4 in. (101.6mm) Dust Collection Duct Size and Fitting Guide
A 4 in. (101.6mm) duct is the main line of a shop dust collection system. Dust collectors, blast gates, floor sweeps, and big stationary machines like table saws and planers all connect to 4 in. duct. It moves the high air volume a real dust collector needs.
This is a system size, not a hand-tool port size. You will not find a 4 in. port on a cordless sander or router. So this page is about the duct network: how 4 in. runs the shop, and how to branch it down to smaller machine ports and tools.
GulpDust makes 4 in. fittings, blast gates, reducers, and floor sweeps in PETG. Use them to split the 4 in. main, gate off idle machines, and step down to the tools you are running.
The Adapter That Fits a 4 in. Port
Each adapter grips the 4 in. tool port on one end and steps it to your shop vac or dust extractor hose on the other end. Friction fit, no clamps. Made in the USA.
What Uses the 4 in. (101.6mm) Duct Size
The 4 in. size is the backbone of a shop dust collection system. A single-stage or two-stage dust collector puts out 4 in. The main duct runs 4 in. along the wall. Blast gates, wyes, and tees are all 4 in. so you can branch the line to each machine.
Big stationary tools tie into 4 in. as well. Cabinet saws, planers, jointers, and drum sanders often have a 4 in. outlet or step up to one. That is why 4 in. is the size that ties the whole shop together.
How to Branch 4 in. Duct Down to a Machine or Tool
Run the 4 in. main to each machine, then use a reducer to step down to the machine port. A table saw with a 2-1/4 in. port takes a 4 in. to 2-1/4 in. reducer. A tool with a smaller port steps down again.
Add a blast gate at each branch so you only pull air where you are working. Closing the idle gates keeps the airflow strong at the machine you are using. GulpDust makes the 4 in. wyes, tees, blast gates, and reducers to build this out.
4 in. Dust Port FAQ
Which power tools have a 4 in. (101.6mm) dust port?+
None in the hand-tool sense. 4 in. is a dust collection duct size for the shop system, not a port on a cordless tool. Large stationary machines like cabinet saws and planers connect to 4 in. duct, often through a reducer or an adapter, not with a native 4 in. tool port.
What is 4 in. duct used for?+
It is the main line of a dust collection system. The dust collector, the wall duct, the blast gates, and the branches to each machine are all 4 in. It carries the high air volume a dust collector needs to keep chips moving.
How do I connect a 4 in. duct to a smaller machine port?+
Use a reducer. A 4 in. to 2-1/2 in. or 4 in. to 2-1/4 in. reducer steps the main line down to the machine port. Add a blast gate at the branch so you can shut off idle machines and keep the pull strong.
Do you make 4 in. fittings?+
Yes. GulpDust makes 4 in. wyes, tees, blast gates, reducers, and floor sweeps in PETG. Buy them printed and shipped from the US, or download the STL and print them at home.