Connect a Bosch GCM12SD miter saw port to a 4 in dust-collector hose
How to join a Bosch GCM12SD miter saw port to a 4 in dust-collector hose, and what stops it leaking dust.
Not compatible without stepping down. A 4 in dust-collector hose is far larger than the Bosch GCM12SD miter saw port, so it needs a 1-1/4 in to 4 in step reducer.
Rings drawn to scale from the measured diameters in the table below.
The two ends
| End A | Bosch GCM12SD miter saw port (1-1/4 in ID) |
|---|---|
| End B | 4 in dust-collector hose (4-1/4 port in OD, 4 in ID) |
| Fit type | hose cuff into female socket |
| Reducer needed | 1-1/4 in to 4 in step reducer |
Shop notes
The port socket is about 32 mm and the hose tip about 102 mm, a gap of 70 mm, so the hose tip simply swallows the port socket with no contact. A 1-1/4 in to 4 in step reducer is needed, and even reduced the airflow is mismatched between the Bosch GCM12SD miter saw port and the 4 in dust-collector hose.
Wrapping tape to close a 70 mm gap never seals cleanly and chokes the airflow further. Step the sizes properly, or pair each end with a fitting closer to its own size.
The reducer to buy
Search Amazon for 1-1/4 in to 4 in step reduceraffiliate searchRelated connections
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