compressor revisited - painting &blasting.

[whit_iii]

I might take advantage of the tax free weekend to purchase a compressor. In performing research within this site and others, it would appear that at least 8 cfm minimum, but if one plans to paint oneself 20cfm at 100psi is needed. This is essentially stating spend at least 400, but you should spend 800. Has anyone done their own painting using a compressor and if so what type of compressor wrt cfm and tank size? Should one just bag trying to paint their own stuff and go for the lessor compressor?. There have been similar requirements stated for blasting ~15cfm. I would be curious to know similar information...what type of blasting, compressor type and tank size. Thanks for the info.

 

[sparkydave]

I'm curious, what kind of paint outfit takes 20CFM? I didn't think even an HVLP took that much. I have a garden variety CH automotive paint sprayer that takes 5 SCFM at 40 PSI. I have an oil free compressor which is supposedly a little better for painting since it minimizes the chances of having oil getting into the spray, but I have a filter/water trap on it anyway. Bear in mind that the oil free compressors are cheap, very noisy, and don't last as long. At 20 CFM you would certainly need something massive. Oh yeah, and don't fall for the horsepower ratings, they are usually inflated (no pun intended).
-Dave

 

[whit_iii]

Depending on who you ask the min. is 8, but the pro's say 20. Elsewhere I have found that for any tool, you should have a compressor capable of 50% more than the tool demands. For example, a tool needed 6 CFM should have a compressor rated at 9 CFM. From the Mactool webside for compressors: Impact wrenches require anything from 5 to 20 (3/8; 1/2; 3/4). body sander, bead breakers require 12. HLVP paint spray is listed at 15. The craftsman site seems to indicate much small rates.


https://members.tripod.com/~bobstory/faq.html#CFM1
18.2. WHAT SIZE AIR-COMPRESSOR DO YOU NEED TO PAINT A CAR?
The compressor should be capable of delivering a minimum 20 cfm at 90 psi.

30. Compressor PSI
30.1. but it only put out about 9 cfm @ 90 psi. Am I nuts to hope to do any painting with a rig like this? It looks like a two stage almost doubles the price. Let's assume I'm not after a show quality paint job. I'm considering painting an old
You can, but it will be awkward. When your pressure drops the paint will not atomize well, and will orange peel. If you wait for the pressure to build up, the paint will dry and you will have dry spots. Maybe if you do it in sections?

18.1. My question: WHAT SIZE AIR-COMPRESSOR DO YOU NEED TO PAINT A CAR? Will a 25 gallon 5hp compressor work for painting that has a 5 SCFM @ 90 psi / 7.5 SCFM @ 40 psi. If so, any limitations? If not, what kinds of problems will I most likely encounter?
You will run out of air. This will lead to dry spray areas, since you will not be able to paint fast enough to keep the surface wet.
=======
But other sites reference the following:
https://www.theautoist.com/body_repairs.htm
A compressor that can produce at least 8 cubic feet a minute flow at 40 PSI with a 20 gallon tank. Horsepower and compressor type don't matter, the above specs do. This little compressor won't keep up with any air sander, but it will a paint gun or any pneumatic powered wrench in a home tool box.

 

[beaulieu]

one other thing , get a real "piston" compressor

Sears sels "oil-less" compressors that use a diapram ,
these do not work as well, 2 of my friends have had to replace them, one with low hours and needed a whole new pump.

 

[Guest]

When dealing with some main workshop tools such as a compressor, always get better then you think you need. You won't regret it.
Gary

 

[whit_iii]

painting &blasting Personal Experiences???

Based on this info, I don't think I will end up doing any of my own painting....Hopefully 8cfm would be enough to run sand blasting. I would be interested in hearing folks personal experiences doing sandblasting and/or painting and what type of compressor they have.

