by Mike Jordan » 16 May 2018, 08:29
I urge you to do the job properly using the purpose made metal ducting together with blast gates and mounting fittings. Don't be tempted to fool about with plastic drainpipes and similar supposedly cheaper methods. You can cobble these together and make a working system but it has no fire resistance and generates static electricity. The time saving with the metal pipes is well worth the few extra pounds of cost, everything will fit together easily. Keep the flexible pipes connecting the machines as short as possible to keep down the friction losses. Mine has a 150mm range pipe and 100mm down pipes each with a blast gate, these are the minimum sizes for efficiency in my opinion. Connect the down pipes into the side of the range pipe to prevent chippings from more distant machine falling down and blocking down pipes from machines nearer the extractor. The very best place for the extractor is outside the workshop, the finest and most dangerous dust will get through the filter bag and into you!
There is a fair chance that you will now be snowed under by instructions on how to make plywood blast gates etc.
I try to buy nothing from China.