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#21
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On Mon, 09 May 2005 23:40:59 -0700, in àõ Abrasha wrote:
You probably stopped using the lathe and mill, and your need to know disappeared. I use my lathe and mill almost daily. Didn't stop using them, though I need them much less often than you do. But I'm not currently in an environment where I'm teaching their use, nor do I often read about their use, so the precise vocabulary describing their use gets rusty. The actual skills and knowlege needed to use the tools are not nomenclature based, I think... Peter |
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#22
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Abrasha wrote in
news Peter W.. Rowe, wrote: On Sun, 08 May 2005 17:37:37 -0700, in ¸õ Abrasha wrote: The motor that typically cames with the Taig does not have enough power to cut a 2 mm deep groove in a 15 mm diameter silver rod. The cutting force would stop the spindle dead in it's track, or the rubber band (the drive belt that comes with the Taig is no more than a big rubber band) would just slip. Abrasha http://www.abrasha.com Is that really an issue that would stop this? I don't have a Taig, but my sherline mill can't be that different, A Taig LATHE and a Sherline MILL are two very different tools! And no, you cannot cut a helical groove on your Sherline mill, unless you have one with an indexing head (dividing head), which is coupled to the automatic power feed of the table. This is only possible on the Sherline, if it is equipped with stepper motors. Which means a CNC interface. And even if you have all of this, how are you going to hold the 15 mm silver rod. You have to have an indexing head on one end and a tail stock on the other end. Given that the table of the Sherline mill in only 13" long, that won't leave you much length and room to maneuver for the rod. nor is my little old unimat lathe. Your little old unimat lathe is good only for the most basic of tasks. It not useful for the task that the original poster asked about. Cutting a helix on a 10-15 mm diameter silver rod. BTW, I realize that he posted asking how to cut a spiral. I assume that he wants to do this on a cylindrical surface and not a tapered surface. I quote the following from "Audels Machinists and Tool makers Handy Book, New York 1941" "The enlightened machinist will not erroneously use the word spiral or helix as is almost universally done even by some writers. To correct such error is almost hopeless and perhaps nothing can be done about it. However: By definition a helix is a curve generated by a point which both rotates and advances axially on a cylindrical surface. For instance the lead screw thread on a lathe is a helix. By definition a spiral is a curve generated by a point having three motions: 1, rotation about an axis; 2, increasing its distance from the axis, and 3, advancing parallel to the axis. When a cylindrical piece of work is placed between centers and rotated by the index head as the table advances, the cutter will mill a helical groove. When a tapered piece of work is placed between centers and tilted so that the top element is horizontal and then rotated by the dividing head as the table advances, the cutter will mill a spiral groove." neither can do deep cuts in a single rapid pass, but with a slow feed rate, When you are cutting a helix, the feed rate is determined by the pitch of the spiral. You cannot just set your feed rate "slow". Besides, both the Taig and the Sherline do not have lead screws, so what feed rate are you talking about? Unless you have a lead screw and change gears, you cannot set a feed rate. Your feedrate in only manual on both machines. Not very useful when you are cutting a helix in any set up. and perhaps several passes as successivly increased depth, it should be possible. I've cut things in silver deeper and wider than that on the sherline, doing it that way. The low power machines, which also suffer from less rigidity in the machine, simply mean you need to have a lot of patience, doing the cuts slowly with multiple light cuts. At least, that was my experience. Yes, it's slow enough to be quite annoying to anyone who's used full sized machinery, but it can be done, nevertheless. I had one poject involving turning on the Unimat, with a bracelet shape starting around 3 inches in diameter in platinum. That was a bitch to cut too, and to keep the lathe from stalling took a tool bit with very little radius at it's point (to make the cut dig into less metal at a time), and very small amounts on each pass. But it eventually worked. I'd guess the big problems would be simply generating the spiral desired without going over budget on the machine, as well as the difficulties involved in cutting silver. Back in graduate school, I cut pretty much this type of spiral in a slightly larger brass rod without trouble. 1: You didn't cut a spiral, but a helix. 