Walk into a cabinet shop at seven in the morning and the loudest thing in the building is the compressor catching up from overnight. By nine the router has run twenty sheets, the edgebander is at temperature, the case clamp cycles every ninety seconds, and somebody in the finish room is pulling a trigger on a gun that wants clean, dry air and nothing else. That is four completely different demands hanging off one system. Compressed air for woodworking shops usually fails for one reason: the shop sized the machine for the CNC and never counted anything downstream of it.
Why a wood shop is not a generic shop
Two things make this trade different.
First, you are running two load shapes at once. Machine air is short and sharp: a tool change, a pop-up pin, a pod releasing. Finishing and sanding air is long and steady, and it never lets up. A compressor that handles the first one beautifully can fall on its face during the second.
Second, you are making dust on purpose, all day, and then asking for a defect-free finish in the same building. Every cubic foot your compressor swallows comes out of a room full of airborne wood flour. Every cubic foot that reaches the spray gun has to be cleaner than the room it travels through. Those two facts drive most of the decisions below.
What the CNC router actually draws
Most three-axis routers with an automatic tool changer land somewhere between 10 and 25 CFM at 80 to 100 psi once you add up spindle purge, the ATC cylinder, pop-up pins, and chip blow-off. Machine builders commonly call for at least 100 psi at the port, which means you want 120 to 130 psi at the compressor so the machine still sees its number after the regulator, the filter, and a hundred feet of pipe.
Here is the part shops miss. If your hold-down uses venturi vacuum generators rather than a regenerative blower or a rotary vane pump, the vacuum is your single largest air load and it runs the whole time the machine cuts. Venturi generators run roughly 1.2 to 14 CFM each at 90 psi depending on size, and a pod table can have several. Count them before you count anything else.
Air quality matters here too, not just in the finish room. A typical router spec is a pressure dew point around 37 F and filtration that stops particles above one micron. Wet air in a spindle purge line is how you get a bearing failure you did not budget for.
Typical demands across the floor
| Equipment | Typical CFM at 90 psi | Load pattern |
|---|---|---|
| CNC router machine air (ATC, purge, pins, blow-off) | 10 to 25 | Intermittent, spikes on tool change |
| Venturi vacuum generator, each | 1.2 to 14 | Continuous while cutting |
| Edgebander | 3 to 8 | Intermittent, steady during a run |
| Case clamp or frame clamp | Large burst, low average | Short, high instantaneous draw |
| Pin nailer or stapler | 0.3 to 2 | Very intermittent |
| 6 inch random orbital sander | 15 to 20 | Continuous while in the hand |
| HVLP or LVLP spray gun | 8 to 14 | Continuous during a pass |
| Blow gun | 3 to 5 | Short bursts, constant abuse |
Look at that table and notice which line is biggest. It is not the router. It is the sander. Two guys sanding doors will pull more air than the machine you built the shop around. We get this call a lot, and it almost always starts with "the compressor was fine until we added a second sander." Our air tool CFM chart has the rest of the numbers if you want to price out your own floor.
Sizing the compressor
Do not add the peak numbers. Add the average ones. For each item, take its CFM and multiply by the fraction of the hour it is actually flowing, then total those and add 25 to 30 percent headroom so the machine is not pinned at 100 percent load all day.
A real example. Small custom cabinet shop, one router with venturi pods, one edgebander, two sanders, nailers, and a blow gun:
- Router machine air, 12 CFM at 50 percent duty: 6 CFM
- Venturi vacuum, 8 CFM at 60 percent duty: 4.8 CFM
- Edgebander, 5 CFM at 40 percent duty: 2 CFM
- Two sanders, 18 CFM each at 30 percent duty: 10.8 CFM
- Nailers, 2 CFM at 40 percent duty: 0.8 CFM
- Blow gun, 3 CFM at 20 percent duty: 0.6 CFM
That is about 25 CFM average. Add 30 percent and you need roughly 32 to 33 CFM of real delivered air. A rotary screw makes somewhere around 4 to 5 CFM per horsepower at 100 to 125 psi, so this shop is a 7.5 to 10 HP machine, not the 5 HP piston in the corner. Browse rotary screw air compressors in that range and compare the CAGI sheet numbers rather than the horsepower on the sticker.
Why a screw and not a bigger piston? Duty cycle. A piston is built to rest. A wood shop with sanders and a venturi table asks for air continuously for eight hours. That is exactly the demand pattern a rotary screw was designed for, and it is why the piston you own keeps overheating in July.
Drying and filtering it
For a heated shop, a refrigerated dryer is the right answer. It gives you a pressure dew point in the 35 to 40 F range, which satisfies the typical router spec and keeps water out of the finish. Reach for desiccant only if your lines run through an unheated attic, a lean-to, or outdoors where the pipe can drop below that dew point, or if you spray a two-component finish that specifies drier air. Our comparison of cycling versus non-cycling refrigerated dryers covers which one pays for itself in a shop that shuts down at five.
