Diamond grinder wheels – thoughts?

[peterhodParticipant @peterhod]

Hi Guys

 

I have just bought a new 8″ bench grinder to replace my 30 year old one. I only use it for grinding drills and occasionally grinding lathe tools.

I have rather got out of the habit of grinding lathe tools as I use mostly indexable carbine tipped tools. I want to get back into it again

I normally just have a fine grey wheel for h.s.s and a green grit wheel for carbide. I have been thinking of a diamond wheel for carbide, I can get one for £32. What are your thoughts please?

Thanks

Pete

[bernard towersParticipant @bernardtowers37738]

As far as I’m concerned green grit wheels need effective dust extraction to make them worthwhile so my preference is for diamond. dont fall into the trap of cheap chinese wheels they are much too fine for most work unless you sharpen No80 drills daily!!!

[Pete RimmerParticipant @peterimmer30576]

I have a 8″ diamond (CBN) wheel and a 4″ CBN cupwheel that i use to touch up lathe tools. for wholesale grinding I would use a standard aluminium oxide or silicon carbide wheel but for finishing, setting angles, touching up cutting edges the CBN is hard to beat and makes little dust. They work especially well for Stellite which dulls standard wheels quickly.

[David George 1Participant @davidgeorge1]

I recently started to modify a engraving tool grinder to sharpen my carbide tools on and whilst I have used a diamond cup wheel with a flat plate support to rest the tool on similar to a standard grinding wheel the wheel had a slight wobble on the face which when sharpening carbide turning and boring tools on I would like to dress the wheel true and flat. I have had to buy a diamond dressing attachment which was second hand for just over £100.0 which was a great price from a new one of at least £300.0 .   You also have to have a dressing stick to clear the diamonds in the wheel after dressing and my wheel now runs true and cuts well better than when I first bought it.

 

Picture of dressing diamond wheel.

Thoughts on using a diamond wheel need attention perhaps a CBN wheel may be easier to dress?

David

 

 

[bernard towers]

On bernard towers Said:

As far as I’m concerned green grit wheels need effective dust extraction to make them worthwhile so my preference is for diamond. dont fall into the trap of cheap chinese wheels they are much too fine for most work unless you sharpen No80 drills daily!!!

One problem is  ‘what is a cheap chinese wheel?’. Most of this stuff is made in China and the same thing is available under different brand names at all different prices.

I think I will probably stick with a green grit wheel as it seems that if I went the diamond route I would need 2 diamond wheels, one for roughing and one for fine sharpening. At the moment I fine finish my tools with a diamond file. My main thing is sharpening carbide boring tools.

My new 8″ grinder was only £49 from Screwfix and amazing quality for the money – I would recommend it. My old grinder is a heavy duty Clarke one that is £150 today. I prefer the Screwfix one apart from the tool rests which I will remake at the weekend. The old one vibrated. When I put the green grit one from the old grinder on my new grinder, that grinder vibrates as well. I dressed the wheel but it still vibrates although appears to run true. It’s a Silverline one.

I’ll think on this.

Pete

 

[John HaineParticipant @johnhaine32865]

CBN wheels often have the grit bonded to the true surface of a steel wheel by an electrolytic process.  Provided they are properly made they should inherently run true, if you tried to “dress” then you would just remove all the abrasive!

[bernard towersParticipant @bernardtowers37738]

Sorry but most of them may be made in China but a lot of GOOD ones are made here and in the US.Mine are mostly Norton.

[PeteParticipant @pete41194]

In a home workshop and even with the best bench grinder in the world, diamond wheel grinding should be thought of as a light finishing or lapping tool. What the precision grinding industry can and does ought to be ignored since there using optimized, heavy, rigid machines, specialized wheels, the correct flood coolant etc for there high production rates. And for anything other than solid, braised, or replaceable tipped carbide tools, your wheel speeds will be far too high for even finish grinding. Yes it can work for awhile, but the high heat that’s generated between the diamond grit in the wheel surface and non carbide surfaces on the tool your grinding causes a chemical reaction between the carbon in the diamonds and the iron in the steel that seriously degrades and ruins the diamonds.

For all of these reasons, low rpm lapping tools along with at least a bit of water cooling and lubrication are the much better method. The now out of production Glendo Accu-Finish machines ran at around 300 rpm to keep that heat under control. But they were intended as and are only a light finishing or surface lapping machine. I’d be using one of those green grit silicone carbide grinding wheels for the bulk metal removal and shaping, and a slow speed diamond wheel for the finish lapping. Before those Accu-Finish machines were discontinued, they and any other slow speed carbide grinder I know of were quite expensive. $1500 + and $200-$300 for each different diamond wheel grit. There’s one much cheaper and possible way around that. While there easier to find in North America than the UK, I did find this. https://www.einhell.co.uk/p/4418008-tc-wg-200/ With the right diameter of diamond face wheel to pick up the water, and your own shop made tool rest, it might work just as well. Machining your own wheel adapters to fit whatever wheel mounting size and design one of those wet grinders use is probably going to be needed as well.

