Thread: Dust extractor run length

6" pipe will be everyone's recommendation for fine dust removal. Plus a larger impeller DC unit, or at least one with a modified inlet.

Length is less of a problem than the 4" ducting , which is a MAJOR problem.

It won't matter what size wood dust extractor is used it won't draw more than about 425 CFM though a 4" pipe.
425CFM is not considered enough for medium to larger machinery.

The best thing to do is replace all the 4" pipe with 6" pipe and (provided the dust extractor is up for it) you will get 3x the air though it.

Most 2HP DC have a 4" bottle neck in the front on the impeller and a slightly larger bottle neck between th simpler outlet and the dust bag holder. Both these need to be enlarged otherwise using the 6" ducting is a wasted.

Likewise the machinery dust ports need to be opened up. Lots of examples on this in the dust forum.

Read the sticky on modifying the generic 2HP DC at the top of the forum for more details.

Good afternoon Gordon. Whilst your 4" pipe may not be ideal, it's a lot better than many of us have whilst we wait to implement the correct system.

The difference in cost between the generic 2hp and 3hp units is around $150, and I think well worth it. The inlet is bigger (6" rather than 5") and the dual filters will give you better air throughput and a longer time between bag emptying.
This way if you ever choose to change your piping over to 6", you won't have to mess about with modifying your extractor.

I don't think the lengths you're talking about are an issue. For what it's worth I drag a 7m length of elephant trunk (6" flexible hose) around the shed from machine to machine as required with enough suction to collect most chips.

As long as you're aware that with the 4" ducting you're not going to be collecting the fine dust which can be a health hazard and act accordingly you'll be fine. Even with the 4" setup you will be collecting a lot of the chips which will keep your workshop a lot cleaner.

I have a generic 3hp unit from Carbatec, and am just up the road from you in Margate. If you'd like to drop in for a cup of tea and have a look over it, just send me a pm.

Originally Posted by LanceC

I don't think the lengths you're talking about are an issue. For what it's worth I drag a 7m length of elephant trunk (6" flexible hose) around the shed from machine to machine as required with enough suction to collect most chips. .

It depends on the starting flow, but @1000 CFM my testing shows that a 7m length of 6" soft PU flex will halve the flow rate. For PVC flex the 50% loss of flow happens at about 11m while for still Poly the half loss flow length was 14m. This will have a less of an effect at lower flows but it highlights the problem of using long lengths of flex.

Originally Posted by BobL

The best thing to do is replace all the 4" pipe with 6" pipe and (provided the dust extractor is up for it) you will get 3x the air though it.

Most 2HP DC have a 4" bottle neck in the front on the impeller and a slightly larger bottle neck between th simpler outlet and the dust bag holder. Both these need to be enlarged otherwise using the 6" ducting is a wasted.

So there's little value in running 6" pipe if all machine ports are 4"?
Or is it still worth running 6" pipe during an initial install, because individual drops and machine ports can be upgraded from 4" to 6" over time?

Originally Posted by mpot

. . .Or is it still worth running 6" pipe during an initial install, because individual drops and machine ports can be upgraded from 4" to 6" over time?

Yep that's it.

If the machine is small dust generator (eg a scroll saw, Drill press, small sander) the you can always plumb those in with 4" ducting up to a 6" ducting trunkline. My experience is its better to run 6" everywhere and go down to 4" near the small machines.

I have my DC outside and 6" ducting running around my shed. The TS cabinet, lathe, large belt/disc sander, planer/thicknesser are all serviced direct by 6" ducting with ports opened to 6"

The TS OH guard has 6" ducting to directly over the TS and then uses 4" drop down to the guard.

The Bandsaw is serviced by 3 - 4"ducts. connoted to 6" ducts.

The DP is located about 4m away from the nearest 6" duct and that is the only machine that is attached using 4" ducting mainly because I have no room to run 6" to the DP.

I also have a metal dust/chip catching drum that I use to catch dust from bench grinders, wire wheels, etc and that is connected by 4" flexy as that needs to be mobile.

i also have the 3hp dust collector. just remember the extra horse power doesn't make the blade turn any faster, or suck any harder. it can just handle drawing higher amounts of air for longer. the impellors between a 2hp and 3hp are pretty much the same.

if you have the space go the 3hp just for the extra bag capacity. if not opening up the 2hp will suit you fine as you'll really only be using 1 machine at a time.


as a bit of a side tangent for BobL
what is the reason that 4" piping outlets is the standard on all machines?

Originally Posted by havabeer69

. . . as a bit of a side tangent for BobL
what is the reason that 4" piping outlets is the standard on all machines?

I reckon its a hang over from the 1960's which is about when most of the current generic crop of DC were designed.
I see some European gear has gone with 5" and have been that way for a while.

But not 6”?

Originally Posted by mpot

So there's little value in running 6" pipe if all machine ports are 4"?

Its definitely not wasted, as the biggest advantage you'll have even if the machine port is 4" is having the ability to add multiple pickups. For example my table saw still uses the original ~4" but i've added a 4" pipe at the rear of the machine and one overhead. This allows me to pick up the dust thats ejected into the cabinet but also the stuff thats thrown by the blade upwards.

Similarly with the bandsaw, i use the two existing ports that came with the bandsaw and added a third just above the table. Have a good read through the dust extraction forum, loads of helpful info there.

Do the 3HP machines still run on 10amp power? Something to check when purchasing a machine.
Not everyone has access to 15amp in their workspaces and in my experience, 3HP motors require 15amp.

Originally Posted by PJM16

Do the 3HP machines still run on 10amp power? Something to check when purchasing a machine.
Not everyone has access to 15amp in their workspaces and in my experience, 3HP motors require 15amp.

That's for single phase. A 3HP 240 3Phase plus VFD can run from a 10A supply provided the motor is supplied with soft start. At full power they draw about 9A.

Thanks so much everyone for all the info /advice ,looks like I should have run 6 inch pipes ,but will have to go with 4 inch for now as they are installed , maybe upgrade later .also the 3hp machines sound like the best option . Any tips on sound proofing materials , I was thinking I might enclose the dc in a small area and sound proof the walls etc . I see Harvey Norman sell sound proofing panels for home audio systems , anyone know how effective these are ,thanks again Gordon

Anyone have a preferences for Hafco , Carbatec ,or Leda dc’s