2: You cut a certain very special kind of helix, i.e. a screw thread, which is not what the poster is after I think. Screw threads are cut on lathes equipped with leadscrews. Helices are cut on milling machines, in a manner I have now described in several posts. I repeat. To cut a helix, you need: 1 A milling machine, 2 A universal dividing head (indexing head) 3 The ability to couple the dividing head to the automatic table feed, so that the work rotates as the table advances. To cut a spiral you need: Everything above, plus 4 A tilting table so you can create a horizontal cutting surface. But it was a full size rockwell tool room lathe doing it. It was quite capable of that sort of thread, Threads and spirals are two very different things. Abrasha http://www.abrasha.com A Four axis cnc machine with steppers, an air spindel that runs up to 50K and the fourth axis is full indexed to the other three is available in the $2000 range from www.maxnc.com. A closed loop machine similar to the above with servos instead of steppers is available for about another $1000. http://www.maxnc.com/page12.html -- James C. Woodard "Too many laws make scofflaws of all" http://home.comcast.net/~gwyddon/ |
#23
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"Andrew Werby" wrote in
: "Abrasha" wrote in message ... Andrew Werby wrote: "norwick" wrote in message ... I need to cut a spiral onto a silver rod. The sides of the cut can be at 90 degrees/and/or inclined. I envisage this to be done by a lathe (milling machine?). Diameter of rod could be 10-15mm, spacing between edge of the next groove ca 3mm, groove width & depth ca 2mm (ideally there should be some scope for visual considerations). Non electric system would be acceptable (or very slow speed lathe), machine size should not be more than 1m, weight under 50kg. Cost should not be more than $1000-1500, but this assumes that it can be used for other applications, eg cutting tool steel etc. [You could do this on a miniature CNC milling machine (like the Taig mills I sell) equipped with a rotary table, chuck, and tailstock. You'd need to program the toolpath to advance the tool along the X (long) axis while rotating the A axis (the rotary table) so that the grooves were properly spaced. A ball-end tool would give you a round-bottomed groove; a regular endmill would give a flat-bottomed groove. The weight and size of this machine would be about what you're asking for above, but the price would be higher - about $3k, with the accessories you'd need. These machines can be used for many other things, but for best results with tool steel anneal it first, and use carbide cutters.] The motor that typically cames with the Taig does not have enough power to cut a 2 mm deep groove in a 15 mm diameter silver rod. The cutting force would stop the spindle dead in it's track, or the rubber band (the drive belt that comes with the Taig is no more than a big rubber band) would just slip. Abrasha http://www.abrasha.com [Want to bet? Taig recently started providing a bigger motor with their mills than previously. The 1/4 hp Franklin motor now standard would have no problem cutting a 2mm groove in a piece of silver - or a piece of steel, for that matter, in one pass, if one went at an appropriate speed using a 2mm 2-flute cutter. It could also make multiple faster cuts at shallower depths. The Gates drive belt, while it may superficially resemble a "big rubber band" is actually quite resistant to slipping, when tensioned correctly. The pulley settings can be changed to provide more torque, or more speed, as needed. Have you ever actually used one of these mills?] Andrew Werby www.computersculpture.com Does Taig also now offer 4th axis capability? -- Saint Séimí mac Liam Carriagemaker to the court of Queen Maeve Prophet of The Great Tagger Canonized December '99 |
#24
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"Abrasha" wrote in message ... Andrew Werby wrote: [Want to bet?] No. However your reply seems to indicate your need to be right by trying to bluff me into a bet. [Bluff you? I was just correcting your misperceptions, and providing a little new information you may not be aware of. But I wondered if you'd be willing to put a little money where your mouth was - guess not...] So I challenge you to produce the helix, the original poster asked about, on your mighty Taig mill. I say, it can't be done. Go ahead, prove me wrong. You've got the Taig. If you succeed, (which I know you won't), you have a strong selling point. If I am not mistaken, you are after all trying to sell these things, which seems to make you a bit biased. I find that rather amusing. [Yes, I sell these things, which is one reason I don't like seeing them unfairly disparaged. I imagine you're "biased" about the things you sell, but I'm not churlish enough to assume you'd lie about them. I don't claim the Taigs are the best mills in the world, but they're quite capable within their limitations.] Don't get me wrong. The Taig is a very valid and verstile tool and a useful one at that. [Thanks for that...] And it cannot do what the original poster asked. You can try to