entropy
having dreams about rocks
Member since June 2020
Posts: 71
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Post by entropy on Jul 4, 2020 17:01:37 GMT -5
Stop by Home Goods (a discount department store) and look at the plethora of teflon coated frying pans and cook plates. most are less than $10. Sure looks like perfect candidates as high heat transfer/non-stick heat sinks. Most are thick machinable aluminum with the tough teflon coating. I had great success using a teflon frying pan on the electric stove. I found if I put the pan on the burner and the pipe on the pan and then turned it to high(burner cherry red). As soon as it turned cherry red I would crank the heat down till the burner was not cherry red and let them sit for 5 to 10 minutes to soak heat I got the best repeatability in welds. Or put the burner on low and set the pipes on the pan and let them soak for 15 minutes. Then crank heat up till they were soft. If they stick to the teflon pan or leave plastic on the pan you were too hot. A shiny smooth surface was the sweet spot. I'll have to swing by Walmart and see what they've got. This is actually a really good idea (machining my plates from pre-coated aluminum). Per the HDPE welding instructions, the melt-bead should be 3/16" thick upon removal from the heat-source. Thus the raised-face section of the hot-plate must be at least 3/16", plus some clearance. Honestly I was shooting for 1/2" raised-face, but that requires a pretty thick hotplate/pan as starting material. I think the minimum raised-face would need to be 1/4" (providing some clearance between the non-heated sections of the endcaps) - with at least 1/8" aluminum remaining throughout - for burner engagement/heat-transfer. This means a 3/8" thick hotplate/pan. Who knows - I might get lucky and find one. . . . Also - it's interesting that you've had better luck preheating the plastic prior to increasing heat for the melt. This makes sense to me - considering it should increase the working time for making the joint. It's strange that not one pipe weld procedure has a preheat (they go straight to the 400 - 450 degree F mirror). Perhaps it's because a preheat adds significant complexity to field-welding.
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entropy
having dreams about rocks
Member since June 2020
Posts: 71
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Post by entropy on Jul 4, 2020 17:23:07 GMT -5
I just had 1.5" DOM tubing pop into my head to use as shafts. I build suspension and roll cages out of it, it's some pretty tough stuff and can be had in any OD and wall thickness you want, pretty much. Pillow block bearings are readily available to fit... I did a quick search for yield specs but didn't spend a lot of time and didn't find what I was looking for. DOM tubing is an excellent choice - for connecting pillow-block bearings directly to the rollers (without machining & welding on a spindle). The thing to remember though - for really long runs (think 10 to 15 foot long roller bars, with bearing supports at-ends only). The pipe/tube OD needs to be pretty big to prevent bending while supporting that long of run. I could see using 4" pipe for 20' long tumbler bars. Large bore pillow block bearings are not cheap, but more importantly, they are load-rated for WAY more than the load they'd be seeing (dozens of tons of loading, in lieu of a few thousand pounds - which is all that's needed). Taking this into consideration, it really would be worth the time & effort to make a spindle (or have a spindle made) so that a larger diameter pipe/tube can be supported on-ends with smaller pillow block bearings. With this approach, whether or not to use tube or pipe is purely a factor of cost & availability. It has been my experience that pipe is more common, and overall less expensive than tubing. That's not to say if some vendor out there is sitting on a surplus of tube he's willing to sell cheap. . . . .. . ? If one is building a smaller tumbler - say 4 foot long bars, it might be worth sticking with 1.5" tubing with 1.5" pillow block bearings. There's still a pretty good finished-bore pully and/or chain-sprocket selection out there (off-the-shelf) with 1.5" bores. The keyway would be the most problematic design feature. There are creative ways around having to machine a keyway.
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entropy
having dreams about rocks
Member since June 2020
Posts: 71
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Post by entropy on Jul 4, 2020 17:37:23 GMT -5
Please note, there is no perfect formula for tumbling. Everyone needs to learn their tumbler, the mix of the rocks being tumbled, the length of time, the grit size, etc, etc. I am repeating myself from a week ago, I bet there are 20 to 30 or more different processes used by folks out here and all of them can produce well polished rocks. It's almost a tumble by experience. Even I do not have one process I follow and will vary it for numerous reasons, sometimes just because I want to know how something will work or not work. Seeking counsel from the more experienced can eliminate years from the learning process, and also prevent very costly mistakes. Example: making a 30" diameter steel tumbler, and attempting to polish large rocks . . .
