Subject: Sandblasting question...

From: [email-masked] (Joe Wiggins)
Date: Wed, 26 Jan 94 15:20:28 GMT

I'd like to get a sandblasting outfit so I can do it myself and not be
dependent on the one local (undependable) guy who does it.  My mechanic
tells me that small home versions are worthless... that it takes forever
to prepare a small piece of metal for painting for example.  Sears has
sandblasting kits for as low as $40 (and recommends using them with at
least a 1 horsepower compressor).  

Has anyone actually done home sandblasting?  Is it easy?  Fun?  What
size/capacity compressor should be used?

If this is the wrong newsgroup, is there a more appropriate one?

Thanks in advance,
Joe

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From: [email-masked] (Chuck Lampman)
Date: Wed, 26 Jan 1994 15:37:11 -0500

> size/capacity compressor should be used?

Yeah, I use the type of set-up you're talking about in restoring old 
cars, and it is dirty, hot, slow miserable work.

Most home outfits are siphon-type guns, meaning that the abrasive 
container isn't pressurized. This means more air and less sand than 
the expensive pressurized ones. They only let you do two or three 
square inches a minute, which is painfully slow. Add to that the 
fact that anything less than a 5hp compressor is going to spend 
about 2/3 of its time recharging, and you'll get precious little work
done in a given amount of time. 

And, of course, even though you are bundled up and wearing a hood, 
the sand will get in every orfice of your body, and every fold of your 
clothes. In summer, the cover-up is stifling here in Georgia, and 
the sand sticks to the sweat. 

I still get the damned thing out once in a while, though- sometimes
its the only way to get the job done. Sigh.
 
Chuck Lampman
[email-masked]

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From: [email-masked] (Eric Murray)
Date: Wed, 26 Jan 1994 19:50:52 GMT

In article <[email-masked]> [email-masked] (Joe Wiggins) writes:
>Has anyone actually done home sandblasting?

Yea.

>  Is it easy?

Pretty much.

>  Fun?

Not really.

>  What size/capacity compressor should be used?

At least 2hp.  You want enough motor to keep the compressor
tank at full pressure.  If you have to stop to let the motor
catch up every few minutes, you'll be hating life.

Also get a decent air mask (the filter type, preferably with
pre-filters that are replaceable).  You don't want to be breathing
all the dust from the sand, or you'll be coughing up brown gunk
for a week.  Get all the grease & dirt off the metal... grease will
cause the sand particles to stick, and then you're trying to
sandblast sand with sand- not too effective.

I made a sandblasting area using plastic sheeting in a storage
room that's attached to the house.  I put a tarp down on the floor
to catch the sand so I could recycle it.  Make sure you have good 
lighting- I didn't, and had to re-setup a couple times to do some
most blasting when I thought I was "done".

I was sandblasting a motorcycle frame to remove a lot of rust.
If I were doing something larger, or wanted to do a really good
job (i.e. for concours) I'd farm it out to a shop.

Your mechanic is right about the time it takes, "forever" is
pretty close.

--
  Eric Murray                                             [email-masked]
      "Archiving the net is like washing toilet paper!"- Leader Kibo

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From: [email-masked] (f.w.kerfoot..iii)
Date: Wed, 26 Jan 1994 20:57:12 GMT

>From article <[email-masked]>, by [email-masked] (Joe Wiggins):
> 

I have the inexpensive Sears snadblaster and a 2 HP Sears compressor.
It is at best marginally suitable for large jobs. I did the tube
frame of a Lotus 23 with it, removing many layers of paint, and I later
did most of the unibody of a Porsche 911. For that kind of task I would
try very hard to buy something bigger, or subcontract it out. On the
other hand I recently used this combination to prepare my 3/4"/ft
live steamer for painting (piece by piece), using a homebuilt plywood
sandblasting box, and it worked wonderfully. I don't think you would
want anything more agressive (read "faster") for this kind of work.
For the record, I used #0 sandblasting sand, which I reuse (at least
of the model work). I also added a water trap, including a home-made
condenser (6' of copper tubing carrying the air, submerged in a bucket
of water, with ice if you want).

Frank Kerfoot
[email-masked]

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From: [email-masked] (Eric Murray)
Date: Thu, 27 Jan 1994 00:15:56 GMT

>From article <[email-masked]>, by [email-masked] (Joe Wiggins):
[..]

