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Thread: Grex pneumatic ROS

  1. #1
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    Grex pneumatic ROS

    Anybody have the Grex 2" Angle Random Orbit Sander ?
    http://www.woodcraft.com/family.aspx?familyid=20343

    If so, your thoughts please .........
    How big of a compressor do you have? I have a 5hp 20 gal that delivers 7.1 cfm @ 90 psi, so it sounds like I should be OK. Getting conflicting info from various retail web sites -
    • The Grex website says Operating Pressure: 90 psi (6.2 bars) Air Consumption: 2.2 SCFM
    • according to Woodcraft it requires a 60 gallon capacity compressor, or equivalent, to operate?
    • Packard says It is powered by an air compressor that is at least 2-1/2 hp. but goes on to say Average Air Consumed - 8 cfm and states Operating Pressure - 90 psi


    I would like to get the sander but not bad enough to also get a larger compressor then what I have.

    Thanks in advance ..... Tony
    Last edited by Tony Falotico; 09-24-2008 at 10:59 AM.

    Tony, BCE '75

  2. #2
    Tony,
    I have this sander and it uses quite a bit of air. I too have a 5 HP 20 Gal. compressor (oilless) and it will pretty much run all the time using this device and you know how loud an oilless is! I'm going to move the big compressor from the garage to the shop and put the smaller one in the garage because hopefully it will make using the sander a little easier as the sander does a decent job. Again it does use a lot of air!

  3. #3
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    I have it and love it. It's my magic scratch eraser. 99% of the time, I use a firm "wave" backing pad, with "wave" sandpaper. I can remove more material faster with my right angle drill, but for finish sanding, the Grex is hard to beat.

    I started out with a 13 gallon (or so) oiled buzz-bomb compressor from Auto Zone...I think it had a 3.5 HP rating, but it was false anyway. (No way you're getting 3 or 5 HP out of a 110v 15 amp circuit.) It ran all the time when I was using the sander. and the sander would slow down after a few minutes, so I would have to wait for the compressor to catch back up.

    A few months ago I upgraded to a compressor with a "real" 5 HP motor (23 amps at 220v on a dedicated 40 amp circuit). Man, what a difference that made. Actually, the difference is in the CFM output. Now the compressor will get ahead of the sander and stop for a few minutes before it starts back up. (I usually use the constant run valve that lets it keep the motor running after the the tank is full...it saves the start/stop cycles on the motor.)

    The recommendations for a 60 gallon or 2 1/2 HP compressor are misdirected. It's the CFM that really matters. I've also noticed the discrepancy between the 2.2 CFM and 8 CFM quotes you mentioned. In my experience with the Grex, I tend to believe the 8 CFM number is closer to the truth. (Just a gut feeling...I've done no scientific measurement.) Keep in mind that many air tool manufacturers understate the air consumption, and many compressor manufacturers overstate the CFM output of their machines.

    Anyway, if you've got the air to push it, the Grex is great. With your current compressor, it'll be running all the time, and you may have to let it catch up from time to time. It still may be worth it to you, though. It gets great results.

    I wish someone would make a similarly-sized electric 2" ROS. It's not real efficient to run a 5 HP motor to power a 2" sander, especially when you consider the fact that power is lost at each stage of conversion.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  4. #4
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    for most pneumatic tools that use a spinning motor a fellow should figure a wide open 1/4" line.....if your compressor can`t keep pressure up with an open line then using constant demand air tools could grate on your nerves.
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

  5. #5
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    Vaughn,
    I assume the "wave" sandpaper you are referring to is the scalloped edge stuff, but what is the "wave" backing pad and where did you get it? I have the Grex. I bought a set of the softer pads, about 1/2 inch thick soft foam, and it is too soft for all but the lightest pressure against the bowl. I'm wondering if your "wave" pad may work a little better and I might want to pick one up. I concur about a smaller compressor. I originally had a Craftsman 30 gal, 4 or 5 advertised horsepower (probably less) that would run constantly and I would also have to wait for it to catch up at times. This meant I didn't use it all that much. But, I did use it sometimes to get out a scratch or two that showed up at say the 220 grit stage, without having to go back and start sanding from 100 or 120. But for me it is a not a go to tool for every piece.

    Ken

  6. #6
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    Ken, I don't where Vaughn got his, but I do remember seeing these ... http://www.packardwoodworks.com/Merc...dinner-newwave

    Tony, BCE '75

  7. #7
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    Ken, they've also got the wave backing pads at Craft Supplies USA:

    http://www.woodturnerscatalog.com/st...ing_pads?Args=

    I've got both the thin (firm) pad and the thick (soft) pad. The soft pad is about useless, but I use the thick pad for pretty much everything.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  8. #8
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    Tony and Vaughn, thanks for the links. Tony, if your not planning to get more air tools, and it will be some time before you upgrade to a larger compressor, you might try the HF version. Not near as elegant a design as the Grex, but it seems I've seen it on sale for about $19. You could play around with it to see if you like the action and then upgrade if you use it a lot. Just a thought.

    I've not used the HF random orbit sander, but have one of their $10 air die grinders that I can get a little deeper into taller forms and it seems to work OK.

  9. #9
    Quote Originally Posted by Vaughn McMillan View Post
    I've got both the thin (firm) pad and the thick (soft) pad. The soft pad is about useless, but I use the thick pad for pretty much everything.
    Vaughn,
    I think you got your works mixed up. Is it the thin pad that you use for everything?

    TIA for the info!

  10. #10
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    Quote Originally Posted by Kurt Whitley View Post
    Vaughn,
    I think you got your works mixed up. Is it the thin pad that you use for everything?

    TIA for the info!
    You're right...the firm pad is the one I use the vast majority of the time.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

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