Stumpy Nubs of Blue Collar Wood Working is doing a blog on this very topic.

 

I think I would check your filter. I have a 1.5 hp cyclone that I built that is pulling through 15 or 18' of 4" line that goes across the ceiling and drops down to the table saw without any problems.

 

@GT350 the filter is one of those Micron bags. The single line is schedule 40 PVC with 3 Rockler dust ports and all fittings glued. I've checked closely and don't find any leaks.

 

I'm guessing you already checked to make sure nothing is clogged and the fan is ok? My joints aren't glued but your runs are a bit longer. Could the inside of the bag be completely coated?

 

With 4" ductwork, you will only move maybe 400 CFM, and that won't change with more power. My guess is you need to upsize the ducting.

 

You need 5" ducting, though at 1200 cfm (actual, not advertised) and 25' you might not have the power to do 5" ducting.

 

BTW, as you make the duct bigger, you gain the ability to pull in smaller dust farther away from end of the duct, but you will be trading off velocity in the pipe…you lose the ability to pull in bigger chips and run the risk of clogging the duct. It's a trade off and you need to find the happy medium for your given DC and shop situation.

 

Try upgrading to a wynn filter. I did that and added a baffle (Chinese wok) inside the dust collector and suction greatly increased. Also, it is very hard to fully capture all the dust from a table saw.

wynn filter: http://www.wynnenv.com/35A_series_cartridge_kit.htm

Wok idea: http://lumberjocks.com/projects/48671

 

I have often thought of adding another blower downstream from the main impeller.

This is a bit different from the current stumpy design, as his blowers are back-to-back.

My idea was to add another HF unit to the end of a very long run. That way the debri is pushed by the first impeller into the ducting and sucked out at the end by the main dc impeller.

Did not test this before I sold my HF unit.

I think for the price the HF will add some much needed CFM at the end of your very long run. You could change the TS port to 5", run the 5" to the first HF unit, then maybe even 4" all the way back to your original DC unit.

 

I haven't tried this personally, but I don't think it will be very effective and here's why:
Ideally, you have two DC's pulling air at exactly the same rate/velocity; in this case, the power of the two DC's will help each other and effectively double your suction power, but not your velocity. Since they're basically pulling the same volume of air at the same speed, each only has to work half as hard. Now if you reduce the diameter of your duct, you would then see an increase in velocity.
In theory. Now for the but:
But in execution, if you have two inline DC's like this, the blowers will almost certainly be operating at different speeds (even identical DCs may have minor variations in motor speed), and you are going to have a power loss as the faster motor will be spending part of its power trying to speed up the slower one, which won't work well since the motor has a specific speed it wants to run at and doesn't want to turn any faster or slower than that. If you were really invested in this idea, you could start messing around with motor speeds and ducting diameter to get them power-matched.
Or, you could hook them up side-by-side instead. This way each motor can run optimally at its own preferred speed and you get the full power amplification of both motors running simultaneously. Your velocity will also go up, since when you duct the two DC's together you're effectively reducing the hydraulic diameter of your ducts by half. The downside is that you'd have to have two separate filter apparatus, although you could get by with only one cyclone separator.

 

Thanks for all the comments. I'm going to install a wok in the DC this weekend and wash the filter bags as was recommended. I've had the unit 12+ yrs and have only shaken the filter bag. I considered a 5" mainline but opted for a 4" because the Rockler Dust Right® 4'' Dust Separators http://www.rockler.com/product.cfm?page=25225&site=ROCKLER are 4" fittings. Hopefully after I wash the bag I'll see an improvement.

 

I see a big problem!! Check out your first picture, that is way to sharp of a turn! That could easily be taking 200 CFM out of your system right at the blower!

 

Cole, do mean from the DC to 2-stage? I was thinking about mounting the DC directly above the 2-stage so it would be directly inline.

 

I had the same problem with my table saw. I had a old 1hp foley belsaw dust collector on hand that I bought used years ago for my planer but it was totally useless for that purpose. I just hooked it directly to the table saw with the discharge hooked to the line from my jet dust collector. It works great, but it seems like the old Belsaw blower is doing most of the work. my next step will be to buy a bag for it and wire it to come on when the saw is turned on. I will then become a dedicated collector for the table saw.

