Another DC Question

[Coop]

My current dc at my ts leaves a lot to be desired. The port is on the back side of the cabinet and collects very little of the dust that is dumped at the front, due to the rotation of the blade, is sucked up. I’m thinking considerably about adding a second port to the side of the cabinet. Current setup is a 4” flex hose to an ell. If I replaced the ell with a tee and extended the hose around to the side and connect it with an ell, how efficient would the port with the tee be? Would I be better off just blanking off the back port and trying one on the side? 

[JohnG]

How high do you set your blade when ripping/crosscutting a board?

Pic of the current setup? Can some of the flex be replaced with rigid or some 90* elbows replaced by 2 45* or a sweeping 90*?

I have a single rear 4” (sawstop) and rarely get anything noticeable spitting out the front. 

[Mark J]

1 hour ago, JohnG said:

How high do you set your blade when ripping/crosscutting a board?

How does blade height affect dust? 

[Tpt life]

If you have plenty of static negative pressure on the cabinet, you need flow. I consider drilling a hole or two opposite where it collects, and introduce some flow across that area. If it fails, a rivet, screw, tape, or magnet can re-seal. That’s how I think, no pressure to try it yourself. I ran a Jet that collected in huge amounts, but had a side door. I’d have to open that and scrape with a stick while the DC ran…every day. 

Edited November 27, 2023 by Tpt life
Misspellings

[BillyJack]

On 11/26/2023 at 7:13 PM, Coop said:

My current dc at my ts leaves a lot to be desired. The port is on the back side of the cabinet and collects very little of the dust that is dumped at the front, due to the rotation of the blade, is sucked up. I’m thinking considerably about adding a second port to the side of the cabinet. Current setup is a 4” flex hose to an ell. If I replaced the ell with a tee and extended the hose around to the side and connect it with an ell, how efficient would the port with the tee be? Would I be better off just blanking off the back port and trying one on the side? 

What saw?

[Ron Swanson Jr.]

On 11/27/2023 at 7:00 AM, Mark J said:

How does blade height affect dust? 

The job of the gullets on the blade is to carry away the sawdust. If your blade is set too high and those gullets are raised above the work piece, then it will spit out the dust that they carry as it spins above your board. 

On the other hand, if your blade is set so that the teeth just barely clear the surface of your work piece, then the gullets will not release the dust up into the air, and instead it will fall into the shroud surrounding the blade in the cabinet, and into the DC collection point. 

I have a Sawstop PCS and a 1250 CFM DC. It has a 4" port on the back of the cabinet. It gets most of the dust but i do still have to clean out the bottom of the cabinet from time to time. 

 

--Doug

[Ron Swanson Jr.]

On 11/26/2023 at 7:13 PM, Coop said:

My current dc at my ts leaves a lot to be desired. The port is on the back side of the cabinet and collects very little of the dust that is dumped at the front, due to the rotation of the blade, is sucked up. I’m thinking considerably about adding a second port to the side of the cabinet. Current setup is a 4” flex hose to an ell. If I replaced the ell with a tee and extended the hose around to the side and connect it with an ell, how efficient would the port with the tee be? Would I be better off just blanking off the back port and trying one on the side? 

Yes, that L is likely contributing. Anything with a softer bend to it, like a Y with one branch sealed off, or a gentle curve with the flex hose should help. 

Also, how large is your DC unit, and how taxed is it with lines leading to other machines? Blast gates can go a long way towards focusing the suction on 1 machine at a time.

-Doug

 

 

 

[gee-dub]

As a rule, a tee is never a good thing in a dust collection system.  I agree that knowing the saw model and DC type would help.  I thought you had a pretty hefty DC but I may be misremembering.  Most cabinet saws have plenty of leaks around the control wheels, under the table, etc. to allow return air.  If you unplug the saw, fire up the DC, pull the throat plate, and place your hand near the throat do you feel good air flow? Let's make sure we know that before we try to fix the wrong thing

I changed my tablesaw from a single 4" to a single 6".  The difference in collection at the throat was dramatic.

