500 likely to be worn out? How much is it going to cost to get them into good running shape? Once it's tuned up, will the Chinese mill perform as well as the older Bridgeport? The light Chinese machine you chose is never going to match the performance of a Bridgeport in good condition. OTOH the Griz model I indicated probably would equal or surpass a used Bridgeport with very minimal setup. It is possible to find a Bridgie which has only had light use, and has been well maintained. That would be a good machine to have. But it is also possible to find one that's got serious and expensive problems. You can't generalize too much about used equipment. Everything depends on the exact details of the condition of the particular machine. To answer your question, yes it is possible to get a used Bridgeport in good condition for $2500 (sometimes less if you bypass dealers and handle it as a private sale). The real question is, how can you be sure the one you choose actually is in good condition? And what will it cost to repair it if it isn't? If you aren't intimately familiar with the machines, it'll probably pay to hire a good independent Bridgeport tech to inspect any used machine you might want to buy. He'll be able to spot problems that you'd probably completely miss, and tell you whether it is worth the cost of repair. Note that while Machinery Values offers a 30 day return privilege, you'd still be stuck with the freight charges both ways, and these machines are heavy, so that could be a fair sum of money. It'd be better to get the machine checked up front before it is bought and shipped. At least they say it can be inspected under power. That's a good sign. Gary |
New Chinese mill vs old high quality mill
In article , Gary Coffman says...
especially since the Griz doesn't have back gears. Whoops. That would rate that particular machine a 'no thanks' for me, right there. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
New Chinese mill vs old high quality mill
I spent several hours removing the shipping grease on my Enco 9x49" variable
speed mill, but that was all. It didn't require any repair. |
New Chinese mill vs old high quality mill
Bill Ross writes:
Are old mills on the market for $2,500 likely to be worn out? Very likely at that price. My Bridgeport Series 1 price survey has been: $1500 for serviceable but with severe wear or broken head, $2500 for running but with moderate to severe wear, and $3500 and up for running with light to moderate wear. How much is it going to cost to get them into good running shape? I am now working myself on scraping a well-worn (e.g., middle of knee concave by 0.005", gibs shimmed with pieces of crate strapping metal!) Bridgeport. It has been quite educational and a project of making tools and gages in itself. Quite a few $100s in cash to buy books and tools, and quite a few hours making and improvising some of the tools. Getting this kind of rebuild done right is perhaps $3000 to hire out, and you probably have to ship the machine to get it in the hands of someone who does it. I figured out why some of these old machines have such pretty body-shop repaint jobs on them: the effort to do that is a small fraction of the effort to get the machine back to factory alignment. The most valuable lessons of all are that I am now become knowledgeable at evaluating all aspects of Bridgeport wear. There's no way you can work on repairing alignment without knowing everything there is to know about measuring it first. Sometimes you learn the hard way. I spent a week rough and finish scraping the knee ways, and then discovered my datum surface was off. I am also converting the ways to teflon bearings, which should make this machine last forever before realignment is needed again. |
New Chinese mill vs old high quality mill
The pricing on Bridgeport's vary greatly with location. I could find a VERY
good Bridgeport for $3000 it might take a few but they are out there. I some locations that might not be possible. As to the Griz, I would want to see one (same with the Bridgeport) before buying. I looked at a 18" grizzly band saw just 2 days ago and was not very impressed with its quality. Every part on the machine was as minimum as it could be. I own a Millport milling machine and its an import copy of a Bridgeport. I use both mine and my dads Bridgeport and see no real difference. Take a look www.motherearthrecycling.net/shop/shop.htm But I was able to try before I buy, and the seller offered it to me at a very LOW price. |
New Chinese mill vs old high quality mill
In article , Richard J Kinch
says... I am also converting the ways to teflon bearings, which should make this machine last forever before realignment is needed again. Teflon? You maybe mean turcite, or rulon. Plain PTFE would be a poor choice for a way bearing surface IMO. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
New Chinese mill vs old high quality mill
--Lotsa good "old iron" out there; some of it not too worn out,
too. And remember there are some pretty reasonably priced ways to bring a beater back to life, like replacing the bronze nut (forgot the proper name) that the Acme screws run thru, or even just tightening up the old one... If I had room for a Bridgeport-sized machine I'd start looking for an old Webb. Used to operate one when I worked in So Calif; they're massive, have more Y-axis travel than a standard Series 1 and you just can't wear them out. -- "Steamboat Ed" Haas : Somewhere in Texas a Hacking the Trailing Edge! : village has lost an idiot... http://www.nmpproducts.com/intro.htm ---Decks a-wash in a sea of words--- |
New Chinese mill vs old high quality mill
I have a few questions.
