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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Cheap Plastics Bender, and a bit of a ramble
I bought a toaster oven from Goodwill for $10 and removed all four 12
inch long Calrod heating elements. I say Calrod, which is a brand name, and mean the type of element in a metal tube with MgO insulation, not the wire coil in a quartz tube. They were wired 2/2 series/parallel in the toaster oven and each rate 575 watts. I chucked one in the lathe drill chuck and placed the wire end loosely in a tailstock drill chuck, then applied abrasive paper. I noticed the outermost ends could be sandpapered to a bare steel finish, while most of the length would not give up its grey oxide finish, most likely from use in the oven. I strapped one onto the inner surface of a bend I'd made before in 1/4 inch acrylic, connected it to a 300 watt lamp dimmer, ran the power up slowly until the dimmer made the noise characteristic of passing and clipping AC power, and ran the power all the way down, to find that at this setting, the element would not even boil water. I ran it up very slowly, and eventually got a pretty clean re-bend in the acrylic. A half-wave rectifier would have doubled the control range. Full power to one element would fry the cheap $5 dimmer. Four elements in series definitely would not. I'll clean the stuck plastic off the element with lathe sanding as before. Maybe I'll wrap it with Tefflon tape next time. There was only a little sticking. I have the $40 metal bending brake from Harbor Frieght and hope to integrate one element into the brake to heat plastics at or near the bend point so they can be accurately bent. I'll need a bend clamp or stop while the whole setup cools. I overloaded my bender and the steel pivot body cracked. Cheap Chinese **** and one year warranty expired. I'll have to duplicate the bending bar clamp holes and the mating threaded holes in the back half of the new bender. The pivot body, of course, was made of compressed Diet Tab bottle caps. I'm just reporting on some of the fun I've been having here at Replikon Research, working mostly on the MOEPED for my one-credit Seminar and Project at NVCC, PHY 298, and developing a fully expanded specification for a self-reproducing universal machine tool. And it is fun. A fully expanded universal machine tool could make it's own transparent plastic machine guards, could mill flutes in a drill, mill or reamer bit, grind or regrind bits, etc. There are lots of loose ends to finish off. Doug Goncz Replikon Research Seven Corners, VA 22044-0394 (Why not send me a QSL? That's a valid, complete postal address, at least the clerk said it is.) |
#2
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
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#3
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
On 2008-11-04, wrote:
[ ... ] I'll clean the stuck plastic off the element with lathe sanding as before. Maybe I'll wrap it with Tefflon tape next time. There was only a little sticking. I would not put Teflon on anything which could get as hot as those rods. Overheated Teflon produces a toxic gas -- phosgene, IIRC. If you *insist* on using Teflon there -- I would strongly suggest that you have very good ventilation -- pumping the air around the heating elements to the outside. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#4
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
On Nov 4, 4:21*am, wrote:
... I have the $40 metal bending brake from Harbor Frieght and hope to integrate one element into the brake to heat plastics at or near the bend point so they can be accurately bent. I'll need a bend clamp or stop while the whole setup cools. I overloaded my bender and the steel pivot body cracked. ... Doug Goncz Take a look at these; http://www.wttool.com/product-exec/p...ake_WT_Import_ Not wide, somewhat clumsy, but will bend heavy stock and custom male dies would be easy to make. This is my home-made sheet metal brake; http://picasaweb.google.com/KB1DAL/H...95632358276434 http://picasaweb.google.com/KB1DAL/H...33136395165634 http://picasaweb.google.com/KB1DAL/H...33137678036386 The frame is channel iron bolted to stubs welded to the hinges, so it can be assembled with a shorter frame to bend thicker stock. Jim Wilkins |
#5
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
On 5 Nov 2008 01:30:35 GMT in rec.crafts.metalworking, "DoN. Nichols"
wrote, On 2008-11-04, wrote: [ ... ] I'll clean the stuck plastic off the element with lathe sanding as before. Maybe I'll wrap it with Tefflon tape next time. There was only a little sticking. I would not put Teflon on anything which could get as hot as those rods. Overheated Teflon produces a toxic gas -- phosgene, IIRC. Can you get something better? I recall the name "Kapton" but I don't know what it means. |
