# Okay revisiting my dust collection again (can't leave well enough alone?)



## WorksInTheory (Jan 5, 2014)

This is my current set up. I reconfigured the Harbor Freight special ala April Wilkerson and early Jay Bates. I also changed the impeller to the Rikon 12". I kept the run pretty short and tried to keep it big and straight as long as I could. The total run is about 10 ft distance. I feel though I think somewhere I messed something up that is sucking the performance out of it, pun intended.

Everything works okay, better than nothing but could be better. The big issue that doesn't seem to be working is question #3.

I have 3 questions (marked by the blue circles for reference):

1) Does piping outside vs putting on a filter bag (I do reduce the mouth of the bag to fit the 5" diameter outlet but left the rest of the bag that came with HF as is.) affect the performance. Theory is that piping outside will be better than using the bag.

2)Is running 6" (yes it's increased from 5" just because it was easier to get 6" HVAC ducting) at the beginning helpful or should I run 4" for the whole run for more velocity?

3)Finally, this is the real issue that lead to this post, I hacked a SawStop TCG Dust Shroud Blade Guard to fit my table saw. So now I need to split the dust collection to 4" to the bottom and then 2.5" to what I believe is 1.5" port of the SawStop dust shroud.

3a) One way I can do this is just use the 2.5" hose I have going to the router table fence. That's a split then that happens way back

3b) The other is to split the current 4" Table Saw to a 4" and 2.5" and make the split closer to the point of the table saw.

Not sure which is better though either way seems to not have much suction coming off the dust shroud.

I guess I could connect a shop vac instead to that but I have poor electricity in the garage and running the DC, the shop vac and the table saw… I feel I will just trip a breaker and also that's a lot of noise at the same time.

Looking for thoughts and also anything else I am not thinking off. I will also try to seal off more stuff sources of leaks (got some of that xtreme tape).


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## ibewjon (Oct 2, 2010)

Motor size? Why the impeller change? It was designed with the original impeller, that might hurt performance. Also, 6" duct may be too big for the unit. I have a 2 HP north state DC converted to use a jet pleated filter. I also used 5" heavy guage steel duct because that is the size of the machine.4" drops with y fittings. Do you have y or T heating fittings? I don't know why any company makes t dust collection fittings. There are no t intersections on the interstates, just y exits and entrances. I also use long radius DC pipe fittings, heating 90's slow the flow. I have over 40 feet of duct with 4 90's to my 8" jointer, and it works great.


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## Lazyman (Aug 8, 2014)

While using 6" should offer less resistance, I wonder what effect the lower velocity has on the actual effectiveness? Also, how air tight is your shop? If you are venting outside, you need a way for the same amount air to get back in so, if it is really airtight, you could actually have a net reduction if airflow compared to a filter. Try cracking a window or door open and see if it makes any difference. I don't have a DC but on a shop vac at least, you can sort of tell the difference by the pitch of the motor changing when you reduce the resistance. I saw a youtuber using a phone or tablet app a while back to measure the actual change in pitch of a motor to estimate the RPMs with the changes in load.


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## rwe2156 (May 7, 2014)

Venting outside will improve performance, but as Nathan said, you will have to take into account the heat loss issue.

Assuming this is a 2HP blower. I think 6" is a good choice. I would run the 6" as far as you can rather than reducing.

DC ducting does not follow the same principles as HVAC. I would focus on maintaining CFM's and let air velocity take care of itself. You do this by keeping the ducts as large are you an as close to the machine as you can.


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## ibewjon (Oct 2, 2010)

How big is the motor? Can you post a picture of the DC?


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## WorksInTheory (Jan 5, 2014)

Good news bad news - not insulated freezing cold garage with lots of air holes (like my garage door is not straight along the bottom and left and right corners you can see light. No waters or furnaces in the garage either.



> Venting outside will improve performance, but as Nathan said, you will have to take into account the heat loss issue.
> 
> Assuming this is a 2HP blower. I think 6" is a good choice. I would run the 6" as far as you can rather than reducing.
> 
> ...


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## WorksInTheory (Jan 5, 2014)

It looks pretty much like this - from Jay Bates. 




Or April Wilkerson: except mines more like Jay's where the motor part goes right into the thien vs having a hose connection. 