1. How did you conduct yor "Price Survey?" In the NY-NJ area I thought $2500 was the very high end for a manual Series 1 machine. I knew plenty of examples of one being sold for $500. Yes it is true not every one is still in good shape, but if you can run a few operations before you buy it, hop in the car and go see it. Can someone recommend a good test regimen? Armed with this, does a non expert really need to hire a technician? 2. Someone said that a vfd could be used as a speed control on a Grizzly that runs on house current. That's wrong, right? 3. Is there anyone who would actually prefer a new Enco to a used but sound BP? In '98 I bought both a 1979 series 1 cnc and a big Enco lathe. I bet I spent fifty bucks just on band-aids from all the sharp edges and burrs on the Enco. I also spent probably fifty hours just on setup, adjustment and maintenance. In the end, it did do a lot of work for me, and had a lot of guts, but I never overcame vibration problems that left surface texture and increased finishing time. A guy down the street, on the other hand had a very old, very big Clausing (12x60 maybe?)that was a dream machine. I used to rent time on it when precision really mattered. I think he paid about $4000. $1200 more than my Enco, but it came with a closet full of tooling and no plastic drive gears. The BP, on the other hand was true blue. The electronics on it were ****. After two $400 repair visits I invested in an Ah-ha controller. That was very easy to install and get running. The machine itself,however, ran like new. Ways, VSD, spindle bearings, steppers, etc. I didn't even change the oil pump. I have certainly used old BPs that WERE worn out. You need to spend some time shopping, and be patient, informed, and a little lucky. In my experience, low end imports like Grizzly and Enco will require tons of service right from the start, and torture you for as long as you own them. Good used domestic gear, on the other hand, in non-industrial use, will easily outlive you! Enough said. Robobass Richard J Kinch wrote in message ... Bill Ross writes: Are old mills on the market for $2,500 likely to be worn out? Very likely at that price. My Bridgeport Series 1 price survey has been: $1500 for serviceable but with severe wear or broken head, $2500 for running but with moderate to severe wear, and $3500 and up for running with light to moderate wear. How much is it going to cost to get them into good running shape? I am now working myself on scraping a well-worn (e.g., middle of knee concave by 0.005", gibs shimmed with pieces of crate strapping metal!) Bridgeport. It has been quite educational and a project of making tools and gages in itself. Quite a few $100s in cash to buy books and tools, and quite a few hours making and improvising some of the tools. Getting this kind of rebuild done right is perhaps $3000 to hire out, and you probably have to ship the machine to get it in the hands of someone who does it. I figured out why some of these old machines have such pretty body-shop repaint jobs on them: the effort to do that is a small fraction of the effort to get the machine back to factory alignment. The most valuable lessons of all are that I am now become knowledgeable at evaluating all aspects of Bridgeport wear. There's no way you can work on repairing alignment without knowing everything there is to know about measuring it first. Sometimes you learn the hard way. I spent a week rough and finish scraping the knee ways, and then discovered my datum surface was off. I am also converting the ways to teflon bearings, which should make this machine last forever before realignment is needed again. |
New Chinese mill vs old high quality mill
On Sun, 4 Jul 2004 08:51:43 -0400, "Wayne" makowicki wrote:
The pricing on Bridgeport's vary greatly with location. I could find a VERY good Bridgeport for $3000 it might take a few but they are out there. I some locations that might not be possible. Hell yes. In California, you can get a nice one for $2500 WITH a DRO. Though again..the trend is slowly reversing as industry starts cranking up again after the recession. Ebay was the first hard evidence that the economy was finally turning as I watched the prices of DV-59s start to rise again. Hummm I wonder if I should write a paper titled "Manufacturing in America and the DV59 Index" G Gunner sitting inside for a few, and avoiding the 104 F temp @40% humidity...brack!!!!!!!!!!!!!!! That rifle hanging on the wall of the working-class flat or labourer's cottage is the symbol of democracy. It is our job to see that it stays there. - George Orwell |
New Chinese mill vs old high quality mill
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New Chinese mill vs old high quality mill
In article , Gunner says...
