Truing up

I have an aluminium based cup style CBN grinding wheel that has diamond face.

Having mounted it on my bench grinder it is running out on the diamond face.

How are these normaly trued up?

Edited By John Rudd on 15/11/2018 15:12:03

Edited By John Rudd on 15/11/2018 15:13:40

Hi john the last time that I did this I had to make a new flange drive for the grinder as that was running out causing the wheel to run out. I made a new piece that located on the main spindle then stepped down the bore to suit the drive size then the outer was a copy of the original washer but relieved so that it clamped in the wheel in the right place this was a press fit and Loctite just to make sure. then I made a bush to locate the centre of the wheel and another washer to clamp the outside of the wheel. it isn't recommended to dress these much but you can get a dressing kit which consists of an arbour and a very soft dressing wheel which you wind in to the revolving diamond wheel creating lots of dust and a dressed wheel.

David

David,

I've checked the grinder spindle, in fact dismantled it, put the rotor in the lathe and machine 'sufficient' from the spindle to ensure minimal runout. A new backing piece was also made to ensure the grinding wheel was sitting true to the spindle axis...

Wheel face is still not running true, about 1-2 thou out of true. I have read that this acceptable, but not sure if this correct....and they can be trued using Carbide?

Mine was running out, so I used one of these silicon carbide cleaning/truing stones from Axminster; I'm sure other sources are available.

Bill

Bill,

Looks like thats whats needed and fits the bill nicely... Axminster are just up the road from me, so a visit is in order..Many thnx for the tip..

Why not true the aluminium relative to the diamond material?

Axminster writes:

"The aluminium oxide has no effect on the diamond surface itself, except to restore its free-cutting action."

and I read that as it only cleans and does not true.

As Nick writes, best seems to be to true the aluminium relative to the diamond, but you have to be careful not to damage the diamond face if you clamp the grinding wheel. Niko.

I read somewhere of a guy who used a green wheel on his surface grinder to true the face of his CBN wheel.

I dont have a surface grinder nor access to one, clamping the wheel to a surface is done how?

I bored mine on the faceplate using conventional clamping methods (and care).

I bored mine on the faceplate using conventional clamping methods (and care).

[Can't see how to remove this duplicate post - sorry]

Edited By ega on 16/11/2018 09:52:25

With this type of wheel you can't true them up by resurfacing as the cutting surface is only a fraction of the base material much the same as diamond stones. So you will need to investigate at other problems or the wheel you have has not been machined correct in the first place.

The wheel I had seemed to be diamond dust embedded in a very hard rubber like compound.
I've no idea what John's wheel is like, but the stone seemed to do the job OK on mine.

I'm assuming it removed some of the bonding material, more preferentially on the high spots to start with, until the very highest diamond grit particles were undermined and removed. It then went on to expose fresh sharp diamond grit edges on the rest of the wheel.

Initially my cup wheel only cut on about 1/3 of its face, and a small portion opposite, both of which were also becoming glazed. This suggests to me that the cutting face wasn't perfectly flat, and no amount of refacing the backing plate would cure the problem.

After I'd offered up the stone, it seemed to cut more freely, and on all of the wheel's face.

I'm certainly no expert, never having received any formal training, so happy to be corrected by anyone who actually knows what they are doing.

At the end of the day, I figured that it would do the job or not, with little to lose at a small few quid for the stone, and a cheap replacement wheel off ebay is only about £6.50

An article worth reading HERE

Bill

You have it right Bill the diamonds (or CBN) are held in a binding matrix which should erode at a slow rate to expose fresh cutting edges as the erosion releases worn-out diamonds. The make-up of the binder determines the 'hardness' of the wheel and the size and density of the abrasive medium gives the wheel various other characteristics.

Some wheels do not erode because the diamonds are electro-plated onto a metal carrier, but the aluminium wheels with the brownish-coloured cutting edges certainly can be dressed.

John Rudd, you can use various methods to hold an ally part for surface grinding, just as you can actually surface grind aluminium, brass, 300-series stainless etc. Or you could simply bolt it to the table through the centre hole.