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Forum topic by Jraysmitty posted 07-07-2017 02:22 PM 388 views 0 times favorited 8 replies Add to Favorites Watch
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Jraysmitty

4 posts in 1695 days


07-07-2017 02:22 PM

Topic tags/keywords: dust collection

Hello everyone,
I have a Jet 1 1/2 hp cyclone dust collector with 6”duct work system. I am having troublekeeping the wood chips from settling in a 6’ trunk from my router table. I have 6” duct and it reduces to 4” about 3’ from the table. any ideas on how to keep the dust moving?
Thanks Jim


8 replies so far

View Julian's profile

Julian

1239 posts in 2529 days


#1 posted 07-07-2017 02:27 PM

Try using 4” hose from the dust collector and keep the hose short as possible.

-- Julian

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pintodeluxe

5466 posts in 2652 days


#2 posted 07-07-2017 03:11 PM

You may have to switch the hard piping to 4” for another 5 feet approaching the router table. As diameter decreases you lose CFM, but you gain air velocity.
Avoid sharp bends or 90 degree angles in the ductwork.

If that fails, you might consider dedicating a shop vac to the router table. I use a standard shop vac with over and under-table collection and it works great. I didn’t bother piping my cyclone to the router table because I tend to use it for very short periods of time.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Carl10's profile

Carl10

68 posts in 295 days


#3 posted 07-07-2017 03:52 PM

Jim,

You are likely not going to be able to use 6” duct with that machine. I had the same machine and with no filter/bag/piping I was getting just over 800 CFM through the 6” opening. (It was with a handheld meter, i did repeated measurements for consistency and this is also consistent with reviews of this machine). This is about 4000FPM (the velocity needed to keep chips airborne in your 6” duct. When you reduce down to 4” you drop the cfm to less than half (as the area is less than half of a 6” duct). What you can try is opening another gate (if you have others) while using the router. That will let more air through the ‘system’. Although it sounds counter intuitive, you want more openings in the system to increase the speed that has been throttled down by the 4” pipe.

There is a review of single stage collectors showing how little air moves when the bags start building up dust.

What I was considering before I sold my machine was to use 5” ducting, but that would be borderline.

Hope that helps,

Carl

View crank49's profile

crank49

4026 posts in 2809 days


#4 posted 07-07-2017 06:02 PM

Use a drop out expansion chamber next to the router table, with a short 4” hose or pipe to the chamber (can be a trash can with hose connectors on the lid) then use your 6” hose from the lid to the collector. Air & Chips enter the chamber where the air flow expands, dropping the velocity, causing the chips and dust to settle to the bottom of the chamber (trash can). The larger 6” duct or hose to the collector will not pull chips and dust off the pile in the bottom of the can because the velocity is not great enough. This is a very simple, very old, tried and tested method of dust and chip separation from the air flow going to a collector.

View JBrow's profile

JBrow

1274 posts in 759 days


#5 posted 07-07-2017 08:32 PM

Jraysmitty

I like Carl10’s idea to increase air flow. Rather than opening a second blast gate, cutting in a second 4” port at the router table would result in air flow slightly lower than if a single 6” dust port were connected to the router table. One port could be top side to collect debris at the router bit while the second port could collect debris that escapes the top side port.

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Redoak49

2904 posts in 1827 days


#6 posted 07-07-2017 09:46 PM

The testing that Wood Magazine did showed that the 1-1/2 and some 2 hp dust collectors are very marginal for using 6” duct. One critical thing may be the openings on your router table. What is the actual size of the openings at the router table. That is, what size is the opening around the router bit you are pulling air through. My guess is that it is much smaller than an equivalent of a 4” pipe.

Using a shop vac with much higher suction, not cfm, makes sense.

Using the hand held anemometer is not very accurate. I did some testing and posted the results in a blog. Small changes in how you hold the anemometer makes HUGE differences in the meter flow rates.

You are better off measuring static pressure and using a performance curve from Wood Magazine to estimate flows in your system and the effects of changes.

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crank49

4026 posts in 2809 days


#7 posted 07-07-2017 10:21 PM

Of course, you guys are only going to keep on looking at the difference between 4” and 6” pipe and discussing what a 1 1/2hp vs 2hp collector will do so I don’t even know why I waste my time giving advice. Never mind that I was an engineer for 40 years and solved all kinds of air flow dust collection problems in commercial scale wood working pattern shops and grinding and molding environmental controls.

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Jraysmitty

4 posts in 1695 days


#8 posted 07-08-2017 02:11 AM

Thanks for the advice. What I have read it is important to keep the duct work 6” and reduce it at the machine to maximize airflow. I do not want to use a dedicated shop vac. It does not perform like a dust collector with a cartridge filter. Thanks carl10 and crank49 for your thoughts
Jim

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