Air Compressor for multi-use (powder coating, impact wrench)

[burningman]

I am looking to buy an air compressor tank for two purposes: powder coating and car work (removing lug nuts from wheels of car)

From what I understand, powder coating only requires a small PSI, whereas car work requires upwards of 120PSI and constant use of air.

Can anyone confirm what specs are needed for a compressor that will be used for powder coating and auto work?
Thanks.

[panterafanatic]

You need high pressure for car lug nuts since it takes a lot of power to loosen/remove them. Not sure the actual PSI needed, but 120 should suffice. Powder coating on the other hand, I have no idea.

Asked my old man (he's an auto mechanic) and he said that 100-120 PSI will do, but you'll want 5 or 8 HP, and about a 30 gallon tank. They use about 160PSI, but I doubt you'll need to use it as much as a shop. The reason for the bigger tank is that cars require much more volume per minute than low pressure powder coating

[tiges_ tendres]

I have a mid sized unit.  Once you get into that 120psi range, the price does jump up considerably.  For stuff like powder coating, just buy an in line regulator and adjust down to 5-8 psi.  So it doesnt really matter what psi capabilities the unit is for powder coating, tank size is probably more important.  It gets really irritating when the thing is refilling every 10 seconds. 

I cant speak for other uses.

[burningman]

Thanks for the replies. I've spotted an 8 gallon Campbell Hausfeld with a bunch air tools and 120 max psi for around $299. I'd better check the horse power.

[KazooMan]

Wooooooooohhhhhh,

Let's not get overboard here

I bought an air compressor MANY years ago to do two main tasks.

(1) Blow put my sprinkler system in the fall 

(2) Power an impact wrench to use when I switch between my summer and winter wheels.

Neither of these tasks requires a huge compressor.  Mine has what I would estimate as a 5 gallon tank.  It has a maximum pressure cutoff of just over 100 psi.  To blow out the irrigation system I let it build up the pressure unti it shuts off and then open the valve for that sector.  It blows out the water and then some mix with air and water.  When the compressor turns on again I shut the irrigation valve and then repeat the process.  After two or three cycles all I see is a blast of water vapor coming out of the heads.  Takes less than an hour to do the whole system and I have paid for the compressor MANY times since I bought it by not hiring this simple task out (and I have loaned it out to friends to do the same).

As for the lug nuts on your wheels, you should consult your owner's manual.  My impact wrench gives a suggested input pressure of about 90 psi.  When I use that I can follow up with a good torque wrench to finish the job.  Any more pressure and I would over tighten the bolts.  You do not want to over tighten the lug nuts or bolts on your wheels.  None of these pieces of equipment is outrageously expensive, but I would suggest that the place to spend your money is on a good torque wrench. 

I have to admit that I don't have any expertise in regards to air compressors and powder coating.  What I would be concerned with is not the maximum pressure rating of the compressor but the actual delivery rate.  A tiny compressor with a minuscule tank can build up 100 psi.  You need a certain amount of air FLOW at a certain PSI rating to do powder coating.  I don't have any idea what these specs might be, but you should check them out before buying.

[burningman]

Thanks for your advice. I have a buddy who uses a 5 gallon for his car with no problems. he just complains about the constant refilling.
I think the 8 gallon might be the compressor I get.

[amptramp]

I have a 15 gallon pump with up to 125 psi capability.  The advantage of a large tank is that there is less of a jolt to the pressure when the compressor cycles on, so it is better for painting.  But it takes several minutes to come up to pressure, so a smaller unit would be fine (and cheaper) if you are not looking for the ultimate in control - and powder coating should not require as much control as paint because the material flows together after application when it is heated.

One recommendation: drain the tank after every use.  Under pressure, the moisture in the air condenses and can cause the tank to rust.  There is a radiator drain%^&* type valve on the bottom of the tank - open it after every use.

[jdub]

I would highly recommend a decent moisture separator as well if you're doing any kind of coating- it'll help prevent problems with application, adhesion, etc. and will keep the equipment in better shape, too. 

[head_spaz]

For airbrushing a small hobby compressor should be fine.
But for semi-regular use with impact tools, you're gonna want at least a 20 gallon tank, and a high volume compressor so it doesn't take forever to recharge.

[burningman]

I would highly recommend a decent moisture separator as well if you're doing any kind of coating- it'll help prevent problems with application, adhesion, etc. and will keep the equipment in better shape, too. 

I've never heard of a moisture separator. Do you know of one for Campbell Hausfeld brand tanks?

[PRR]

I air-wrenched lugs on a 1979 Thunderbird with a 3/4 horse half-gallon compressor.

