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How fast is your grinder?

Discussion in 'Grinders' started by metal99, Apr 1, 2013.

  1. metal99

    metal99 Member

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    I'm in the planning and gathering stage if building my own 2x72 belt grinder. I have researched belt speeds and got a lot of different feedback.

    What are your preferred belt speeds when grinding your bevels? I'm going to go with a 17XX rpm motor and step pullys but I'm not sure what size my drive wheel should be. I can get a 4", 6" and a 10" drive wheel. what would you guys use?
     
  2. Rob W

    Rob W Active Member

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    my KMG 2 x 72 is a 1.5HP 3450 one speed hogger
    my other 2 x 72 also has a 1.5 Baldor but is 1725 and used for everything else that requires less speed
    9'' disc is a 1725 1/2 hp frwrd/reverse..............if I ever switched my KMG to a pulley or VFD I'd stick with 4" drive .........
     
  3. Hunterbow Smithy

    Hunterbow Smithy New Member

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    I just bought a 1.5 hp / 1725 rpm motor that I am controlling with a VFD. I decided to go with the 1725 rpm motor because I read that being a 4 pole motor it won't stall as easily as a 3450 rpm motor. Can anyone verify if this is true or not?
     
  4. metal99

    metal99 Member

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    Rob, is the drive wheel on your KMG a 4"?
     
  5. Grayzer86

    Grayzer86 Active Member

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    Hey Metal, i built my own 2x72 and went with a 6 inch drive wheel for my 1750 motor. This gives me a direct drive speed of roughly 2650 sfpm. It works and is controllable but too slow for most cereamic belts to work properly. I am not running step pulleys right now, but that would give me a range of speeds roughly 1326, 2650, and 5300 sfpm, with an average three step system. Currently i am running at one speed and have changed pulleys so i am at about 4000 sfpm now. The new speed is a huge improvement but i wouldnt want much faster on a homebuilt rig. A 10 inch drive wheel would be a bad plan, this gives roughly 2800 at low speed, 4580 at 1:1, and a 2:1 high that is an unmanagable 9160 sfpm. FWIW i have seem guys run up to 7000 sfpm on baders, but its not something i would personally do. Personally i feel that on a 1750 rpm motor a 4 inch drive is too small for a step pulley setup since that would run a sfpm of roughly 875, 1750 and 3500. Most likely if you went this route you would never use the two lower settings and run on high always anyway.
     
  6. metal99

    metal99 Member

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    Thanks for all the info!

    I kind of figured the 10" would be to much lol. I think a 6" might be my best bet. Would the slowest speed on a 6" drive be ok with fine grits like 400+?

    Where did you get your wheels from?
     
  7. Grayzer86

    Grayzer86 Active Member

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    I can't see any issues with the fine grits running in the 1300 to 1400 range. I am not an expert on all this so take my opinion for what it's worth I guess. I got my drive wheels from usaknifemaker, since I found they had about the best prices, and I was not interested in getting them machined by someone. My thought on this was that I couldn't get them made cheaper locally anyway. One thing I will say is that with a 6 inch drive wheel rather than a 4, you will want to make sure that your drive shaft is perfectly square and dead straight. Any wobble and vibration will be amplified by the larger rotating mass of the wheel. My first drive shaft was warped and my 100 lb bench started to walk right across the floor on the first shakedown run.
     
  8. metal99

    metal99 Member

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    Besides princess auto where els could I buy a keyed shaft? I want to make this thing run as smoothly as possible. Thanks for all the advice!
     
  9. metal99

    metal99 Member

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    Usaknifemaker has a machines 3/4" keyed shaft that I think I'm going get.
     
  10. Grayzer86

    Grayzer86 Active Member

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    Just be careful with that since most all drive wheels you will find will be 5/8. Having a 5/8 motor shaft and 3/4 driven shaft may make it harder to find properly matching step pulleys but not sure.
     
  11. metal99

    metal99 Member

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    Usaknifemaker has a 6" drive wheel in both 5/8" and 3/4" the shaft that they sell is an actual KMG shaft. I haven't bought a motor yet so maybe I can get one with a 3/4" shaft too.

    The government decided to put our entire tax return towards my wife's student loan... So my grinder and new tv budget have been destroyed :( I figure it will take a couple months to gather all the stuff I new to build it now. I was hoping to have it running next month! But...
     
  12. Rob W

    Rob W Active Member

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  13. metal99

    metal99 Member

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    Those are pretty good plans! I have to make mine a little differently because of space issues. It's only going to be good for flat grinding and profiling.
     
  14. Grayzer86

    Grayzer86 Active Member

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    Check out the DSM grinder on youtube, Looks pretty wicked, i have been told the first run of frames will sell for 650 is, but that leaves wheels and motor to buy. they are direct drive though so no belt setup needed.
     
  15. metal99

    metal99 Member

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    I'll chekem out!
     
  16. metal99

    metal99 Member

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    That's a pretty cool grinder! A little to much money for me tho :( I want to keep this build around $300
     
  17. Rob W

    Rob W Active Member

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    Kinda cool looking too.........
     
  18. Grayzer86

    Grayzer86 Active Member

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    Yeah she is a pricy beast. I love the way it looks but not sure exactly how adaptable it really is.
     
  19. metal99

    metal99 Member

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    Ya man it looks awesome! I'm just going to basically frame out a triangle out of 2" square tubing and make a tensioner out of square tubing and maybe a gas shock. I know it won't be as solid as a kmg or others like it but I can't see the need to make it 200lbs lol. As long as its ridged it should be good I think anyway lol.
     
  20. Grayzer86

    Grayzer86 Active Member

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    Have you looked at the No Weld Grinders? They are about as basic as it gets using simple materials and construction, and have removable tool arms so it can be upgraded whenever you want. I can change between platen, slack belt, and contact wheel in about 30 seconds. I ordered the plans and built it from them (still have them) and it has been excellent.
     

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