Dust hose clamps: sizing by outside diameter and spiral direction

Short answer

Size a hose clamp to the outside diameter of the hose where it sits over the fitting, not to the hose's nominal label. A 4-inch hose stretched over a fitting is wider than 4 inches. Bridge clamps add a second check: they must match the direction of the hose's wire spiral, left-hand or right-hand.

Picks that fitAll picks and how to choose

Measure where the clamp sits

A hose clamp squeezes the hose onto the fitting underneath. So the size that matters is the hose's outside diameter once it is on the fitting. Rockler advises measuring both the inside and outside diameter of each port and hose connector, because the port's outside diameter has to match the hose's inside diameter.^[1] Once that joint fits, measure around the outside of the hose on the fitting, and buy a clamp whose stated range covers it.

How to measure a dust port covers the measuring itself.

Bridge clamps and spiral direction

A bridge clamp has a raised bridge that steps over the hose's wire so the band sits flat between coils. That only works if the bridge follows the wire.

Lee Valley says its left-hand bridge clamps fit only hoses with a left-hand spiral, which you can identify when the wire spirals counterclockwise at an open end. Lee Valley sells right-hand clamps separately and says the hose needs at least 1/2 inch between coils.^[2]

To check yours, look straight into a cut end of the hose and follow the wire away from you. Counterclockwise is left-hand by Lee Valley's description; clockwise is the other hand.

Worm-gear clamps

A worm-gear clamp is a plain band tightened by a screw. It has no bridge, so spiral hand does not matter. Pick one whose range covers the installed OD, seat it on the fitting rather than past its end, and tighten it until the hose stops turning on the fitting. We give no torque figures.

Clamps that come with parts

Some parts include a clamp or need one:

Infinity Tools says each MagSnap port includes a hose clamp.^[3]
Infinity says hose clamps are required on its 4-inch blast gate.^[4]
Magport says its 4-inch collar has a 4-inch outer diameter that fits 4-inch flex hose.^[5]

Read the contents before you buy extra clamps.

Clamp types side by side

Clamp type	Sized by	Spiral hand	Comes with	Source
Left-hand bridge clamp	Installed hose OD	Left-hand hose only	Sold alone	Lee Valley
Right-hand bridge clamp	Installed hose OD	Right-hand hose only	Sold alone	Lee Valley
Worm-gear band	Installed hose OD	Either	Varies by part	General
Clamp in a port kit	The kit's own port	As the maker states	Infinity MagSnap ports	Infinity Tools

Clamps on our list

Check your hose's spiral hand first. The ranges below are the seller's sizing, not verified fit.

Picks that fit3 products

Left-hand spiral 4 in hose: the POWERTEC 70226 5-pack of left-hand bridge clamps. Right-hand spiral 4 in hose: the Rockler 4 in keyed bridge clamp 5-pack, which Rockler describes as right-hand.

Do I need a clamp on every joint?

Use one where the part maker says so, as on Infinity's gate. A joint the maker designs as a friction fit, such as POWERTEC's 70291 into a machine port, is a separate case; follow that maker's instructions.