A lot depends on what tools,and how much you use them.If you are doing body-work,you want a 2-stage(not just 2-cylinder,but 2-stage,they have 1-large primary-cylinder,and a smaller secondary that increases pressure).For high-demand/high volume(D/A sanders,sand-blasting,etc...)you want a minimum of 60gal,2-stage with 150-175psi,then regulate it down for your tools that need certain requirements.For once in a while,short-duration work,smaller compressors will work,but it will be slower-going for sanding or blastingStay away from direct-drive oil-free units if you are looking for long run-cycles like sanding,they get very hot,and don't last long.I had a 30gal,single-stage Craftsman for a few years,it worked decent for normal stuff like impacts,etc...but sanding killed it.I bought a 1962 Kellogg 2-stage,60-gal.that was like new,and when I'm running a D/A,it will come on,build to 150psi,and shut-down,while sanding.Granted,its' a very large unit compared to what most would use at home,but its' comparable to larger shop-style compressors.I ran a 30gal.Direct-Drive Sanborn in my service-truck,it worked fine for doing tires on big-trucks,just had to wait for it to catch up every few lug-nuts,but it ran a 1" tire-gun.I tried it for sanding once and it wasn't doing well.Line-size matters too,as do couplers.I run 3/8 hoses for normal stuff,1/2" for big-stuff,but I use a larger than normal 3/8"-coupler at the tank,it makes quite a difference(standard couplers are 1/4",and are restrictive).You can run an impact and see the difference with the fittings.At least use the larger fitting at the inlet-end of the hose,then your only restriction is at the tool,which is 1/4" anyway.If the compressor has a Regulated-Manifold,remove the line that feeds it,and "T" it there or use another plugged,spot on the tank to tap in for your supply,alot of those manifolds are ultra-restrictive.My Sanborn couldn't run a die-grinder very well as shipped,I connected direct to the tank and it was great after that.Hope this helps.