Ebay was the first hard evidence that the economy was finally turning as I watched the prices of DV-59s start to rise again. But probably most of those were being sold for omni-turn conversions, right? Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
New Chinese mill vs old high quality mill
robobass wrote: 3. Is there anyone who would actually prefer a new Enco to a used but sound BP? You have experiences from 1979, but here are some posts from 2003: http://www.google.com/groups?hl=en&l...nyroc.rr.co m http://www.google.com/groups?hl=en&l...g.googl e.com -- A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian. |
New Chinese mill vs old high quality mill
On 4 Jul 2004 15:17:37 -0700, jim rozen
wrote: In article , Gunner says... Ebay was the first hard evidence that the economy was finally turning as I watched the prices of DV-59s start to rise again. But probably most of those were being sold for omni-turn conversions, right? Jim Actually no, they are not. They are being put back into service in the many small (often minority owned) machine shops that are starting to spring up again. I suspect the time of cheap machines is about over for a while. Cheap great! machines that is. Btw..a Harding Chucker (HC), DSMA, and AHC are probably the best for putting Omniturns on. A very nice rigid retrofit capable of marvelous work. Gunner That rifle hanging on the wall of the working-class flat or labourer's cottage is the symbol of democracy. It is our job to see that it stays there. - George Orwell |
New Chinese mill vs old high quality mill
I hate to jump in on this because I have an apparent conflict of
interst. I currently have a Bridgeport mill on ebay. I traded it from a man who rents space in the same room I am in, in an old factory. It was his manual backup mill, he uses a Lagun CNC most of the time. He traded it to me for a mill with a 49" table. This one has a 36" table. Opening bid is set at $1,800. Because it ends early tomorrow, it will probably sell for the opening bid, if it sells at all (the holiday factor). It is a very nice machine and has hard chrome ways. There is nothing wrong with this mill, and it has a Servo powerfeed on it. I traded him a Chinese Bridgeport clone for it, so go figure that into the Chinese vs American iron argument. He's a professional machinist with 30 tears experience. I don't usually use this venue to mention product, but this is a good Bridgeport, right in the price range mentioned. A little shipping and you are at the $2,500 budget. Paul (papapault) |
New Chinese mill vs old high quality mill
Now I do think there is a difference in Taiwanese tools and tools made in
China. I am FAR from an expert but I have seen some real CRAP from the China makers, and very little good stuff. Just the other day I looked at a good size drill press with a MT3 spindle that had a lot more play than my 50 year old delta. Almost all of the stuff from China I see is of poor workmanship. Now look at a Takasawi engine lathe that is Taiwanese made, and its a work of art. My mill is Taiwanese and it is a very nice machine, its over 20 years old and has been used a good amount and it is still very tight. The man I bought it from had both the Millport and a Bridgeport and said he used the Millport more, its the mill he preferred to run. My father is a close friend of the seller and had said for years that he liked the Millport more. I now own the machine and am very happy with it. |
New Chinese mill vs old high quality mill
Wayne wrote: Now I do think there is a difference in Taiwanese tools and tools made in China. I am FAR from an expert but I have seen some real CRAP from the China makers, and very little good stuff. I agree, there are many nuances. The idea of "high tech" is really "new tech". The long established industries moved from England to the US for cheaper labor 200 years ago. Now industries that anyone can do move from the US to Japan, from Japan to Taiwan, and from Taiwan to China. Higher up the chain gets higher quality, but higher prices. 25 years ago, I would have said, buy Bridgeport, but keep an eye on Jet of Japan. Right now I think Taiwan made cast iron machinery through Enco is the best trade off between cost and quality for individual hobbyist. Sometime in the future, China made will become the best quality per cost deal. -- A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian. |
New Chinese mill vs old high quality mill
jim rozen writes:
Teflon? You maybe mean turcite, or rulon. Plain PTFE would be a poor choice for a way bearing surface IMO. "Turcite" (not turcite) is just a brand name. My understanding is that Turcite B is PTFE, and Turcite A or TA and TX or X are acetal-PTFE copolymer. If you have some other information, I'd like to hear it. |
New Chinese mill vs old high quality mill
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New Chinese mill vs old high quality mill
In article , Richard J Kinch
