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  1. #1
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    Default Slow Speed bench grinder with CBN wheels

    Based on a few great threads (this one, this one, and this one), it sounds like the right setup for hollow grinding plane irons and bench chisels is:
    • 1HP 200mm slow speed grinder
    • 180 grit CBN wheel with a 40mm grinding surface
    • A sturdy adjustable support and tool rest


    I'll no doubt get the wheel from Jim at CWS.
    The Tormek BMG-100 with big tool rest seems ideal as a mounting kit, albeit a bit pricey.

    But what about grinders?
    The options I'm aware of are the Sherwood, which is probably a bit underpowered. Carbatec and Rikon, which are similar spec around $300. Vicmarc looks great, but seems to only be sold as a complete system, and aimed more at turners. I'm not a turner.

    Seems like the Carbatec is solid and reliable.

    Think I've answered my own questions... What am I missing?
    Is the Woodcut Trugrind a decent alternative to the BMG-100 if I just want a simple tool rest? Any other options there?

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  3. #2
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    Default

    Slightly more info on how I intend to use this...
    'til now, I've avoided owning a grinder. I have a variety of sharpening and honing gear. Course diamond plates for heavy shaping, 3 ceramic whetstones up to 8,000, and some diamond pastes that I use with a platen to sharpen one of my super-hard plane iron steels (CPM-10V).

    I'm not trying to replace all that. But preparing primary bevels has become a bit of a chore, and I suspect I'll get sharper edges much faster if I start hollow grinding, then moving to ceramics for honing. I'm building up quite a range of chisels and plane irons, too many are sitting idle because I haven't got around to preparing them yet. CBN setup seems like the logical next step!

  4. #3
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    Default

    I tried to avoid a grinder also. After spending far too long trying to establish primary bevels and sharpen, I eventually caved. Bought the Carbatec 200mm slow speed grinder when they had a special on.

    Vicmarc CBN wheel.

    Amazed at how quickly it works.
    Now sorting how to do easily / quick / repeatable setup for the angles.

    Grinder rest does seem to be the weak / difficult bit. I bought a $50 adjustable rest from AliExpress / China.

    I wonder how good the Timbecon Heligrind setup is (the base, not the bit for turning tools)

  5. #4
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    Pick the grinder with the slowest speed you can find/afford.

  6. #5
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    Default

    CBN wheels are nice absolutely not necessary (Expensive) slow speed grinder basically just the latest fashion absolutely not necessary.

  7. #6
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    Mar 2016
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    Melbourne
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    Default

    I landed with same decisions earlier this year. As a preference, I looked for coveted Vicmarc slow grinder but found they are not sold anymore so ended up with the Carbatec one on a special. I haven’t bought the CBN wheel yet but intending to buy Vicmarc 180g 40mm wheel from CWS as well.

    I am using Veritas grinding jig as I already had it. Seems to work well. I may relook at this when I get the CBN wheel.

    You will need good overhead lighting.

    5494917A-C1CF-45D5-8A35-D111FF828CD2.jpg

  8. #7
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    Quote Originally Posted by China View Post
    CBN wheels are nice absolutely not necessary (Expensive) slow speed grinder basically just the latest fashion absolutely not necessary.


    I don’t consider $270 for a lifetime tool (CBN wheel) to be expensive.
    Similarly, I generally buy once. As a hobbyist, if a slower speed makes the learning curve a bit less dramatic, I’ll pay a few bucks for that.

    the grinding jig is the only part of this puzzle I’m not too sure about

  9. #8
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    Quote Originally Posted by pippin88 View Post
    Grinder rest does seem to be the weak / difficult bit. I bought a $50 adjustable rest from AliExpress / China.

    I wonder how good the Timbecon Heligrind setup is (the base, not the bit for turning tools)


    Seems like the usual conundrum in product offerings. There's are cheap options at ~$50 or less, but they all look a bit useless. Then a big gap. And the reliable and fit for purpose options are $200+. I'll probably just stump for the Tormek arm. It's well known reliable option.