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EricD
Cave Dweller
High in the Mountains
Member since November 2019
Posts: 1,142
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Post by EricD on Jul 4, 2020 18:24:23 GMT -5
I just had 1.5" DOM tubing pop into my head to use as shafts. I build suspension and roll cages out of it, it's some pretty tough stuff and can be had in any OD and wall thickness you want, pretty much. Pillow block bearings are readily available to fit... I did a quick search for yield specs but didn't spend a lot of time and didn't find what I was looking for. DOM tubing is an excellent choice - for connecting pillow-block bearings directly to the rollers (without machining & welding on a spindle). The thing to remember though - for really long runs (think 10 to 15 foot long roller bars, with bearing supports at-ends only). The pipe/tube OD needs to be pretty big to prevent bending while supporting that long of run. I could see using 4" pipe for 20' long tumbler bars. Large bore pillow block bearings are not cheap, but more importantly, they are load-rated for WAY more than the load they'd be seeing (dozens of tons of loading, in lieu of a few thousand pounds - which is all that's needed). Taking this into consideration, it really would be worth the time & effort to make a spindle (or have a spindle made) so that a larger diameter pipe/tube can be supported on-ends with smaller pillow block bearings. With this approach, whether or not to use tube or pipe is purely a factor of cost & availability. It has been my experience that pipe is more common, and overall less expensive than tubing. That's not to say if some vendor out there is sitting on a surplus of tube he's willing to sell cheap. . . . .. . ? If one is building a smaller tumbler - say 4 foot long bars, it might be worth sticking with 1.5" tubing with 1.5" pillow block bearings. There's still a pretty good finished-bore pully and/or chain-sprocket selection out there (off-the-shelf) with 1.5" bores. The keyway would be the most problematic design feature. There are creative ways around having to machine a keyway. Good points you make there. I agree that with the lengths you are talking about, making the shafts out of large diameter pipe and machining spindles out of round stock would be the way to go
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jamesp
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Member since October 2012
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Post by jamesp on Jul 5, 2020 5:02:32 GMT -5
My little 15 pound tumbler turns at 21 rpm. Non-adjustable. I ran it for a week (stage one), and after that week 100% of the grit was gone (the water looked like mud). This makes me wonder how much time I was wasting - tumbling rocks with no grit in the mix. Perhaps I should've opened it up after day 3, and added more grit? Probably so. The key to efficient step 1 grind: abrasive size-slurry quality-cohesive forces-rock size-conductivity-suspension(tumbling speed not mentioned) Step 1 only, the longest, most tedious step in tumbling(the finishing steps are short term): By dumping the contents of the tumbler into a tub and continually washing and draining off the top until the muddy water is gone an accurate assessment of the condition of the abrasives can be made. Most quartz at 2.7 and silicon carbide at 3.5+ density will quickly fall to the bottom of the pan for observation. Do this at 1-2-3-4-5 days to find the life of your SiC for your given tumbler system's signature. If rolling 1 inch rocks the abrasive will break down very slow. If running 2 inch rocks expect exponential increase in abrasive breakdown. If running a 2 pound rock with a bunch of 1 inch rocks expect extreme rates of breakdown.(breakdown = rock wear in most cases, not all). Chances are if you have a water slurry the rocks are just cracking the SiC and not wearing SiC thru a rubbing action. Another similar test that reveals the performance of your slurry is to pour the slurry immediately from the rotating barrel into a say tall 5 gallon bucket(think separator) thru say a 1/4" screen to keep the rocks out. Pour quickly, terminate pour quickly. Again wash the slurry with clean water and drain the water off the top until you have separated the the abrasives that were in suspension to the bottom of the bucket. This test is best done say 20 minutes after adding fresh SiC 3/8"-10-30-46-60 or what ever you are tumbling with to find out if your slurry is carrying a high percent