Table Saw Dust Collection Re-thinking

[fredhargis]

Does keeping the blade as low in the cut as possible help with above the table dust production?

Thank you!

Andy

My opinion is that it doesn't help. The dust is being thrown by the blade at the rear of the cut, and I doubt balde height will change how much it throws. The only solution to that (again, my opinion) is an overblade pickup with good air flow.

[Alan S]

Does keeping the blade as low in the cut as possible help with above the table dust production?

If it helps, it might indicate misalignment of the blade.  That's because the teeth rising at the back of the blade should not cut anything.  They will if the blade is misaligned.

The blade can also act as a fan to blow dust from inside the saw out with the back teeth, but this is not likely to be substantially diminished by lowering the blade.

[titanxt]

I was just guessing at whether or not keeping the blade low in the cut would reduce the ability of the blade to throw dust. I am not having any particular issue, just curious if that  had any effect.  

I am wondering if I should upgrade to the 4" dust port Shark Guard instead of the 2.5" model that I have now. Looks like it would provide a lot more above the table dust collection as it seems like this area is usually the biggest offender of spewing dust. Thoughts?

Andy

[jteneyck]

I was just guessing at whether or not keeping the blade low in the cut would reduce the ability of the blade to throw dust. I am not having any particular issue, just curious if that  had any effect.  

I am wondering if I should upgrade to the 4" dust port Shark Guard instead of the 2.5" model that I have now. Looks like it would provide a lot more above the table dust collection as it seems like this area is usually the biggest offender of spewing dust. Thoughts?

Andy

The dust that comes off the top of the blade is either of the back of the blade because of misalignment, as mentioned above, or has gone all the way under the table and back up through the stock again if off the front.  If the blade alignment is good, then the dust collection under the table isn't doing it's job.  Adding a larger port Shark Guard on top may help, but it shouldn't be needed if you have sufficient suction in the right places under the table.  

It would be interesting to compare a blade with a lot of hook to one with very little with respect to how much sawdust gets thrown off the top of the blade.  Seems to me the one with a lot of hook will want to carry dust further.     

John

[titanxt]

John, that is a good perspective on where that dust might actually be coming from. I will mess with the lower cabinet for a while and see if that effects the upper amount of dust.

[titanxt]

k... I pulled out the foam that was on the left and right side of the cabinet. I had removed the foam that sealed the front of the cabinet to the bottom of the table some time ago. I also removed the magnetic strip that I had sealing the semi-circle cutout for the elevation/angle knob. The only thing blocking the cabinet was the piece I have in back that closes in the rear of the cabinet. With all the available opening unobstructed, I crosscut some 3" wide scrap. At the end of the cut where the blade exits the cut and the waste falls free, I have a pretty good amount of dust belching out of the cut. It is comprised of small and large pieces - not just the fine dust and not just the larger chips that the DC would not necessarily be able to suck up into the over the blade DC. I also adjusted the blast gate on the 4" opening on the bottom of the cabinet to see if that had any effect on the OTB DC ability. I could not see any measurable change. 

I removed the zero clearance insert and the blade. I noticed that I had a large amount of saw dust stuck in the cabinet. 



It is hard to tell from the picture, but the saw dust goes all the way to the bottom of the table on all four sides making a cone that sloped downward to the 4" opening. I got my hands down in there and with the DC on, I cleaned it out. You can see in the next picture the amount of dust that was caught in the separater. It is hard to tell from the picture but the center of that volcano shaped pile is about 12" deep.... It was a sizable amount of dust.



So, increasing available air to the cabinet did not seem to affect the above the table dust control. WITH THE SAW UNPLUGGED, I put my hand under the OTP DC Shark Guard and I really didn't feel a lot of air movement. Maybe I was expecting more suction like a vac. 

I am guessing that my cabinet could benefit from having a funnel-like insert that will make a funnel toward the 4" opening. Maybe that will focus the available air that is coming into the cabinet down and out of the cabinet taking more fine dust with it???

