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Thread: Diamond v's CBN Wheels
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7th January 2019, 03:52 PM #1GOLD MEMBER
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Diamond v's CBN Wheels
Has anyone here used both and can report on the differences if any they found.
CHRIS
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7th January 2019 03:52 PM # ADSGoogle Adsense Advertisement
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7th January 2019, 04:08 PM #2
Chris, at what speed are you grinding - Tormek or half-full speed bench grinder? The Tormek is slow and barely gets any warmth, even with water (which is not recommended with the diamond wheels anyway), while a half- or full speed grinder can develop a healthy head of steam. Heat, carbon steel and diamonds do not play well together. That is why CBN are preferred in that setting.
Regards from Perth
DerekVisit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.
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7th January 2019, 05:26 PM #3Taking a break
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My understanding is that diamond should really only be used on carbide because it will literally dissolve into steel at grinding temperatures..
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7th January 2019, 06:49 PM #4GOLD MEMBER
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Mr Cosman ever the master salesman, he has to earn a living somehow so good on him, extolling the advantages of diamond wheels.
I have CBN on a half speed grinder and I asked the question out of curiosity as the CBN does all I need it to do. Is the diamond wheel an advantage over the CBN or is it Rob C. not wanting to leave what he knows, that being he uses diamond plates so diamond wheels logically follow on. I have never used a diamond plate that did not rapidly lose its effectiveness but I haven't bought one for many years either. The video is book marked at where he is talkng about it.
CHRIS
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7th January 2019, 07:25 PM #5
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7th January 2019, 07:37 PM #6Taking a break
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It's a chemical reaction. Diamonds are made of carbon, which is soluble in steel; the carbon bonds with the iron in the steel and it strips it away, the heat generated accelerates the process.
There's plenty of stuff on the internet that can explain it better than me, but that's the gist of it.
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7th January 2019, 07:40 PM #7.
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I have both types of wheels and use the CBN wheel primarily for HSS but it can also be used on some kind of carbides.
The carbide I use on it regularly is called crobalt and is acast alloy that contains approximately 50% Cobalt. The remaining 50% consists of Tungsten, Chromium, their carbides and minor additives
The recommendation for not using diamond on steel probably comes from when industrial diamonds and diamond wheels were expensive and applies to aggressive, all day, industrial scale, situations where large expensive wheels need to last as long as possible. But diamond wheels are so cheap these days that if they wear out they can be cheaply replaced.
CBN wheels work great on any hard steels but not so well on mild steel because it is too soft and it will gum up the wheel.
Interesting I also have a 125mm diamond edged thinnish kerf cutting wheel that was sold specifically for cutting regular mild steel (<0.3% carbon) and it works a treat. It does however run at 12000 rpm so LOTS of heat! Yes it will wear out but it is supposed to last 30x longer than a standard abrasive wheel. It also cuts concrete and stone.
The optimum speeds to run an 8" CBN is between 1450 and 2850 rpm. Lower speed gives you less efficient but greater control of grinding. Higher speed gives you more efficient grinding and you need less pressure so that reduces wheel wear. The degree of "coolness" of the grind depends on the pressure so slower may not be better if more pressure is applied.
The optimum for an 8" diamond wheel is between 1450 and 2150 rpm, while for a 6" wheel its between 1900 and 2850 rpm. If you decide to buy a diamond wheel then a 6" wheel on a 2850 rpm, or an 8" on a variable speed, grinder would be the go.
This is a useful guide to wheel RPMs etc http://graffdiamond.com/files/common...tes-013522.pdf
I have posted this photo a number of times but for those that have not seen it here is my variable speed grinder with diamond/CBN wheels.
The diamond wheel is the 6" wheel on the side and cost ~$10 from thk.hk.
I bought a dozen or so different diamond grit wheels for SWMBO's lapidary activities and in 4 years (she has her own flat grinder and shaper) and she has so far used a total of one of the wheels so I have all the others there to play with.
TP2.jpg
For a guide on what should ideally be used to grind what materials this is a useful chart - remember these guys are selling into industrial scale environments.
http://graffdiamond.com/files/common...tes-117175.pdf
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12th January 2019, 12:58 PM #8SENIOR MEMBER
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12th January 2019, 03:36 PM #9.
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9th October 2019, 10:38 AM #10
A late contribution to this thread.
I have posted on my experience with diamond resin matrix wheel wear in another thread.
In summary, after 8-1/2 years of regular use I have found minimal wear. At the seven year mark I reported...
"after seven years of constant use the remaining diamond matrix has only reduced by 0.02mm in thickness. This is the first time that I have been able to measure any loss of matrix at the outer edges of the rim
Diamond and/or CBN Grinding Wheels
I've not remeasured in the last 18 months, but expect there has been little change.
In my experience too much credence has been given to the exaggerations about the iron in the tools eating up the diamond, at least in a hobby setting. As Bob suggests, perhaps more relevant in industrial settings.
As CBN wheels have come down in price to compete with diamond this is not such a hard decision anymore as it was back when CBN was relatively much more expensive.
And, as always....
Stay sharp and stay safe!
Neil
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15th October 2019, 10:48 PM #11GOLD MEMBER
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15th October 2019, 11:23 PM #12
Cosman's "diamond" wheel ...
Regards from Perth
DerekVisit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.
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16th October 2019, 11:40 AM #13GOLD MEMBER
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At this link WoodRiver CBN Grinding Wheel
– RobCosman.com the wheel is shown as CBN but the imbedded video at the link shows him referring to it as a diamond wheel as does the link itself. Here is an explanation from a YT comment that asked the question
>Semantics, Harry. Cubic boron is considered "artificial diamond" and is commonly referred as "diamond" throughout the industry, from my observation. I think we are all supposed to recognize that using actual diamonds as grinding wheels would be beyond the pay grade of most people in the woodworking industry! )<CHRIS
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16th October 2019, 12:29 PM #14GOLD MEMBER
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16th October 2019, 01:12 PM #15.
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That is not my understanding - over the last few years industrial diamonds as used on grinding wheels have become relatively inexpensive and are not the same as CBN which is more expensive than industrial diamond.
The world wide production of gemstone quality diamonds fluctuates but is currently about 4X greater than demand. In a normal market, under these conditions the price of gemstone diamonds should plummet,
BUT
Diamond gemstone buyers just keep buying up these excess diamonds to hold the prices up to their exorbitant levels.Apparently there are large volumes of these diamonds in vaults all over the world, Every now and then a tinpot 3rd world dictator tries to sell off their diamond stash but so called reputable diamond trading companies try to step in and offer prices the dictators can't refuse. Despite this there is a lot of dodgy under the counter, back of the parking lot trading going on. Russian and Africa being a prime source of these unofficial diamond
The result of all this plus increased artificial industrial production generates very large amounts of industrial diamond suitable for abrasive/cutting/grinding devices. This is why diamond wheels are now relatively cheap. The ones I get are out of HK. thk.hk. Although they are budget priced they are good quality products especially for DIY operators.
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