bluff me all you want, it can't be done. You can't do it. [Unfortunately, I don't have a silver rod 10-15mm in diameter - care to provide one? Or would brass be okay?] Taig recently started providing a bigger motor with their mills than previously. The 1/4 hp Franklin motor now standard would have no problem cutting a 2mm groove in a piece of silver - or a piece of steel, for that matter, in one pass, if one went at an appropriate speed using a 2mm 2-flute cutter. We weren't talking about a groove. We were talking about a helix! That's what the original poster wanted. Something very different. [He was talking about a helical groove: " I need to cut a spiral onto a silver rod. The sides of the cut can be at 90 degrees/and/or inclined. I envisage this to be done by a lathe (milling machine?). Diameter of rod could be 10-15mm, spacing between edge of the next groove ca 3mm, groove width & depth ca 2mm" I understand this as a cut wrapped around the long axis of the rod, somewhat like an elongated Whitworth thread. Did you envision something else?] However, you claim that the Taig, does a 2 mm depth of cut cut in steel, on a 15 mm diameter (original poster's measurement) in one pass? Prove it! [How - are you going to come over and watch? Or would pictures be sufficient?] SNIP Have you ever actually used one of these mills?] No, I have no need to. I have a real mill, with a 3/4 HP, 3 phase motor. Actually, it is a rather wimpy mill as far as true power is concerned. I'm ready for something more powerful, like a Bridgeport. [I've got a Bridgeport. There are some things it is best for, and some that are better done on the Taig.] But a Taig, gimme a break, why would I ever want to use one of those when I have a Clausing 8520? [Is it retrofitted for CNC? Do you have a rotary table for it? If not, it wouldn't do the job we're talking about here, while the Taig will.] Now go and make that helix, you claim you can make on it. I say, you can't do it! Abrasha http://www.abrasha.com [If you're wrong, will you at least eat your yarmulke?] Andrew Werby www.computersculpture.com |
#25
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Andrew Werby wrote:
[Unfortunately, I don't have a silver rod 10-15mm in diameter - care to provide one? Or would brass be okay?] No brass is not OK. It has a much higher sfm than silver. You said the Taig could do it in steel. Well, do it in steel then. However, you claim that the Taig, does a 2 mm depth of cut cut in steel, on a 15 mm diameter (original poster's measurement) in one pass? Prove it! [How - are you going to come over and watch? Or would pictures be sufficient?] Pictures would be sufficient. I trust you. Include setup, process as well as finished work pictures. You could post them on your site. [Is it retrofitted for CNC? Do you have a rotary table for it? If not, it wouldn't do the job we're talking about here, while the Taig will.] I never claimed that my mill will do the job. [If you're wrong, will you at least eat your yarmulke?] No. Abrasha http://www.abrasha.com |
#26
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Andrew Werby wrote:
[If you're wrong, will you at least eat your yarmulke?] Be careful with remarks like that! Abrasha http://www.abrasha.com |
#27
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""Séimí mac Liam"" wrote: Does Taig also now offer 4th axis capability? -- Saint Séimí mac Liam Carriagemaker to the court of Queen Maeve Prophet of The Great Tagger Canonized December '99 [They've had it for quite a while. The rotary table is actually made by Sherline; Taig adds their own base and stepper. The standard Taig control is now wired to run the 4th axis; they used to require a return trip to the factory to activate it, but now that's not necessary.] Andrew Werby www.computersculpture.com |
#28
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"Abrasha" wrote in message ... Andrew Werby wrote: [Unfortunately, I don't have a silver rod 10-15mm in diameter - care to provide one? Or would brass be okay?] No brass is not OK. It has a much higher sfm than silver. You said the Taig could do it in steel. Well, do it in steel then. [While I'm not going to invest the time and effort to do the spiral cut (although I would if you cared to back your bluster with your bucks) I did an experiment yesterday; cutting a slot across a piece of mild steel 3/4" wide. I set up a 3/32" 2-flute carbide cutter (a little bigger than 2mm diameter) and set the depth of cut to .08" (a little deeper than 2mm). The spindle was set to the second-highest speed (about 8000 RPM). The feedrate was .5 ipm. The Taig mill, with its stock spindle motor, had no problem at all cutting that slot. The motor didn't slow down. The belt didn't slip. I think this proves my point. It's not generally considered good practice to cut slots this deep in one go; the usual recommendation is to choose a depth no greater than half the cutter diameter. This is not because the machine can't do it, but because it's likely to break the cutter. That's why I went with a