Dust Collection Questions - improving chip separation, fine dust filtration and over all suction

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Forum topic by OneShot posted 01-19-2021 02:06 PM 351 views 0 times favorited 5 replies Add to Favorites Watch
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1 post in 229 days

01-19-2021 02:06 PM

Topic tags/keywords: chip separation improvement fine dust filtration improvement over all suction improvement

Hey guys,
I need to make some improvements to my dust collection set up. My goals are to improve the chip separation, fine dust filtration and over all suction.
1) I have been doing some research on Thien baffles and built one for my shopvac to play around with. It seems to work well but the suction loss was about 30%, understand that suction loss is normal when running through a baffle or cyclone. My thought was to build a Thien baffle to fit on my larger dust collection system that I use for the larger tools. As I am doing my research I don’t see a lot of comparisons between a Thien baffle and an Oneida Cyclone. There is one video on youtube that shows the baffle creates more loss than a cyclone. The video showed 440CFM through a Thien baffle and 636 CFM through an Oneida Cyclone. I wanted other opinions. Has anyone done comparisons on the suction loss difference between a Thien baffle and a Cyclone such as ones that Oneida manufactures?

2) I bought an anemometer off Amazon to measure airflow. As everyone says, I have measured firsthand how much resistance the filter bag causes as compared to removing it. Maybe my bag needs cleaned however the loss between bag vs no bag was about 21% on my Delta unit and 54% on a smaller Protech unit I have. Not sure if that much loss is normal or not. I would love to vent outside however I live in a climate where I pay to heat my shop so I do not want to blow all my heat outside. My question is, has anyone experimented with building a box to exhaust the dust collection unit into fitted with standard HVAC filters using a Merv 12 or 13 to filter out the fine dust? or is it simply best to invest in an aftermarket filter like the ones Wynn offers to filter out the fine dust? Assume both cases would improve airflow as compared to the filter bag?

3) Last question, my large collection unit is 1hp and I would like to upgrade to a 2hp unit. I see lots and lots of people buying the Harbor freight unit and applying the blower with Thien baffles, Cyclone, Wynn Filters and making upgrades to the inlet size, impeller. The initial price seems great, but my question is after all the upgrades I would probably have $600-$700 in it. The idea of incrementally upgrading overtime is good but in the end with that much money are there other options you guys would recommend that would be a better result?

Thank you for any help and guidance you can offer.

5 replies so far

View ibewjon's profile


2268 posts in 3803 days

#1 posted 01-19-2021 02:39 PM

It has been stated in another thread on LJ that starting with hf and doing upgrades is about the same price as buying a jet or griz new PLUS the added work and time. To me, it is a no brainier. My time is better spent on wood than being a sheet metal worker. And I think griz may have a dc with a 1 micron filter. And add an air filter to collect the dust missed at the tool. And an anemometer measures air speed, not cfm. Dwyer instrument makes an air flow meter. About $200.

View HarveyM's profile


159 posts in 3032 days

#2 posted 01-19-2021 02:40 PM

Fine Woodworking tested them in issue 232. They found on a 1 1/2 hp single stage dust collector the super dust deputy kept the air flow at about 420 cfm over time. The Thien started at just over 500 cfm at the start but the filter slowly clogged & at around 100 lb of dust & chips it’s air flow dropped below the cyclone. So if you use a Thien clean the filter every couple of bags.

-- Just a Duffer

View tvrgeek's profile


1429 posts in 2659 days

#3 posted 01-19-2021 03:27 PM

Just got an answer back from CleaVIew on why they make only 5 HP and larger. As I suspected, it really does take that much to control the stand off cloud of fine dust, you know, the stuff that kills you. Chips don’t. Go read all the papers from Bill Pentz. I am about to replace my temporary ducting with a full 6 inch to the tool system, inlet flairs long radius and all the best I can pull off.

You take air speed and duct size to calculate CFM. Web sites do it for you. For example, my Jet, through my TS 4 inch hose, I measured 14M/s which calculates as 960 CFM.

I measured the velocity around the TS throat plate @ .4 M/s before I tidied up the cabinet so it inly has about as much gap as the inlet. It now reads 4.1M/s. Perfect dust collection? Not even close but it is the 10 times better the numbers suggest. New dustwork wil improve and I have one more idea how to get the dust out of the gullets before they are carried back into the shop.

I only have the electrical capacity to upgrade to 3 HP from my 1 3/4. So it is what it is.

View clagwell's profile


363 posts in 802 days

#4 posted 01-19-2021 05:29 PM

...You take air speed and duct size to calculate CFM. Web sites do it for you. For example, my Jet, through my TS 4 inch hose, I measured 14M/s which calculates as 960 CFM….
- tvrgeek

Those numbers seem to off by a factor of four. I think you used the diameter instead of the radius to calculate the area of the hose.

For a 4” diameter duct:

14 m/s → 245 CFM
960 CFM → 55 m/s

-- Dave, Tippecanoe County, IN --- Is there a corollary to Beranek.s Law that applies to dust collection?

View JAAune's profile


1932 posts in 3326 days

#5 posted 01-19-2021 06:29 PM

My advice is to save up for a better collector. Take the time saved from not doing dust collector mods and apply it towards analyzing and rebuilding the dust shrouds on your machines. Even a shop vac will capture a lot of dust if it’s properly contained and directed towards the vacuum port.

The above strategy will end up with you getting a nicer collector and getting better collection with your current DC and your future one.

-- See my work at

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