Best way to connect two 4" pipes to router table

[safari]

I have just completed a router table that has two 4" outlets. I am unsure of the best way to run these pipes from the 6" main. I could use a 4" take off and then add a 4" Y although I think this would perhaps cut the air volume too much. Alternatively would it be better to have two separate 4" pipes from the 6" main? I am at a bit of a loss as how to proceed so any advice would be appreciated.

[BobL]

I would use a 6" to 4" Y and run 6" to underneath the router and 4" above the router.

[safari]

Thanks BobL. Didn't think of that combination

[soundman]

The other thing you could do is make up a "trouser adaptor".
The off the shelf Y adaptors are very poor in the air flow department...and the hoses ofte dnt come out in a convienient manner.

I have in the past made up several " trouser adaptors".....I call them that because that is what they look like.

I generally start with a standard off the shelf joiner.....in your case a 4 inch.

cut it in half so you have two little sections of pipe the right size for your dust hose.

then get a short length of the correct size plumbing pipe...in your case 6 inch.
what you now need to do is truncate them two small pipes so they fit together in a fairly shallow Y of a diameter that approximates a sloghtly oval, 6 inch pipe....band saw and belt sander should dress them up nice

with masking tape and conduit cement....glue these together

now get ya self a bucket or the kitchen sink full of boiling water......with appropraite care.........put one end of you 6 inch pipe in the hot water till 3 or 4 inches of the pipe has gone soft.....this will take a while...the softer the better.

then jam this over the y piece you have just made...some rag of thick gloves will be required to handle the hot pipe.

it should snug up pretty well, but you may need to press in a little gap in the middle of the flat either side.

Let this cool while you hold it or run it under cold water to speed the setting up.

now take it all appart and glue it together with sicaflex or similar.

By the time you have done two or three of these you should be able to get a pretty danm neat smooth flowing "trouser adaptor"

cheers

[John Samuel]

I would use a 6" to 4" Y and run 6" to underneath the router and 4" above the router.
I note that Bill Pentz's site says to be careful to ensure the pipe to the cabinet (below the router) should connect to the side of the router to avoid motor damage. Diagram can be found here ... Dust Collection Research - Ducting (http://www.billpentz.com/woodworking/cyclone/ducting.cfm#tool_ducting)

Currently, I have a 6 inch line over the cutter only, and very little dust gets into the cabinet. Debating with myself about running a line to the cabinet because I like the chip collection that high airflow at the cutter provides. Any thoughts?

[soundman]

Just some thaughts.

I question the benifit of sucking top and bottom on a router or spindle moulder.

If the area of the cutter is more or less enclosed, rather that a waste pipe sitting there hopeing for the best.

there will be a negative pressure area around the cutter...if there is also some sort of gap between the cutter and the work surface.
Suck top or bottom and there will be a negative pressure area that causes air flow thru the gap in the throat plate.

Assuming that the dust extraction arrangement encloses the cutter head ...and....if the workpiece is large and flat, it obscures any air flow from any other source but that comming thru the throat plate.

So extracting both above and below the table may be counter productive.

So some examples.
My spindle moulder.(sold a few years ago), had a fence arrangement that included a 4 inch dust collection outlet intergral.
This fence arrangement enclosed the cutter head completely except where it projected thru the fence.
Once the fence was adjusted for the cutter head projection, the gap could be as little as 4 inches by 3 inches and at worst 4 inches by 5 inches.....If I was running a dummy fence ( much of the time), where I had machined the cutter thru the back of the fence the gap could be quite small indeed...may be as little 5mm clearance arround the cutter head projection.......I was running a plain 6 inch rebating cutter head and the selected throat ring would have cleared by about 10mm all round.

So worst case .... a thin board with a face down rebate and the factory fences...there was pretty well full air flow of the 4 inch hose thru the fence with may be a little residual suction thru the throat plate.

In the best case a face to the fence rebate of a wide board.....once the cut progressed and the board was supported by both fences, the cutter was completely enclosed and the whole of the air flow came thru the throat plate.

Routers and moulders tend to project their waste out of the cut at more or less right angles to the edge being cut......large diameter moulders very much so.

Appart from on the exit from the cut, very little of anything in the way of dust or chips left this machine, inspite of removing large quantities of material in one pass.

There was a very small amount of heavy chips that would find their way into the the case below the table.
I consider that the air flow thru the throat plate was important and applying suction to the case below the table would have been counter productive.

I also have a pissy little router table about the size of a shoe box, its purpose is exclusivly edge rounding.
It has an old Bosch POF400 flush mounted into the top, and I use the Bosch accessory dust extraction device with a vacuum cleaner.
Edge rounding projects quite a lot of material toward the base of the machine.....this time the extraction is below the table, the hole in the throat plate is about the size of the incomming hose....the cutter spins in that apiture.

This machine in spite of its cheapness has always performed well in dust capture (way better than the Festo that replaced it for hand held work).
I believe the air flow thur the throat is vital....Because when the work piece if fully engaged there is nowher else for the air flow to come from.

So my considered opinion is that in routers or moulders, we want air flow thru the throat of the machine over the cutter......sucking above or below the throat plate may advantage different cutting operations and different machines.......but sucking on both, I believe in most cases may be counter productive.

cheers

[safari]

Thanks for the input. I ended up taking two separate 4" takeoffs from the 6" main and used a blast gate on each line so that either top or bottom pipe or both together can be used depending on the job. So far I am pretty happy with the performance.