View Full Version : Building my own air compressor, have some ?s.

01-15-2008, 06:46 PM
Yes, I'm building my own air compressor. I just bought a 60 gal craftsman 6.5hp, 14 amp, oil free compressor, with a blown rod. My plans is to use a Harbor Freight 5 hp 15cfm @ 40 psi, 13 cfm @ 90 psi air compressor pump, with a 5 hp 21 amp motor. One question I have can I still use the craftsman pressure switch for the new 21 amp motor? I would reuse the 6.5 motor, but I have to machine a new front cover, and come up with some type of mounting configuration for it. I just don't have enough time right now. Also what are you thoughts about my plans?


01-15-2008, 07:31 PM
the thing with that pump is it puts out that rating @ 5HP, the motor isnt going to run @ 5HP under load more like 3HP so its gonna drop the pump output down alot, i would try to find a 6.5 HP motor, ebay is your best friend for this type of rebuild.

Phil V
01-15-2008, 08:08 PM
If you have to buy the 21 amp 5 hp motor and the compressor pump then you're further ahead to just buy a whole new air compressor. That 21 amp 5hp motor is putting out an actual full 5 hp while that supposedly 6.5 hp crapsman compressor motor at 14 amps is in reality a 3 hp motor.

A 21 amp 5 hp motor lists for around $340.00 and the Horrible Freight compressor pump is going to cost you close to $150.00 to your front door. Thats close to $500 while you could buy a brand new compressor for less money than that.

As far as reusing the pressure switch - A lot of those switches are rated at 15amps which wouldn't hold up to the 21 amp 5 hp motor. Look the pressure switch over closely and it should state what amperage its rated for.

I just got a smokin' deal on a 220vac single phase 22 amp 5 hp GE compressor duty electric motor. I was at Tractor Supply last Sunday and I was looking at compressor motors (I was bored and needed to get out of the house for a while). Anyway there sits a 5 hp 22 amp motor with a yellow tag on it stating it was " defective, the wiring at the back was done wrong ". It had a reduced price tag down to $20.00 (brand new motor). So I figured for $20 how far wrong could I go. Actually I figured someone bought the new motor, got it home and decided they didn't want to sink close to $200.00 into their old air compressor so they brought the motor back and said the motor was "bad" so they could get their money back. I got the motor home and hooked it up to 220v and it was bad. So I took the rear plate off and the first thing I checked was the thermal overload protection switch/breaker. It read bad with my ohm meter so I rewired the switch to a different lug on the back of the switch. Put it all back together and it runs great. I put it on my Quincy compressor project which is now complete and looks as well as runs like brand new. It will be going on ebay here in next day or so.

01-16-2008, 08:50 AM
I bought the HF compressor, ( I took the head off of one, and it seems fairly decent), for $90.00, I bought a TSC 5hp motor for $175.00, and the craftsman compressor for $70.00. Where can I buy a 21 amp pressure switch at? I've looked a few compressors for over $600 at that cfm, I think I'm doing ok.