Results of dust collection mods to Ridgid contractor saw

tvrgeek

Scott
User
Well, talking is one thing. Numbers and pictures count.

Dust collection for my saw was terrible. Common Ridgid contractor saw. I have a 1 3/4 jet CD. Less than perfect ductwork, but still, at the saw a 4 inch hose had 14 M/s flow.
With my closed base 4 inch hose, 2 1/2 to shroud, the flow through the finger hole in the throat plate was .4 M/s.
Foamed the top to base ( we can on a contractor as the trunnion is mounted to the top, not base)
Gasketed the box
Two door sweeps from HD. They slip out of the guide so easy to bend.
Plate and gaskets on the back edge.

The box and outfeed table and braces was tricky as the motor swings almost as high as the table on full tilt. Don't want it vacuum tight as it takes airflow to carry dust, but the flow was so far away from the blade, it was doing about nothing. I think a great improvement would be to swap hoses, so the 4 inch to a larger port on the shroud, and just the 2 1/2 to pick up what falls in the box. Still a little sloppy I need to clean up, but wanted to share my results.

4.2 M/s flow on the plate! Yea, 10 times the airflow. Crosscuts gave almost no top side dust. Ripping a face with the blade exposed will still fill your pockets with sawdust. Only mitigation will be a top side hose.

Am I happy? Much better. But darn, I still want that Harvey 300 and G700 pair but still squirming about the $4K bill if I can justify it. But for only a few bucks, a big improvement. My DC ductwork is very poor and if I keep the Jet, it will get proper size smooth run metal dust. I don't know if it is totally the duct, or loaded filter, but my at-hose is 1/3 of spec. I expect closer to 2/3.

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pop-pop

Man with many vises
User
Clever idea to box the motor rather than trying to seal the cabinet opening for the motor & belt.
 

Hmerkle

Hank
Corporate Member
Clever idea to box the motor rather than trying to seal the cabinet opening for the motor & belt.
I thought so too!
I have an old craftsman / atlas contractor saw and it could be on legs for all the open spaces in the "cabinet"!
 

McRabbet

Rob
Corporate Member
Just remember that you must have enough openings to be able to exhaust the dust from your saw. If you block all entry of makeup air, your dust collection will not be effective.
 

tvrgeek

Scott
User
From my original post:
" Don't want it vacuum tight as it takes airflow to carry dust, but the flow was so far away from the blade, it was doing about nothing. "
 

McRabbet

Rob
Corporate Member
I read your original post and noted what you stated above in post #5. The 14 m/s linear flow you quoted translates to less than 250 cu ft/sec through your 4" hose which is insufficient to remove much of the dust generated by the blade during a cut. The approach you've taken has improved your performance, but in order to get good dust removal, you need closer to 700-800 cfm which cannot be attained with your Jet. I would predict that you'll find the interior of your saw filled with sawdust over time because the current airflow cannot keep it suspended long enough to get to the duct port at the bottom (gravity will help since the port is at the bottom).
 
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Oka

Casey
Corporate Member
Rob has a good point. Rememebr all air sytems like this need to be close to neutrally balanced. So if you have a draw of 500 cfm, you need enough opening to be within 10% of 500cfm at the intake intake opening. One thing I am planning on doing to my saw is to stream line (make smooth) the interior of the saw. Most saws the interior has too many edges or pocket cracks that just retain dust. If you can make those vertical sides flat and smooth you can cause all dust not captured from the primary vacuum opening to fall to the bottom and if you have that ported, then you can get almost all, not 100% but close enough to make you happy.
 

tvrgeek

Scott
User
I calculate differently. Or rather this calculator translated differently.
14 LM/s translates to 45 LF/s which is roughly 2730 LF/m into a 4 inch hose, this gives 952 cfm.

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Spec for the DC is 1100 cfm, so my trunk is not horrible, but can be better. The two largest openings are for the tilt lock knob, and it is almost as large as the hose, and the flap between the outfeed, motor box and top. Total opening is probably closer to 20 sq-in, where the hose is 12. I do not believe I am starving it.

I have two ports. One on the bottom where any gravity assisted dust falls to a sloped panel. The second port goes to the blade shroud. I believe this is backwards of what it should be. I should have the highest flow as close to the source as possible. Modifying the shroud looks like quite a job. An idea I have is to add a 2 inch port to the opposite side of the shroud as the current port from the outside. Then the primary airflow is across the gullets.

Another thought I had was to remove the shroud. Then point a nozzle from a leaf blower right at the lower half of the blade. Again, the idea is to get the dust out of the gullets before it is carried back up through the wood. The way it is now, flow is down the side of the blade and out the bottom corner of the shroud. Centripetal force may be holding the dust in place. It could be possible to but a very close diverter to the left of the blade right above the shroud port to cause a pressure difference across the blade, again assisting flow through the gullets. That may be easiest to do from the top. All this may be hard to visualize I know.

I don't care about having to slip the bottom plate out every now and again to get dust on the various flanges out. It is airborne dust that is important. About nothing else. I can say, when I fired it up, I heard a lot of dust make it's way out before I tried the first cut. I made it easy to slip out as if I didn't, you know for sure I would drop the arbor nut!
 