conservative feedrate. ] However, you claim that the Taig, does a 2 mm depth of cut cut in steel, on a 15 mm diameter (original poster's measurement) in one pass? Prove it! [How - are you going to come over and watch? Or would pictures be sufficient?] Pictures would be sufficient. I trust you. Include setup, process as well as finished work pictures. You could post them on your site. [If you trust me, take my word (above) for it, and apologize for disparaging these fine tools in the absence of any actual experience with them. If you don't trust me, even if I went through all the procedures you suggest, you'd probably say I faked the pictures and lied about the rest.] [Is it retrofitted for CNC? Do you have a rotary table for it? If not, it wouldn't do the job we're talking about here, while the Taig will.] I never claimed that my mill will do the job. [Then we've answered your question: "But a Taig, gimme a break, why would I ever want to use one of those when I have a Clausing 8520?" The Taig will do this sort of job; the Clausing won't. Sheer horsepower is only part of the equation when considering a mill's cutting function. Spindle speed is also an important factor. When using small endmills like this, one has to remove a certain amount of material with each flute, as it goes by - this is called "chipload". If your spindle turns slowly, like on your Clausing (or my Bridgeport) you can't remove enough material fast enough to sustain a reasonable feedrate, no matter how much torque your motor has. If you try to go faster than the rate at which the material is being removed, the tool will break. On the other hand, if you want to use a large tool, say 1/2" diameter, then you can spin much slower, since each flute takes a bigger bite of material, but requires more force to do so. In this situation, where you want to remove a lot of material in a hurry, the larger mill with the slower but more powerful motor would be a better choice.] [If you're wrong, will you at least eat your yarmulke?] No. Abrasha http://www.abrasha.com [Well, you won't bet, you won't eat your hat, will you at least admit you were wrong?] Andrew Werby www.computersculpture.com |
#29
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"Andrew Werby" wrote in
news ""Séimí mac Liam"" wrote: Does Taig also now offer 4th axis capability? -- Saint Séimí mac Liam Carriagemaker to the court of Queen Maeve Prophet of The Great Tagger Canonized December '99 [They've had it for quite a while. The rotary table is actually made by Sherline; Taig adds their own base and stepper. The standard Taig control is now wired to run the 4th axis; they used to require a return trip to the factory to activate it, but now that's not necessary.] Andrew Werby www.computersculpture.com Didn't find it on their web site today. -- Saint Séimí mac Liam Carriagemaker to the court of Queen Maeve Prophet of The Great Tagger Canonized December '99 |
#30
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thanks guys, you have been a great help!
Ben, I am trying to find a copy of the Amateurs Lathe to learn some more... Peter suggested how it is possible - while Abrasha convinced me how it isn't. - Thanks Andrew, it was a brave deed to take on the challenge - pity that I just can't justify $3k for a Taig mill (at the moment). Carl West's Firefox hint is intriguing ! I am all for low tech solutions, if there is one. I kept on pondering how to rig up a system where the revs are low enough to prevent silver tearing... I don't mind shaving little bits off at a time to get the required depth. But if there is a machine for it - why try inventing one? To save money? The helix/spiral doesn't have to be absolutely precise in dept/width - but visually it must be accurate, i.e. lines equidistance from each other. Unfortunately the task must be repeatable, and cannot be constructed (soldered). Sherline UK have now responded to the same enquiry: To meet your budget the only system I can offer you is a lathe with a screw cutting attachment, cost UKpounds770.00. This would entail setting the screw cutting attachment on its most coarse pitch ( 5 TPI approx 5mm pitch) which would achieve your spiral. As the screw cutting operation is fully manual this system of generating the spiral would be very slow but on the other hand very safe. To generate the spiral on a mill would entail a very expensive system costing UKpounds 2,500.00. The only way of achieving this on a Sherline mill is to convert it to CNC and add a CNC rotary table supported on a vertical plate. This is a far more accurate, quicker and versatile system to produce spirals with very few limitations. For those interested (re previous comments): http://mathworld.wolfram.com/search/index.cgi?q=spiral http://mathworld.wolfram.com/search/...helix&start=10 http://onlinedictionary.datasegment.com/word/helix http://onlinedictionary.datasegment.com/word/spiral So this is it, folks! Thanks again, I'm am only a step away from my spiral/helix! Hopefully! norwick |
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