of the large particles in suspension. Suspended large particles of SiC rules wear rates on both tumbler barrel and rocks. Sticky slurry will greatly increase grinding forces yet increase load on motor due to increased grinding forces and associated friction. Conductivity and cohesive forces play a big role in making a slurry 'sticky'. Colloidal slurries are made of tiny flat plates(felspar crystalline plates)offering best suspension performance due to flat shapes). Colloidal slurries are also sticky because of the flat plate construction within. Fresh colloidal slurry out performs used colloidal slurry due to flat particle break down from use. These are my findings relative to abrasive life and slurries less the effect of barrel size and barrel speed.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Jul 5, 2020 5:26:23 GMT -5
jamesp, Do you ever try and recover/reuse grit during cleanouts? Example - assume I'm running SIC-30 (with Bentonite) turning 8" DR-11 barrels 85% full at 55-ish rpm - for three days. Is it worth trying to salvage any of the remaining grit after 3 days? I'm assuming the gold-panning technique would work - aka washing away the clay, and recovering any loose grit for reuse. This seems cumbersome. Grit seems cheap (relatively - if purchased in bulk). Is it worth the effort to reuse grit? Exactly. The gold miner's pan trick. Not after I know my tumbler's abrasive life. With a good slurry/suspension the condition of the particle size can be detected by simply rubbing the slurry between forefinger and thumb. No need to do the more telling separation wash(gold miner's pan trick) down test. Experience will guide. I have had SiC 30 last only 12 hours when tumbling a 2 pound rock with 1 inch rocks at 60rpm/6 inch barrel using colloidal clay slurry. You are asking the best questions and figuring the best analysis methods IMO. Ever. Well done entropy. The absolute best wear rates were done using a 2 pound rock, 1 inch rocks for media, 60 rpm, 6 inch barrel filled 80%, clay colloidal slurry and fused SiC 50 grinding wheels broken to +/- 1 inch chunks. I found about 200 pounds of 6" x 1 1/4" SiC grinding wheel remnants in an industrial junkyard. The owner sold the lot to me for $50. Someone should learn to fuse SiC 10-20-30-46 into 1 inch tumbling 'pellets'. Hell on barrel but hell on rocks too. www.flickr.com/photos/67205364@N06/sets/72157649671884531
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Jul 5, 2020 5:44:51 GMT -5
I just had 1.5" DOM tubing pop into my head to use as shafts. I build suspension and roll cages out of it, it's some pretty tough stuff and can be had in any OD and wall thickness you want, pretty much. Pillow block bearings are readily available to fit... I did a quick search for yield specs but didn't spend a lot of time and didn't find what I was looking for. DOM tubing is an excellent choice - for connecting pillow-block bearings directly to the rollers (without machining & welding on a spindle). The thing to remember though - for really long runs (think 10 to 15 foot long roller bars, with bearing supports at-ends only). The pipe/tube OD needs to be pretty big to prevent bending while supporting that long of run. I could see using 4" pipe for 20' long tumbler bars. Large bore pillow block bearings are not cheap, but more importantly, they are load-rated for WAY more than the load they'd be seeing (dozens of tons of loading, in lieu of a few thousand pounds - which is all that's needed). Taking this into consideration, it really would be worth the time & effort to make a spindle (or have a spindle made) so that a larger diameter pipe/tube can be supported on-ends with smaller pillow block bearings. With this approach, whether or not to use tube or pipe is purely a factor of cost & availability. It has been my experience that pipe is more common, and overall less expensive than tubing. That's not to say if some vendor out there is sitting on a surplus of tube he's willing to sell cheap. . . . .. . ? If one is building a smaller tumbler - say 4 foot long bars, it might be worth sticking with 1.5" tubing with 1.5" pillow block bearings. There's still a pretty good finished-bore pully and/or chain-sprocket selection out there (off-the-shelf) with 1.5" bores. The keyway would be the most problematic design feature. There are creative ways around having to machine a keyway. Tubing w/solid welded shaft ends makes great sense. The local industrial junkyard had about 50-10' x 1.5" solid sticks of cold rolled rod for 30 cents/pound. I bought only 4 sticks. Used two rods cut in half to make my 4 shaft/2 speed tumbler. Could have easily spanned 8-9 feet with only outboard bearings.