For a desoldering iron application, I think you'll end up wanting something
more effective than a Harbor Freight generator (not that I've tried them,
but I've used numerous different brands of commercial desoldering stations).

The Air-Vac desoldering iron venturi generator is very effective for two
reasons.. it's designed very well (and provides instantaneous vacuum at the
tip), and because it's located on the handpiece (being closer to the tip).
The older irons are often on eBay and sometimes don't even get any bids.
These desoldering tools are the style with the glass collection chamber
above/alongside the heater-tip assy.

Many other systems use an electric pump with a reciprocating diaphram and
rubber-like reed valves. The glass collection chamber is inside the
handpiece (which is more compact), and the handpiece has a long piece of
flexible tubing between the handpiece and pump. This introduces a little
delay in the vacuum, but they work fairly well.
The electric pump is typically a 12V, 1 to 2 amp PM DC motor (about 2" x 3")
that's run intermittently with 24V.
The pump diaphram is about 1-1/4" diameter with about a 1/8" stroke.

Nearly all of the heater-tip assemblies of the more recent models are low
voltage heaters.. typically 24V. For a scratch-built improvised design, you
wouldn't need closed loop temperature control, but a temperature adjustment
will be a good idea (triac or variac), so you can turn the temp down for
more delicate, easily damaged circuit board work.
For circuit board work, you'll definitely want the tip to be earth grounded.
The Pace heaters are short, and aren't as versatile as the longer heaters
are.

The glass vial is a nice sight glass feature, but a metal tubing chamber
works just as well. Silicone rubber seals are usually used at the ends of
the chamber.

Another feature you might want to include would be the versatility to enable
you to use hot air coming out of the tip for surface mount components or
some other non-contact application (such as heat shrink tubing). You'll
probably want to implement a needle valve similar to a CFH gage, since the
air flow needs to be low to maintain heat.

Fitting numerous features into a handpiece are a bit complicated, but you
can use a foot switch to energize the solenoid for the air source (that way,
the iron heat is replenished/saturated when the vacuum is off), or on/off
for an electric pump.

For solder/flux vapor filters you can use a variety of materials, but you
should avoid steel wool if you're doing circuit board repairs.. a single
strand of wool can be hard to find if the circuit doesn't work (I found that
out many years ago).
I've used roll-type bandage gauze for filters.. it's a convenient size to
roll up into the pellet shape.

WB
................

"Norm Dresner" wrote in message
...
I'd like to build a desoldering station. Conventionally this is done with
a
soldering iron and a vacuum source. In the best units the tip of the iron
is hollow and the vacuum draws through it. But I don't want to purchase a
vacuum pump for the same reason that I don't want to purchase a commercial
soldering station: cost. I have a compressor. Since there are COTS
desoldering stations that work from a compressed air supply it's possible,
using the Venturi effect, I believe. Are there any on-line tutorials for
creating a vacuum from an air source?

TIA
Norm