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Need some advice on buying sealed units

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  1. #1
    gettin loaded started this thread.
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    Need some advice on buying sealed units

    Right now I'm getting $2 lb. Copper and $70 ton for shred what would be a good fair price to offer thanks in advance


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    I know locally at one yard they are paying .15 cents/lb for them.......Seems like pretty good price........Check what your local yards are paying and either match it or pay a bit more

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    Best advice about sealed units......RUN. Not worth your time.

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    I would second that. Some jobs just aren't worth doing even if you get the material free. You would be cutting your throat if you had to pay for them.

    It's best that that kind of work was done with specialized machinery on industrial scale.

    It's like hand stripping finely stranded wire as opposed to just throwing it into a granulator.
    Last edited by hills; 08-06-2020 at 05:00 AM.

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    If you're selling Cu at $2/lb I wouldn't buy higher than .11 or so. Less if there's a lot of home fridge and freezer compressors in the mix.

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    sell mine to a friend at 15 cents. He is getting $2.02 on copper, about 7.5 cents for the steel (at short steel price) and has a buying for the oil.

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    It might be wise to consider the expense side of it though.

    There's the cost of buying the units.

    There's the cost of tools. Plasma cutter is probably the best tool for that job but it's easily in excess of 1,000.00 $ to buy that tool. A 4" angle grinder is probably the most commonly used tool.

    Expendables like torch heads or grinding wheels. Grinding wheels sell for about three bucks and they often wear out after one or two sealed units.

    Time is money. It's easily fifteen minutes per unit.

    The disappointment factor: Some units have aluminum windings so there's little value there.

    ~ You aren't necessarily making money when you get paid at the scrap yard.~

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    Quote Originally Posted by mthomasdev View Post
    sell mine to a friend at 15 cents. He is getting $2.02 on copper, about 7.5 cents for the steel (at short steel price) and has a buying for the oil.
    Dang if you can sell the steel that high your friend has a good gig going! Sealed unit Cu recovery (as several forum members can attest) is actually pretty good on average especially if you can get volume from a supplier with primarily HVAC sourcing more likely to be Cu recovery than aluminum.

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    The commercial refrigeration ones could be really nice. They're built to run for decades so everything about them must be heavy duty.

    The household ones like fridges, dehumidifiers,window ac's, and freezers seem to yield somewhere around a pound of #2 copper. It might be a good idea to do trial run of a dozen or so and then run the numbers to see if the juice is worth the squeeze. It's kind of a messy, stinky, oily job even if you drill a hole in the bottom and let them drain into a bucket for a week ahead of time. Personally, i would rather work on a dry motor than one that's been oil filled.

    YMMV

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    Best ones to do are scroll and rotary compressors, Never found a alum wound one. But the Reciprocating and small fridge, freezer, older dehumidifiers types have a chance of being alum wound.

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    I found that Heat pump compressors often have Aluminium windings in them, even if they are Copper, they are a pain to get into & don't return much more Copper than a fridge compressor.

    Most fridge compressors returned 2lbs of Copper for me. On average. I found it's was 'less than a Kg, so 2Lbs sounds write .
    Only got a few fridge compressors with Aluminium wiring in them, very rare.
    Also ours are 240.V AC, I don't know if that makes a difference ( it wouldn't surprise me at all )

    Newer fridge compressors are a bit under the 2Lbs. You can see that the cases are smaller & in the end I didn't count them, but just counted the bigger ones @ 1Kg each.

    Grinding discs? I use a 9 inch grinder & disc. Much more economic. If you intend to cut a lot of them open, get a 7 inch grinder & once the 9 inch disc has worn to 7inch ( mark the guard @ 7 inch dia ) take it off and put it aside for the 7inch grinder.
    Likewise when it gets to 5 or 4 1/2 for your smaller grinder.

    Grit size & bonding material is designed for a certain speed. It's measured in 'Metres/minute' , not RPM.
    The grinders RPM is just a bit higher than the match for its max diameter disc. It's going to do it's best cutting or grinding a little bit after it starts to wear the disc.
    Once a 9 inch disc is worn down to 7 inch dia, its way out of its maximum efficiency Metres/Minute at its outer diameter.
    So it's better to take the disc off & put it on a higher RPM 7inch grinder so it's back within its ' efficiency window Metres/Minute '

    Because the disc is smaller, the higher RPM will not exceed the rated centrifugal forces on the disc & it won't break apart due to centrifugal forces.
    That's the reason why you should NEVER put a bigger disc on a grinder than its designed for. To a point the centrifugal force in the grinder motor helps offset those in the disc.
    Exceeding the disc dia messes this up & just when something happens & you want to push the grinder away from you, it's centrifugal forces decides it's going to go up, arc over, twist your wrist & come right back at you.
    Always use a angle grinder with its original guard, its there for a reason & it stops bigger discs being used.
    Given a choice, use a guard with the bottom 1/3rd of the grinding face covered, it helps stop pressure on the disc when you place it face down on the ground, which is more important these days with the thinner cutoff discs.
    And damage to what you put it on, and any cables that are about.
    And preferably with the over centre clamping on the guard so you don't need extra tools & can easily shift it if needed.

