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Thread: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

  1. #26
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    I'd be very surprised if you got close to 12,000 with any kind of load on it... but you never know??? Hey Oscar.. you got one of those optical tachs??? you know the cheapies... 10-15 bux I think I paid for my last one... I use em on small engines, drones, etc would be curious just how that 3m performs with some air data too

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    Last edited by ronsii; 01-17-2021 at 10:06 PM.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Oh it will bog with added pressure, just like any air tool. 12,000 RPMs is the free-spinning speed I'm sure. I don't disagree with you there.
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Oscar View Post
    Oh it will bog with added pressure, just like any air tool. 12,000 RPMs is the free-spinning speed I'm sure. I don't disagree with you there.
    I am kinda curious just how much it will bog... with a good load on the disc... I know it's subjective for how much the disc is biting in and how much pressure you're putting on the grinder and all that... but still curious

    Don't tell me I'm gonna have to buy one and find out for myself

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by ronsii View Post
    Oh Shoot!! I didn't mean to stop you from posting


    And.. they're also handy for keeping your hands cool when it's hot out and the rest of you if it's got a rear exhaust
    In cold areas that is not a plus. Put a zirconium disc on that thing with a little beeswax and you will almost never want to use a carborundum disc. We had a really big right angle grinder years ago but you couldn't use it with anything else and you couldn't even use it for a long time so it fell out of favor. I think it was the Dotco brand. Too big and heavy as well.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Oscar View Post
    I just got this baby today. Holeee Schikes! It is a bad piece of equipment! It's the biggest air-hog I own. It's pretty much a "dead short" to the compressor, aka it's like just opening a 1/2" air hose wide-open, no restriction. It brought my 10HP Polar Air 35 CFM air compressor to it's knees fast!







    Highly recommended!
    Congratulations, nice tool. Remember to put air tool oil in it and get an automatic draining water filter if you do not have one already.

    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Oscar View Post
    Technically it should still work, but I suspect that if throttled-down it won't spin at 12,000 RPMs, which is what 4.5" discs/wheels should be ran at. So it might even be less effective than a less powerful grinder that is running 11,000-12,000 RPMs. And yes 3M's Cubitron II's excel in any grinder. You should try them. They're out of this world.

    So you have 4.5" discs rated at only 8,500 RPMs??
    The 4.5's are rated higher.... I was looking at the 7" and 9" discs I had on the Blue Point and the DeWalt. Nothing special, one Jet, bunch of brand X's.
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by whtbaron View Post
    I wonder how it would compare to the lesser brands if you had to throttle it back for a 3HP compressor? Do you think it would still have the advantage, or would that just decrease the performance to the other brands? I had a Blue Point for years that I liked, but when I had to get it rebuilt by SnapOn it basically came back as a gutless air hog. Wish I'd put the money into a new one now. I think they charged me $350 for the rebuild. I need to take it apart some day and see what's going on. Either there is excess wear on the housing, or maybe it's something simple like stuck impellers that are too tight.
    See if you can get a replacement set of vanes for your grinder. While stuck vanes is the most common failure, worn ends, or too loose in the pocket will also affect performance. Also most have a centrifugal governor valve seat that may be stuck partially closed. I have a bunch of air grinders that I take into salt water, I have to disassemble and lubricate after every job.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by filetobeef View Post
    i like air tools but never really understood why the fanfare. noisy,needs compressor so even more noise,air hose gets in the way,not efficient and they stall more brutally than electrics.

    understand out in the field where no electricity is available but in a shop? idk!
    Weight is one benefit. You can get very high HP ratings in a small, lightweight package. That tiny 4-1/2 grinder packs as much horsepower as a large 7”/9” Milwaukee grinder we’re all familiar with, at a fraction of the size and weight because the power source is completely separate from the tool.

    You’re right about regulation, electric does a much, much better job of it, but at the cost of weight and size. Even cordless. You’d have to step up to the 6”, M18 Fuel grinder to get an equal comparison of power, which is still much larger and heavier. Another thing to mention is efficiency, compressed air being the least efficient mode of power, by a large margin, but it’s use in industrial applications is also over 70%.

