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Thread: Disc Sander RPM

  1. #1
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    Default Disc Sander RPM

    I've just acquired a 2nd Bench grinder, with a Multitool sanding attachment fitted to one side. Since other end of the grinder is vacant, I am thinking on machining a 230 mm aluminium disc to be used as a disc sander. Having looked at the rpm of some of the bigger disc sanders available I'm now a bit concerned that the 2850rpm will be to high.
    having a 230 mm alloy disc flinging around my shed is not something I want to experience.
    Hafco AL320G Lathe
    Toolex RF31 Mill/Drill
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  2. #2
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    I don't think the alloy disc is the real problem. It's the surface speed of the sand paper. Too fast and you will literally burn the timber that you are sanding. Don't know what the effect of too fast on metal would be.

    Michael

  3. #3
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    Hi oldhack
    If you could machine the disc and screwcut the bore without removing it from the chuck it should be ok.
    Or perhaps do the bore then screwcut a mandrel, screw the disc on and machine it from there. I think vibration might be your only problem at those speeds though I may have missed something.

    Phil

  4. #4
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    Bench Grinder's normally run at 2880 rpm, whereas a bench sander/disc sander is normally rated at 1440 rpm.

    At 2880 rpm your going to have to be real quick with whatever your sanding, or you will just burn of the timber at those speeds and stuff up whatever your sanding.

    Makes more sense to go get a purpose built Sander from Carbatec. ----

    https://www.carbatec.com.au/sanding-...d-code-dsb-12b

  5. #5
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    I would agree with both Michael and Phil, too high a speed will burn timber, but not worry metal at all IMO, but the machining of the disk needs to be carefully undertaken if vibration is to be minimised. Machining on a mandrel particularly if done between centres would enable you to fully machine the plate in the one setup, other than the original drilling, boring and perhaps reaming for the shaft size of your grinder. A machined aluminium disk will take far higher speeds than a grinding wheel of the same size before self destructing due to overspeeding. Sounds like a good project.

  6. #6
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    Hi OldHack, Guys,

    A 9 inch alloy disc threaded on to the spindle should not be a problem. Burning could be an issue if you apply too much pressure to your work piece. The one at a cabinet maker that I know, is 14" inches in diameter but only runs at 1440 rpm. He uses 60 or 80 grit paper on it. The backing is plywood glued to a metal disc and he glues the sandpaper to the wood backing. When it needs new sandpaper it is peeled off and the plywood backing is cleaned with a wood block with sandpaper on it.
    Best Regards:
    Baron J.

  7. #7
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    Quote Originally Posted by mardtrp View Post
    Bench Grinder's normally run at 2880 rpm, whereas a bench sander/disc sander is normally rated at 1440 rpm.

    At 2880 rpm your going to have to be real quick with whatever your sanding, or you will just burn of the timber at those speeds and stuff up whatever your sanding.

    Makes more sense to go get a purpose built Sander from Carbatec. ----

    https://www.carbatec.com.au/sanding-...d-code-dsb-12b
    I'm not sure that there will be that much difference between the two sanding machines, in terms of scorching wood. The Carbatec one referenced would have a maximum peripheral speed of around 1380 metres a minute, while the maximum peripheral speed of 2060 metres a minute would apply to the 9" disk at 2850 rpm. For sensitive parts, you could always move toward the centre, thus having lower speeds, or as John suggests apply a bit less pressure to avoid scorching wooden workpieces.

  8. #8
    BobL is offline Member: Blue and white apron brigade
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    I have a 300mm disc on my 3HP belt sander with a VFD.
    On wood I run it at ~1200 rpm and for metals up to 3200 rpm where it fair strips away material especially with a new belt.
    For the outermost edge of the disc thats a linear speed of 1100 to 3000 m/min
    230 mm at 2850 rpm = 2000 m/min.

    But I don't use the outmost edge of the disc

    Wood is best sander at under 1000 m/min,

    Tdo this at 2850 rpm you will have to stick to the innermost 110 mm of the disc.

  9. #9
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    Doesn't every multitool attachment include a disk sander?
    I'm assuming you want a second one?

  10. #10
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    With our 60 cycle power you will find both 1725rpm and 3450rpm disc sanders with 12" discs although the faster is more common. Motor is a little cheaper. There are also a few 9" disc sanders that run at 3450 rpm. A 9" disc on your 50 cycle power will spin a third or so less than one on 60 cycle here. Maybe a touch fast for some jobs but with a light touch and more importantly sharp sandpaper you should be okay oaky for most things.

    https://www.grizzly.com/products/Gri...-Stand/G1014ZX

    When I bought my 6"x48" belt/12" disc sander I opted for one with the 1725rpm motor because the 3450's are too fast and I'm a patient man.

    Pete

  11. #11
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    Quote Originally Posted by Ropetangler View Post
    I would agree with both Michael and Phil, too high a speed will burn timber, but not worry metal at all IMO, but the machining of the disk needs to be carefully undertaken if vibration is to be minimized. Machining on a mandrel particularly if done between centres would enable you to fully machine the plate in the one setup, other than the original drilling, boring and perhaps reaming for the shaft size of your grinder. A machined aluminium disk will take far higher speeds than a grinding wheel of the same size before self destructing due to overspeeding. Sounds like a good project.
    I have a suitable sized piece of 30mm alloy plate off cut, so my thinking was to machine a boss of around 20mm on the rear of the disc, thus allowing approx 10mm for the disc itself. Not sure on disc connection to grinder atm, although I' thinking a similar method as the multitool drum attachment but on a smaller scale ie small cover just bigger enough to accommodate locking nut and washers.

    https://www.youtube.com/watch?v=se-zZnD2DXY
    Hafco AL320G Lathe
    Toolex RF31 Mill/Drill
    Saber Bandsaw

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