Last ducting question (really!) before ordering...

[Jean-Claude Vaudrin]

So, when they tell you to run 6" ducts as close to the machines as possible before reducing, how should I apply that to both over/under DC at the table saw? Imagine a wye at the far end of the table saw.

1. Should I have the wye immediately split into two 4" runs that go all the way to the over/under ports? (So a 6x4x4 Y and longer runs to the ports.)

or

2. Can I have the wye split into two 6" runs that go as close as possible to the over/under ports and use a reducer to 4" at the last moment? (So a 6x6x6 Y until the ports and then two reducers.)

How would both options impact cfm values?

Merci beaucoup!

[Jim Becker]

With a 6" drop to the TS, I'd branch with a 6" to 5" + 3" wye at a convenient spot to pick up the connection to the overarm collector and run 5" to the saw cabinet. That's exactly how I have things setup with my slider. (although I rarely use the overhead collection)

[Jean-Claude Vaudrin]

Wow, Jim, you must be THE MAN! Many people read the thread, but no one else dared to contradict you and offer different numbers!

And of course it had to be 5 and 3... Just when I thought I was getting a handle on all the 6 and 4...

Thanks!

[Dominik Dudkiewicz]

As already suggested by Jim, two 4" is not the best way to go. I run a 6" to the cabinet and a 4" to the overhead, but would prefer a 5" to the cabinet and a 4" overhead as I find the increased flow overhead does more to capture dust than a higher proportional flow from the cabinet. So I would recommend a 5" to the cabinet and a 4" overhead.

Cheers, Dom

[Jean-Claude Vaudrin]

Thanks. And I can't find anything about using 26 gauge ducts and ordinary (cheaper) 30 gauge fittings. I understand the logic about longer pipes collapsing, but I can't imagine a much shorter 30 gauge fitting (specially the adjustable 90 ones) doing the same with a 2hp DC...

[Jim Becker]

26 gage snap lock is fine. HVAC fittings, however, are "backwards" relative to the flow direction so you have to re-engineer them relative to the crimps. While a "good" wye from Oneida and other is pricy, they are fit for purpose. You could also construct what you need by using a saddle wye on the 6" pipe for the over-arm connection and then a reducer just past it to 5" to head on to the saw.

[Terry Hatfield]

I split a 6" drop with a 6x4x6 wye. 4" to the overhead and 6" to the cabinet. I have gates on both so I can isolate one or the other or meter wherever in-between.

[Ole Anderson]

Jim and I both use 5" bottom and 3" top runs to the TS. I use my top going to the 3" SharkGuard every time I can.

[Jim Becker]

Part of the choice here is dictated by whether metal or PVC duct work is at play. In Terry's case just above, he's using PVC so only "even numbers" are available. Therefore a 6x6x4 is the most likely choice with fine-tuning at the gates to balance the available air flow. For metal duct, odd-numbers are available so splitting 6x5x3 provides a pretty good natural balance for air flow when both gates are open and 5" at the cabinet generally works just fine. For those of us with Euro equipment, 5" is close to the 120mm ports that are typically on the machines anyway.

[Jean-Claude Vaudrin]

26 gage snap lock is fine. HVAC fittings, however, are "backwards" relative to the flow direction so you have to re-engineer them relative to the crimps.

Thanks. I will go with 26 gauge snap lock, even though my HVAC guy can get me spiral pipes for cheaper. I read that the spiral pipes had more leaks. But has anyone ever heard of 30 gauge fittings (not ducts) collapsing?

[Jim Becker]

No way would I use snap lock if I could get spiral for less money! Spiral is the better solution!!!

[Karl Loeblein]

Thanks. I will go with 26 gauge snap lock, even though my HVAC guy can get me spiral pipes for cheaper. I read that the spiral pipes had more leaks. But has anyone ever heard of 30 gauge fittings (not ducts) collapsing?

You might be able to seal up any leaks on the spiral pipe with a tub of Gray Duct Sealant.

[Jean-Claude Vaudrin]

I split a 6" drop with a 6x4x6 wye. 4" to the overhead and 6" to the cabinet.

Thanks for the info and the pictures. That's quite the shop! And I really like the diy overhead guard. I might just copy it until I can get a Shark Guard.

I went to a business not a kilometer from where I live to see if they had ever heard of 30 gauge fittings (not ducts) collapsing, and the guy told me to come into the shop and have a look. They make all types of big CNC machines for woodshops. You should see the place. I think I'm going to forget about my basement shop and just move into theirs...

[Jean-Claude Vaudrin]

For metal duct, odd-numbers are available so splitting 6x5x3 provides a pretty good natural balance for air flow.

Thanks, I'll just adjust my runs before ordering, then. As soon as I clarify why the spiral is cheaper than the snap-lock. I'll keep you posted.