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

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.

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

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.

...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?

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 http://altaredesign.com