difference between a white aluminum oxide and a blue aluminum oxide wheel

[whensparksfly]

what is the difference between a white aluminum oxide and a blue aluminum oxide bench grinder wheel?I have the blue/grey fine and rough will this work for sharping hss or do i need a white wheel?
thanks

 

[BillFarworth]

No necessary you can do the sharping hss with the fine grey Disk.White disk is stated as Very fine!
Check this site:

http://www.peterchild.co.uk/osc/sharpening-grinding-wheels-c-29_37.html

 

[Pete.]

I have a white and I find it does a great job of sharpening, holds it's shape well and cuts quite cool, compared to the old blue wheel it replaced.

 

[hotrodder]

Colour doesn't denote coarsness Bill. White is a 'premium' Aloxide... it breaks down better than the grey wheels i.e. cuts faster and cooler. Because it breaks down exposing fresh grit easily they can wear relatively quickly. Adding some chromium oxide makes them 'tougher' so you get a fast cut that runs cooler and doesn't wear as quickly. These are pink and then red as chromium content increases. Blue is a sometimes described as microcrystalline, sometimes as ceramic. 'Ceramic' covers a lot of ground, probably just a different form of Aloxide [/cynical]. Never used 'em but the claim is that they are 'better' still in that they self sharpen very well as they wear and wear very slowly i.e. need dressing far less often. I'm thinking (alright guessing) that the blue wheels might only work properly on harder steels kinda like how green/silicon carbide is fantastic on the right material and pants for 'general' grinding

All of 'em will sharpen HSS, the difference is in how effeciently- pausing to cool the work, dress the wheel etc

 

[whensparksfly]

where do i get a pink 8 inch wheel

 

[BillFarworth]

Colour is not fact hr you are right general speaking the white in this kind of stuff means very fine comparative the Grey and Blue.It like the abrasive stuff .White is for the end bit fine polishing.I assume it is the same .
Maybe wrong.I don't have one and manage to Sharpe my chisels quite well if I do so work with a water stone by hand in the end .

 

[hotrodder]

Dunno if they do 8" but RDG tools sell 'em alongside white, grey and silicon carbide wheels. No idea what the quality is like. A proper industrial supplier will have a wider range but they'll often be sold in 'grinding wheel speak' rather than English i.e. instead of coarse/med/fine it'll be like this... http://www.mscdirect.co.uk/TRU-00390M/SEARCH:KEYWORD/product.html with 29A46K describing what it is... 29a is the grain type, 46 is the grain (grit) size and K is hardness. While the A in 29a denotes Aloxide it'd be too simple to have 29a = the pink flavour. Here for example WA is white aloxide and PA is the pink/red flavour... http://www.abtec4abrasives.com/benchpedestal-grinding-wheels-with-a-diameter-of-200mm-8-300-c.asp

Bill, white wheels are available from 46 grit same as other flavours. They might go onto finer grits than some of the other flavours but then no one uses say Aloxide paper in 2000 grit or silicon carbide in 60 grit. Different abrasives/blends work differently, it's a sharpness versus brittleness thing and how the grains break down in use. Plain ol' grey wheels will work as you say but they tend to blunt instead of breaking down exposing fresh grit (friable is the techy term) which means on harder steels they don't cut as quickly and heat the tool more.