 

As has been mentioned, try to eliminate any sharp 90º bends. Also, it is a good idea to minimize the amount of flex hose in your system. Flex hose has about 3 times the air resistance of smooth walled duct for the same diameter.

 

Also, be aware that if you did too good of a job sealing up all the cracks in your tablesaw, that your air volume will be reduced. For example, if all the gaps are sealed and the only place that the DC can pull air is around the slit in a zero clearance insert, then you will have a huge amount of loss to SP and highly reduced CFM.

 

Pete, I noticed that also. I made the same mistake on my router table, closed up all the holes except the throat plate. Restricted airflow so much that it would not suck anything. re-opened up the router table, drilled a few well placed holes and viola! back to decent dust collection.

I think sometimes we get trapped by the less is more. The thinking being if I close up all the other ways air can get sucked in, then the remaining opening will pull that much harder. Maybe for shop vacs, where static pressure is higher and volume (cfm) is low. Not so for our dust collectors. Volume and CFM are king, you need to feed the beast in order for it to move air.

 

I have a HF 2HP with 4" PVC duct and one of the garbage can separators in front of the Collector, works OK, but Table saw still spits saw dust out the front. I recently found a large Craftsman Shop vac in the Trash, fixed the motor and it works pretty good, I am thinking of adding it to my HF 2HP dust collector system by punching another hole in the garbage can separator and hooking the Shop vac to it. System is in an adjacent room so noise from loud shop vac should not matter, I may try it this weekend.

 

@Pete, that's a good point I'm thinking that closing up the space between the cast iron table and the cabinet may not have been the best idea. I think I'm going to scrap out the GreatStuff foam I sprayed in there.

This wknd I'm going to re-engineer my DC so the motor is directly above the 2-stage.

 

Where is the dust coming from?

 

I emptied the bags and they were pretty caked up. Should these go in the washing machine or just give them a good shaking? Also, I had forgot what the inside looked like. I was going to mount a wok but I don't think it will be necessary.

 

You should still do the wok idea. Although your dust collector has an abnormal inside shape, The wok stops the circular dust motion in the lower bag which stops it from coming up into the filter bag.

 

Running two blowers is doable, but if you don't do it right you'll fry both motors and risk fire. You have to regulate the airflow. We'll get into it more on this weekend's episode of Blue Collar Woodworking.

 

Why not just make the new dust collector solely for the tablesaw?

 

There are a couple of issues to think about when running two blowers together. First, tests have shown that it is better to hook one to the back of the other, in series, rather than mount them side by side in parallel. Second, the blowers will "supercharge" each other, meaning the combined airflow will actually cause the motors to run faster than they are designed to, which will quickly burn them up. This can be prevented by regulating the amount of airflow via a blast gate. Third, using mismatched blowers (one larger than the other) will increase the chance of burning them up.

Proper ducting is also important. For fine dust collection you need more airflow than 4" ducts will allow. But to install 6" ducts you have to have a powerful enough blower. Mounting two together, if properly done, along with a properly designed cyclone, can be a great solution. But hooking a single stage dust collector up to 6" ducts will increase your risk of fire because you won't have enough airflow to keep the ducts clear of dust.

In my opinion, there are two ways to approach dust collection:

1- Collect as much of the wood chips as possible to keep the shop clean-ish with a single stage dust collector like a Harbor Freight or Jet. Wear a dust mask to keep the fine dust out of your lungs.

2- Take the time and spend the money to switch to 6" ducts and get (or build) a big enough blower and cyclone system to collect all of the fine dust.

You can't get any more than #1 without spending a fair amount of money. On Blue Collar Woodworking we are trying to come up with a way to do it as inexpensively as possible by using our current HF dust collector, adding a second one (bought used for $100) and building a wooden cyclone and wooden 6" ducts. That will save a lot of money compared to buying a $1500+ cyclone system. But it still won't be cheap. 6" flex hose is very expensive even if you only use as little as possible. Filters for fine dust collection that still allow enough airflow cost about $300. (You can do without the filters if you vent outside the shop). And there are a lot of miscellaneous expenses that add up quickly.

I think it's worth it. But not everyone can afford it. The bottom line is this- There's no use trying to get fine dust collection with a single stage unit and 4" ducts. You simply can't do it. If your current setup collects most of the chips, you're getting as good a result as you can. If you want better the only way to do it is to go a lot bigger.