>of water, with ice if you want).

I'd forgotten about the water problem- I also had that.  Wet sand
doesn't work very well.

I'm curious about your water trap- did you need to provide a place for
the water to go, or just let it build up in the coils?
I'd be kinda concerned about soldering a 'Y' into the copper tubing
for the water to run into.  The air pressure might rupture the
soldered joint.

Or is 60-70 psi ok in soldered coppr tubing?

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From: [email-masked] (f.w.kerfoot..iii)
Date: Thu, 27 Jan 1994 01:33:19 GMT

>From article <[email-masked]>, by [email-masked] (Eric Murray):

All I did was place the 6 feet or so of tubing between the tank output
(I have a ball valve directly on the tank output for leak-free shutoff,
then a pipe to compression fitting) and the standard water trap supplied
by Sears. The water trap by itself doesn't do much, since the water at
that point is still in vapor form, so it passes right through the trap.
With the 6' of tubing passing through cold water, the air is cooled enough
to condense the water into tiny droplets. The droplets move with the air
flow until they reach the Sears water trap, where they accumulate in the
plastic cup forming the bottom of the trap. There is a simple bleed valve
to remove the water (the air pressure forces it out very nicely).
I had to find a separate mounting for the trap, since the copper tube
couldn't support it very well. I coiled the copper tube in about a 8"
diameter coil with the turns spaced about 1", so the whole coil fits
nicely into a bucket. I only add water to the bucket when I need dry air
(typically sandblasting, but painting is another place where it would be
useful). I have never had a "wet sand" problem when using the condenser.

> Or is 60-70 psi ok in soldered coppr tubing?

I don't know about soldered copper. I used 1/4" seamless copper and
compression fittings, and I really didn't worry much about my 125 PSI
or so max. There is not much area there. My intuition would tell me that
1/2" nominal (9/16"OD actual) copper pipe with soldered fittings
would be fine at 125 PSI, but it probably would be wise to look it up.

Frank Kerfoot
[email-masked]

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From: [email-masked] (Richard Engelbrecht-Wiggans)
Date: Wed, 26 Jan 94 19:44:25 CST

In article <[email-masked]>
[email-masked] (Eric Murray) writes:
 
>
>Or is 60-70 psi ok in soldered copper tubing?
>
Residential water pressure can run that high, and
soldered copper plumbing rarely fails. (But there
is relatively little chance of injury from a pipe
full of water bursting. Something full of air
bursting could be dangerous. So, just because
soldered copper is good enough for home plumbing
doesn't necessarily mean that is good for 60-70
psi air.)
 
..Richard E+17

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From: [email-masked] (Michael Burlage)
Date: 27 Jan 1994 04:31:15 GMT

>>Or is 60-70 psi ok in soldered copper tubing?

I have a 1/2 inch copper water pipe in my lawnmower repair shop
for an air line. it has seen 125# of air daily for 4 years
with no problems so far...

-- 
"Onward through the fog"
                         - Power-Hitter
[email-masked]
[email-masked]

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From: [email-masked] (gary preckshot)
Date: 27 Jan 1994 17:12:59 GMT

[..stuff about sandblasting..]

> size/capacity compressor should be used?

Yup, and I also was well acquainted with it professionally when I was a
field engineer at a US Govt Dam.
Easy? Yeah, you don't need a Ph.D.
Fun? Only for a little while.
Size compressor, etc. ---

Sandblasting was one of the main reasons I went from a so-called 3 Hp
Crapsman compressor to a 5 Hp 2-stage CH compressor.  A lot has been
written in this and other groups about compressor horsepower.  The best
indicator is SCFM, which apparently is still an average value, rather than
peak.  Looking at a recent Grizzly catalog, I noted a "5Hp" compressor that
supplied 12.5 CFM at 175 psi, and a "7.5Hp" compressor that supplied 25 CFM
at 175 psi.  Why do you suppose that was?  Answer: the duty cycle of the
smaller compressor was less than 100%.

So, what does that have to do with sandblasting?  Sandblasting uses A LOT
OF AIR.  You need at least 12.5 CFM, and more comfortably 18.  If you buy a
so-called 3HP compressor that supplies 7 CFM, you're gonna wait while that
sucker pumps back up, and then you're gonna wait while its little motor
cools off so you can push the little red button back in so's it'll run
again.  Of course, if you get one of those cutesy Crapsman plastic
sandblasters, maybe other things will hold you up rather than the
compressor.

