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Thread: A Grinding Dilemma

  1. #1
    Join Date
    Oct 2006
    Location
    Tokyo Japan
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    15,588

    A Grinding Dilemma

    OK, I really need to get myself a slow speed grinder, I used one to sharpen my lathe tools on the other day at the workshop I attended, and it was sweet. Add to this, I'm hosting the next workshop for the dozen or so members of our turning club at the Dungeon, so I need to have a good slow speed grinder to use to sharpen tools.

    I have my eye on this one from Woodcraft.............


    8" Slow Speed Grinder

    Quiet, smooth 3/4 HP, 1725 RPM slow speed grinder is great for sharpening tools without generating the tool destroying heat that you get so quickly from 3450 RPM grinders. Unlike most grinders, which include cheap useless gray wheels, this slow speed grinder comes equipped with 1" x 8" 120 grit and 60 grit white aluminum oxide grinding wheels. Grinding wheel hole is 7/8" with a bushing to reduce it to the 5/8" arbor. Includes tool rests and spark/chip deflector shields. 40 lb., China.
    It is $94.95, I have a $10.00 off coupon, and the shipping will be $100 I'll have to pay about $10 import duty.

    Total then of $194.95 US

    The other choice I have is this one.........



    This one is a local company's import from China, it is a 6" unit, not 8", the stones are not as nice.

    It has 1" wide by 6" diameter wheels, runs at 1400 RPM, the two stones that come are a white #80 and a blue #36.

    This unit is on sale for 15,750 yen or about $135 US, and there is free shipping this month......

    So, my question to you all, is the 8" better than the 6" and is it worth the extra $60?

    I think if I bought one extra wheel, replacing the blue #36, that would cost about as much as the difference in price.........?

    I guess the biggest thing is which is better, the 8" or the 6".........?

    Of course, if I buy from Woodcraft, I'd have no warranty etc, but really how many warranty issues does one have with a bench grinder?

    Opinions please
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  2. #2
    Join Date
    Nov 2006
    Location
    London, Ontario
    Posts
    3,351
    Can't you just get a mandrel, maybe like this one from LVT and a cheap motor and make your own?
    Attachment 4036
    With the right step-down pulley arrangment you can set the speed as you like.

  3. #3
    Join Date
    Nov 2006
    Location
    Zushi, Japan
    Posts
    739
    Stu,

    I would go with the Woodcraft. Can you ask Glenda what the shipping be on two of those and maybe we can both order one and reduce the shipping cost. Currently I am using a six inch standard 3600 RPM. A slow speed would be nice.

  4. #4
    Join Date
    Oct 2006
    Location
    Tokyo Japan
    Posts
    15,588
    Art, I could, but I'd like to be able to stick it in a spot that the toy DP is in now, and that is not a large space, besides, by the time I buy the mandrel, the stones, and the motor and belts, I'm right at the price of the 8" slow speed grinder.

    Sometimes it is easier to just buy it out of the box

    Alex, I'll ask them what the cost for shipping two would be.

    Cheers!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  5. #5
    Join Date
    Oct 2006
    Location
    The Heart of Dixie
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    4,265
    I have no idea how much difference this makes when you get down to practical matters. But what you are looking at is more SFM surface feet per minute than RPMS. Of course the two are tied together. But the 8" will have a higher SFM than the 6". Again, have no idea if that has any practical bearing on the use.

    And to toss out another option. What about a 3 phase with a VFD? Then you can vary the speed to anything you want.

    I noticed my Queen City grinder is a 1750 RPM's but it can swing a 10" or 12" stone. I haven't done the math but I bet it close to regular grinders SFM.
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  6. #6
    Join Date
    Nov 2006
    Location
    Mountain Home, Arkansas
    Posts
    11,697
    Go with 8", 1725 rpm. Smaller and/or faster will burn your tools.
    Grit preference is all over the board. When I started with turning a local professional told me to use 80 grit. He said 100 was too smooth and only sorta polished the metal. 60 was too coarse and removed far too much metal. I got the 80 and am pleased. Others are sure to chime in saying 100 is best, or 120, or whatever. But IMHO, 80 is the way to go.

  7. #7
    Join Date
    Jan 2007
    Location
    San Francisco East Bay Area
    Posts
    59
    Hi Stuart;
    I have the Woodcraft grinder in your photo. I'm "fairly" pleased with it. That said, here's what I've found. The arbor will not take the OneWay balance system. When at speed, there's a slight vibration that causes a very slight tool bounce. I have it mounted with a Wolverine system. I get generally good results, but I'm trying to tweak it for less vibes. I removed the side shields and with the arbor nut off, I rotated the wheels several times to find a heavy spot. Marked them with a small pencil mark. Did the same with the opposite wheel and tried to keep the wheels 180 deg offset from each other. It's better, but not perfect. With a better measuring system I'll measure the arbor, then switch wheels left to right, or switch them out all together, or put them on another persons grinder. You know where this is going. I'm going to squeeez whatever I can from this inexpensive unit. Like I said, it works ok, but I think it could be a bit better.

    ps: You're going to host 12 people in you shop.. . I've seen your shop, Are you going to stack them sideways
    Best Regards, Mike in CA

  8. #8
    Good 'what ever time it is in Japan', Stuart.

    Several years ago over at Wood Central, I commented that a slow grinder was recommended for sharpening in-order to prevent burning of the tool.

    I was quickly set upon by Forest Addy, a machinist by trade of some 30 years. Forest explained to me and others that the burning of a tool by a hight speed grinder is due to the grinding wheel not being properly dressed. He says that a clean, properly dressed wheel running at 3600 RPM will work just fine and as well as an 1800 RPM grinder. Essentially, wheel speed is not the determining factor in burning a tool, but rather the glazing of the wheel that in turn causes excess friction between the wheel and the tool. The result is a nice blue tip tool.

    I went to the MSC Industrial Supply site and bought a 2 carat diamond dressing tool. I use it before every grinding session, and to date I must say that I believe Forest.

    Disclaimer: I have a Grizzly 3600 grinder that I use for gardening tools and the like. I also found a too good to pass up 50% off deal on a Baldor 1800 RPM grinder and use it for grinding WW tools. I use the diamond dressing tool on both.

    Recommendation, if you have a 3600 RPM grinder, buy a diamond dressing tool and use the high speed grinder. If you don't have any grinder, I think I would look for an 1800 RPM machine. But in any event get a dressing tool, or you will eventually have blue tips. (Been there, did that, didn't like the tee-shirt.)

  9. #9
    Join Date
    Oct 2006
    Location
    The Heart of Dixie
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    4,265

    OK here we go

    Waiting on the paint fumes to settle so I decided to follow up on my post.

    Ken, very interesting info. Never heard that one before.

    I have never seen a speed recommendation but thought that might be interesting to some.

    Low speed grinder
    RPM=1750 Diameter=6" SFM= 2749
    RPM=1750 Diameter=8" SFM= 3665

    High speed grinder
    RPM=3500 Diameter=6" SFM= 5498
    RPM=3500 Diameter=8" SFM= 7330


    Just for my own curiosity My Queen city Grinder

    RPM= 1720 Diameter= 10" SFM= 4503
    RPM= 1720 Diameter= 8" SFM= 3602
    RPM= 1720 Diameter= 6" SFM=2701

    Jeff
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  10. #10
    Join Date
    Oct 2006
    Location
    Houston, TX
    Posts
    363
    Just to add to the confusion, I think someone said that Oneway recommends the high speed.

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