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Thread: CBN Wheell and rpm
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27th February 2014, 09:46 AM #1Member
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CBN Wheell and rpm
I just purchased a Optigrind 200mm diam grinding wheel and the manufacturer's information states that the revs should not exceed 2200 rpm for this size. I made some enquiries about low speed bench grinders but it appears 8" benchgrinders are not available in Australia (there is only one 6" low speed model available from Carbatec). Carroll's advised me that 2800 rpm is OK to use - the rated speed of my bench grinder.
I would greatly appreciate opinions/experiences from users of CBN grinding wheels regarding this issue. I have not started using the wheel as yet and cannot comment on it's performance.
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27th February 2014, 11:31 AM #2Retired
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We run ours at 2880 on a Abbot and Ashby 8" grinder.
The wheels are perfectly balanced so should be no dramas.
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27th February 2014, 12:29 PM #3
Optigrind CBN Wheels
As advised I did check with the supplier of these wheels and asked why they dont comitt on their paper work that it is suitable for our speed of 2800 rpm
Their reply was that the wheels are used in USA on grinders of 3600rpm with no problems.
It is just one of those quirks where they try to cover themselves for the silly factor.
Initially we did get some complaints that guys were still overheating their tools and this come about due to the fact they thought they still had to press hard to get it to work as there was not enough sparks coming of the wheel.
You only need a light touch with these wheels , too heavy and you just waste a lot of steel. Get in touch with your feminine side.
Granted they work fabulous on slow grinders and the 6" cruesen is great for this or the ultimate is the Tormek with the 280g wheel
Personally I have used the CBN on a 8" spark grinder from day one of supplying with no problems.Jim Carroll
One Good Turn Deserves Another. CWS, Vicmarc, Robert Sorby, Woodcut, Tormek, Woodfast
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27th February 2014, 12:57 PM #4
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27th February 2014, 04:13 PM #5Retired
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Loooove my new 180 CBN.
It's as and Jim say - feather fingers. Really get in touch with your non-caveman.
It would be interesting to see what would happen if they offered a 360 or 400, if such a thing were possible. It would be like a magic polisher.
I'm sort of hoping that with use the 180 "settles down" a bit....but given they last a billion years or so, I might be waiting....
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27th February 2014, 07:45 PM #6SENIOR MEMBER
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I've heard talk that it's safe to put an 8" CBN onto a 6" grinder, as it's well balanced and the bearings will be under no strain.
As for running a CBN wheel at 2800, is the recommendation based on the optimum speed for grinding, or the speed at which the CBN will start flying off the wheel? I'm pretty sure it's the former, as there are many people running 8" CBN wheels on 3600 rpm grinders in the US.
I'd say the worst that can happen at 2800 run is that you'll take too much off the chisel.
Of course, if it's based on the mechanical strength of the wheel, then don't do it.
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28th February 2014, 08:23 AM #7Senior Member
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These wheels can be made in any grit you want, if you want to pay for it. It is much easier to get standard grits, which for these wheels is 80, and 180. Dave, at D Way does make a 3 by 6 inch hone plate that is 320 and 600 grit. Personally, I think that is way to fine for practical use. Probably the most confusing thing for me is those who prefer 60 grit wheels 'because the more serrated edge cuts better'. Not having anything that coarse, I really can't say. I have tried the Tormek, and it does work, but I could not see any improvement from the 80 or 180 grit CBN wheels.
For speeds, they should be safe on the high speed grinders. They come bubble and spin balanced. I would hesitate to put 8 inch wheels on a 6 inch grinder. True, the bearings should not be under any strain because they run so smooth, but the smaller motor might wear out trying to spin that much extra weight. Also, the load from sharpening could add to that. I don't really know. I did concrete construction for 30 years, and really prefer things to be over built rather than the least you can get by with. I do prefer slow speed just because I don't want to waste steel. When brand new, they are very aggressive. Far more so than coarser grit standard wheels. After they break in (a month or three depending on how much you use them), they still seem to cut much faster than comparable grit standard wheels, but do leave a much more polished surface. Not sure why, they just do.
The light touch is always needed for any sharpening. Most of us tend to over do it, and swing back and forth a couple of times 'just to make sure'.
robo hippy
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28th February 2014, 08:51 AM #8Senior Member
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What is the difference between the Optigrind & woodcut CBN wheels?
Which wheel would be best suited as a change over to my 200mm diameter wet stone tormek ?
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28th February 2014, 09:44 AM #9
I was recommended this one by Jim from CWS, i just purchased it, i havent used an Optigrind before but ill let you know how the woodcut goes once its installed
http://www.cwsonline.com.au/shop/ite...-x-40mm-x-180g
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28th February 2014, 10:40 AM #10Senior Member
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The biggest difference between the Optigrind and the Woodcut is that the Optigrind is 1 1/2 inches wide, and has about 5/8 inch on the side for a flat grind. The Woodcut is only 1 inch wide. Can't remember if it has side grind or not. If it does, it only had 1/4 inch. The side grind isn't some thing I can see using.
robo hippy
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28th February 2014, 04:20 PM #11Senior Member
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28th February 2014, 04:31 PM #12
Yep thats right. I posted the link a few posts ago for those wetstone grinder users that may be interested
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1st March 2014, 09:39 AM #13Member
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I installed my new Optigrind wheel yesterday. It exceeded all my expectations. Vibration free very fast stock removal with very little heat build up and very little dust. I like the side grind for sharpening skew chisels as I prefer a flat grind to a hollow grind for these chisels. They give me better control and less chance of a dig in. Apparently the Woodcut wheels without a side grind are made in China and Optigrind are made in Austria.
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1st March 2014, 12:21 PM #14
Vicmarc 1440 RPM 8" Grinder
I'm suprised this hasn't been mentioned. I now have in my possession a low speed 8" grinder. Vicmarc are now getting them made. I'd be happy to help out with anyone interested in one. I haven't quite had time to have a good play with it and the new griding system Vicmarc have also recently put out but my initial reaction is favourable. The grinder comes with 2 white wheels, a 36 and 60 grit. I plan to put my cbn on it. I also will have a You Tube review done within the next 2 weeks. I will take it to Shepparton Wood Show Labour Day weekend if anyone wants to see it up close and personal.
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1st March 2014, 01:36 PM #15
Interesting Brendan. Which country does Vicmarc source these grinders from and what sort of money are we looking at?