I've got a Harbor Freight pressurized steel tank blaster and it works ok. 
It isn't a wonder of modern technology, but I dunno what I'd do with a
Crapsman computerized blaster.  Count grains, maybe?  Sandblasting is
crude, but much better than wire brushes, sandpaper, or grinders.  You
should expect equipment of appropriate crudity and strength.

Gary

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From: [email-masked] (john.r.miller)
Date: Thu, 27 Jan 1994 18:59:21 GMT

> If this is the wrong newsgroup, is there a more appropriate one?

I have been sandblasting with one of the small units for several years.
They are a "suction" based design, the air from the compressor passes
over a hole in the gun and the sand is sucked out of the hole and into
the air stream (of course, a hose is connected from the "hole" in the
gun to the canister that contains the sand).

In general, this type of arrangement works good for removing paint and
crud from wood and metal surfaces. However, it takes a lot of time to
remove heavy rust such as what you find on car frames or old boat
keels. To effectively remove the heavy rust, you must have the
pressurized type of sandblaster. The canister containing the sand is
pressurized and so the sand is forced out of the canister under pressure,
not "sucked" as indicated above.

This type of sandblaster is much more
expensize (10x the price of the suction type) and can be dangerous. You
should wear a full body suit and hood and have an external air supply when you
use it. Furthermore, they use a lot more air to do their job and require
a much bigger compressor. The suction type only requires a filter mask,
hood and gloves and about 1.5 - 2 HP.

I won't have anything to do with the pressurized blasters, my suction type
does the job 90% of the time, for the other 10%, I hire the job out and
let them take the risks.

The sears sandblaster for 40$ is just fine, check harbor freight, I have seen
the same thing there for about 10$ less.

					john miller

					Columbus, Ohio

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From: [email-masked] (Basse)
Date: Thu, 27 Jan 1994 20:01:06 GMT

> If this is the wrong newsgroup, is there a more appropriate one?

It depends on how much you want to do.  I have one of the $40 ones with a 1.5
hp compressor driving it.  It's a lot like a spray gun.  It takes me about 
15 to 20 minutes per square foot to sandblast metal.  Works great for cleaning
spark plugs.   Less then 5 seconds per plug.  It's a hassle to constantly refill
the 1qt. canister though so I built a plywood box with a glass window and a 
funnel shaped bottom to catch the sand.  I recycle this sand by drawing it back 
into the gun with a hose placed on the pickup tube after I removed the 1 qt. 
canister.   The box also keeps the sand from going everywhere.  It's a terrible
mess if you don't use something to contain it.  I guess it depends on how big 
your project is and how much time you want to spend on it.
My two cents worth.
Hank

--
Hank Basse      | IBM internal: basse@basse
512 838-1442    | [email-masked]
Only my opinion.| [email-masked]

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From: [email-masked] (Basse)
Date: Thu, 27 Jan 1994 21:39:58 GMT

In article <[email-masked]>, [email-masked] (Eric Murray) writes:
> for a week.

To keep the dust and sand off yourself and clothing, you might try a plastic 
rain suit with a hood made of a garbage bag with a plexiglas window duct taped
into it and maybe a hat to help support the whole thing (like a beekeeper).
The whole suit and hood can be kept under a slight positive pressure with a
vacuum cleaner with an extension hose connected to its blower outlet. 
If the vacuum runs too fast and blows too much air, it can be throttled with
a light dimmer or rheostat.  This should ventilate the suit-hood combination 
fairly well and prevent grit from getting on you and in your lungs since all 
openings and leaks will have air coming out.  Just an idea, might work.
Hank Basse

> Get all the grease & dirt off the metal... grease will

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From: [email-masked] (Andy Dingley)
Date: Thu, 27 Jan 1994 20:53:19 +0000

In article <[email-masked]>
           [email-masked] "Joe Wiggins" writes:
> I'd like to get a sandblasting outfit

Home sandblasting sucks.