The reason I didn't do a lot of pics is I have a lot of stuff leaning up against stuff right now but here's an attempt to see part of it:










The impeller change is a well known change. Apparently the impeller is really small for a DC this size/spec.


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## WoodenDreams (Aug 23, 2018)

I have the HF #31810 dust collector. 660 CFM with 4" inlet/outlet, I don't have any issues with it. I don't think the CFM it produces can handle the 6" tubes. I'd stay with the original inlet size. If you have the HF #97869 dust collector, 1550 CFM with 4" inlet. this should handle the 4" or 5" with minimal air flow lose. I'd be hesitant to use 6" tubes. Also the quality of the Blast Gates can vary in the seals.


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## ibewjon (Oct 2, 2010)

I still think the 6" duct is too big for the unit. By the time it sucks the air out of the pipe, there is nothing left to move the chips.


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## Rayne (Mar 9, 2014)

I agree the 6" is probably killing a portion of your performance. I would look into local HVAC dealers for 5" snaplock duct. It's most likely cheaper than what you bought (I know mine was by a long shot). That might resolve any issues you have; just make sure there are no air leaks anywhere.


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## ibewjon (Oct 2, 2010)

Remember to tape all the joints with aluminum tape. Buy some air duct sealer and paint it down the length of the snap lok joint, and also paint the joints in 90's and y's. If you have T fittings, replace with Y 's.


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## WorksInTheory (Jan 5, 2014)

I received a ton of 6" and 4" HVAC pipes left over from a friend's DC project. So was saving money.
Would changing it to 4" be better?



> I agree the 6" is probably killing a portion of your performance. I would look into local HVAC dealers for 5" snaplock duct. It s most likely cheaper than what you bought (I know mine was by a long shot). That might resolve any issues you have; just make sure there are no air leaks anywhere.
> 
> - Rayne


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## WorksInTheory (Jan 5, 2014)

Thanks - yes I do tape everything - actually love taping, weird addiction.



> Remember to tape all the joints with aluminum tape. Buy some air duct sealer and paint it down the length of the snap lok joint, and also paint the joints in 90 s and y s. If you have T fittings, replace with Y s.
> 
> - ibewjon


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## WorksInTheory (Jan 5, 2014)

Thanks for all the tips so far - anyone comment on the table saw dust shroud part?



> 3)Finally, this is the real issue that lead to this post, I hacked a SawStop TCG Dust Shroud Blade Guard to fit my table saw. So now I need to split the dust collection to 4" to the bottom and then 2.5" to what I believe is 1.5" port of the SawStop dust shroud.
> 
> 3a) One way I can do this is just use the 2.5" hose I have going to the router table fence. That s a split then that happens way back
> 
> ...


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## ibewjon (Oct 2, 2010)

If you have the 4", it is no cost to try it. Once the pipe size is correct, the saw should be an easy fix.


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## WorksInTheory (Jan 5, 2014)

True but it is a pain in the ass to undo all the 6", esp since it's all taped up and then do the 4" (they are in sheets you have to roll up, cut, etc) and I do have to buy the joints (45's, Y's) - so before I do all that would want to see someone can validate that will definitely improve it.



> If you have the 4", it is no cost to try it. Once the pipe size is correct, the saw should be an easy fix.
> 
> - ibewjon


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## ibewjon (Oct 2, 2010)

Try the saw connected with 4" flex. The flex has a greater loss, but it is worth a try. It's not working the way it is…. nothing ventured, nothing gained.


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## WorksInTheory (Jan 5, 2014)

Thanks ibewjon - hmm… I might need to get an anemometer or however you spell it. Right now as it is there is flow at the table saw blade from underneath - not much at the dust shroud when I split it. But I don't have reference on how much it should be and also will need to be able to tell meaningful change if I change it up to 4".

What good but cheap anemometer does everyone use?



> Try the saw connected with 4" flex. The flex has a greater loss, but it is worth a try. It s not working the way it is…. nothing ventured, nothing gained.
> 
> - ibewjon


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## WoodenDreams (Aug 23, 2018)

You can make your Y connections by cutting the 4" tubes, (put a hole in one and cut the other to fit the Y direction),so the two peices fit together in a Y. Then use PCV cement or tape the two pieces together.


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## Rayne (Mar 9, 2014)

For the Dust shroud on the table saw, you're not going to get ideal suction no matter what due to the split and weak DC. It'll capture some, but not all. Can't hurt to look for the correct hose for the shroud and then create/find an adapter to connect to a 2.5" connection on the split.


