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variable speed or not

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by meljack, Sep 3, 2019.

  1. meljack

    meljack

    3
    Sep 3, 2019
    I am new member and in the market for a grinder .variable speed or or fixed speeds.is there a big advantage with variable speed?
     
  2. drail

    drail

    362
    Feb 23, 2008
    You need low speed for most knife work to keep from overheating the blade. Are you talking about a bench grinder?
     
  3. ShannonSteelLabs

    ShannonSteelLabs KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Sep 9, 2015
    Variable speed will suit ideal belt/SFM rates.
    36 grit at high speed
    60 grit an high speed
    120 grit at medium speed.
    220 grit at low medium
    320 at lower speed.
    And so on. Hope that helps!!!
     
    Joel Mercier and Natlek like this.
  4. meljack

    meljack

    3
    Sep 3, 2019
    thank you that helps
     
  5. meljack

    meljack

    3
    Sep 3, 2019
    a 2x72 knife grinder single speed 3600 rpm
     
  6. Drew Riley

    Drew Riley

    Oct 17, 2007
    I used a 1750 RPM motor on 3 step pulley jack shaft for years. The day I bought a variable speed setup, I kicked myself for not having done so sooner. It really is a game changer, and you'll find yourself using the full range of speeds for anything from sharpening and finish work, up to full on hogging. What's really nice, is that VFDs are cheaper than ever, and I've seen up to 2hp VFDs from China for around $60. I see up to 2hp 3 phase motors for sale for anywhere from $50 to $150 all day long. So, you could potentially have a pretty nice variable speed set up for well under $200, give or take a bit of wiring, and maybe some filter sheets to keep the metal dust out.

    If I had to start all over from scratch, there's no way I wouldn't put a VFD on my grinder anymore.
     
    Ken H> likes this.
  7. Stacy E. Apelt - Bladesmith

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

    Aug 20, 2004
    If you make one knife, you can do it on almost anything. If you make more knives as a hobby/business, you will need variable speed. A three speed pulley system will give you three speeds, but it will never be as convenient or adjustable as a setup with a VFD and 3Ph motor.
     
    Scaniaman likes this.
  8. Busto

    Busto KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jul 26, 2011
    As a side note....as your knife making evolves you may find the need for a disc grinder for flattening materials. With the proper VFD you can utilize a rotary switch to switch power between grinders and have one VFD not one for each grinder. Select a VFD with both forward and reverse direction switching.
     
  9. Ken H>

    Ken H>

    Dec 31, 2011
    About the ONLY 2X72 that can "get by" with a single fixed speed is a dedicated grinder just for high speed grinding. Any general use 2X72 grinder NEEDS to be variable speed. The cost of a Chinese VFD is perhaps less than buying pulley's, shaft, and bearings for a 3 speed pulley setup.

    I used a 3 speed setup and thought that was all that's needed, until I built another grinder with VFD. No comparison - variable speed for sure.
     
  10. AA Forge

    AA Forge Custom Knife Maker Moderator

    Apr 8, 2010
    Although I completely agree that a variable speed grinder is very nice, I don't agree that it is a must. I say that from the perspective of using a 2x72 grizzly for the past 10 years of full-time knife making. I've always been more of a "learn your tool" than "must have said tool" type though.

    From blades to handles I've made several thousand knives to include anything from chefs knives to bushcraft knives and so on with my simple 2x72 grizzly. Just my 2cents is all:)
     
  11. 07Vette

    07Vette

    208
    Aug 2, 2009
    Going from step pulleys to VFD is like going from a B&W TV without a remote control to a new flat screen HD TV.

    Do you need a remote control and HDTV? No.

    Do you want it? Absolutely.
     
    Ken H> and Natlek like this.
  12. DevinT

    DevinT KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 29, 2010
    Next question.

    Hoss
     
  13. kmf600

    kmf600

    106
    Jul 2, 2018
    I use a single speed grinder. It's not easy to use it on the higher grit belt, so I hand sand a lot. A lot, a lot
     

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