Carborundum (silicon carbide) grinding wheel

Due to increase of use of carbide tooling I have installed green carborundum wheel on my grinder. It works well with carbides, eg it sharpens them but it is rather crap for HSS. Of course I can also install normal corundum wheel on the other side of spindle but by doing so I will loose my roughing up wheel which is used and abused quite a lot and I cannot live without it.

Is there any way out of this conundrum, eg a grade of wheel which will deal with both carbide and HSS or buying second grinder is the only practical way forward (because replacing wheel on the spindle is invariably associated with trueing)?

Martin

You could fit a CBN (cubic boron nitride) wheel which will happily do both but they are a bit spendy! This from Axminster only £100 bar 4p

John

Edit: Add link

Edited By Journeyman on 26/03/2018 18:22:08

A diamond wheel will deal with both materials.

Mike

I think JS used to have a thin diamond disk sandwiched with a standard wheel for touching up carbide.

Edited By Mike Poole on 26/03/2018 18:30:56

Why not buy another grinder just for green grit wheels?

Get another grinder for green grit and mount them like this to save space. (Yes these 2 both have pink wheels, coarse and fine and the lower grinder is a 1400 rpm oldie) These are for woodturning tool sharpening on the front of the wheel.

Thanks for comments.

@Robbo & Baz,

This is perhaps the best idea. Issues related to space were causing most concerns. It is important for stones of top grinder not to allign with your eyes, just in case...

Just try not to buy too many similar machines because even if now space is still there it is not difficult to stuff up workshop to the point that some other machines might no longer be feasible.

@Journeyman,

All suppliers of CBN electroplated wheels searched by me are shy of recommending them for carbide. I am sure they will cope, but maybe their life is going to be drastically reduced...

@Mike,

Diamonds are not recommended for HSS, unless used on low speeds, much below speed of my grinder. I have some cheap Chinese variete on lapping machine and it is doing its job very well

With a bit of work, it's quite possible to change wheels without losing balance & alignment or to use a cheap grinder (<£20). Buy some AlOx and diamond cup & dish wheels and you have the best of both worlds.

See Harold Halls pages here and a book recommendation... **LINK**

HTH

Jon

Now that is an arragement I really like - why did I not think of it! With the addition of whetstone wheel for joinery tools and wire brush and mop wheel my grinding alcove is a bit congested and this is an excellent solution. Will make a nice welding project to do a suitable steel frame.

Can you weld wood ?

.

Allegedly

**LINK**

http://www.constructionchemicals.co.uk/Wood-Weld-PU-Wood-Adhesive-5-10-Minute-Cure-310ml-.html

MichaelG.

This one made out of 18mm melamine faced chipboard reinforced with oak fillets and left over from a kitchen construction was intended as a prototype to test the feasibility of the idea. So there are some bare edges where it has been adjusted (ie bits sawn off). However it works so well that a "proper" one has never been made.

It has been in use for 15 years + and is plenty rigid enough for the weight of the top grinder and the light loads imposed when sharpening tools.  As it is for sharpening turning chisels very little metal is removed so mess is minimal.

Edited By Robbo on 28/03/2018 11:35:08

Yes it's called grafting, but the wood needs to be alive.

regards Martin

I think that is a bit of a ‘stretch of the imagination’

Question might be: Are my wife’s broken arm bones welding themselves back together? I don’t think of it as such.

Well it's about as close as you are going to get. Welding is essentially forming a new crystal lattice of metal atoms or molecules grafting forms a cellular lattice of living wood. Probabbly the closest welding gets to grafting is diffusion bonding where metal molecules or atoms diffuse across an interface forming a single crystal.

regards Martin

I have read somewhere that using a diamond wheel on HSS is not a good idea because the carbon (diamond) can transfer to the steel at the temperature of sparks, messing up its (the steel's) carefully worked out properties. This sounds plausible but is it right?

Tim

Diamond seems a popular choice in compact drill and milling cutter grinding machines, it may be that the theory does not give a serious problem in practical use or the manufacturers just ignore it.

Mike

I suppose it's possible, but not very likely. Firstly there's not much carbon in a diamond wheel. Secondly, compared to Diamond, most steels soften at a much lower temperature. Therefore steel fragments are shaved off and carry the heat away before the diamond gets hot enough to decompose.

Sparks are spectacular but I think they're mostly caused by tiny steel particles catching fire as they fly through the air, not directly by friction during the cutting process. If that's true, much of the obvious heat in grinding occurs away from the cutting surface. Anyone tried grinding steel in a vacuum or in an inert gas?

Of course it's easy to overheat the work during grinding. HSS doesn't like that at all. I suspect any damage to HSS from a diamond wheel is more likely caused by overheating than carbon transfer.

Just guessing - do we have an expert opinion?

Dave

It is rather diamond what is being destroyed by hot steel and not steel being affected by diamond. Diamond grinding discs used to be expensive (now thanks to Chinese this got changed), so reckless use leading to accelerated wear was discouraged.

At lower speeds problem is not as great.

Martin

This is a cheap diamond wheel sold as a tile cutting wheel from Harbor Freight. Just twinned along side a silicone carbide bench grinder wheel.