[jteneyck]

Very nice work and write up.  The base of my Unisaw fills up with dust and chips pretty regularly.  I have a 1200 CFM DC and something around 800 CFM must be going through the 4" hose connected to the TS.  And that clearly is not enough to pull al the dust and chips out from that big rectangular box.  This is exactly why many modern saws now have a shroud around the blade.  

But I don't particularly care if the base of the cabinet fills up as long as the DC is doing a good job of keeping sawdust out of the air.  I can clean out the base, as needed.  

I have an old Sears guard over the blade, one that has a standard vacuum hose molded into it.  The hose is connected to my central DC system.  When the blade is buried in wood during a cut I would guess that 90 - 95% of the sawdust is captured.  It's only when the blade is exposed on one side that much dust escapes because of the open gap under that side of the blade.  An articulated guard or brush seals would solve that problem but it doesn't bother me so I haven't done anything.  In either case, nothing escapes out of the base of the saw.  

I also have a Sears contractor saw with the motor hanging out the back, much like yours.  I built a plywood box under the bottom of the saw to connect a 4" hose to.  It's pretty small in cross section, maybe 10" x 10".  Nothing collects in it; the DC keeps it clean.  I have the same type blade guard as on the Unisaw.  There is no foam or covers around the motor/belt, tilt opening on the front, etc.  Performance is very similar to what I described above with the Unisaw.  Nothing blows out of the base.  

If you want to keep the base of your saw clean I think you need to reduce the cross section and funnel the dust towards the hose outlet, as you discussed.   How many CFM is your DC?  A larger hose on the Sharkguard will only help if you have a large enough DC to increase the pressure drop.  Have you measured the static pressure in both the 4" line and the hose off the Sharkguard?  I can't remember exactly, but until I got something around 4" on my BS I couldn't keep up with the dust.  

John

[titanxt]

I have a Delta 50-760 1.5 HP 1200 CFM collector. I use a Wynn pleated .5 micron filter and not the bag that came with it. It has a 5" port on the collector and I run a 5" hose with a 4" step-down to the separator. From there, everything is 4" with the exception of the OTB guard which is 2.5" I would like to think that at 1200 CFM it should remove a lot of dust. I don't have a lot of extra, unneeded hose, and I go from machine to machine and there is no built in duct work in my small garage space.

I am curious about how much or if I would see any performance upgrade by replacing the foam between my cabinet and the bottom of the table and upgrading to the 4" guard. I have been watching Youtube videos of other table saws in action that have ATB dust collection and they leave very little dust to escape onto the table. I also wonder if by installing the funnel-like insert inside of the cabinet if it will force more free air into the cabinet space and downward out the 4" hose because of the smaller space? I wonder if the large cabinet space under the table is a lot of space for air to just sit??? Kind of like drawing the air through a bathroom versus drawing the air through a bedroom with the same CFM.

Andy

[fredhargis]

My shark was a 4" model, and it worked great. It's pretty tough to find a DC that will pull any air through a 2.5" opening. Hooking a shop vac to it would probably improve the performance versus the DC.

[Kwood]

I have a rigid contractor saw.  What I did was find a large enough clear plastic container that covered the motor and belt assembly, and I put some pool noodles on the top edges of that container to help seal it against the saw frame.  I simply used bungies to attach it to the saw, hooking them to whatever protrusion I could find on the table saw frame, and making small holes in the container to hook the bungie to on that end.   Easy to remove when I need to.     Of course the container has to be below the miter slots of the saw.  So you may need to remove part of the plastic container lip at that upper edge.  No big deal.  

My combination outfeed/workbench table can't be pushed right up against the saw because of this setup, but I don't really find that to be much of a problem.  Long pieces still will be supported by the table, and short pieces are prevented from falling to the floor by the plastic container.

I have a pretty good 5 hp collector that I hook up to the bottom of the saw, and as long as I remember to turn it on, it does pretty good to keep the inside of the saw free of mounds of dust.

I could make a better looking solution to this problem, but I don't believe in overdoing it.........cause I'm pretty lazy.  Lol.