I left the hose that feeds to the blade shroud within that port (same as with the original 4" design).  With my setup there was no direction to point the port that wouldn't involve some sort of turn so I have a short piece of flex. 

Sub-optimal but the best I could do given all the other things involved (outfeed, router table, vertical duct path).  There are a lot of things in the home-shop DC world that involve doing the best that you can even thought it may not be textbook perfect

[BillyJack]

I cannot see how you would get  an advantage from a 4” to 6” hose on a Sawstop..

[gee-dub]

On 11/27/2023 at 7:38 AM, BillyJack said:

I cannot see how you would get  an advantage from a 4” to 6” hose on a Sawstop..

I'm no rocket scientist.  I can only tell you it moves a lot more air.   My drum sander does great with a single 4" so go figure.

[BillyJack]

It may feel like it is moving more , but it can’t. You have a 4” hose inside connected to a choke point..you may be pulling more from the floor of the saw, but not from the saw blade..

 

Its like a funnel..

[Tpt life]

Air compresses. You can get some higher flow with a single pinch point, but will lose some efficiency as the air must compress at the “nozzle,” and the will add a bunch of noise. 

[Ron Swanson Jr.]

This post has reminded me to do something long overdue -go through my table saw cabinet with some flashing tape and seal up any leaks i can find. 

 

--Doug

[Tom King]

I use a couple of rubber magnetic sheets over the curved slot in the front of mine and all the other joints taped up on my old Unisaw.  The magnetic sheets can be moved when the blade is tilted.   I think I still have old socks stuffed between the top and the cabinet.  I have an intake box where the motor cover went that has a slide in 12x12 furnace filter.  The filter is not to filter incoming air, but to allow air to be drawn in over the motor without allowing anything to be slung out.  That and an overblade pickup works great.  Picture is before I changed to the magnetic sheets.  Looks junky but works great. 

I did away with the router wing.  It made too much of a mess and would have been too much bigger to add anything to it and still be able to move this saw around.  This is my jobsite saw and gets moved with the front end loader.  The whole thing is on a mobile base.

 

.

[BillyJack]

How come you DC comes off the front?

[BonPacific]

On 11/26/2023 at 5:13 PM, Coop said:

My current dc at my ts leaves a lot to be desired. The port is on the back side of the cabinet and collects very little of the dust that is dumped at the front, due to the rotation of the blade, is sucked up. I’m thinking considerably about adding a second port to the side of the cabinet. Current setup is a 4” flex hose to an ell. If I replaced the ell with a tee and extended the hose around to the side and connect it with an ell, how efficient would the port with the tee be? Would I be better off just blanking off the back port and trying one on the side? 

Do you have over-the-table collection?

I'm not sure adding a second port to the cabinet itself would help that much. How strong is your DC and how long is the run of ducting? Reducing a junction or two, or increasing the length of a larger trunk, might do a lot more to help.

[BillyJack]

DC has to work down…

6 to a 4” 

you have to have a main truck and drops…

 

I have a 1.5 shop fox and can run two good 4” pipes to the tool, but they have to come off the 5” 

 

[Ron Swanson Jr.]

On 11/27/2023 at 1:31 PM, BillyJack said:

DC has to work down…

6 to a 4” 

you have to have a main truck and drops…

 

Agreed. And the closer to the tool that the reduction happens, the more suction you will get. 

[BillyJack]

You really want to focus on the main tools, table saw, sander, etc and work down from there.

 

I have all PVC, but have not taped any of it..

[Tom King]

On 11/27/2023 at 1:21 PM, BillyJack said:

How come you DC comes off the front?

When I bought that old saw, the panel that goes there was missing.  I thought maybe the duct might be in the way, but decided to try it before buying a replacement panel, and it has never been in the way.  I don't believe I have ever kicked it once.

