Depends what you want to run, you need about 3 to 4 hp to run "proper"
air tools continuously, otherwise you are doing stop start to wait for
the reservoir to fill.
Whatever you do, don't buy anything except belt coupled motor and
compressor, the direct coupled cheap stuff is absolute crap and won't
I've got an old 1hp vtwin ingersoll rand that I paid a tenner for
because it wouldn't get up to pressure, strip it, clean the valve
plates and it is as good as new. The IR sits on top of a big reservoir
and is so quiet I can stand next to it and talk on the phone.
I also have a more compact (towable on a trolley) single cylinder 2.5
hp "home made" job with a lot less reservoir per compressor
In extremis I can of course parallel these two up for 3.5 hp.
I mention these two because they make a nice example of the compressor
engineers common attitude that cfm is everything and reservoir is
nothing, in practice one is mobile and one is static, and thankfully
coincidentally the static one is the quietest one, so it gets used all
The noisier portable one is used when portable is required, or when
extra oomph is required.
The IR is enough to run things like an air ratchet intermittently, eg
a recent rear body transplant on a landie where it is often many
seconds between fasteners.
Most important thing is get proper PCL type connections, and buy a new
pressure regulator and a new dryer for your output air line,
compressed air is otherwise full of gunk...
Should also mention, tanks need draining of condendate regularly, or
they rust from the inside out, the old IR tank is made from 1/4"
Should also mention, when running long airlines, eg I've got 10 and 15
metres, so 25 metres of airline, especially the narrower 8mm stuff,
significantly reduces the flow at the end of the line, hence me having
a portable and a mobile trolley one.
As for tools....... one bonus of air tools is you can use em with
impunity outdoors in the damp.
Blow Gun - use it all the time.
Tyre inflator - use it regularly, godsend, esp at 50p a pop machines
Cut off saw - great tool when you need it.
Air ratchet - again, great tool when you need it.
Die grinder - great tool when you need it.
Orbital sander - great tool when you need it.
air hammer/chisel (not the wheel nut air hammer) - useful tool
air drill - nice for drilling out studs and things
Spray guns (various) - again great tools when you need them.
Quickest way to kill any air tool is forget to oil it once a week
whether you use it or not.