duct size for bottom of table saw

[Bob Slater]

Finally hooking up the table saw to my dust collector. it is an oneida 2Hp cyclone. I have the overhead guard hooked up to a 4 inch spiral duct and can potentially run a 4 or 5 inch intake to a cover I am making for the bottom of my General table saw. Would I be better to go for the 4 or 5 inch duct for the lower part?

Tia.

[David Kumm]

What is the size of the main you are running both into? Dave

[keith denbesten]

I have a 5" going to the bottom of my delta and a 4" to a shark guard on top. But I have a 3HP Onieda and a 7" branch line feeding it. Works great!

[Jim Andrew]

Your setup is similar to mine. I have a 2hp cyclone, a 4" shark guard, and 4" to the cabinet on my tablesaw. Would prefer now to have gone with 5" to cabinet saw and a slightly smaller to the guard. The sawdust tends to build up in the table saw, and the shark guard works excellent.

[ian maybury]

It's a bit unpredictable from this distance, and a lot to do with what you consider to be acceptable - but don't forget to consider how long the ducting run to your saw is. Also how many bends there are. If it's more than two or three bends and say 10 or 15 feet you could at 2HP be running into a situation where the available CFM to run a 4in top connection and 5in lower for even basic chip collection is marginal. Restrictive ports relative to the duct size anywhere on the saw would make the situation worse.

i.e. the 4in top connection may be hogging more than its fair share of the available CFM at present, but it's performance (if the CFM is marginal) won't be maintained with a larger lower. It may still be OK, but the larger lower may meanwhile not perform as expected either.

My inclination would be to install a correctly sized branch and hook up some 5in hose of the expected length to see how well it and the top guard pull in that situation - before that is i altered the saw internals.

ian

[Rick Potter]

My Unisaw has a slot along the bottom beneath the table. Delta sells an adaptor that converts it to a 5" hole. For years I had an added adaptor from 5 to 4", and had it hooked to a 4" hose, off a 6" main. A few years back, I changed to a 6" hose all the way down to the Delta 5" adaptor. Definitly works better.

I guess the Delta engineers put the 5" on there for a reason. I also plumbed for a 4" to the blade guard, but haven't gotten around to finishing it yet.

Rick Potter

[G Douglas Fowler]

I also have a 2hp cyclone, 7" main, 6" drop to the TS with a 5" gate at the port. The drop to the blade uard is 3"/3" gate. If your want effective dust collection at the blade, don't use zero clearance inserts unless it is necessary for what you are cutting.

[Ole Anderson]

I am another one with the 2 hp yellow one. I have a 5" bellmouth at the bottom of the Griz 1023 with 5" flex wyeing into a 6" ending up in a 7" main. 3" shark guard at the top.

[Michael W. Clark]

If you run a 6" duct over to the saw, a 5" on the cabinet and a 3" on the guard matches pretty well. You may need to add blast gates in one or both of the branches to regulate the airflow in each. The air is going to take the path of least resistance, so if you have a 4" on the guard, you will likely need to choke it back some to balance the flow. If you change the guard to a 3", it will add some resistance, forcing some air to the 5".

The best way to figure your diameters is to pick two that the areas add up to approximately the area of the duct to the saw. I would opt for more CFM on the cabinet than the blade guard, so that is the reason for the 5" and 3" as opposed to two 4" ducts.

[Ole Anderson]

You see a lot of systems with the 5"/3" combo as Bill Pentz talks of recommending a 5" bottom/3.5" top duct to the TS in his web site.

And here is a link to the 5" bellmouth flange: http://www.pennstateind.com/store/N-BELL05.html

The bellmouth decreases your inlet losses compared to a square edge orifice.