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Finished My Disc Grinder Build

Discussion in 'Grinders' started by Bluefish, Jun 20, 2018.

  1. Bluefish

    Bluefish New Member

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    Finish have a 9” disc grinder made from a thread mill motor. Seems to work pretty good so far. Hope is that it cuts down on the hours of hand sanding.

    https://imgur.com/gallery/vbeoppK
     
  2. dancom

    dancom Dust Maker Best Shop Tool

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    That looks really good man! Nice solid mount. I hope it serves you well.
     
  3. Griff

    Griff Active Member

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    Nice @Bluefish!

    Is the variable speed the main want for a disc grinder? I am asking because it seems the big difference money wise, like everything else with a VFD, as a normal woodmakers 12" disc grinder comes in at $350 roughly and these 'knife makers' disc grinders are all double or triple that!
     
  4. dancom

    dancom Dust Maker Best Shop Tool

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    Griff, I don't think variable speed as a big deal on a disc grinder. Perhaps depending on what you are doing with it, but I have found that I run mine pretty much wide open all the time.

    If you want variable speed, move the piece you're working on from near the center to the edge of the disc.;) The surface speed at the outer parts of the disc can be very fast.
    Speed at outer edge of disc 9" (1800 RPM x pi x 9)/12 = 4240 SFM.
    Speed at half way between centre and edge of disc 9" (1800 RPM x pi x 4.5)/12 = 2210 SFM.
    Double these for a two pole (3600 RPM) motor.

    I think it's way more important to be able to reverse the motor, which is a feature I don't see on a lot of generic imported 12" models. Having open access to both sides of the disc is important for right-side left-side work.

    On a budget I would buy a good, balanced disc, find a used reversible single phase motor around 1 hp and wire in the reversing switch. Should be able to do that for $350. Expect half the cost to be the disc itself.

    Dan
     
  5. Griff

    Griff Active Member

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    Thanks @dancom!

    I see TruGrit has two 9" billet discs available, 5/8 Arbor, and one of those with a 1 degree bevel.
     
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  6. Bluefish

    Bluefish New Member

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    Yes this is variable speed and reversible, I turned the disc myself, added a 1 degree bevel. It’s run off of a treadmill motor. Cheap and easy. Cost of materials was basically nothing. $20 maybe and a bit of time. Pretty much paid itself already, nice to come out of heat treat, 5 mins on the disc then jump to 600 grit hand sand.
     
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  7. dancom

    dancom Dust Maker Best Shop Tool

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    @Griff Looking good in blue anodized. I bought the 1° bevel disc from USAKnifemaker. $83 US plus all the gory shipping and details. It is also a 5/8" keyed bore. It runs very true.
     
  8. dancom

    dancom Dust Maker Best Shop Tool

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    @Bluefish I was wondering how you attached the wheel to the treadmill motor. Damn those are hard things to work with.
     
  9. Bluefish

    Bluefish New Member

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    Just a simple 16mm shaft and key with set screw. No threads on this one.
     
  10. Bluefish

    Bluefish New Member

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    Had to dr the key as only had standard brooches, 5/8 x 3/16 worked then ground the key to fit... handmade step key.
     
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  11. dancom

    dancom Dust Maker Best Shop Tool

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    Ah ok. Some are metric with LH threads etc. Nice.
     
  12. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    Nice grinder! I have to say, i think i like making tools and machines as much as making knives. I know i'm better at it. Not to say i'm that great at either but my grinders grind and my knives cut. There's just something really satisfying about engineering and building a machine with your own two hands that can be used to create so many other things. Very satisfying. I'm sort of satisfied for you and it's not even my grinder : )
     
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  13. Bluefish

    Bluefish New Member

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    Yes i’m The same, love the machine builds. I think my machine build list is as long as my knife build list. Heat treat oven, molten salt pot, hydraulic press, better 2x72.... and that’s just the short list.
     
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  14. dancom

    dancom Dust Maker Best Shop Tool

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    It's a slippery slope man. Next thing you will be looking at making your own lathe and Junk Yard power hammer. :)
     
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