I really hate to ask another question about DC but here goes

[Leather Man]

I have a Jet 1200 2HP DC with the cannister. I am going to use 6" S&D pipe for the main trunk. Will it be OK to use 4" pipe from the 6" pipe to the machine or should I use 6" pipe to the machine also? Most of my machines only have a 4" connector. Also, is there a disadvantage of having my 6" pipe close to the floor instead of overhead? Thanks for your input.
Ben

[scottspencer]

Many people use 4" drops from their machines to a larger main b/c the machines often have 4" ports, and standard wye's and gates are cheaper. Theoretically it's better to stay with the larger drops, but 4" should be fine....keep them as short as possible. There's no disadvantage that I'm aware of by placing the main on the floor. Same rules apply...corners aren't good, tighter corners are worse, short runs are better, larger diameter is better to a point, smooth is better than corrugated, etc.

Regards,
Scott

[Steve Wilson]

Use 6" drops to your tool and then size down to 4" if you have to. 4" flex is very resistive and will quickly kill your CFM.

[srpoly]

Try to stay with the 6" as far as possible. Hoods can be modified or even fabbed up pretty easy. Blast gates are hard to come by in 6", so I made my own out of scraps. Only cost me time.
FWIW- If you have a very short run- check the motor with an amp meter with the blast gate open to make sure you're not pulling too many amps.

[Sonny Edmonds]

Keep your pipes long and your hoses short.
I have mine overhead. But if underhanded works better for your shop, why not? I didn't want to step over things.
I use 6" for as much of the main runs as possible, then a swept 6" elbow and reduce to a 4" PVC riser.
Why?
Because velocity in the risers keeps particals from becomming suspended and ging-gangeling there.
I also have a dirty air booster blower under my center area that kicks the volume up tremendously for anything connected there (including rolling tools).

I mentioned I didn't want to step over things. I also did a lot of online and in person looking at dust collection and conveyance systems.
Next time you are in a home depot look up at the pipes. :7

:D

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[Leather Man]

Thanks guys for the replys. It has helped alot. Sonny, if I put my 6" pipe above and use 4" drop to the machines will the 4" pipe compromise the use of the 6" main pipe? Were you saying that if I use 6" drops the DC may not have enough airflow to suck the dust up into the main pipe? Thanks
Ben

[Sonny Edmonds]

The only compromising would be that the 4" has 12.4 Sq. Inches of cross sectional area. So the CFM total capability would drop slightly.
However, 6" vertials may not produce enough velocity in them to efficently transfer everything that the system picks up from a given point. So pieces of debries inside the pipe reach a point where they won't go up any further, and they just rattel in the vertical section. That causes you to have to dismantel part of the system to clear the bugger out. (Been there, done that. ;) )
Once 6" pipe is on the horizontal run, everything just merrily rolls to the collection point, Your blower and filtering system.
Keeping the pipes long means as little use of hose as you can manage. The PVC S&D type pipe is very slick to conveying debries through it.
Example: 20' of 4" flexable hose will outright kill the suction of a 1200 CFM rated blower, streached out in a straight line.
Chopped into a little here and a little there for connection points, you might still have 20' in the entire shop, but not involved with any one machine at any given time. Because the entire manifold is actively under suction, but only one branch or circuit is doing anything when its gate is opened.

Every shop is a bit different. So only experiance and a bit of "Kentucky windage" will get you in a happy place with your system.
I went overhead in two shops now and think it works best for me. If my shop was in a long line of stations, probably just above bench height would work better. But I don't want tripping hazards around sharp stuff or cast iron tables.
That stuff hurts like heck when you conk your head on it! :o :7

:D

[link:www.sonnyedmonds.com | Sonny Edmonds] http://home.earthlink.net/~sonnypie/vortex_smiley.gif
"Precision Firewood Specialist"
God Bless America !
One Nation Under God!
"Lurkimus turdius orifus"

[Leather Man]

Thanks Sonny, The added response has helped alot.
Ben

[Original Bart]

Leatherman

The best advise I have seen it to keep your runs all 6" all the way to your machine & make the hoods & entry points into your machines 6" too. Your not only trying to get the chips your trying to get the fine dust which is what damages your health. With 6" all the way your flow will be much better as Sonny has said. Please don't compromise your system. Do it right the first time.

[brent]

The way I look at it, catching the chips is just an added benefit of drawing the fine dust away. Ideally you would never have to sweep your shop because the DC would just collect every last bit of it. chips and shavings that get away from the DC and wind up on the floor are easily enough swept up. The fine stuff that you don't easily see is the real demon in our shops.
It seems like when we discuss 4" vs 6" we never talk about the applications of those runs. Although I do not profess to be an expert, it seems to me that we need to look at where those drops are going. I have 5" on all of my goofy-hillbilly-looking DC setup. The exception is the floor sweep. I ran 4" vertical there because I am not worried about catching fine dust (lots of CFM) but rather having velocity in the vertical pipe going up to pull up the chunks. If a drop is connected to a downdraft table, then velocity is not an issue. You are catching dust that will float in the air, it will certainly move up your 6" pipe. You just want to move as much air as you can so you grab as much of it as possible. If you ran a 6" main, I would run a 6" drop to it. But other tools are going to leave heavier droppings and you may want to address them differently.
One thing that I find helps is a spotlight. I have a 1million candlepower (or some outragious number) spotlight that somebody gave me last year for christmas. Did not know when I would ever use it, but I found out it works well for seeing the fine floating dust. That is the really bad stuff we need to get. Naturally it is easier to see at night, but even during the day you can see right in front of the light any dust that is floating around. I was amazed when cut a board on the miter saw and then ran the light across that area. There is a ton of fine dust that comes off of that saw if you don't pull it in.