Blasting Media - Which Grit Grade??

[Fortunate Son]

Hi - have been a reader of the forum for about a year now and am (slowly) learning to MIG weld whilst restoring my 1971 VW Dormobile Early Bay Window.

I have a quick question that I am hoping you may be able to help with - I have recently taken the plunge and bought a compressor, spot blast gun and will be getting a bench top type blast cabinet soon (if Santa gets his finger out!). Thing is I can't work out which grade aluminium oxide grit to get. I will more than likely be buying from Machine Mart (for convenience) and they sell 60/80 blend, 80/120 blend and 60, 80 and 120 single (malts?!!)

I understand these grades in sandpaper speak, but what do they mean for blasting? I will be blasting fairly light surface rust only as I have cut out anything that has pitted deeply. I also have the facility to re-sieve media as I work in materials testing labs that have sieves - maybe I could buy blended grit and regrade into separate sizes??

Your advice on this one would be much appreciated guys. Cheers in advance, Andy

 

[rtbcomp]

Welcome to the forum.

To be honest I wouldn't use aluminium oxide for steel, it's a bit expensive, especially if you buy it from Machine Mart.

Look in the gritblasting section of the Links forum for more ideas (and greater confusion).

 

[Uncle Joe]

I've got to agree with rtb on this one. Aluminium oxide is a bit to expensive to use on steel.

If you are still intent on using it though, use the finest grade that will get the job done, and still allow for successful keying of any surface treatment.

 

[rtbcomp]

On the other hand if you went for the coarsest that your gun can handle you'll get more multiple uses out of it before it turns to dust.

Finer grit tends to cost more than coarse.

 

[Uncle Joe]

True enough, but then the poor people that sell the stuff wont get rich, will they?

At least my supplier only has my black diamond in one grade! I think thats because nobody else is mad enough to use it!

 

[stormin]

True enough, but then the poor people that sell the stuff wont get rich, will they?

At least my supplier only has my black diamond in one grade! I think thats because nobody else is mad enough to use it!

Black diamond! I bet that cuts well. What pressure are you using it at?
How much per tonne?

 

[Chipper]

I got a 25kg bag from some ebay shop. Was a good price vs the other online sellers I found. No idea who now, was a while back. For the very small and occasional bits I do, with sift/re-use, it actually seems to work out cheap compared to throwaway sand (not to mention the PITA of cooking sand dry and the dust). As I say only occasional use, smallish bits though.

 

[brightspark]

Black diamond! I bet that cuts well. What pressure are you using it at?
How much per tonne?

there flogging j blast expendable for £5.90 for 50kg on teeside or newcastle

 

[rtbcomp]

there flogging j blast expendable for £5.90 for 50kg on teeside or newcastle

I normally pay £5.00 + vat for 25 Kg for J-Blast Supafine

 

[brightspark]

I normally pay £5.00 + vat for 25 Kg for J-Blast Supafine

ildouble check that price they only keep 0.2 to 1.5mm grit they dont stock supafine

 

[brightspark]

ildouble check that price they only keep 0.2 to 1.5mm grit they dont stock supafine

I've just checked scangrits price for grade 2 0.2 to 0.7. It's £116 per tonne collected or £40 delivered