(don't do center bearings on a tumbler shaft) 1.5" pillar blocks w/eccentric locking collars were purchased from Surplus Center in Nebraska. Would have bought the whole lot of rod if going into a contract tumbling business. Tumbler very heavy lol. Welded to the top of a salvage heavy duty 30"x 48" welded factory roll around cart. Perfect size for 5' shafts. Easy build. 18 inch pulley for reduction, also from Surplus Center, it was fitted with a taper-loc. Taper-loc perfect for rusty enviro. Finishing tumbler, slower rotation. rarely used, because I use a vibe for finish. small batch tumbler. Energy efficient 1/8 or 1/12 hp air over motor sips electricity
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Jul 5, 2020 6:03:02 GMT -5
Left barrel at 74 rpm if memory serves. Slurry too thin so the damaging rattling sound. Not to mention 2 pound rock within.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Jul 6, 2020 6:31:45 GMT -5
Anxious to see the ultimate 8" SDR 11 HDPE barrels. Waiting patiently...
I have a simple idea on how to heat the perimeter of the end plate to the pipe for a butt weld. Heating the end of the pipe is as simple as setting the pipe section on edge in a teflon coated frying pan on an adjustable temp hot plate/oven top. Gravity in your favor. Heating the outside face of the plate for a butt weld is a bit more tricky.
I say take another teflon coated frying and and using that lathe cut a ring the size of the end of the pipe and bolt/screw it to the center of another frying pan. Then align the flat plate of HDPE on this ring and cook her to weld temp. Those pans are often thick and have excellent conductive heat transfer properties. And most of those aluminum frying pans are made by machining anyway.
Then butt weld the small pipe to the face of the other plate using a smaller ring screwed to yet another frying pan. Cut hole in other plate the size of the I.D. of the small pipe.
6 inch Fernco rubber caps sure work better than 4 inch rubber caps for several reasons. I would use/obtain 6" HDPE pipe cut 3" long for the reduction. I could not find a combo SDR 6" pipe that would press fit into SDR 8" pipe.
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entropy
having dreams about rocks
Member since June 2020
Posts: 71
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Post by entropy on Jul 6, 2020 13:05:09 GMT -5
jamesp Interesting - what are the several reasons you'd go with 6" pipe for hand-holes, in lieu of 4"pipe? I'm thinking (and just speculating here) that you can fill, empty, clean, and generally access the inside of the barrel easier - with a larger hole. Is it that simple? Is there anything special about the rubber cap itself - that is more desirable in 6" in lieu of 4"? Aluminum conducts heat 3 times faster than Steel. And Steel conducts heat 3 times faster than Stainless Steel (which means Aluminum conducts heat about 6 times faster than Stainless Steel - a useful rule-of-thumb). The only reason I'm hesitant to machine a ring of pre-Teflon-coated Aluminum, and connect it to another block of metal (steel or aluminum) is because it will be difficult to thermally join the metals together. Because aluminum transfers heat so quickly, the aluminum ring will become cold when the HDPE touches it - unless there's a steady-flow of heat entering the ring from the underside. Even the smallest air gap between the ring and the plate will introduce heat-transfer problems (cold spots on the ring). I was looking at thermal grease (the type used for solving this same exact problem for connecting Aluminum heat-sinks to electronic chips) and the grease tops-out just under 400 degrees F max operating temperature. I cannot weld the ring to a plate of aluminum, because the weld-heat will damage the Teflon coating. Ideally I need to find a piece of pre-Teflon-coated Aluminum that's thick enough for me to machine a raised-face hot-plate out of - without having to join it to another piece of metal (prior to placing it on the burner).
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EricD
Cave Dweller
High in the Mountains
Member since November 2019
Posts: 1,142
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Post by EricD on Jul 6, 2020 13:12:30 GMT -5
Has anyone on the forum tried heating HDPE on bare steel? HDPE is pretty slippery stuff. Would it stick when heated?
