On Mon, 08 Nov 2010 08:03:41 -0600, Ignoramus27561
wrote:

On 2010-11-08, Michael Koblic wrote:
Air tools are a new thing to me. At this point all I own is a brad nailer
which I have not used in anger.

I have been looking at the general principles guiding air tool use and there
are questions that I have not found satisfactory answer to:

1) Air tools are usually given specs including operating pressure (often 90
psi) and air flow (in CFM). If the available compressor is not rated for the
given flow "the tool will not perform properly". How is this
manifested?

If the compressor cannot keep up, inlet pressure will drop.

Then you stop and let the compressor refill the reservoir enough so
the regulator works.

E.g. a grinder: Will it turn slower? Less torque? Both?

Both

Neither, if you just quit and let things catch up when pressure
downstream of the regulator drops below 90 PSIG.

Will it not turn at all? Will it keep turning till the operating
pressure drops to some level and it stops, i.e is it an on-off
thing?

Yes

No.

2) Lowering the compressor operating pressure should increase the available
flow.

Usually, not by much.

What does lowering the operating pressure do to the air-tool? I am
looking at pressure x flow as similar to current x voltage but I am not sure
this analogy holds in this application. If the electrical analogy holds I
cannot see the air tool "suck" more air because the pressure dropped, in
fact I would intuitively assume *less* flow.

Usually that is the case indeed.

3) In practical terms, if a tool requiring "average" 3 CFM is operated from
a 2.7 CFM @90 psi will it just underperform all the time or will it require
a shorter duty cycle (and when "on" it will run at full power)?

It will underperform.

It'll work just fine if you just stop to let it catch up when
reservoir pressure drops to below what the regulator can regulate.