What Size Air Compressor for Framing Nail Gun? A Buyer's FAQ (2-Gallon to 25 HP)

If you're the person stuck with the "can you order…?" questions at a shop, a construction crew, or a small plant, this one's for you. I took over purchasing for our company in 2020—roughly $180K a year across a dozen vendors for equipment, supplies, and replacement parts. I'm not an engineer. I'm the person who figures out what to buy and who to buy it from, then makes sure finance doesn't reject the invoice.

Air compressor questions land on my desk more than any other equipment topic. Springs are a close second. That's how I ended up ordering from Lee Spring Co. for springs and a completely different vendor for compressors—and learning the hard way what actually matters when you're buying both. Here are the questions I answer, usually while standing in a hallway with a cup of coffee.

On this page:

• What size air compressor for framing nail gun?
• Is a 2-gallon air compressor worth buying at all?
• When do you need a 25 hp air compressor?
• What does Lee Spring Co. actually make?
• What is "Lee Spring Army"?
• What's the most expensive buying mistake—springs or compressors?

What size air compressor for framing nail gun?

You need at least 2.2 SCFM at 90 PSI. The framing nailer's spec sheet will tell you its own consumption—most framing guns fall in that 2.2–2.5 SCFM range at 90 PSI—so your compressor has to deliver at least that at the same pressure. I tell our crew leaders to buy a 6-gallon portable unit with a 2.6 SCFM rating at 90 PSI. That little bit of headroom makes a real difference when the gun is cycling through a day of framing.

And here's where the trap is: CFM ratings can be measured at different pressures. A compressor that claims "3.5 CFM" at 40 PSI might only deliver half of that at the 90 PSI your nailer actually needs. Per FTC advertising guidelines (ftc.gov), performance claims are supposed to be truthful and not misleading—but as a buyer, you have to confirm what pressure the rating was tested at. It's not enough to trust the big numbers on the box.

What I mean is that the sticker price and the horsepower rating tell you almost nothing. The SCFM at 90 PSI tells you everything. If a unit doesn't list SCFM at 90 PSI clearly, that's a red flag for me. Next question.

Is a 2-gallon air compressor worth buying at all?

Yes—just not for framing. A 2-gallon air compressor is a supporting player. We keep one in the maintenance room for brad nailers, staple guns, air dusters, and the occasional tire inflation. For a finish crew doing trim work, it'll run a brad nailer all day if you don't abuse it. For continuous framing, no—the tank is too small and the pump can't keep up.

From the outside, a 2-gallon unit looks like a toy. The reality is it's one of the most-used pieces of equipment in our building, because it's quiet, it's portable, and it runs on a regular 120V outlet. Everyone ignores it until the day it gets borrowed and doesn't come back.

The tradeoff is runtime for portability, and I'm fine with that. If your work takes you around a property—punch lists, touch-up, quick repairs—a 2-gallon compressor is the right tool. If you're parked in one spot shooting framing nails for hours, step up to a 6-gallon or larger. Know the duty cycle before you order.

When do you need a 25 hp air compressor?

When your demand is continuous and spread across multiple workstations. A 25 hp air compressor—typically a rotary screw unit—delivers around 80 to 100 CFM. That's a different universe from the little pancake unit. We made the jump when we added a second CNC machine and a blasting cabinet. Our old 7.5 HP piston compressor couldn't hold the pressure when three high-consumption tools ran at once.

Don't hold me to exact numbers, but the way I see it, if you're running multiple tools simultaneously for hours at a time, you've outgrown piston compressors. They're built for intermittent duty. Rotary screw units handle the sustained load without punishing you with heat shutdowns or pressure drop.

Before you buy a 25 hp air compressor, do a demand audit. List every tool in the facility, note its SCFM and duty cycle, and add it all up. Apply a diversity factor—nobody runs everything at once. That total tells you what CFM you need, and only then can you talk about motor size.

I still kick myself for one purchase: a "great deal" on a used 20 HP unit that could not keep up with our actual demand. If I'd done the audit first, I'd have seen it coming. Five minutes of checking would have saved me about three weeks of calls and a very awkward conversation with my VP.

What does Lee Spring Co. actually make?

Lee Spring Co. makes industrial springs—compression, extension, torsion, spring washers, garage door torsion springs, and custom-engineered parts. In our maintenance room, springs are everywhere: pressure switch springs, valve springs, safety relief valve springs. If a machine has a moving part that pushes back, there's a spring inside it.

What I appreciate as a buyer is that leespring (lee-spring) gives you an online catalog with a spring design calculator and search filters that don't require an engineering degree. You punch in the wire diameter, outer diameter, and free length, and the catalog narrows it down to a few options with load data. For someone like me who orders replacement parts, that's gold.

We've also ordered custom springs from them a couple of times. One was for a redesigned vibration mount; another was for a door torsion spring that had to meet an exact cycle count for a commercial garage door. The parts arrived with proper documentation and clean invoicing, which honestly matters as much to me as the spring itself. I've had vendor invoices rejected by finance for less—$2,400 in expenses that came back to haunt me because a supplier couldn't produce a proper invoice. Lee Spring has never been that vendor.

What is "Lee Spring Army"?

If you've typed "lee spring army" into a search engine, you're not the only one. It's not a military division or a veterans' program. People use the phrase because Lee Spring Co. carries enough product categories to equip an army of machines—compression springs, extension springs, torsion springs, disc springs, wave springs, spring washers, garage door torsion springs, die springs, and custom parts.

In my opinion, the nickname fits better than their marketing probably intended. Once you have their catalog saved, you tend to stop looking elsewhere for spring supplies. One supplier, one purchase order, one invoice. For a buyer who manages eight or nine vendor relationships, cutting one off the list is meaningful.

So if you were worried that "Lee Spring Army" meant you'd stumbled onto some kind of military surplus site—no. It's just a company with a huge inventory and a memorable nickname. If you need a spring, they probably have it in stock. If they don't, they'll make it.

What's the most expensive buying mistake—springs or compressors?

Not checking the spec twice. It doesn't matter which product category; the failure mode is the same. Five minutes of verification beats five days of correction, and I have the purchase history to prove it.

For springs, the classics are ordering the wrong free length, mixing up hand direction, or choosing the wrong material for the operating temperature. A spring that looks right in the photo but fails after a hundred cycles costs you two weeks of downtime, not just the $12 part price.

For air compressors, the mistake is buying on peak horsepower instead of SCFM at working pressure. I've seen a 5 HP compressor outperform a 7.5 HP unit because the bigger motor was rated at a pressure nobody in the building actually uses.

My checklist after five years of buying both:

1. Confirm SCFM at the pressure your tool draws—not a hand-wavy "max CFM."
2. For springs, verify outer diameter, free length, load, and material. All four, not three.
3. Ask for the duty cycle in writing. If no one answers, that's an answer.
4. Look for a supplier who's done this before. Experience is a spec too.

There's something satisfying about an order that just works—no second email, no "oops, that's the wrong part," no reworked invoice. Buying the right thing the first time is the most underrated move in procurement. It's the only way to make a purchase disappear from your memory, which, if you ask me, is exactly what a good purchase should do.