    Having the power source completely separate does have advantages, but like anything else, there are also disadvantages. I use a lot of air tools, I have some 9” polishers that are in the same range of power as the grinder Oscar posted, but I grab the corded 115V polishers 9 out of 10 times in that size range. Other tools, like D/A sanders, I use air much more than electric. Depends on the application.
    Last edited by Mike_L; 01-18-2021 at 05:22 PM.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    If you have the air, this is what you need for heavy duty grinding.

    https://www.intlairtool.com/cleco-40...-hp-6-000-rpm/

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by bakodiver View Post
    See if you can get a replacement set of vanes for your grinder. While stuck vanes is the most common failure, worn ends, or too loose in the pocket will also affect performance. Also most have a centrifugal governor valve seat that may be stuck partially closed. I have a bunch of air grinders that I take into salt water, I have to disassemble and lubricate after every job.
    It hasn't been used much since the Snap On boys rebuilt it, so I would assume the vanes are new. I must say it looked different than I was expecting. The grinder itself is pushing 45 yrs old, so chances are I've simply worn out the body the vanes run in. I should have got a new one instead of rebuilding... I think it would have been $500 then compared to the $350 I wasted on a bad rebuild. Not sure what they're worth now, but probably more than I'd pay. For the limited amount I use it, it will likely get replaced by a cheaper brand. Most of my grinding now gets done by the 4.5 electrics anyway, and I do have the 7/9" corded as well as a 20 volt 4.5. I haven't run short of grinders yet, but there are times I would prefer to be using the air.
    Where is the centrifugal governor valve? I didn't completely disassemble, but I didn't see anything like that.
    Last edited by whtbaron; 01-18-2021 at 09:07 PM.
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Welder Dave View Post
    If you have the air, this is what you need for heavy duty grinding.

    https://www.intlairtool.com/cleco-40...-hp-6-000-rpm/
    But you're back to a 12 lb grinder that only spins at 6,000 rpm... not much advantage over my 7/9" DeWalt.
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by whtbaron View Post
    But you're back to a 12 lb grinder that only spins at 6,000 rpm... not much advantage over my 7/9" DeWalt.
    Well yea, but it does spin slower because it uses a much larger diameter disk. 7" units are typically, what, 8,500 RPMs? So it makes sense that a 9" disk spins at 6000 RPMs to keep the circumferential/linear velocity at the edge in the same range as a smaller disk spinning faster.

    Yeah, just looking at the size/quantity of those air exit holes of that Cleco grinder screams "I want 120 CFM!!"
    Last edited by Oscar; 01-18-2021 at 09:51 PM.
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by William McCormick View Post
    Congratulations, nice tool. Remember to put air tool oil in it and get an automatic draining water filter if you do not have one already.

    Sincerely,

    William McCormick
    What's air tool oil??
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Oscar View Post
    What's air tool oil??
    Youíll want to add a drop or two into the air inlet each time you use.

    If you plan to use a dedicated outlet(s)/branch for air tools then you may consider installing an automatic oiler. Just donít hook up your paint pot to it. LOL.




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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Oscar View Post

    Yeah, just looking at the size/quantity of those air exit holes of that Cleco grinder screams "I want 120 CFM!!"

    Iím a firm believer of OVERKILL but I finally conceded my 200 CFM Quincy was too big for a hobbyist.