Hmerkle

Hank
Corporate Member
I read your original post and noted what you stated above in post #5. The 14 m/s linear flow you quoted translates to less than 250 cu ft/sec through your 4" hose which is insufficient to remove much of the dust generated by the blade during a cut. The approach you've taken has improved your performance, but in order to get good dust removal, you need closer to 700-800 cfm which cannot be attained with your Jet. I would predict that you'll find the interior of your saw filled with sawdust over time because the current airflow cannot keep it suspended long enough to get to the duct port at the bottom (gravity will help since the port is at the bottom).
@McRabbet if there is sawdust in the interior of the cabinet and the DC runs after the machine is turned off, why in a less than "Neutral balanced" (I like Oka's terminology) wouldn't the DC continue to pull sawdust into the collector?
 

tvrgeek

Scott
User
Started the process to convert to 6 inch end to end. Darn that spiral pipe is expensive. Amazon has the self-clearing blast gates much cheaper than other places. For this iteration, staying overhead and hope the drop is not really in my way.

Measured at my through wall 6 inch duct today. Calculates at over 3250 CFM. Confident I can provide at least as much at the TS as needed and still have the overhead to add the larger Oneida cyclone.

Once it is plumbed, can't measure airflow but I can use a vacuum gauge and translate. Then open up the airflow so I am not starved. One idea is to put a 2 1/2 hose from outside to the blade shroud so the "leakage" is pulling directly across the gullets. That's where the dust is.

With my 4 inch, I use these nifty twist lock dryer duct quick disconnects. Can't find anything in 6 inch. May have to make something using a flange and neo-magnets.
 

McRabbet

Rob
Corporate Member
@McRabbet if there is sawdust in the interior of the cabinet and the DC runs after the machine is turned off, why in a less than "Neutral balanced" (I like Oka's terminology) wouldn't the DC continue to pull sawdust into the collector?
Unfortunately, the dust will not be picked up unless the dust collector air flow is increased substantially. The reason the dust accumulated in the first place was because the dust-laden air inside the saw cabinet loses velocity while inside the large cavity and it cannot retain the dust -- it drops into the cabinet. When the creation of new dust ceases (i.e., the saw is turned off) and the dust collector continues to draw air through the cabinet, there generally is insufficient velocity to re-entrain dust into the moving air stream and it stays put. If the user agitates the accumulated dust, some will get picked up. If one had a high volume dust collection system (say 1200 cfm through 6" duct), little dust would build up inside the cabinet because the higher velocity air will sustain dust in suspension and it gets drawn out of the cabinet. Even then, there will almost always be nooks and crannies where dust drops out of the air stream and some will accumulate.
 

tvrgeek

Scott
User
Had another thought. One could reduce the voids with some foam blocks, carved to fit so as to reduce the size of the "low pressure box" which if we are old enough to remember, was the common design for a dust collector before cyclones. It would not help reduce the dust carried back through the table in the gullets which is the important issue. It is the air I want clean, not the inside of the saw.
 

bowman

Board of Directors, Events Director
Neal
Staff member
Corporate Member
Sounds like you need an overhead air filter then
 

tvrgeek

Scott
User
Everyone does! I have two. I fitted my split HVAC with large external MERV 13 filters and build an old furnace fan into a box with MERV 13 filters. I have a through wall fan to clear out if I do something really bad like spray paint. They do a pretty good job, but nothing replaces preventing the dust from getting into the room to start with.
 

Scott H

Scott
User
I calculate differently. Or rather this calculator translated differently.
14 LM/s translates to 45 LF/s which is roughly 2730 LF/m into a 4 inch hose, this gives 952 cfm.
I may be wrong here but the calculator is asking for "R" which to me indicates a radius. Four inches is the diameter, right?
 

tvrgeek

Scott
User
Quite right. I missed that.

So I can hope for around 900 CFM without a bigger machine. That is still a lot of air provided I get it to the saw. It will be all 6 inch, spiral duct, long radius curves etc. I am going to re-mount the blower on it's side and that will eliminate two more 90's. As I use MDF quite a bit, a cyclone is in the plan. I may add one to my Jet, or if I decide it's not big enough, whatever 3 HP system I find. The Laguna looks nice. I just don't have the electrical power for a Clear view, 5 HP
 

tvrgeek

Scott
User
Old ductwork
New ductwork
Up to 620 CFM into the 6 inch with an additional 130 into the 2 1/2 drop to be moved between router fence and blade guard.
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tvrgeek

Scott
User
Just looked at my sub-panel and the various loads. I think I can run the 5 HP ClearView DC. It is specifically designed for higher drop 6 inch systems. Second choice is not quite "clear", it is the 3 HP Oneida which would probably be fine as it meets the US OSHA spec, but as a hint, falls short on the EU spec. For the same cost, CV would seem better. Unfortunately, I now have to run a 10Ga line as I only wired for 20A. So much fun.

New duct made a noticeable improvement on the band saw.

Don't ask me why it posted the picture twice.
 

wolfsburged

Bill
Corporate Member
How are you measuring your airflow performance? I am interested in trying to get some measurements on my installation to baseline for improvement.
 

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