Better vacuum around blade?

[Dedpedal]

I have my 3000s both hooked up for shop vac and dust separating thing on a bucket. Would blocking the opening beside the blade help pull more sawdust and is it safe? I’m really digging this model saw and love to improve it.

[leehljp]

It has been a looong while and I think someone did this. It seems like someone used a flexible material to do that, a tire inner tube flap cut to fit. The more you can close off, the more it can help. However, the flexible material such as inner tube will allow for air to come in. This is necessary. In another thread on this forum yesterday - here: https://www.sawdustzone.org/forum/di...ons#post842552. . . . by not letting enough air get in, as if sucking through the opening of a zero clearance throat plate, the suction will be severely hindered.

[Dedpedal]

Thanks! I didn’t think of that. I guess a small hole and enlarge it till I achieve balance may be the route I take.

[d_meister]

Blocking the bottom is the most important. I use a vac with a small cyclone, and it works great. Very little sawdust accumulation inside the saw.

[Dedpedal]

Blocking the bottom is the most important. I use a vac with a small cyclone, and it works great. Very little sawdust accumulation inside the saw.

What do you mean by the bottom?

[d_meister]

The cabinet, as supplied, was completely open on the bottom. I slipped a piece of plywood to blank that off between the saw and the stand. When I did it, my intention was primarily to stop the sawdust falling down on the stuff stored in the stand.. There's a limit to how much you can blank off before the vac starts suffering. Airflow within the saw probably helps to "sweep" the interior. There's enough source air from the cabinet side vents and the tilt slot. I use only zero clearance throat plates with the saw blade gullet exposed, and not much higher.

[Dedpedal]

I understand now. Thanks a ton!

[Jim Frye]

My BT3K is completely enclosed except for the tilt quadrant in the front and whatever space there is in front and behind the zero clearance throat plates. I have all other openings closed off including the underside of the saw cabinet. I have multiple ZCTPs, one for each blade I have, plus some angled cuts and several for the dado set I have. The ZCTPs have a 1/2" hole bored at each end of the blade opening to help with pulling dust from the cut back down into the cabinet. I made an articulating cover for the rear opening where the vac connection protrudes from the cabinet. I also made a "belly pan" for the underside of the cabinet that includes a 1 1/2" vac connection to clean the pan wihen it gets chips and dust in it. If you go to the articles tab at the top of the page here, there are literally dozens of how to articles for the BT3Ks. Start at page 18 and work your way forward.

Update: I was down in the shop and changing the cut setup on my saw. I noticed that I have half of the motor vent slots in the right side of the cabinet closed off. Don't see that side very often as it's normally covered by accessory tables and the router table.

[Jim Frye]

I reread your original post and it occurred to me that you were referring to the gap between the blade shroud and the underside of the table. Early on I thought about trying to come up with some sort of adjustable filler for that space. In the end, I decided it was easier to enclose the entire saw cabinet as much as possible and let the vac create a vacuum inside the entire cabinet. That way, the space above the blade shroud doesn't matter. Any dust that escapes past the shroud opening is contained in the bottom pan.

[capncarl]

I closed off the bottom of my saw with a piece of 1” thick roll type air conditioner filter. Enough air from the dust collector keeps enough dust and chips collected that it doesn’t sag like a dirty baby’s diaper.

[LCHIEN]

OK, I'll chime in with my opinions.

first of all (these are more factual) good dust collection requires both high velocity (feet per minute) and high airflow (CFM). velocity carries bigger chips away so they don't fall out of the airstream and plug up the hose/pipe. High CFMs are required to pull in the fine particles that are thrown off by the cutters and pull them into the hose/pipe. You can monkey the Hose diameter to increase the ft/min rate but it won't affect the cfm rate except to make it smaller by way of increased restriction. Also too large a hose with a given CFM makes ft/min too slow.
The sweet point is a hose of about equivalent of two four inch hoses or pipes flowing about 1600-2000 CFM. for single machines. which is most of us hobbyists.

Another fact is that a proper factory DC will have its impeller and motor size matched so that it pulls rated power when the DC is moving the rated CFMs through minimal restriction. If you block off the hose the DC will make a lot of noise which sounds like its working hard but actually its working at its minimum power because its not moving any air (very low CFMs). The amps will fall from the rated amps to probably 1 or 2 Amps. This is not doing any good. DC impellers are designed for optimizing air flow and not making a good vacuum. Blocked off inlet you will probably only get a couple or few of PSI vacuum.

Now for the opinions.
Some people have claimed to want to block off all openings in the saw and then put the DC or vacuum hose on the mostly sealed cabinet. I've see people block the bottom, block the vents on the side and use a tight-fitting ZCTP and even block off the arc of the opening in in the rear that the DC port moves in when the blade is tilted. IMO that's a terrible idea. You will kill the CFMs. And worse, you remove all air cooling from the motor.

Here's my solution:
https://www.sawdustzone.org/forum/di...c-dc-bt-photos
I made a plywood board that just rests on the bottom of the saw and has a cutout for one of those plastic belly pans to 4" hose.
There is a lot of room for the air to flow into the cabinet for both motor cooling and for the DC to pull in as CFM. IN addition to the 4" hose to the DC I also have a 4" hose from the "Y" at the DC to the dust port on the back you can see. The 4" hose has a 2" reducer right at the saw to fit that port. The only improvement that might be worth making would be a "T" at that point to a 2.5" hose going to the shark (blade) guard port.
Now a lot of dust still gets thrown off the blade especially for shaving cuts. But most of it is carried in the teeth gullets as it cuts down on the wood and carried below the throat plate. (if you have a work piece on top the throat plate is essentially closed off so no need to seal it). From the gullets it drops mostly into the blade shroud of the BT3's and dumps the rest into the cabinet and possibly I suspect some rides all the way around and gets thrown off the top onto your table saw table (that a blade guard hose might catch). But the pain of routing the hose for that has made me put that off.

WHatever you do, if you use a DC, you need to let the cabinet breathe in some air. Don't seal it tightly.

If you look at the photo with the end cover taken off, this is after some time of operation and the inside is extremely clean.

[Dedpedal]

That’s great! Now I’m thinking differently.