Thread: Tablesaw improvement question

Is it a contractor saw or Cabinet saw.

Cabinet saw.

With my cabinet saw which is a 12" older Carbatec saw I run a 4" from the saw to 6" ducting. It is reasonable but where it is let down is a lack of overhead dust extraction. The reason I didn't want to put a 6" ort on the saw was I didn't want to modify as for me I thought it might affect re sale but in all honesty a simple reducer from the saw itself would suffice f a new owner of I went 6". I have a two stage system which is in another shed. I find that my separator fills very quickly as it has a capacity of 1 litres.

I'm sorry to say that DC won't have an 850 CFM throughput as it has a 2HP/12" motor/impeller, only one filter and a Cyclone. This means with a clean filter it will have less throughput that a generic single bag 2HP DC with no cyclone. according to Bill Penz, cyclones can rob up to 45% of air flow which is consistent with what I have measured
The flow rates on the generic 2HP DCs are about 560 CFM. see The Generic 2HP DC

Remember a 4" duct can only carry about 400 CFM and even though those DC have two x 4" ports they end up fighting each other for air flow which is why the second 4" port performs so poorly.

The advantage of a cyclone to keep a DC filter clean is lost if the air flow is so low that it simply doesn't collect the dust to start with. All this is why I spent so much time to try and improve the flow on the generic 2HP DC.

If you had more flow I would suggest removing the shroud and opening up the port to accept a 6" ducting as suggested by tomartomau .

Ordinarily I would still suggest installing 6" ducting but with such a low-flow DC there is a strong likelihood of dust settling out in 6" ducting.
If you plan to upgrade the DC soon then I would say go with 6" but otherwise go with 4" and add extractor fans to your shed to ventilate the fine dust that won't be collected.

I have just taken the angle grinder to my cabinet saw.
I got 2 100mm bell mouths mounted them on a piece of ply as close to each other as possible, then marked out a rectangle on the metal.

On the inside of cabinet I removed the shroud what a poxy piece of uselessness. Then cut 2 pieces of ply that sloped from the access door down below the bell mouth opening, (2 pieces as I could not get 1 piece in, the 2 fit tight beside each other, I had to cut notches for where the cabinet metal joins are.

The 2 bell mouths go into a 100mm Y join, this then meets with another Y that goes off to the (proposed, ie still to be done) overhead; as per John Samuels (pic)

I am hoping this works, and also figure I will have this saw until I fall off me perch and then its someone elses problem.

As Bob said, your system needs to be paired with your DC. Having the "ideal" 6" ducting with an inadequately powered DC is just asking for trouble.

Collecting dust in the cabinet/around the blade is part of the solution. Above blade collection is the other part.

My saw has the stock 4" port right at the bottom of the cabinet. I've cut a second port directly behind the motor with a second 4" port and also have a third 4" port above the blade. Once this was installed night and day difference in the amount of fine dust in the air as measured by a particle counter.

Thanks to everyone for their replies. I haven't yet read through those posts that BobL linked. I'll have a good look at them after the weekend.
My take away from this is I need to experiment with my DC to see what it's capable of, then see what I can do with the tablesaw. Unfortunately, I don't have much ducting to test with at the moment. Trying to work out what to do before investing in that.

Testing with a cheap anemometer, straight from the 146mm ID port in the DC I get 4410 ft/min, which if I'm doing this right is 794 cfm.
With the stock 6" to 3 x 4" adapter, straight from one port it's not giving me a measurement, with 2 ports open 4626 ft/min, so 390 cfm.
At the end of 2m of 100mm flex hose, and other ports closed, 5630 ft/min, 475 cfm (that sounds a bit high? Am I doing this incorrectly?).
At the end of 2m of 100mm flex hose, and 1 port open but nothing attached to it, 3346 ft/min, 282 cfm. Other port with nothing attached at 5433 ft/min, 459 cfm.

I plan to vent the DC outside without the filter, hoping the cyclone will pick up the bulk of the waste (otherwise will have to rethink that), which should help a little right?

Also, I was initially confused by the contractor/cabinet question since I added a picture to my post, but now I see it's not there. Looks like I didn't do it correctly. Probably doesn't matter now, but I'll try again.
IMG_4984.jpg

You have a cabinet saw. Contractor is the open bottom ones sitting on legs with the motor hanging off the back

DRAFT: FAQ - Dust Extraction (Practical Aspects) Second post in the sticky explains in part why your readings are not consistent or predictable. Basically the size of them means the air has to speed up to get through and around (that Bernoulli guy) them leading to higher readings in addition to them being sensitive to position and angle presented to the duct skewing the readings.

Pete

Originally Posted by Meranaldar

Thanks to everyone for their replies. I haven't yet read through those posts that BobL linked. I'll have a good look at them after the weekend.
My take away from this is I need to experiment with my DC to see what it's capable of, then see what I can do with the tablesaw. Unfortunately, I don't have much ducting to test with at the moment. Trying to work out what to do before investing in that.

Testing with a cheap anemometer, straight from the 146mm ID port in the DC I get 4410 ft/min, which if I'm doing this right is 794 cfm.
With the stock 6" to 3 x 4" adapter, straight from one port it's not giving me a measurement, with 2 ports open 4626 ft/min, so 390 cfm.
At the end of 2m of 100mm flex hose, and other ports closed, 5630 ft/min, 475 cfm (that sounds a bit high? Am I doing this incorrectly?).
At the end of 2m of 100mm flex hose, and 1 port open but nothing attached to it, 3346 ft/min, 282 cfm. Other port with nothing attached at 5433 ft/min, 459 cfm.

A single pressure/velocity measurement is highly unreliable in measuring the sorts of air flows inside a duct at the speeds generate by dust extractors. The turbulence alone can make differences of 2 - 3X greater than the real flow.
Have a read of this DRAFT: FAQ - Dust Extraction (Practical Aspects)

The only way to use pressure measurements reliably is using a calibrated Pitot tube which measures a difference between two pressures into and sideways to the flow. To be accurate the tube has to be significantly smaller than the diameter of the ducting, Again an accurate reading will require the use of a test duct, measuring multiple times across the flow, and performing a numerical integration like this
DRAFT: FAQ - Dust Extraction (Practical Aspects)

It sounds like you should really read that entire thread>