#6
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
David Harmon wrote:
(...) Can you get something better? I recall the name "Kapton" but I don't know what it means. http://en.wikipedia.org/wiki/Kapton --Winston |
#7
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
On 2008-11-10, David Harmon wrote:
On 5 Nov 2008 01:30:35 GMT in rec.crafts.metalworking, "DoN. Nichols" wrote, On 2008-11-04, wrote: [ ... ] I'll clean the stuck plastic off the element with lathe sanding as before. Maybe I'll wrap it with Tefflon tape next time. There was only a little sticking. I would not put Teflon on anything which could get as hot as those rods. Overheated Teflon produces a toxic gas -- phosgene, IIRC. Can you get something better? What temperature are you working at? IIRC, you were working with heating elements from cook stoves, which certainly get hot enough to decompose Teflon. Look up where Teflon starts to decompose, and *avoid* that temperature. Or just figure out how to hold your breath for the duration of the operation. :-) What about a porcelain coating? What plastic are you bending, which could determine what is more likely to handle the temperatures. I recall the name "Kapton" but I don't know what it means. Well ... I *think* that it is the transparent orange plastic which is used an an electrical insulator while being a thermal conductor for mounting semiconductors to heat sinks. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#8
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
Hi!
I'm quitting tobacco on a taper method and am so distracted I can't mill straight slots in a 1x2 bit of poplar, so I figured I'd just ttalk about the latest design. Drawing out the agony helps make sure I give myself credit for every positive step, and that I'll never relapse; the experience is unforgettable. Two knurled 10-24x2 inch brass flat head machine screws press two 1x2x15 inch bars of wood together running in two clearance holes in the upper bar, and two through tapped holes in the lower bar. Sometimes I reinforce such tapped holes with CA glue and run a stud in and out until they pass class 2. Tapered sides make the knurled heads accessible. A groove holds a Calrod element on each mating face. Pressure takes the minor bends our of the rod elements. The side walls near the face are tapered 30 degrees to allow a 120 degree bend to 60 degrees included angle. A few coats of varnish over a computer printed card makes it a lasting asset. (Decoupage) Holes adjacent the Calrod ends accept the (bent) element wires, and from the far side, wood screws in tapered holes make contact with the wires and accept a ring terminals. A DPDP switch in a simple harness made from the toaster oven's power cord alternately applies choppped AC power from the dimmer to the elements in series, and measures their DC resistance in series with a meter. Ther resistance changes as the elements heat up. I hope to find a percent resistance (maybe 125%) at which the elements reliably heat acrylic from both sides for bending, without any bubbling or sticking. The ohmmeter serves as a thermal monitor, uncalibrated. I'm so disturbed by the slow decrease of tobacco use I spend my time wondering about things like "Am I breaking symmetry with this next operation? How should I label the parts? What operation will follow this one?" I'm just grinding through it. I make a LOT of mistakes right now. I can't see the finish from here; there's a good drawing in emachineshop.com format available. A sequence of operations is not available. That's what I am developing. That Kapton you all mentioned would ba great. Teflon tape might, not evaporate at these low working temperatures but it is risky. I flamed a bit of silver wire insulated with teflon deep in a vehichle chassis once and smelled the phosgene formed. Yikes! I do not want that here, so perhaps a wrapper fo Kapton would be appropriate, with the splines used for screen doors holding it in place. Off to read Wikipedia on Kapton. Thanks to Gerry, Jim, David, and Don! Doug On Nov 4, 4:21*am, wrote: I bought a toaster oven from Goodwill for $10 and removed all four 12 inch long Calrod heating elements. I say Calrod, which is a brand name, and mean the type of element in a metal tube with MgO insulation, not the wire coil in a quartz tube. They were wired 2/2 series/parallel in the toaster oven and each rate 575 watts. I chucked one in the lathe drill chuck and placed the wire end loosely in a tailstock drill