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Post by parfive on Jul 6, 2020 14:26:49 GMT -5
10 x 3 = 30
30 x 3 = 90
or
90 / 3 / 3
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Jul 6, 2020 15:17:11 GMT -5
jamesp Interesting - what are the several reasons you'd go with 6" pipe for hand-holes, in lieu of 4"pipe? I'm thinking (and just speculating here) that you can fill, empty, clean, and generally access the inside of the barrel easier - with a larger hole. Is it that simple? Is there anything special about the rubber cap itself - that is more desirable in 6" in lieu of 4"? Aluminum conducts heat 3 times faster than Steel. And Steel conducts heat 3 times faster than Stainless Steel (which means Aluminum conducts heat about 6 times faster than Stainless Steel - a useful rule-of-thumb). The only reason I'm hesitant to machine a ring of pre-Teflon-coated Aluminum, and connect it to another block of metal (steel or aluminum) is because it will be difficult to thermally join the metals together. Because aluminum transfers heat so quickly, the aluminum ring will become cold when the HDPE touches it - unless there's a steady-flow of heat entering the ring from the underside. Even the smallest air gap between the ring and the plate will introduce heat-transfer problems (cold spots on the ring). I was looking at thermal grease (the type used for solving this same exact problem for connecting Aluminum heat-sinks to electronic chips) and the grease tops-out just under 400 degrees F max operating temperature. I cannot weld the ring to a plate of aluminum, because the weld-heat will damage the Teflon coating. Ideally I need to find a piece of pre-Teflon-coated Aluminum that's thick enough for me to machine a raised-face hot-plate out of - without having to join it to another piece of metal (prior to placing it on the burner). 6 inch cap benefits: access for big rocks easy viewing easier dumping/filling much more ballooning for volume increase if rolling gas producing batches they are deeper making plenty of room for 2 band clamps for gaseous loads the 4 inch ones wear out after a long while, not the thicker 6 inch cap As far as heat transfer, my problem was too much heat transferred using an electric stove top using an aluminum frying pan. I'd see no problem fastening the ring to the pan. 400F is enough to get a weld. And best done slow so the heat travels deep into the plastic. Get the plastic to 300F say 1/2 inch in and then bump the heat to attain weld temp. If doing production then speed becomes a concern. I sure like the strength of my slow welds. Actually had bad luck heating that material fast... Plus I had some crappy cuts and needed the deeper heat to increase plasticity deeper to make up for gaps.
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entropy
having dreams about rocks
Member since June 2020
Posts: 71
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Post by entropy on Jul 6, 2020 15:24:51 GMT -5
The welding instructions say that if the heating plate has any stuck HDPE on it, it will overheat & contaminate (compromise) follow-on welds. The plate must be clean prior to each weld. I've also read that without a nonstick coating, the HDPE will stick to the heating source. I took this at face-value - seeing as every major brand of HDPE heating-mirror on the market has a PTFE coating of some sort (cloth or spray).
That being said, the spray Teflon coating option is rapidly falling lower on my list of potential options. The only outfit willing to take the work thus far (i.e. coating my (qty-2) 30-pound steel hot-plates with high-temp PTFE) has a $420 minimum order. And that's not including shipping (they're out-of-area). I was told the cost to coat my two plates was "well within the $420 minimum order." Translating that, what they're really telling me is that "we're going to price-gouge you WAY more than you should be paying for this small & insignificant contract"
Most powder coating shops have a PTFE coating, but the max service temp is typically between 300 and 400 degrees F (depending on brand of powder). The two-part liquid spray (good to 500 degrees F) is normally done on a mass-production assembly line (think pot & pan company).
I will almost certainly be using the PTFE craft-cloth for my heating plates (if I continue down the steel plate path). The option of fabricating from pre-coated aluminum is still on the table - depending on the thickness of starting material that's out there. The PFTE craft-cloth is super-cheap, is temperature rated, and is actually used on many commercial welding mirrors. However these are flat mirrors (without a raised-face). . . .