says... Plain PTFE would be a poor choice for a way bearing surface IMO. "Turcite" (not turcite) is just a brand name. My understanding is that Turcite B is PTFE, and Turcite A or TA and TX or X are acetal-PTFE copolymer. If you have some other information, I'd like to hear it. The only information I *do* know is that pure PTFE cold-flows - a lot. It would be a poor choice for way sliders. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
New Chinese mill vs old high quality mill
jim rozen writes:
Plain PTFE would be a poor choice for a way bearing surface IMO. "Turcite" (not turcite) is just a brand name. My understanding is that Turcite B is PTFE, and Turcite A or TA and TX or X are acetal-PTFE copolymer. If you have some other information, I'd like to hear it. The only information I *do* know is that pure PTFE cold-flows - a lot. It would be a poor choice for way sliders. Yes, we've all seen that, but: do you have actual experience with PTFE cold flowing in the low pressures of a machine way? I believe you are confusing a high-pressure cold-flowing property with conditions in a machine way. The references I can find (such as the _Merck Index_ entry for PTFE, and http://www.glenair.com/conduit/choose.pdf) state that PTFE cold flows under *high pressures*. An example would be highly compressed regions in gaskets. The pressures contemplated are 1000 psi or more. Cast iron machine ways are designed with a meximum of 100 or 150 psi. For example, a Bridgeport Series 1 saddle has about 27 sq in of bearing surface, and worst-case loads would therefore be well under 100 psi, at which level cold flow is a non-issue. The reason for this pressure limit (well below the strength of the bearing itself) is to maintain oil film lubrication. I plan to run tests to prove this by just putting test masses on top of test squares, and seeing what happens. I've already been testing the material from MSC (vs Turcite B which is hard to get and exorbitantly priced). For this I have been using cast iron angle plates, which I scrape to 0.0001" flatness, but so far I have just been proving the process of bonding with epoxy and getting a bearing-quality flatness on the PTFE surface. The manufacturer is cagey about just what Turcite B is, but it does exactly match plain ol' PTFE's peculiarities in the published mechanical properties. So my suspicion is that it is simply PTFE at a premium price. There are no other candidate substances possible to my knowledge. It isn't like there is some secret Coke formula involved. I also speculate that some case of what is called "cold flow" are merely ordinary plastic deformation. If you look at the low numbers of the mechanical properties for PTFE, and considering the uniquely vanishing coefficient of friction, then you can see how it would happen in many applications. But not in machine ways by my analysis. Another difference in machine ways is that the thin layer is bonded to the relatively unyielding metal way. This eliminates any stresses from forces accumulated across a long distance. |
New Chinese mill vs old high quality mill
Ned Simmons writes:
Both Turcite and Rulon are families of filled or reinforced PTFEs. I don't believe any of the flavors are straight Teflon. Both my mill and lathe have this stuff on the ways, though I don't know whether it's turcite or rulon or another brand. It's definitely not plain Teflon--it's much harder and more resistant to abrasion and gouging. There is a bit of confusion going on here. There is more than one material called "Turcite" (brand name). There are dozens of Rulon varieties, involving PTFE with more or less other things. Turcite A appears to be acetal-PTFE copolymer or blend (like Delrin AF brand), which sounds like what you are describing. Another (Turcite B) is what I suspect is PTFE alone, which is what the manufacturer suggests for machine ways (they also call it "Slydway"). I've never seen any credible evidence that these materials last longer than a properly maintained traditional way, but they do make a noticeably improvement in the "feel" of the machine by reducing stiction. Plenty of evidence in the mfr literature. Polymers have certain properties that improve life vs cast iron ways. Just lowering the coefficient of friction significantly has to improve wear dramatically. Since you have the metal underneath a thin layer of polymer, you get the best of both, strength and rigidity of metal with lubricity and wear of the polymer. But the blockbuster benefit is that the cast iron components of the bearing just doesn't wear at all, just the polymer layer, at least in our lifetimes. When the polymer layer wears out of alignment, it is replaceable in a relatively simple process. Compared to having to rescrape and realign metal, that is an *immense* economy. |
New Chinese mill vs old high quality mill
Richard J Kinch writes:
I've already been testing the material from MSC (vs Turcite B which is hard to get and exorbitantly priced). By the way, this is what I've been testing, MSC item 32017774: http://www.mscdirect.com/mscProductSearch.process?query=32017774 This 0.03125" thick and bonds with ordinary epoxy. At $27 for 2 sq ft you have plenty to do a Bridgeport saddle with several retries. |
New Chinese mill vs old high quality mill
In article , Richard J Kinch
says... Yes, we've all seen that, but: do you have actual experience with PTFE cold flowing in the low pressures of a machine way? No. I've attempted to use teflon for small bearings, with poor results. Another reason to stay away from pure teflon is, it is very tough to bond it using any regular adhesives. Probably most commercial engineering polymers will show mechanical properties somewhat similar to teflon, though not the friction co-efficients, obviously. My best guess would be to use teflon-loaded delrin available inexpensively from mcmcaster carr. It will exhibit pretty much the same slide characteristics as pure teflon, but will not cold flow. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
New Chinese mill vs old high quality mill
jim rozen writes:
Another reason to stay away from pure teflon is, it is very tough to bond it using any regular adhesives. You can't be referring to the MSC item I cited, which is treated on one face to be bondable with ordinary epoxy. My best guess would be to use teflon-loaded delrin available inexpensively from mcmcaster carr. It will exhibit pretty much the same slide characteristics as pure teflon, but will not cold flow. Delrin (trademark for acetal, capitals, likewise Teflon for PTFE) AF (presumably abbreviation for "anti-friction", namely acetal with PTFE component) does improve the structural properties, and comes close to pure PTFE for dynamic friction, but does not come close to pure PTFE for the static friction ("stiction"). Getting down around 0.04 static COF would seem to be a huge improvement for CNC movements like tangents of curves that have minimal motion in one axis vs another, where stiction causes staircasing. From what I read this is what many CNC machine ways use for just that purpose. |
New Chinese mill vs old high quality mill
jim rozen writes:
"Turcite" (not turcite) is just a brand name. My understanding is that Turcite B is PTFE, and Turcite A or TA and TX or X are acetal-PTFE copolymer. If you have some other information, I'd like to hear it. The only information I *do* know is that pure PTFE cold-flows - a lot. It would be a poor choice for way sliders. I just discovered this MSDS from the mfr which states the Turcite B is indeed just PTFE: http://www.mtsandtg.com/TurciteBSlydway.pdf |
New Chinese mill vs old high quality mill
Richard J Kinch wrote:
jim rozen writes: "Turcite" (not turcite) is just a brand name. My understanding is that Turcite B is PTFE, and Turcite A or TA and TX or X are acetal-PTFE copolymer. If you have some other information, I'd like to hear it. The only information I *do* know is that pure PTFE cold-flows - a lot. It would be a poor choice for way sliders. I just discovered this MSDS from the mfr which states the Turcite B is indeed just PTFE: http://www.mtsandtg.com/TurciteBSlydway.pdf I don't see it saying Turcite B is just PTFE. True, in section 2 it lists nothing besides PTFE (polytetrafluoroethylene) and Chromium III Compound (0.5% by wt.) as hazardous ingredients. But in section 8 it says "This compound contains Chromium III compounds [...] and 25% Cu metal". -jiw |
New Chinese mill vs old high quality mill
James Waldby writes:
I don't see it saying Turcite B is just PTFE. True, in section 2 it lists nothing besides PTFE (polytetrafluoroethylene) and Chromium III Compound (0.5% by wt.) as hazardous ingredients. But in section 8 it says "This compound contains Chromium III compounds [...] and 25% Cu metal". MSDSs are government (regulatory) documents and you have to be careful interpreting them for physical facts . There is just a tiny bit of the metallic portion (0.5% total stated on the first page). This I suspect is just the very thin coating on one face made by converting the pure PTFE to a thin bondable layer. This is what makes the product glueable with epoxy. Otherwise, nothing sticks to PTFE. It helps to have seen this stuff, snow white PTFE on one face, a muddy brown on the other (the uncolored MSC version). The "25% Cu" appears to be a misprint. It should have been enclosed in the parenthesis just preceding. That is, of the 0.5 percent chromium III compounds, 25 percent of the weight of those compounds consist of Cu. The point is, the bulk polymer is pure PTFE, not acetal, or something else. |
New Chinese mill vs old high quality mill
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New Chinese mill vs old high quality mill
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New Chinese mill vs old high quality mill
Ned Simmons writes:
No confusion, note that I referred to Turcite and Rulon as families of materials. Right, I was confusing another's comment citing "turcite" as if it were a single thing. You did say they were filled or reinforced PTFE. I found one reference today that identified one Rulon as ECTFE. See my earlier comment on the specific gravity of Turcite B. The higher density would be consistent with a metal filled PTFE. See my earlier reference to the MSDS, which doesn't list any metal content in any proportion that would increase density. But if you're right, then that would require about 10 to 15 percent metal by volume, depending on the metal. It seems you're misusing the term copolymer. No, I said "copolymer or blend" (too lazy to check which). You're correct, it is the latter. Rulon 142, which is claimed to be a direct replacement for Turcite B is definitely *not* just PTFE. So what is it, then? One thing that I worry about on my machines is the fact that once grit or a particle gets imbedded in the plastic it'll likely get dragged back and forth for a long time. They claim that is actually a benefit, that particles embed at or below the surface so as to encapsulate and not wear the opposing metal. And of course this is a problem with metal/metal bearings. There was a deep score in the Bridgeport knee way I'm rescraping, and I eventually discovered (only by the disassembly and scraping process) a single tiny grain of carbide or diamond had been embedded in the opposing surface. |
New Chinese mill vs old high quality mill
Ned Simmons writes:
See my earlier comment on the specific gravity of Turcite B. The higher density would be consistent with a metal filled PTFE. Say, have a look at: http://www.busakshamban.us/pdf/mds_t47.pdf Turcite T47 == Bronze-filled PTFE w/ sp gr 3.02 to 3.14. Lots more he http://www.busakshamban.us/ref_library_global.htm?print=1 Seems the trademark "Turcite" applies to anything, pure PTFE, UHMW-PE, bronze-filled, graphite-filled, carbon fiber, etc. |
New Chinese mill vs old high quality mill
In article , Ned Simmons
says... One thing that I worry about on my machines is the fact that once grit or a particle gets imbedded in the plastic it'll likely get dragged back and forth for a long time. My mill has bellows way covers so is pretty well protected, but the lathe has a dovetail bed with a nice wide flat surface to catch anything that falls on it. But isn't the ability of softer way sliders a plus? Then the abrasive particle will simply embed deeper as time goes on, whereas in cast iron/cast iron systems, it will embed in something *hard* and keep on wearing the bed ways? Has anyone created bed sliders out if, say, brass or bronze? If not, the reason probably is that they get charged as a lap does, and will wear the harder bed rapidly. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
New Chinese mill vs old high quality mill
In article ,
says... Ned Simmons writes: Rulon 142, which is claimed to be a direct replacement for Turcite B is definitely *not* just PTFE. So what is it, then? -Rulon 142 not an insulator http://www.rulon- meldin.com/Data/Element/Node/ProductLine/product_line_edit. asp?ele_ch_id=L0000000000000001708 -It's "TURQUOISE in color with a bronze tint." http://www.boedeker.com/rulon_p.htm -"Rulon ® is the Saint Gobain Performance Plastics tradename for a family of reinforced proprietary PTFE compounds." http://www.boedeker.com/rulon_p.htm -It's specific gravity is higher than any plastic I'm aware of. All admittedly circumstantial evidence, but I'd have to say it's most likely a metal filled PTFE. Taking into account the color and the Turcite B MSDS, probably a copper based filler. Ned Simmons |
New Chinese mill vs old high quality mill
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New Chinese mill vs old high quality mill
In article , Ned Simmons
says... That's not too unusual. One of the best references on the common engineering plastics I have is put out by Erta. They list properties of acetal, various nylons, PET, etc., but they're all called Erta(something). I could also *highly* recommend a book called "Engineering Polymer Sourcebook." By, umm... hmm. Forgot the author's name. If there is interest I will post it up in the morning, from work. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
New Chinese mill vs old high quality mill
jim rozen writes:
I could also *highly* recommend a book called "Engineering Polymer Sourcebook." Wasn't the abridged version in _The Graduate_? |
New Chinese mill vs old high quality mill
I'm loving those VFD's... Felt like Merlin himself when I hooked the latest one
up and it really produced 220 three phase from an 115 one phase household current outlet... Sure seems like magic. So much of single phase motors for me. |
New Chinese mill vs old high quality mill
In article , Richard J Kinch
says... jim rozen writes: I could also *highly* recommend a book called "Engineering Polymer Sourcebook." Wasn't the abridged version in _The Graduate_? :^) "Engineering Polymer Sourcebook" by Raymond B. Seymour, McGraw Hill, ISBN 0-07-056360-8. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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