Every old house we set up in requires a different layout.  That is a 20 x 20 room.  Next to that is a 7' wide 40' long hallway.  I had sliding miter saw and two radial arm saws set up in that hallway.  The jointer you can see in the picture is set diagonally so long pieces could come in the doorway behind it, and go out the doorway into the hall.

Outside the doorway to the right of the saw, a 3hp DC sat in the corner of the hallway.  The DC had a 8" trunkline that just turned down to the floor.  To use the tablesaw or jointer, a 6" flex hose was laid in the doorway to the hookup you see open on the tablesaw.  To use any of the saws in the hallway, the flex was changed to a floor hookup that served those tools.  Dust collection was really good since the 3hp blower had such short runs of duct.  You can see there is not much dust in that room.

As was pretty typical of the old houses I worked on, we were set up there for about 2-1/2 years.

[Coop]

I think I worded my initial question incorrectly. First, my dc works well with the airflow measured at all four drops being very close. The drum sander collection down stream from the ts leaves absolutely no dust to contend with. I realize also that the fines from the ds are much smaller than the ts. What I meant to ask, if I replaced the existing ell at the ts with a tee and ran it thru the tee instead of into the bull of the tee, should I just eliminate the tee completely and relocate the single port to where the majority of the dust collects? Or maybe replace the ell with a wye?  Still not sure that makes sense. Oh well, Nothing ventured, nothing gained. I’ll try it both ways and report back.

[gee-dub]

On 11/27/2023 at 9:02 AM, Ron Swanson Jr. said:

This post has reminded me to do something long overdue -go through my table saw cabinet with some flashing tape and seal up any leaks i can find. 

 

--Doug

Don’t close off all your return air. You want the air to flow through the cabinet. 

[Ron Swanson Jr.]

On 11/27/2023 at 11:40 PM, gee-dub said:

Don’t close off all your return air. You want the air to flow through the cabinet. 

Thanks for your reply, @gee-dub!

I'm not sure how that would be possible, to completely close off return air - as even if i sealed everything completely air tight (unlikely) wouldn't plenty of air come in around the throat plate and riving knife? I do use a ZCI most of the time,  but even still, plenty of air will still flow in around that area. 

I was referring to shoring up things like the access doors on the cabinet, etc. to try and put the kibosh on little leaks that detract from suction through the dust port. I did that on my last TS and it improved my DC suction a little bit. 

Of course, there's always the very good chance that I'm misunderstanding your advice here, too!  

 

thanks for weighing in!

 

-Doug

[gee-dub]

On 11/28/2023 at 7:58 AM, Ron Swanson Jr. said:

wouldn't plenty of air come in around the throat plate and riving knife? I do use a ZCI most of the time,  but even still, plenty of air will still flow in around that area. 
 

I'm not trying to make this point take on a life of its own so I apologize if that is happening.  You want an area at least equal to your exit port for return air.  For all but thinner cuts the blade slot is covered during the operation preventing air flow.  I have never noticed spoil rushing into the blade slot once the material has passed by . 

If your saw is on leveling feet or a mobile base there is probably plenty of air return around the base.  I do not know that this is the optimal path to suspend and transport spoil.  Mine sets flat on an elevation platform so my return air is from the wheel slots and around the top of the cabinet / under the top. 

Again, I have done no scientific, sequential testing of air patterns on my saws .  I only tend to go on the attack when things are not working well.  I chased a small leak in my duct system with the smoke from an incense stick for almost an hour once so I get it 

[Tom King]

Mine works great with the 12x12 inlet over the motor.  The bottom of my cabinet is completely open, but I have it sitting on top of a piece of 1/4" plywood inside the mobile base.  I can cut MDF inside a finished house, and absolutely no dust gets in the air or on anything.  I always say that less than 3hp is wishful thinking though, so a short run to a 3hp DC helps too.

I don't think around the blade insert only will do much of anything, especially cutting something like plywood that completely covers it.  I'm not sure about the guts of saws that have blade shrouds though.  Mine has no blade surround inside the cabinet. Air has to get in and around the blade.  My overarm gets what little is slung out the top.