    Put the handle on the left of the grinder... Set the guard at about '10 & 4 oclock'
    Use the correct mounting flanges/nuts for the disc. 9inch cutoff probably uses big flanges both sides.
    Standardise your grinders & discs. Like get smaller grinders with the 7/8ths dia mounting centres (22mm) for your used 9 inch discs.
    And standardise your cutoff discs to be flat discs, without the depressed centres, to suit the bigger flanges.

    The absolute worst case scenario I have seen was a flat 9 inch cutoff disc on a depressed centre flange, with a small locking nut to hold it on...
    Guess why?
    When the disc slips, the nut tightens up, it pushes the flat disc sideways into the depressed flange and breaks the disc around the small nut.
    Now you have a loose new 9 inch disc spinning at max revs off the grinder & into the work or the worker...

    Nah, actually the worst case was a 9inch disc on a 4 1/2 inch grinder.
    I don't like to mention it because every time I do, with a couple of weeks I read of a accident in the newspaper caused by just this situation. Sometimes deadly.

    I would get between 12 & 16 compressors per 9 inch disc. Fix the compressor tightly & don't let the grinder bite or jump.
    Examine the casing so you only cut thru one layer of casing & for where the compressor mounting mounts are inside it.
    Use a smaller grinder to cut the springs & hoses if needed. Use a good lever for the inside plug, carefully as it's got sharp edges now.

    Draining the compressor helps, to a degree. There's oil locked up in the compressor by one-way valves & tubing loops. You won't drain all of it out all of the time.

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  23. #12
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    For whatever it's worth:

    I use my 4 1/2 angle grinder quite a bit when i'm scrapping but i've never really found a cutoff wheel that i was really impressed with. The ones that can be picked up locally are expensive ( 3.50 $ w/ tax) and they don't hold up all that well.

    Seeing as it's stock in trade i ordered a 50 pack off Amazon for 30.00$. I was surprised at the difference in price (.60 ea.) and quality. These ones from Benchmark Abrasives last longer and are better to work with.

    https://www.amazon.com/50-Pack-Quali.../dp/B015VOMD5E

    Worthwhile considering if you go through any amount of them in your work.

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    Quote Originally Posted by hills View Post
    For whatever it's worth:

    I use my 4 1/2 angle grinder quite a bit when i'm scrapping but i've never really found a cutoff wheel that i was really impressed with. The ones that can be picked up locally are expensive ( 3.50 $ w/ tax) and they don't hold up all that well.

    Seeing as it's stock in trade i ordered a 50 pack off Amazon for 30.00$. I was surprised at the difference in price (.60 ea.) and quality. These ones from Benchmark Abrasives last longer and are better to work with.

    https://www.amazon.com/50-Pack-Quali.../dp/B015VOMD5E

    Worthwhile considering if you go through any amount of them in your work.



    I use the harbor freight 4 1/2" cheap ones that come in a 10 pack. I think its about $9 for the 10 pack, which seems reasonable. and they seem to last about as long as the home depot ones that are like $3/ea

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  27. #14
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    Sealed units are a pain in the butt even though I have to many torches, plasma cutter, to many grinders, and endless cutting discs. Call it lazy, but a hole from a 30:06 to drain some oil and sold for prepared iron in this area. A lazy susan was used to cut them apart with all of the above, but finally decided it was not worth the effort. BTW liquid oxygen is used for the torches and still not worth it.
    Give back more to this world than we take.

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  29. #15
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    That 4 1/2 inch grinder above. Price a 5 inch grinder & discs.

    For the difference in diameter of the discs ( I'm not going to work this out )

    Ok, I did.....
    5 inch dia =. 122.7 cm2
    4 1/2 inch dia = 105.7 cm2
    2 inch dia ( worn out) = 20.2 cm2

    First, the worn out surface area of a disc, the unuseable bit you throw out, is 2 inch dia & 20.2 cm2.

    The working surface area of a 5 inch disc is 122.7 cm2.
    The working surface area of a 4 1/2 inch disc is 105.7 - 20.2 = 85.5 cm2

    The difference between the 5 inch dia & 4 1/2 inch dia is 122.7 - 105.7 = 17 cm2

    Working area of 4 1/2 inch disc divided by the extra working area of a 5 inch disc = 5.

    So a 5 inch disc gives you a extra 20% disc ( ??? I hope that's write ) over a r 1/2 inch disc.

    Depending on how you work, like if you are using used 9 inch - 7 inch discs on a 5 inch grinder.
    It's definitely going to help on the 7 inch grinder as the metres/minute won't drop as low = more efficient cutting on the 7 inch.
    Then it's also more efficient on the 5 inch grinder too.

    So. Given a choice now if buying a 5 inch or 4 1/2 inch ( I wouldn't use either for cutting open compressors, just to cut the pipes off, since I have the 9 inch anyway ) price the discs, if they are less than 25% more it might be worthwhile.

    Or if you are going to the used discs route. A 5 inch grinder might be better, it's a bigger wattage too.

