On Sat, 13 Jun 2009 16:44:50 -0700 (PDT), rckchp
wrote:

On Jun 12, 3:56*pm, Michael Horowitz wrote:
I know the compressor requirements are stated when considering a
sandblaster, but is there anyway to measure the effectiveness e.g. is
my blaster taking off paint as quickly as someone elses?

As an example, I can take off an 1/8" strip of paint at about
1"/second, but have no idea what should be happening - Mike

I sandblast for my living (cemetery lettering) and the most common
misconception is more pressure strips/cleans faster.....when actually
the more CFM (cubic feet per minute) is what works best.

true but all you have is a pressure gauge and whatever the compressor
delivers. usually what you get with a pump system that deliveres
slower than you are using it, is a reducing pressure and eventually
the need to wait for a pump up. with the bigger pumps what you notice
is that the compressor just keeps on delivering at whatever pressure
you dial up.

150psi will remove rust, paint etc almost completely in a single pass.
100 psi will remove slowly
80 psi is a very gentle action if at all.

also you can moderate the "cutting" action (if you'd call it that) by
angling the gun off perpendicular to the job.

blasting thin metal distorts the sheet all right. the surface closest
to the gun is peened into compression and this causes the sheet to
grow toward you. (aluminium sheet -thats a good use for 60psi blasting
and a very gentle touch)




In the past
when I was an active EAA member I did a few blast jobs on Cub fuselage
structures. I use a 100 CFM compressor, such as used by utility crews
to run jackhammers, etc. Most tool rental places have 85-185 CFM
machines for rent....anything from 50 CFM up will work fine.

There are two "schools of thought" about how much pressure to use when
doing steel tube fuselage. One says use as low pressure as possible to
minimize damage to the tubing.....the other says to use as high
pressure as possible to intentionally blast thru and expose weak (thin
from internal rust) spots, which can then be cut out and new tubing
spliced/welded in. And of course, never blast thin sheet metal (steel
or aluminum) as the frictional heat can warp the sheet metal .
Chemical stripper works better for sheet metal.