I initially bought one of the Machine Mart spot sandblast guns (siphon type)
and a bucket of silicon carbide grit. It's great, *within* *its*
*limitations*. As a means of taking car bodywork back to bare steel for
retouching rust spots or small dents, then it's great. You don't care that it
only prepares a small spot each time, and as it has a rubber shroud around
the nozzle, then it doesn't need a booth. It also does a nice job of etching
glass through a steel or sticky-backed-plastic mask.

For big areas, you can forget it.

I've since bought a pressure pot sandblaster for about 80 quid (advertised in
the back of Practical Classics). This is *much* better, although it's taxing
on my 12 cfm compressor. My only criticism of this thing is that the delivery
hose is too short, so that to use it in a bench-top blast cabinet I have to
stand the pot on the bench alongside it, making refilling a bit awkward. A
control valve on the nozzle itself might be nice too - I might try one of the
after-market ones.

I really only use my sand blaster in a sealed blast cabinet, so eye
protection isn't an issue. The cabinet is DIY, an old galzanised water tank
turned on its side, with a hinged wooden front. The viewing window is just
glass, with a replaceable layer of cling-film (saran wrap) on the inside.
Hand holes use long rubber drain-cleaning gloves and the blast hose goes in
through one of a number of 6" lengths of lay-flat hosepipe. An air *outlet*
is important too - when I first made it, the air pressure built up and popped
the front door open in my face ! No inside lights or grit hopper yet - maybe
some day.

For big stuff, I started off by doing it outdoors (in the middle of a big
field) but it really does need some sort of booth. If I was going to make a
habit of this, I'd get a steel cargo container and use that - or maybe buy a
custom sandblast booth (the joys of having a recesssion in the UK - lots of
cheap tools, if you only have the space for them). As it is, I've pretty much
decided that anything that will fit in the cabinet can be tackled myself,
anything bigger than that gets farmed out to our local (and equally
unreliable) commercial sandblaster.

You don't need goggles or a facemask for sand blasting, what you need is a
*helmet*, together with a proper fabric hood coming down over your shoulders.
I wouldn't even like to use the full-face visor I use for casting metal, if
that much airborne grit is flying around, I feel you do need the extra
protection of a hood. I sewed my own up from an old construction workers
hard hat and a few lengths of proofed canvas. For breathing, I use the same
filtered air supply that I use for spraying 2-pack paints. A good filter mask
might do, but it's so hot in there that a powered air filter pump would be
well worth it.

One other point - don't try *sand*blasting, always use proper grit. I
believe sand is still used for some materials, but it is a real hazard for
breathing problems and silicosis. Sand fragments into tiny shards which
irritate the lungs, synthetic grits break into more equally sized pieces and
so can be stopped by facemasks.

--
   _                              Andy Dingley
 /  ) ' ,_  _,  /   _ ) _/_       Codesmiths of Newcastle
/_ / / / / (_) /_) (_)  /_        [email-masked]
          (_)                     +44 091 230 1695

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From: [email-masked] (James W. Swonger)
Date: Thu, 27 Jan 1994 19:15:00 GMT

>size/capacity compressor should be used?

 Sandblasting is energy intensive and inefficient. To get a high rate
of material removal you have to have to throw a lot of air and sand. You
by with a little cup-type gun and a 1HP compressor if all you want to do
is clean out some rust spots. Big pieces will require proportionately more
time or more power.

 The bigger blasters need more air; even the small portable one I have
(the kind with the hopper you can carry on a strap) need a 5HP 
compressor. The big commercial outfits have nice, big stationary
compressors which can run big nozzles all day long. 

 Suction feed sandblasters are not as nice as pressure feed ones. The 
former depend on air velocity, hence air pressure, to pull the sand.
If the compressor can only hold 40-60PSI at the flow you need the sand 
delivery will be spotty. I made a pressurized hopper which I use to feed 
my suction-type gun, using a spare compressor tank mounted on end. I 
feed this with regulated air so that the sand flow trickles out when the
blast air is idle; when it's on, the sand has no problems being drawn up.

 For air delivery you'll want a minimum of 3/8" air hose. Forget about using 
1/4", unless you have a high pressure setpoint and can tolerate 20-40PSI
of pressure drop in the hose. I have air plumbed in the garage and use 
garden hose to run the sandblaster; no pressure drop to speak of, and I
can work 50 ft from the garage, on the lawn where sand is unlikely to 
cause marital strife.

 I can't say sandblasting is fun. It's the only tool for certain situations,
that's all.
-- 
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