CBN Wheels

[steadyeddie]

Has anyone bought a 40mm wide CBN wheel to fit a Record 8" grinder ? I'm thinking of upgrading to CBN and I wondered if there were any pitfalls. I've read that the bushing set from Axminster isn't compatible with this type of grinder unless 'alterations ' are made. Thanks in advance, Dave

 

[Deadeye]

I've just been through this in the past few weeks.
Record were unhelpful.
The arbour isn't the diameter stated in the manual (mine was 16mm); and it's too short to take the Axminster bushings and a 40mm wheel; and the Axminster bushings don't fit the Arbour anyway.
I gave up and bought a different grinder.
Which now turns out to be out of stock.
It's not going well.
Sorry.

 

[steadyeddie]

Cheers Deadeye. It appears you are having less luck than me !

 

[Sideways]

Yes. I got the wheel first (Axminster), then farted about for ages looking for a grinder to fit. The record 25+40mm one was the first I found after a lot of looking that seemed credible. There were some quality issues but the grinder and wheel are both OK and fit together using Axy evolution bushes. I believe these are still available in 5/8" versions (their code 104372, but NOT 16mm). It's a little annoying how difficult it is to get details like spindle dia and especially spindle length of a grinder to figure this out in advance. My tip is to buy all the bits online around the same time. Try them together and if things don't fit, send any or all of them back under distance selling right of return. It'll only cost you the postage.
I'm pretty sure that the newer model 8" grinder I bought had 5/8" bushes. I started a thread about balancing it titled something like "chasing down a problem..."
If I was buying again, I'd buy 32mm wheels or 40mm ones with a reduced width at the hub. There aren't many grinders out there with a long enough spindle to take the 40mm wheel I bought with full thickness hub and rather bulky bushes. Axminster didn't set out to sell a wheel no one could use, it sort of happened by accident, but they were unable to point me towards a single grinder that they knew would take the wheel. It would be much easier to buy their 8" trade grinder and 32mm wheels made to fit it. Slow speed (1400rpm) or standard doesn't matter.

 

[steadyeddie]

Thank you. Appreciate the info.

 

[bobajobob]

I fitted a 32mm axminster cbn to my record on the 25mm wheel side so retaining the 40mm alox wheel. Careful consideration needed for guard clearance. Had to make the bushes myself but works fine. Motor is under-powered but ok when up to speed. Made numerous other mods to get an effective system. My 30 year old 6" grinder with pink wheels stomps this.

 

[Robbo3]

Has anyone bought a 40mm wide CBN wheel to fit a Record 8" grinder ? I'm thinking of upgrading to CBN and I wondered if there were any pitfalls. I've read that the bushing set from Axminster isn't compatible with this type of grinder unless 'alterations ' are made. Thanks in advance, Dave

Mike Waldt did a video on installing & using 40mm CBN wheels on a Record 8" grinder (starts at about 5 munutes).
- https://www.youtube.com/watch?v=zeWJl3DRxDw

 

[gregmcateer]

The Toolpost may be able to help - they seem to stock/ know what's what if you're in a jam

 

[steadyeddie]

The Toolpost may be able to help - they seem to stock/ know what's what if you're in a jam

I spoke to Toolpost yesterday. Unfortunately,the wheel I require is out of stock and will be for a couple of months.

 

[GPat]

This is all very interesting. I just bought a Record 200mm grinder and have just ordered the Axminster 40mm wide CBN wheel and bushes. So the consensus is that it will not fit ?? Does anyone know what make of wheel Mike put on to his grinder ??

 

[Spectric]

This adaptor allows fitting a wheel with a 32mm bore to a grinder shaft of 1/2 inch , ie the 6 inch Charnwood .

https://bivenmachinerysales.co.uk/product/charnwood-bore-adaptor-bush-for-cbn-grinding-wheel/

You could easily get this bored out to 5/8 as there is only 3.175 mm difference.

 

[Sideways]

This is all very interesting. I just bought a Record 200mm grinder and have just ordered the Axminster 40mm wide CBN wheel and bushes. So the consensus is that it will not fit ?? Does anyone know what make of wheel Mike put on to his grinder ??

No.
If you read the post above, it says that I have an Axminster 40mm CBN wheel with Axminster machined bushes fitted on the wide end of the Record 8" (200mm) grinder. That's the opposite end to @bobajobob above (nice work BTW !).
So unless they changed any of the bits in the last 4 ? years, yes it does fit.

Note that I left the Record inner flange in place to properly align the wheel within the guard.

 

[Spectric]

@Sideways what is the peripheral speed like for sharpening chiesels on an 8 inch wheel on the Record grinder. I really need to sharpen some chiesels and maybe this is a way to go.

 

[Sideways]

8" wheel at 2800 rpm on a standard bench grinder gives 5,900 surface feet / min.
Cubic Boron Nitride is 2 to 3 times harder than Silicon Carbide and half as hard as diamond.
It's very chemically stable at high temperature. Fine to 1200C even more and that is much higher than for diamond.
The upshot is that CBN can be used for high speed grinding at surface speeds between 6 and 12 thousand SFM. So no worries at all about running a CBN wheel on a standard, not slow speed, 8" bench grinder. The Axminster wheel is labelled 100 to 3500 rpm so notwithstanding all the preamble, supplier also says it's fine on a standard grinder (2 pole motor, 2,800 to 3,000 rpm).

CBN isn't durable enough for sharpening tungsten carbide - it will cut it but the wear rate is too high. For TC you need a green grit wheel or diamond.
CBN is ideal for HSS and other hard alloys. Perfect for modern chisels and should be ideal for HSS drill bits and old style HSS engineering lathe tools.
Don't clog it up with non ferrous or mild steels.

Generally turners use CBN wheels dry because heat isn't really a problem. If you must use a lube / coolant, it's interesting that at high temperatures, water chemically affects the oxide that naturally forms on the surface of boron crystals. It might be wise to do some reading before putting CBN, water and hot metal together.

I got mine for sharpening turning chisels. It's a coarse 80 grit and absolutely eats steel. Great for (re)shaping as it does all the grunt so quickly and with so little effort. Takes a light touch. 120g is the recommended wheel for finishing but the finish off the 80g needs very little done to it. It's not like off an 80 grit belt. If I reground a blade on the 80g, I'd only take the very edge to a finer stone or paper.