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Connect a DeWalt DWS779 / DWS780 miter saw port to a 2-1/2 in shop-vac hose

How to join a DeWalt DWS779 / DWS780 miter saw port to a 2-1/2 in shop-vac hose, and what stops it leaking dust.

Reducer required

Not a direct fit. Joining the DeWalt DWS779 / DWS780 miter saw port to a 2-1/2 in shop-vac hose needs a DeWalt miter saw port to 2-1/2 in hose reducer.

END B63.5 mm2-1/2 in shop-vac hose (2-1/4 in OD, 2-1/4 in ID)
END A41 mmDeWalt DWS779 / DWS780 miter saw port (1-5/8 in OD, 41 mm OD)

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

The two ends

End ADeWalt DWS779 / DWS780 miter saw port (1-5/8 in OD, 41 mm OD)
End B2-1/2 in shop-vac hose (2-1/4 in OD, 2-1/4 in ID)
Fit typemale port into hose cuff
Reducer neededDeWalt miter saw port to 2-1/2 in hose reducer

Shop notes

A 2-1/2 in shop-vac hose has a cuff near 2-1/4 in, far larger than the 1-5/8 in DeWalt miter port, so it cannot seal by itself. A stepped rubber reducer bridges the 1-5/8 in port up to the 2-1/2 in hose, giving the higher airflow of the bigger hose at the saw.

Bigger is not automatically better here. The saw only throws so much per cut, and a loose 2-1/2 in reducer leaks more than a snug 1-1/4 in one. Prioritise a tight step over the largest hose.