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When Do You Get Diminished Returns on a HF DC Unit?

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Forum topic by HorizontalMike posted 11-30-2011 03:06 AM 897 views 0 times favorited 6 replies Add to Favorites Watch
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HorizontalMike

7147 posts in 2378 days


11-30-2011 03:06 AM

Topic tags/keywords: dc dust collector dust collection mortising machine router horizontal router

I have been busy building a horizontal mortising machine that I have/am designing to include dust collection. I have a HF DC unit with a 4in flexible hose. My Triton router takes a 1 1/4in hose that I am linking to a box that hooks up to the 4in main DC hose. Additionally, I am slotting the bottoms of two sides of this box to suck in router dust that falls.

My 2hp HF DC 4in hose has ~12 1/2 sq.in. of area that it pulls at a stated 1550 CFM air suction capacity. I am using LESS than this capacity in my mortise DC box design (maybe 6 or 7 sq.in.)

MY QUESTION IS: At what point (smaller area) does my suction capacity diminish as to become pretty much dysfunctional?

I am going on the assumption that sizing a small bit under 4in might increase suction/flow a small amount. Am I correct/incorrect in my thinking here? I only use my DC on one machine at a time.

-- HorizontalMike -- "Woodpeckers understand..."


6 replies so far

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crank49

3981 posts in 2435 days


#1 posted 11-30-2011 03:23 AM

My experience is the HF 2hp DC is at its peak with a 4” and a 2-1/2” attached to the “wye” inlet and both open and flowing at the same time. That equals the area of the 5” diameter, approximately, of the blower intake. Much bigger and you lose velocity, much smaller and you loose volume.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

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HorizontalMike

7147 posts in 2378 days


#2 posted 11-30-2011 03:49 AM

I am wondering if that decreased volume of smaller overall area will lead to some/any increase in suction at the tool? I know its a trade off, just wondering how much of one. In other words, I would hate to open things up too much and make the Triton 1 1/4 hose lose too much suction at the router.

-- HorizontalMike -- "Woodpeckers understand..."

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crank49

3981 posts in 2435 days


#3 posted 11-30-2011 04:43 AM

Sometimes I pull the 2-1/2” hose off the band saw and hook it to my ROS. Collects that dust just fine. But , I always use my Shop Vac to collect from the router.
I don’t think the DC would have enough static pressure to get the capture velocity needed for the router.
But, I haven’t tried it. It’s just the engineer’s intuition in me that thinks it wouldn’t work.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

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HorizontalMike

7147 posts in 2378 days


#4 posted 11-30-2011 04:58 AM

Well, I built a small ~4×4in box on one side that is slotted but I guess I could always add another box like it on the other side, or better yet run a smaller skinny box extension along the bottom and cut additional slots/pickups. That would put me up to that 12-14 sq.in. range, pretty much inline with a 4in. hose that has ~12.5sq.in. This is good thinking about this now because while I have the pieces all cut, they are only temporarily mocked up to see what works visually. I know I would have already been finished by skipping the DC mod, but that would take all the fun out of it ;-)

I’ve got my shop vac dedicated to my MS so it is pretty much out of the loop since it is mounted under the stand and has its own separator attached to it. It is just easier to run the 4 in hose as needed.

-- HorizontalMike -- "Woodpeckers understand..."

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gfadvm

14940 posts in 2154 days


#5 posted 11-30-2011 05:50 AM

Mike, I use a 21/2” hose from my 4” hose to my router table and it catches nearly all the debris. That didn’t seem too clear so lets try this: dust collector, then 10’ of 4”, then 7’ of 2 1/2” connected to router table. Better?

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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Sawkerf

1730 posts in 2532 days


#6 posted 11-30-2011 06:29 AM

There’s no easy answer to that question, Mike. The stated cfm rating is probably only at the impeller inlet. Since they have no way of knowing what your duct system looks like, it would be impossible for them to give a rating at a distance.

Basically, the flow rate drops off with every foot of duct run, and there are significant drops if you have rough duct walls. Fittings (elbows, T’s, Y’s, etc.) also eat up a lot of flow.

-- Adversity doesn't build character...................it reveals it.

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