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Connect a 1-7/8 in shop-vac hose to a 2-1/2 in shop-vac hose

How to join a 1-7/8 in shop-vac hose to a 2-1/2 in shop-vac hose, and what stops it leaking dust.

Reducer required

Not a direct fit. Joining the 1-7/8 in shop-vac hose to a 2-1/2 in shop-vac hose needs a 1-7/8 in to 2-1/2 in shop-vac hose adapter.

END B63.5 mm2-1/2 in shop-vac hose (2-1/4 in OD, 2-1/4 in ID)
END A47.6 mm1-7/8 in shop-vac hose (1-7/8 in ID)

Rings drawn to scale from the measured diameters in the table below.

The two ends

End A1-7/8 in shop-vac hose (1-7/8 in ID)
End B2-1/2 in shop-vac hose (2-1/4 in OD, 2-1/4 in ID)
Fit typecuff to cuff via a step reducer
Reducer needed1-7/8 in to 2-1/2 in shop-vac hose adapter

Shop notes

The 1-7/8 in hose (about 48 mm) and the 2-1/2 in hose (about 57 mm cuff) are two different vacuum standards, so their cuffs do not interchange. A 1-7/8 to 2-1/2 in adapter lets you run 2-1/2 in tool fittings on a mid-size vac.

The 1-7/8 in size is the orphan of shop-vac hoses. Many tool adapters are sold only in 1-1/4 and 2-1/2 in, so plan on a two-step chain rather than a single perfect-fit part.