chuck, then applied abrasive paper. I noticed the outermost ends could be sandpapered to a bare steel finish, while most of the length would not give up its grey oxide finish, most likely from use in the oven. I strapped one onto the inner surface of a bend I'd made before in 1/4 inch acrylic, connected it to a 300 watt lamp dimmer, ran the power up slowly until the dimmer made the noise characteristic of passing and clipping AC power, and ran the power all the way down, to find that at this setting, the element would not even boil water. I ran it up very slowly, and eventually got a pretty clean re-bend in the acrylic. A half-wave rectifier would have doubled the control range. Full power to one element would fry the cheap $5 dimmer. Four elements in series definitely would not. I'll clean the stuck plastic off the element with lathe sanding as before. Maybe I'll wrap it with Tefflon tape next time. There was only a little sticking. I have the $40 metal bending brake from Harbor Frieght and hope to integrate one element into the brake to heat plastics at or near the bend point so they can be accurately bent. I'll need a bend clamp or stop while the whole setup cools. I overloaded my bender and the steel pivot body cracked. Cheap Chinese **** and one year warranty expired. I'll have to duplicate the bending bar clamp holes and the mating threaded holes in the back half of the new bender. The pivot body, of course, was made of compressed Diet Tab bottle caps. I'm just reporting on some of the fun I've been having here at Replikon Research, working mostly on the MOEPED for my one-credit Seminar and Project at NVCC, PHY 298, and developing a fully expanded specification for a self-reproducing universal machine tool. And it is fun. A fully expanded universal machine tool could make it's own transparent plastic machine guards, could mill flutes in a drill, mill or reamer bit, grind or regrind bits, etc. There are lots of loose ends to finish off. Doug Goncz Replikon Research Seven Corners, VA 22044-0394 (Why not send me a QSL? That's a valid, complete postal address, at least the clerk said it is.) |
#9
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
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#10
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
Gerald Miller wrote:
On Wed, 12 Nov 2008 18:48:10 -0800 (PST), wrote: Hi! I'm quitting tobacco on a taper method and am so distracted I can't mill straight slots in a 1x2 bit of poplar, so I figured I'd just ttalk about the latest design. Drawing out the agony helps make sure I give myself credit for every positive step, and that I'll never relapse; the experience is unforgettable. Go on the patch, I did fifteen years ago and highly recommend it. Gerry :-)} London, Canada I just quit cold turkey - 1-1/2 years ago! Drawing out the agony (for 30 years) didn't help at all. -- Richard (remove the X to email) |
#11
Posted to rec.crafts.metalworking
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Cheap Plastics Bender, and a bit of a ramble
I had to make the bender arms of wood for insulation. I V-grooved them
to hold the elements. I ran each arm under the grooving bit once in each direction; the sides were centered, but there was always a pip in the middle. Rather than eliminate the pip, I set up my old FrankenMill, running the same bit backwards, to locate the holes for the clamp screws. It worked perfectly; with the clamp screws in place, you can look from one end through to the the other end of the element grooves and see they are centered. What fun that was! To make the clamp screw holes the same distance apart, I drilled three holes with a #29 bit and pineed one end together with a large pattern nail I had, then match-drilled the other end from the outside. I tapped one arm 10-24 witha pulley tap and drilled and reamed the other 3/16, leaving a running fit on the screws. I need to go to Home Depot to buy two small springs to separate the arms. I am to quit for 90 hours straight and I have an appiontment with counseling at the end of that 90 hours. The cravings should fade by then. It all starts at 9 PM, in just an hour. Doug |
#12
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Cheap Plastics Bender, and a bit of a ramble
I found a place to buy a sample of Kapton tape for $10 shipping. It'll
be here soon. A 1.5 inch roll would have been $35 plus shipping, and I don't intend to make more benders. I am still kind of interested in milling the element grooves round instead of V. That, and some high-temp epoxy, would take stress off the tape. We'll see how it shapes up. Doug |
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