  10. #9
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    Quote Originally Posted by rogerwilco View Post

    I don’t consider $270 for a lifetime tool (CBN wheel) to be expensive.
    CBN wheel don't last indefinitely and the slower they're run the more careful you have to be about not pushing too hard to remove metal as this will wear the CBM grains faster.

    CBN wheels are designed for optimal metal removal and longevity to operate between 1400 and 3600 RPM. They will work on slower grinders but are not as efficient at removing metal.

  11. #10
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    Unless you’re going to be using Tormek jigs the BMG-100 is a very expensive tool rest that really doesn’t offer any advantage over more basic aftermarket models. If you’re only grinding plane blades and chisels it’s definitely overkill unless you then hone on a Tormek wetstone grinder.

    I also agree that a slow speed grinder may not be the best platform for mounting CBN wheels. A quality high speed grinder like a Linishall will power your CBN wheels quite happily; and the cast iron tool rests may remove your “need” for aftermarket rests.
    Nothing succeeds like a budgie without a beak.

  12. #11
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    I may be missing something but I am quite happy with my regular speed grinder, 6" diameter (gasp!) and a white wheel. A light touch, decent home made tool rest and a tub of water will grind primary bevels marvellously.

  13. #12
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    Quote Originally Posted by Chief Tiff View Post
    Unless you’re going to be using Tormek jigs the BMG-100 is a very expensive tool rest that really doesn’t offer any advantage over more basic aftermarket models. If you’re only grinding plane blades and chisels it’s definitely overkill unless you then hone on a Tormek wetstone grinder.

    I also agree that a slow speed grinder may not be the best platform for mounting CBN wheels. A quality high speed grinder like a Linishall will power your CBN wheels quite happily; and the cast iron tool rests may remove your “need” for aftermarket rests.
    This.

    You've all convinced me that slow speed isn't a priority. I was worried about 'the knack' or light touch required to grind straight and accurate. But, it really doesn't look that hard, especially for chisels and plane irons at 90 degrees.

    I've looked at Linishall many times over the years. Looks like the way to go. I can see the integrated tool rest is nice chunky cast aluminium. Much better than the pressed metal junk that most other machines have. That should work fine for my needs.

    Probably the simplest, powerful, and most cost effective solution out of all the options I've looked at so far. Thanks!

  14. #13
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    ...

  15. #14
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    Quote Originally Posted by The Spin Doctor View Post
    The caveat to that is I grind at 12htz on a 10" wheel, with a grey 60 grit stone. I'll leave those that know can calculalate the rpms of a 3000rpm motor running at 12htz... And then figure out the surface speed, which is the more important factor.
    That's an equivalent surface speed to an 8" wheel doing 864 RPM. I wouldn't exactly call that slow. I call 100 rpm slow.

    I have two 1HP GMF 3P grinders running from one VFD.
    One grinder has 2 x 8" CBN wheels and I run these anywhere between ~25 (1400rpm) and 60 Hz (3600 rpm).
    They're mainly used for lathe (wood and metal) tooling.
    The other grinder has a thin kerf cutting wheel saw and a linishing multitool.
    Both of the CBN wheels have (cheap) 6" diamond wheels on their sides for use in sharpening TC tooling and TIG tips.

    Compared to stone wheels, grinding with CBN wheels remove significant amounts of heat so it's possible to grind at much higher speeds without over heating . I've not tried to quantify it but I'd roughly estimate it's about twice as fast. It's still possible to blue thin edges especially when one is used to removing a lot of metal and then pushing harder to try and remove the same amount of stock.

    Using variable speed has several other advantages, one being if there is some vibe at one speed a slight change in speed can often remove most of it.

  16. #15
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    Quote Originally Posted by BobL View Post
    CBN wheels are designed for optimal metal removal and longevity to operate between 1400 and 3600 RPM.
    Bob, the Carbatec low speed grinder that rogerwilco bought runs at 1400RPM, so a CBN should work well in that case.

    I think we need to define what we mean by "slow speed grinder". Is it a grinder with a mechanical speed reduction, like the Tormek (90RPM)? Or a 4 pole (1400RPM) grinder like the Carbatec low speed grinder?

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