In a shop, you need to go zzzt-zzzt-zzzt-zzzt-zzzt zzzt-zzzt-zzzt-zzzt-zzzt zzzt-zzzt-zzzt-zzzt-zzzt zzzt-zzzt-zzzt-zzzt-zzzt to pay the rent.

I was happy to go zz....zz....t, zz....zz....t, zz....zz....t, zz....zz....t. That's a LOT less work, and a bit faster, than doing big rusty lugs by hand.

Yeah, the motor runs most of the time. It would wear out in a few thousand cars. A bigger tank and motor would run many-many thousand cars. But I only had the one air-wrenchable car. (The Miata lugs I did with a small ratchet.) I still have and use that compressor 20 years later. And it was only like $139.... if it quits it will owe me nothing.

You shouldn't actually install wheels with an air-wrench. It is a time-saver to get the lugs snug while the mechanic's time-clock ticks. He should use a hand-wrench to go from just-touching to exactly-tight. I've always used lever-length, body size, and factory spec to get "right-tight", but a few vehicles need to run in a narrow crack between loose and busted. There was a series of Ford trucks that were shedding wheels due to imprecise tightness. These DO want a torque wrench.

Do you really need an air-wrench to take lugs off your car? I only did because I had the wrench and pump, and that particular Blunderbird had real problems with its wheels. In 40 years I've otherwise only used cross-wrench or 1/2" ratchet with maybe a cheater. (I'm actually doing the Accord with the factory joke; it has not irritated me enuff to buy a metric cross-wrench.)

While you can do lugs zz..zz..t, zz..zz..t, and you can blip a rough sander, some jobs like muffler clamp grinding and engine block drilling do NOT like to stop while the compressor recovers. It's hard to find your spot, you lose it when you pause, the wheel or bit binds on re-start and breaks.

Classic spray painting is lower pressure, like 40psi, but low pressure hardly increases your available CFM. Car-size sprayers use high CFM for quick smooth production. You do not want the pump to run low, spray sputter, lose your wet edge. OTOH there are many other sprayers, and the size a non-car painter might use, with the slow paints, would run on my little pump. (And an air-brush pump is a teeny toy next to my pump; that's about control, not production.)

Same thinking for air-nailer. With the small pump and a finish nailer, I get 2 or 3 nails then the pump runs. When I finish-nail, I work so slow that the pump is recovered before I am set for the next nail. But get a roofing crew, six guys all going bam bam bam bam bam bam, you don't want them butt-sitting at $1/minute while pump recovers. They use 5HP-10HP gas-engine compressors with a good tank to cover peaks.

[burningman]

You shouldn't actually install wheels with an air-wrench. It is a time-saver to get the lugs snug while the mechanic's time-clock ticks. He should use a hand-wrench to go from just-touching to exactly-tight. I've always used lever-length, body size, and factory spec to get "right-tight", but a few vehicles need to run in a narrow crack between loose and busted. There was a series of Ford trucks that were shedding wheels due to imprecise tightness. These DO want a torque wrench.

For wheel installation, I'll be hand tightening before putting the wrench to it, just to make sure the lug nut does get cross threaded.
I'm not sure if I'm following you completely. Are you saying that a torque wrench shouldn't be used for installing wheels? I could do it manually but figured that if I'm going to get a compressor, might as well use it for a couple of things (powder coat, car work etc)

[terminalgs]

look at the SCFM (or CFM) requirements of the tools you want to use, then look at the same numbers on a potential compressor.  It'll usually be something like 8 SCFM @ 45 PSI. 

air-wrenches or impact wrenches (they are different)  can run for a short time to do the job  (like loosening lugs),  so your compressor might need to run a lot, but its not continuous use,  so its not as critical for this kind of tool.     HVLP paint guns,  orbital sanders,  and sand blasters do need continuous use and can suck a lot of air fast, so the SCFM @ PSI measurement is important for these tools.   check your powder coating gun's specs.     If its like an HVLP gun, it needs a huge volume of air to run continuously ( HVLP guns vary from as high as 14SCFM @ 40 PSI to     7SCFM@40 ).   decent sand blasters require a huge volume of air as well. 

you'll see a big difference in price for oil sump compressor vs. dry sump compressors.  the oil sump compressors are much much quieter.

wheel lugs:   start threads by hand,   (1) if you are semi lazy,  set the max torque on your impact wrench to the minimum  and then tighten the lugs,,  the lugs aren't tight enough to drive on,,  but you saved yourself about 10 seconds per lug of spinning a 4 way wrench.  then tighten the rest of the way with the 4-way by hand.  lower the tire, tighten the rest of the way.     do not use an air wrench as the final tightening device...  you will probably over-tighten them.  then, at midnight on a dark road in the dark, you are trying to loosen the lugs with with a worthless factory provided 12" tire iron.  (2) if you aren't super lazy,  tighten all lugs by hand with a tire iron.