Table saw dust extraction

[nothanks]

I think about improving DE from time to time (whenever I'm cleaning-up after a messy job) but don't seem to find the necessary tuit. My saw has a small hose from the crown guard (hinged on the riving knife) that goes inside and joins the under-saw 50mm hose to come out to a 100mm port that I connect to my 2HP HVLP cyclone extractor. I frequently operate without the crown guard(!!) so plug the crown guard hose. I'd like to devise a pivoting and self-adjusting crown guard that's suspended from a hollow tube that's attached to the saw in some way and can be used for DE. The crown extraction would be connected to the under-saw hose with a throttle'able Y connection and then go to the LVHP extractor. Issues: how to make the suspension rigid enough (but allow the saw to be moved), how to improve collection beneath the saw, ... Suggestions and comments invited.

[Andy Burns]

check mike farrington on youtube, ISTR he built a table saw dust extraction system ...

[Tricky Dicky]

For dust extraction to be fully effective it needs to be extracted at the point it is produced. On a table saw that is the point at the front of the blade as it passes under the table. On industrial scale saws you will find nozzles directed as close as possible to that point under the table. What is not captured at that point and spins round with the blade is usually sucked up by the outlet at the back of the saw.

Richard

[nothanks]

Thanks, he's got some good videos (and an envy-makingly HUGE workshop)

[nothanks]

That makes sense, but I'm still using the manufacturer's under-sawblade collection casing because I haven't (yet) managed to devise a better way to collect the dust at the front and not get in the way of the tilting arbour.

[John Rumm]

One of the problems you might find with the smaller hose up top is that its not as well suited to the HVLP extractor because of its higher back pressure. Some people find running a separate LVHP collector (e.g a shop vac style collector) just for the top hose works better.

There are quite a few examples of this kind of thing about - most are quite large since they need to reach over the saw from far enough away as to not curtail the maximum size of sheet you can process.

or

You may find that building a cowl to mount under the table to enclose as much of the blade as you can (either fixed to the trunnions so that it an tilt, or just wide enough that it can accommodate the tilt, and connecting that to the HVLP collector will increase the air speed under the blade high enough that it can capture everything flying off the tips of the blade, before it gets a chance to escape again.

My saw was basically designed to just dump dust into its base for later manual removal. However I added a 4" port to it. Running that into the HVLP does reduce the amount that gets out of the case - but not completely. (not helped by other piercings through the case like by the blade height adjust wheel that let air be sucked in via alternate routes).

I found just adding a bit of tube split round the blade where it exits the underside of the table, was quite effective on this contraption:

That might not be too difficult to mount such that it moves in sympathy with the blade tilt.

[nothanks]

Yes, a little experimentation makes it seem that LVHP is better for both top and bottom with the current internal plumbing.

Thanks for those - thought-provoking and similar to what I had in mind (but I can't believe Axminster sell many at that price)

I'm moving towards using a good LVHP almost everywhere (with cyclone,

50mm plastic ducting and home-made blast gates) and only using the HVLP for the planer thicknesser, and maybe the (rarely used) wood lathe. I suppose, if I ever get around to inventing something, a dust catcher for the chop saw might be HVLP as well.

[John Rumm]

Probably not - and there are probably cheaper alternatives about. It was more just an example. Some of the saw makers do their own ones as well.

IME HVLP shines for really high volume dust or chip creation (so planners / thicknessers), and anything where its difficult to catch the dust in something first and need to rely on really high speed airflow to capture stuff being ejected from a blade tip.

[nothanks]

Yes, HV for chips and large areas (chop saw), and HP for dust. I upgraded my bandsaw to a Sabre-350 a while ago, the saw is great but the dust collection is just a 100mm port into the lower casing - the top of that casing only has a hole for the blade so most of the dust falls on the floor; one day I'll make a cowl to go directly under the table and switch it to LVHP. Ooo, perhaps this is the justification for a 3D printer :-)

[John Rumm]

My EB band-saw is similar - 100mm port on the back of the bottom case. In reality it works to some extent - it seems to stop any dust getting recirculated round and dropped out of the top housing, and there is a grid of holes around the table inset that allows some dust to get sucked away. However its far from perfect. A cowl around the underside could work well.

[wasbit]

I've converted my small bandsaw to the Steve Maskery method which works extremely well with a HPLV system. Post #5. -

In the process of converting a larger bandsaw to the same system as it's much easier to connect up to the shopvac rather than the 4" HVLP hose.

[nothanks]

An excellent (and entertaining) link. Thanks!

[John Rumm]

Yup good link. At least with a bandsaw, the table tilts and not the blade, that makes getting dust collection close to the blade easy.

(although some kind of bellows based cowl that attaches to the underside of the table could also work to suck dust from the annulus in the table around the blade).