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Ask the Expert Question-and-Answer Archive
HVLP Spray Gun & Compressor
https://www.paintcenter.org/rj/nov04a.cfm

Q. I read you article about the HVLP guns. My question is can I use a HVLP gun with a regular 33 gallon Craftsman compressor or do I need a HVLP compressor? Also, which gun do you recommend for a HVLP and Non HVLP? I want gravity fed guns. I would appreciate it. Thanks


I looked at the Craftsman website for the product specification at the 33-gallon Craftsman compressor. According to the specification the compressor can deliver up to 150 psig, but the volume of air that is can deliver at 40 psig = 8.6 Standard Cubic Feet per Minute (SCFM) and at 90 psig = 6.4 SCFM. For most HVLP spray guns this is not sufficient air volume to alloow you atomize paint. Most HVLP guns need approximately 15-25 SCFM for optimum operation. If you look at the Craftsman website it appears that the compressor is intended for operating power tools.
<=

 

[lawguy]

Re: painting &blasting Personal Experiences???

Would it be nice to have 20cfm? Sure, but alot of people have turned out nice work with much, much less. It depends on many things including what type of paint you are using, your gun.

On Tony Barnhill's website, his friend John Weimer states what you need is: "A compressor that can produce at least 8 cubic feet a minute flow at 40 PSI with a 20 gallon tank."

https://www.theautoist.com/body_repairs.htm

Bigger would be nice, but you aren't opening a Maaco.

 

[TRMark]

I recently shot a car with a DeVilbiss Finishline III HVLP. The gun uses 13cfm at 23psi. The compressor is a Coleman Powermate with a 27 gallon tank rated at 8.2cfm at 40psi, 5.6 at 90. I ran out of air and had to adjust the inlet air pressure often to keep it around the 23psi. I piped the air out of the side of the tank at the the large plug. I was concerned about air volume if I were to use the compressor regulator and associated small piping. After leaving the tank the air goes through about 40' of 1/2" pipe before going through a particle filter and dryer. There is an earlier discussion about moisture and pipe on this forum. I will not paint another car until I replace my compressor with an old fashioned piston type. For small jobs it works fine. All this to paint a 77 Lancia, I must be nuts.

 

[Banjo]

I have the craftsman 33 gal. 150 psi compressor. I bought it last fall after a lot of research and comparing. We sprayed my dads MGB using that and a relativly cheap HVLP gravity feed spray gun(one of those value packs from a tool sale).
It came out great. I was very happy at the performance of the compressor.it kept up well, and it handles my air tools wonderfully.
I plan on picking up my blast cabinet really soon so I can't help you there yet.
The only drawback to the craftsman unit is it's noise. It's not really any louder than other compressors, but its a rotary style pump so its an ear splitting buzz instead of the old Chugga chugga of traditional units.
Good luck in your decision.

 

[whit_iii]

Campbell-Hausfeld 26-gallon tank[230 volt]VT6271??

Thanks for the feedback. I think I am going for the following:
Single stage, two cylinder, 3 Running HP, cast iron portable 26-gallon tank (230 volt)
Model: VT6271
Cast Iron twin cylinder oil lubricated pump - for long life and quiet operation
Made in the US with a 3 year warranty - quality construction backed by the best warranty in the industry
3 Running HP 240v motor provides more hp than 115 v motors - unique unit for those who need lots of portable air power
10.3 CFM @ 90 PSI, Max 135 PSI

I wanted to get a 60 gallon tank, but was kabashed due to the potential size of the thing in our garage. I didn't see the 40 psi rating, but I have to imagine it is higher than the 90 psi rating. I was aiming for a CFM above 8 and I think I have hit the mark. I was also kabashed about the prospect of painting the car myself, but some of the books I have read quote $3000 - $8000 for a decent paint job. When I passed that along the agreement to paint the car ourselves might have been approved. We shall see.

If folks have opinions on the aforementioned model I am interested in, I would be curious to hear it. Obviously need to get an electrician here, but that was part of the plan already as the garage couldn't handle a regular compressor either.