The filter order that works:
- Water separator and particulate filter ahead of the dryer, so the dryer is not drowning.
- Coalescing filter after the dryer, to take out oil aerosol and fine solids.
- Activated carbon at the finish room drop only, to catch oil vapor before it reaches the gun.
That last point saves real money. Carbon elements are the expensive ones. Putting carbon on the whole shop means you buy elements to protect a nailer that does not care. Put it where the finish is. If you want the full logic behind those numbers, ISO 8573-1 air quality classes explains what each class actually promises. You can shop air dryers and air filters by flow rate.
Piping the shop
Wood shops have a habit of running rubber hose or big-box poly tubing from the compressor to wherever the tool is, adding a line every time a machine arrives. Five years later there are eleven tees, four couplers per drop, and a pressure gauge at the sander reading 62 psi while the tank sits at 125.
Run a loop. For a 7.5 to 10 HP machine, one inch is the honest minimum for the main. Take drops off the top of the header so condensate stays in the main, put a drip leg with a drain at the bottom of every drop, and give each drop its own ball valve so you can add a machine without shutting the shop down. Aluminum pipe goes together fast, does not rust into your finish, and can be reconfigured when the floor plan changes. See compressed air pipe sizing for the diameter math, and browse aluminum air piping systems when you are ready to lay it out.
One thing not to do: PVC. It is common in wood shops because it is cheap and easy to glue, and it is a genuine shrapnel hazard above ground. Here is what OSHA actually says about it.
Six mistakes wood shops make
Sizing for the router, forgetting the sanders. Covered above, and it is the number one cause of a shop outgrowing a new compressor in eighteen months.
Putting the compressor in the dust. An intake filter in an open cabinet shop can load up in weeks instead of a year. Either duct the intake to clean outside air or give the machine its own room with filtered makeup air. A starved intake shows up as high discharge temperature and short oil life long before anyone thinks to look at the filter.
One regulator for the CNC and the finish room. The router wants 100 plus psi. The spray gun wants 25 to 30 at the cap. Give each its own regulator at the drop and stop chasing the setting back and forth.
No carbon filter ahead of the gun. If you run an oil-injected screw, some oil vapor makes it past the coalescing element. It is invisible, it is measured in parts per million, and it is exactly enough to fisheye a door.
No working tank drain. Manual drains do not get pulled. The receiver fills, rusts, and one Monday morning it slugs a cup of rusty water down the line into a fresh sheet of veneer. An automatic condensate drain is a cheap insurance policy.
Running venturi vacuum on a compressor sized for hand tools. If the pods are venturi, that load is continuous and it is large. Either size for it honestly or move the hold-down to a dedicated vacuum pump and take the load off your air system entirely.
Frequently Asked Questions
What size air compressor does a cabinet shop need?
Most small to mid size cabinet shops land on a 7.5 to 10 HP rotary screw, which delivers roughly 30 to 45 CFM. Add up your continuous loads with honest duty factors, then add 25 to 30 percent. If you run venturi vacuum hold-down or more than two air sanders at once, expect to be at the top of that range or above it.
Do I need a dryer for a woodworking shop, or is a water separator enough?
A separator catches liquid water that has already condensed. It does nothing about the vapor still in the air, which condenses later, in your line, usually right at the spray gun. If you finish anything, you need a dryer. A refrigerated unit is sufficient for a heated shop.
Can I run my CNC router and my sanders off the same compressor?
Yes, and most shops do, but they are different loads and they need different treatment at the drop. The router needs high pressure and clean dry air. The sanders need volume. Size for the combined average, regulate separately, and make sure your piping is large enough that the sander is not stealing pressure from the router.
Why does my finish keep getting fisheyes even though I have a filter?
A single filter at the wall almost never catches oil vapor. Vapor passes straight through particulate and coalescing elements. You need an activated carbon filter as the last stage before the gun, downstream of the dryer and the coalescing filter, and you need it changed on schedule.
Is a piston compressor good enough for a woodworking shop?
For a one-person shop with a nailer and an occasional blow gun, yes. Once you have a CNC, an edgebander, or more than one person sanding, the duty cycle is against you. A piston is built for intermittent use and it will run hot and wear fast on a wood shop schedule.
The short version
Good compressed air for woodworking shops comes down to counting the loads nobody counts. Add up the sanders and the venturi vacuum honestly, buy a rotary screw with real headroom, put a refrigerated dryer behind it, run a looped aluminum main, and hang a carbon filter at the finish room drop and nowhere else. Do that and the compressor stops being the thing that decides how fast you can build cabinets.
