I have one of those siphon fed cheapo jobbies. As people have said, they are
fine for SMALL parts. Anything larger than an engine (4 cylinder) is
a pain. It is slow, uses lots of air, and generally frustrating.
Here is the problem. These units require masses of air. Very few home
compressors (even two stage) put out enough air to run them for extended
times. If you run a compressor continuously (which you will for anything
less than a small job) its gets hot, and the air gets hot, then you get
moisture problems (even with in line filters and moisture traps and meters
of metal tubing) which blocks the siphon fed units and they splutter and
get blocked. I have not used a pressure fed unit.
BTW My compressor puts out 18 cfm @ 90 lbs and it could NOT keep up with
the siphon fed unit even running full time.
The unspoken and generally unknown (I think) info about compressors.
The air out put of a compressor is what they can put out under ideal conditions
when new with clean filters etc. The air requirement of a tool is usually
displayed on the tool box or tool. This is usually the air consumption
for usage 25% or 50% of the time. Many tools require 4 cfm. So you
might think great, my little 4 hp 8 cfm compressor should be fine.
WRONG. Many of those 4 cfm tools like cut off tools or impact
wrenches use 4 cfm at 25% usage. Full time or constant usage will require
4 x 4cfm = 16 cfm. The siphon fed sandblasters require......wait for it......
about 15-17 cfm with medium nozzle at 50% usage. Thus you will need
a compressor that puts out about 30 cfm to run the sandblaster continuously
and the compressor will also run continously to keep up.
Although of course you seldom use impact wrenches continuously so the
small compressors are fine for those tools. Most compressors have
problems with tools that run continously (10 mins + at a time) such as
sanders, sandblasters, etc. I wanted to sandblast the engine bay of my
midget. I will need to rent one of those Ingersol Rand units you pull
behind your car and pressure fed unit.
All this is explained in the De Vilblis air-tool book in your local Home Base
air-tool department.
You can get cheap ceramic nozzles from Harbour Freight, about $6 for 10
I think. Haven't used them yet so don't know if they are any good.
When you sandblast, cover every inch of your body, wear eye, skin and ear
protection and still plan on digging sand from every part of your body
after extended blasting.
Happy blasting.
Cheers Dennis
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