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Building a 2x72 grinder, advice needed.

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Grandalen, Mar 20, 2017.

  1. Grandalen


    Dec 11, 2016

    as the title suggests, i am starting a 2x72 grinder build, using these plans: http://dcknives.blogspot.no/p/2-x-72-belt-grinder.html
    I will also be getting the wheels from Oregon Blade Maker. http://www.ebay.com/itm/261996108844?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

    Main question is this. What is the optimal engine to get? How many HP should i get, and do i need a multiple phase motor?
    And as for speed control, is this usable? http://www.ebay.com/itm/162356552680?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT Or should i get something else?

    Thanks for your input!
  2. mike-E


    Mar 2, 2013
    i wouldnt use those plans unless i had access to free material. for a motor you want at least 1 1/2 h.p. i dont know about that controller. it says it's for machinery. i hope someone else who knows more than me chimes in because that thing has got me curious too. i've been hoping china would produce a simple speed controller instead of a digital/programmable vfd to compete with the k-bac 27d that costs 350-$400.
  3. Kevin McGovern

    Kevin McGovern KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jul 31, 2015
    That controller most likely does not alter the HZ of the motor, as a vfd does. If it worked, it would burn up your motor in short order.
  4. knife to a gunfight

    knife to a gunfight

    Oct 17, 2007
    Couple of things:

    That controller is likely for a small universal motor like a wood router or similar. It's only 60 watts, and they're more/less garbage. You're probably going to want a motor and controller an order of magnitude larger than that. I'd recommend at least 1.5hp if not 2hp. For a controller, you'll want a VFD (variable frequency drive) which is used with THREE PHASE AC motors. You can get something like an iron horse brand motor, brand new for about $150 to $175. Used, I've seen decent 3 phase motors for around $50 to $100. An open frame VFD can be found brand new for about $100 to $130, but you'll want to build an enclosure to keep dust out if, or it won't last very long. A kbac-27d is the favorite VFD for knife grinders, but it will set you back around $350-$375.

    As for those plans, I'd see about using a small 80 to 100lb pneumatic spring to run the tracking assembly up and down, as it will be easier to actuate and give you much more solid tracking.
  5. 12345678910


    Jul 13, 2009
    No that controller is for a universal motor with brushes

    If a twenty dollar controller worked, no one would spend hundreds on a VFD

  6. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    To sum it up:
    The best system for a grinder is variable speed. You want a three phase motor and a VFD ( variable Frequency Device).
    1.5HP works fine, but if you plan on doing some heavy grinding, 2HP is really nice.
    There are so many plans available. The EERF plans are good. Right now one of our members, Kevin McGovern, is doing a build where he is making up plans in CAD with great detail.
    If you search with the custom search engine in the stickys you will find many "grinder build" threads and plans recommendations.

    Another good option is the grinder build kits from several sources. It has all the parts waterjet cut and you do the build. Oregon Blademaker is one, and Polar bear forge is another. Polar Bear's GIB and SLING kits were popular for new makers.

    That speed control isn't worth anything. It wouldn't run any tool, and it is only for a DC or Universal motor. It is often worth the money to buy a motor and VFD as a package so they are known to be compatible and would likely be set up to match voltages. etc.
    BTW, if you have it, 220 VAC is by far the best way to run a grinder.

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