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entropy
having dreams about rocks
Member since June 2020
Posts: 71
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Post by entropy on Jul 6, 2020 15:42:06 GMT -5
The biggest problem I anticipate using an electric range burner is that they're pulse-width modulated.
Example: on medium, the burner turns on for a few seconds, then turns off for a few seconds (cycle repeats). On low, it turns on for just a second or two, then it's off for several seconds (cycle repeats). On high, there is no off-time. It's simply on. If you've ever powered an electric range off a generator, you can hear the burner cycling off & on by listening to the tone of the generator's exhaust. For welding HDPE, I probably need a medium to medium-high temp setting (assuming an 800 watt electric range burner). The on and off temperature regulating nature of electric ranges will introduce temperature transients in the hot-plate. My idea of using a thick steel plate was to provide some thermal buffer to these variations (dampening).
Probably a much better solution would be to use a natural-gas/propane burner. The flame is super precise with a steady-state energy input. In this case, the plate would still need to have enough mass (thermal reserve) for the transient nature of making the weld.
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Post by knave on Jul 6, 2020 15:53:56 GMT -5
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entropy
having dreams about rocks
Member since June 2020
Posts: 71
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Post by entropy on Jul 6, 2020 18:48:38 GMT -5
knave - those are nice, and the vendor is relatively local to me also. The main drawback is that I can only heat the pipe-end with those hotplates. I need a custom plate with a raised-face for heating the tumbler end pieces. I'm going to continue fabricating steel hotplates with a raised-face, and attempt to use them with some Teflon craft-cloth covering. If all else fails (and only as a last resort) I will send the plates out for Teflon coating. I've also been shopping online for Teflon-coated aluminum - pans, grills, etc - for cutting the raised-face portion. Everything I've found thus far is pretty thin. I'm still brainstorming ideas for how to attach a thin aluminum ring that's coated with Teflon - joining it with a larger piece of metal - without disturbing the Teflon coating. I have a few ideas I'm brainstorming. If I do end up fastening a Teflon-coated aluminum ring to another chunk of metal, it would probably have to be a chunk of aluminum also (in lieu of steel) - to maintain similar rates of thermal-expansion.
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Post by knave on Jul 6, 2020 18:51:41 GMT -5
Imo you’re overthinking it. I believe those hot plates have a npt hole in the center for allowing mechanical attachments. Who gives about the thermal expansion if secured from one central point? Just adjust your thermostat up to achieve required surface temps for your attachments, ambients etc. ETA: my mistake, the linked plate is indeed for surface only use.
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EricD
Cave Dweller
High in the Mountains
Member since November 2019
Posts: 1,142
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Post by EricD on Jul 6, 2020 19:11:40 GMT -5
knave - those are nice, and the vendor is relatively local to me also. The main drawback is that I can only heat the pipe-end with those hotplates. I need a custom plate with a raised-face for heating the tumbler end pieces. I'm going to continue fabricating steel hotplates with a raised-face, and attempt to use them with some Teflon craft-cloth covering. If all else fails (and only as a last resort) I will send the plates out for Teflon coating. I've also been shopping online for Teflon-coated aluminum - pans, grills, etc - for cutting the raised-face portion. Everything I've found thus far is pretty thin. I'm still brainstorming ideas for how to attach a thin aluminum ring that's coated with Teflon - joining it with a larger piece of metal - without disturbing the Teflon coating. I have a few ideas I'm brainstorming. If I do end up fastening a Teflon-coated aluminum ring to another chunk of metal, it would probably have to be a chunk of aluminum also (in lieu of steel) - to maintain similar rates of thermal-expansion. Have you considered heating the entire disc before the weld? What advantage would only heating part of it result in?
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Wooferhound
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Lortone QT66 and 3A
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Post by Wooferhound on Jul 6, 2020 20:08:08 GMT -5
jamesp , Do you ever try and recover/reuse grit during cleanouts?
I made a cleanout sink specifically to recover unused grit from my tumbles. The dried out slurry also works to the same effect as adding clay to the mix.
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