    I can buy a pkt of 10x 4 1/2 inch discs for US$6.70 The thin sort
    A 9 inch disc costs me US$6.70 The thicker 1/8th inch, 3.2mm sort
    Area of a 9 inch disc is 254.469 cm2
    7 inch disc is 153.938 cm2
    = A difference of 100.521 cm2 or the same as the whole working area of a 5 inch disc.

    Hopefully this won't confuse you as much as it did me...

    Hints when using a grinder? Let it 'Ring out'. When you start it, wait just that little bit more time when it hits top revs so it 'rings out' & stabilises it's revs, then apply it to the job.
    Or the grinders trying to build up its revs as it's doing it's work. So the motors working at 110% to give 90% revs @ 90% of the discs Metres/minutes which is less efficient & effective at cutting.
    Same with a chainsaw....

    And when changing discs. Unplug it !! It's just too easy to hit the Go switch while changing a disc.
    To make doubly sure, I unplug it and stuff the plug into my arm pit..I know where it is all of the time then, and anybody else is going to think twice about picking it up & plugging it in..
    Last edited by eesakiwi; 08-11-2020 at 08:32 AM.

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    It's interesting to compare the differences between other parts of the world and the U.S.

    4 1/2" is by far the most common size for an angle grinder here.

    The larger sizes are more in the realm of the professional tradesman that uses it on the job every day. They do exist, but i only saw one or two of the larger size during my 30 + years in the building trades.

    It might have something to do with the cost. You can get a cheap 4 1/2" for about 15.00 $ through harborfreight.com. The only 9" available there is 63.00 $

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    Quote Originally Posted by hills View Post
    It's interesting to compare the differences between other parts of the world and the U.S.

    4 1/2" is by far the most common size for an angle grinder here.

    The larger sizes are more in the realm of the professional tradesman that uses it on the job every day. They do exist, but i only saw one or two of the larger size during my 30 + years in the building trades.

    It might have something to do with the cost. You can get a cheap 4 1/2" for about 15.00 $ through harborfreight.com. The only 9" available there is 63.00 $

    I have the 9" one from harbor freight... I am not a fan of it. The trigger seems to stick and it makes me nervous that it sometimes stays on when I let go of the trigger and I have to fiddle with it to get it to stop.... doesnt really seem safe, so I dont use that one much unless I have something real big that the 4.5" one wont get through

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  35. #18
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    The bigger ones can be tricky K.

    It was a good many years ago ... i was working on a construction crew that was doing metal buildings. Construction isn't exactly the safest line of work to be in so the older hands used to keep a watchful eye on the younger guys because they were prone to making a few learning mistakes here and there.

    It was just a rookie mistake. One of the new guys was wearing a loose shirt and the angle grinder grabbed it and started crawling up his chest toward his face. The poor fulla panicked and looked like he was trying to wrestle a wolverine off his chest. Lol ... his eyes were as big as diner plates !

    One of the old timers reached over and quickly unplugged the grinder from it's extension cord.

    No real harm done but it gave him an awful scare and the rest of the crew a belly full of laughs.

    We had all been there at one time or another.
    Last edited by hills; 08-13-2020 at 06:53 PM.

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  37. #19
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    Thats something I learn about the length of the cord on a 9 inch grinder.
    You want it so that when you use it, the plug & socket of the extension cord is bouncing on the ground.
    If something happens I can stand on the cord & jerk the plug out.

    I paid NZ$100 for my generic grinder, so US$65 is right. It's my 3rd one because the 2nd one got stolen & I didn't look after the first one properly.
    It's screws holding the head together were a bit short & loosened & slogged the holes out, the head seperated a bit which increased the gap between the gears & once it skipped over the teeth it was just a matter of time before everything in it went.

    So I bought the new one & replaced the screws with socket headed cap screws that were longer & used some LoctiteŽ to stop them getting loose.
    Almost as good as a $400-$500 Hitachi, which I haven't used for a while, but they didn't seem as good as they used to be. The motors dia is smaller & didn't have as much torque I think.
    Probably some co$t cutting posing as teknikal wizardry.

    I like the 'Soft start' & the over centre clamp on the guards though.
    Last edited by eesakiwi; 08-15-2020 at 08:52 AM.

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  39. #20
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    We use a Milwaukee Sawzall (Reciprocating Saw) with a 9" bi-metal blade 14-18 tpi to cut open the compressors we get. Takes about 3 min to cut the round ones and about 4 min to make the 2 cuts in the taller a/c ones then we pull the interior copper winding. Then we take a sharpened meat cleaver right down the middle btwn the metal fins hit it with a small sledgehammer and it splits them beautifully which takes about 30 sec and makes it so much easier to pull the copper winding out of them. Total time per compressor is roughly 5 to 7 minutes from beginning to end. With a decent blade we can get anywhere from 5 to 10 compressors opened up. Roughly get 8 to 10 done per hour if no breaks are taken but usually we split the windings after a bunch of them fill the bin up. Turn in the steel right away and stockpile up on the copper.

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