[JohnFParticipant @johnf59703]

Defiantly no expert on diamond or CBN wheels but my understanding is that Diamond is good/better for Carbide tools and CBN for HSS.

I have a 4″ CBN cup wheel and used it for sharpening end mills, it works very well.  Speed is 3000rpm and cuts dry.

Diamond I have yet to investigate but I recall the tool grinding department using these for grinding factory made brazed tipped tools as well as re-sharpening commercial ones though many times we sharpen these free hand on a diamond lap with coolant, again running probably 2000rpm ??

A couple of links that may be of interest — John

A Comprehensive Guide to CBN Grinding Wheels

Frequently Asked Questions

 

[old martParticipant @oldmart]

Having the plated type of diamond or CBN wheels has one advantage, they will not shatter. At the museum, we have two grinders using these diamond wheels which do get used for hss and the occasional drill bit, as well as carbide and the small ammount of steel ground on them will not destroy them quickly like being in an industrial enviroment.

CBN is cubic boron nitride, almost as hard as diamond, used for hard steels because it is immune to being dissolved chemically into the iron which has an affinity for carbon as elevated temperatures, diamond is an allatrope of carbon.

[Neil LickfoldParticipant @neillickfold44316]

The two types are what I call Desic diamond or CBN wheels, the plated ones, like diamond files etc

The other is resin bonded diamond and CBN wheels.  The resin bonded is in two sub types, wet grinding and dry grinding.

I have recently purchased a Chinese made D bit grinder and a spare hub,(hub is yet to arrive). It comes with the Brown resin bonded diamond wheel of about 150 grit. I have some sorting to do with the hubs and the spindle taper, so once sorted, will make my own hubs.

Back to the wheels themselves. You can buy from China the wheels at a very good price. My suspicion is that they are seconds, so the bodies don’t run true etc to the diamond / cbn matrix.

My solution, I lapped flat the wheel face on a steel plate and 46 grit from the sand blaster, until it is flat all over. Took about 3 to 5 mins or so and makes a brown powder mess. Used news paper to catch all the dust and grit ect. iThen mounted the wheel to the faceplate with a piece of printer paper between the bond and the faceplate. With a piece of shim stock between the stylus and the bonded matrix, and a central clamp, indicate the compound to be running true as can be. In my case was about 0.06mm between the high and lows . Turn the outer diameter of the Alloy body. and the end face close to the central washer true. Set up some outer clamps, remove and true the inner bore to Ø25.4mm, and out to Ø55mm. Made a plastic washer 25.38 od and 19.98 id to fit the supplied hub. (Hub is undersized at 19.97mm). Remounted the hub, indicated the hub flange face to be true. Mounted the wheel. It runs very well. The inner flange face is cut with a reverse tool , looks like an L and only cut to about 44mm diameter. Just a skim to make it true. The L piece is 11 mm long from the side of the bar.

This will not be as true as if I had a proper drag dressing wheel kit like shown above. They are the best way of dressing resin bonded Diamond/CBN wheels. Another option is grinding some Cast Iron, or a piece of Mild steel. To get a sharp front edge, there needs to be a relief at the front of the material. On way around this is to attach a block of cast or ms to the holder. That way it can be dressed from the inside to out.

I have a vacuum cleaner pipe close to the wheel and workpiece to collect some dust etc. It goes through a cyclone dust collector that also has a clear catch can. I have an added filter inside the vacuum cleaner between the bags and the original filter to catch any fine dust that may escape. I wear a N95 mask to reduce the amount of dust getting into me as well.

With the above, the centre of my wheel had a runout buy 0.3mm and the bore was Ø20.1mm. Some of the offset may have happened with my lapping of the wheel face. (its 50mm thick). But the wheel did run very badly as supplied.  The diamond matrix is actually quite well controlled for thickness and the inner and outer ring being very concentric. It was not very well centred and the stock was not that well made.

[VicParticipant @vic]

I was looking to buy a 4” CBN wheel a while ago but all the affordable versions come from China and frequently listed as “Diamond CBN”. Not knowing exactly what I would be buying I abandoned my search. I am currently using a 4” electroplated Diamond wheel for some small jobs and it seems to work quite well.

[peterhodParticipant @peterhod]

Hi guys

 

thank you for your input. I am going to buy one of these and find out for myself!

I am not in a production environment, I am just a guy working out of his garage the bottom of the garden.

It is only for occasional use, I take onboard what Old Mart said and have similar usage. I actually use small diamond grinding wheels in a dremel type machine to grind tungstens for my TIG. I have been using the same one for over a year and it still works fine. If the diamond grinder wheel lasted me a year that would be fine to.

Thanks again

Pete

[VicParticipant @vic]

A good source for CBN wheels in 6” and 8” diameters is to look at wood turning suppliers. They are quite popular with some wood turners.

https://www.axminstertools.com/axminster-evolution-series-cbn-wheels-180g-103915?utm_source=tag&utm_medium=affiliates&utm_content=4366&tagrid=71390405&glCountry=GB

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