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## ibewjon (Oct 2, 2010)

The best way to measure the airflow is: Does the sawdust get sucked up? I would save my money for an electrical upgrade and a larger DC.


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## Lazyman (Aug 8, 2014)

I don't think you said what kind of table saw you have or what sort of built in dust collection it has. If for example it is basically just a DC port into the base of the cabinet or worse, it may not be creating a downdraft through the insert (check). If that is the case, I would try redirecting most of the suction to come into the hacked SS dust shroud. If all of the other dust simply winds up in the base, capturing more of the dust above the table may give you the biggest bang for the buck and you can just clean out the base every now and then. Worth a try anyway.


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## BobAnderton (Oct 5, 2010)

Regarding the power draw on the circuit in your garage, do you have garage door openers in the garage that plug into electrical sockets in the ceiling? Are those sockets on a different circuit than those on the wall in the garage? In my case they were, and I use the garage door circuit for all dust collection and the one that feeds the sockets on the wall for all tools.

Second comment is in support of running the 6 inch duct as far as you can. It results in much less pressure drop per foot than 4 inch duct at the cfm rates you're getting with a 12" impeller.

For these what-if questions run them both through the static calc spreadsheet here.
(look in the "ducting" pull down menu for the excel worksheet staticcalc)

You'll be able to quantify the effect of different options.


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## WorksInTheory (Jan 5, 2014)

It's a Craftsman 28133 or something like that - the Ridgid 4512 clone - 4" port in the bottom.



> I don t think you said what kind of table saw you have or what sort of built in dust collection it has. If for example it is basically just a DC port into the base of the cabinet or worse, it may not be creating a downdraft through the insert (check). If that is the case, I would try redirecting most of the suction to come into the hacked SS dust shroud. If all of the other dust simply winds up in the base, capturing more of the dust above the table may give you the biggest bang for the buck and you can just clean out the base every now and then. Worth a try anyway.
> 
> - Lazyman


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## Lazyman (Aug 8, 2014)

So it has sort of a square funnel underneath to capture the dust, right? That sort of setup may not create much of a downdraft because the holes where the depth and angle adjustments go through the sides are probably leaking too much air. It will just capture the dust that falls through so you might do better to have most of the suction on the SS shroud and just enough at the bottom port so that the dust that does fall through gets picked up as it falls into the funnel.


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## Holbs (Nov 4, 2012)

4" vs 6" ducting. 
Sorry I came to this party too late. 
You have a less than 2HP dust collection machine with 6" ducting. 
Your efficiency will suffer, but you gotta do with what you have (especially for free). 
Good thing is when you do upgrade to a 3HP machine from searching on craigslist, you would have saved $$$ cause you have 6" ducting


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## WorksInTheory (Jan 5, 2014)

Thanks Holbs. I have both 6" and 4" for free so are you saying i would get better performance going to the 4"?



> 4" vs 6" ducting.
> Sorry I came to this party too late.
> You have a less than 2HP dust collection machine with 6" ducting.
> Your efficiency will suffer, but you gotta do with what you have (especially for free).
> ...


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## WorksInTheory (Jan 5, 2014)

lazyman, I sealed those up with magnetic sheets and also spray foam in other areas.



> So it has sort of a square funnel underneath to capture the dust, right? That sort of setup may not create much of a downdraft because the holes where the depth and angle adjustments go through the sides are probably leaking too much air. It will just capture the dust that falls through so you might do better to have most of the suction on the SS shroud and just enough at the bottom port so that the dust that does fall through gets picked up as it falls into the funnel.
> 
> - Lazyman


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## Holbs (Nov 4, 2012)

I would let someone with Harbor Freight or any 1.5 HP dust collector and 6" ducting speak up as they would have the experience over me.
However, my guess work would say: correct. Better off with all 4" ducting than 4" & 6" pieces matched together or all 6" pieces. Less than 2HP, I do not think is scientifically possible to come close to the appropriate CFM required for the square inch area of 6" ducting.
However, you have 4" and 6" ducting if I remember I read right. Might as well run with it, to be economical. It's not optimal but it will work as a collector.


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## spitfirepete (Feb 10, 2019)

Use good shop vac for TS….no need to run HF at same time. It's what I do.


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