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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by whtbaron View Post
    It hasn't been used much since the Snap On boys rebuilt it, so I would assume the vanes are new. I must say it looked different than I was expecting. The grinder itself is pushing 45 yrs old, so chances are I've simply worn out the body the vanes run in. I should have got a new one instead of rebuilding... I think it would have been $500 then compared to the $350 I wasted on a bad rebuild. Not sure what they're worth now, but probably more than I'd pay. For the limited amount I use it, it will likely get replaced by a cheaper brand. Most of my grinding now gets done by the 4.5 electrics anyway, and I do have the 7/9" corded as well as a 20 volt 4.5. I haven't run short of grinders yet, but there are times I would prefer to be using the air.
    Where is the centrifugal governor valve? I didn't completely disassemble, but I didn't see anything like that.
    Usually just downstream of the trigger, on the end of the rotor shaft. Stuck governor valve doesn't really match your symptoms, as it wouldn't use so much air. BTW I lived in Manitoba as a child, you have my sympathy.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Lis2323 View Post
    Youíll want to add a drop or two into the air inlet each time you use.

    If you plan to use a dedicated outlet(s)/branch for air tools then you may consider installing an automatic oiler. Just donít hook up your paint pot to it. LOL.




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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Yeah.... I heard you laughing the first time...
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by bakodiver View Post
    Usually just downstream of the trigger, on the end of the rotor shaft. Stuck governor valve doesn't really match your symptoms, as it wouldn't use so much air. BTW I lived in Manitoba as a child, you have my sympathy.
    I did take some pics as I was dismantling... I'll have to post a couple up. What part of the province? Hopefully nowhere near Portage and Main...
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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Oscar View Post
    Hook, line, and sinker!! Lmao
    There's always got to be one guy in the group that's think he's funny

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by whtbaron View Post
    But you're back to a 12 lb grinder that only spins at 6,000 rpm... not much advantage over my 7/9" DeWalt.
    Much more ergonomic than an angle grinder and 4 HP. No load RPM means nothing if it it bogs under load. Kind of like a diesel engine compared to a gas engine. Much more torque so won't slow down as much under heavy load. Large air grinders are used in applications like foundries where there's some serious grinding required.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Welder Dave View Post
    If you have the air, this is what you need for heavy duty grinding.

    https://www.intlairtool.com/cleco-40...-hp-6-000-rpm/
    They are big and heavy, but you can put the veined sanding discs in them and really tear up some material. The problem was air consumption that thing is almost ridiculous, you need a screw compressor. When it starts it has torque like an electric grinder. But not really good for anything but standing there and removing material. It is not your friend when grinding inside of anything.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by whtbaron View Post
    But you're back to a 12 lb grinder that only spins at 6,000 rpm... not much advantage over my 7/9" DeWalt.

    Those big ones will run all day and you can lay into them and remove a ridiculous amount of material quickly without wearing it out like you would an electric grinder. The heat of the electric grinder is the problem especially in the sun on a warm day, you could toast an electric grinder in one day trying to do what the pneumatics will do for years. But I never use it, and I really never would unless I had some specific use. It is big and awkward as well only good for heavy workstation grinding.

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    Quote Originally Posted by Oscar View Post
    What's air tool oil??
    If you forget for a duration they tend to pick up metal on the veins and grind away at the veins and housing. Then one day it is running weird, you can even get vibration which is like an alarm clock, haha. But when you oil it, it usually comes back to normal. I have lost a couple from neglect for sure. Water and subsequent rust in one night can ruin one. Steel piping subjected to water can carry rust into the tool and destroy it in one use. I do like the PEX tubing for that reason. Because you are grinding metal there is no doubt some metal is going to get into your air chucks and then your tools, that is just part of racing. So you have to do the oil thing. The automatic oilers are great but you have to set them up and maintain them too.

    Sincerely,

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    Re: 3M 1.5HP Air Grinder - The Rolls Royce of air grinders

    As promised, some pics of the sick Blue Point that is letting too much air pass through. Assuming the vanes are fairly new (which may be a bad assumption to make) my thought is wear on that inner barrel where they run. A governor was mentioned earlier, but I don't see anything between the trigger valve and the round inlets into the barrel. I'm wondering if it's possible the barrel isn't sealing in the outer handle as well. I know it looks like a lot of crud in there, but it was more like staining. It did get oiled once in a while. I wish I had taken more pics of the inner workings, and the orientation of the barrel in the handle as it came apart. I keep wondering if it's simply being reassembled wrong for the air ducts to line up.
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