Joe wrote:
....
Don't knock it 'til you've tried it. My twin hammer Porter-Cable works
just fine with my Hitachi twin tank portable (1.5 gallon, or whatever)
set at 110 PSI. The OP stated 135 lb-ft torque is reached by many
impacts in less than two seconds. Calculations are trumped by actual
facts every time.

Well, mayhaps yours does; even my 1/2" I-R certainly won't off the small
roughly equivalent to OP's oilless de-Vilbiss compressor...and I
wouldn't venture to recommend someone plan on making a purchase on the
basis of a grossly undersized compressor.

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