Thread: Overhead dust extraction - why so BIIIGGG???

Originally Posted by Evanism

I was reading Luckyducks OHDE thread and it struck me as to why they are so damned big.

Long, wide, gets in the way... its all pipes and levers.

Trying to rip or crosscut with one is a nightmare.

Mine is suspended from the roof and I have absolutely no trouble with it - just move it to the right height - its transparent so I can see right through it - away we go.

Can anyone answer me these questions:
- Why don't I just punch a thousand 1/2" holes into my insert? Like some sort of shaddow board on steroids.

1) 1000 1/2" holes has a total cross sectional area of about 180 in² which is around 4 times the total area of most TS inserts
2) 1/2" holes aren't worth a cracker at drawing air and my maths says 1000 x <cracker is still stuff all.
3) Most of the time the holes are covered by the wood and will draw even less than nothing
4) Too many holes in inserts can lead to piece of wood getting hung up i.e. dangerous.

- I currently use a zero clearance insert for each blade, but noticed (!!) the dust collection was terrible. I drilled 3 holes, each 12mm dia at common points along the now-cut kerf at the most likely heights of the blade (blade heights: ~10mm, ~20mm and ~50mm) . Each about 20mm apart. A HUGE amount of the dust gets sucked down these holes as the gullet of the blade centres on the holes. I don't loose the zero-kerfness-loose-my-offcut-into-the-cabinet capacity (better known as the ZKLMOITC) ... ive not seen this before. Is there a reason others don't do this?

If dust is being sucked down those holes what that is telling me is that your cabinet is too restricted so the DC has to draw air from above the table and is losing valuable pressure in doing so. The cabinet suction should be dealing with the sawdust being drive into the cabinet by the saw. The sawdust at the top of the table should be being dealt with by an above the table duct.

- Lastly, WHY does the the dust extractor hood have to be so wide? Why not 1cm?

It doesn't have to be wide, it can indeed be 1cm - but it will have restricted suction and needs to be firmly held in place otherwise you may end up with it hitting the blade

Originally Posted by Evanism

I was reading Luckyducks OHDE thread and it struck me as to why they are so damned big.

Long, wide, gets in the way... its all pipes and levers.

Trying to rip or crosscut with one is a nightmare.

Can anyone answer me these questions:

- Why don't I just punch a thousand 1/2" holes into my insert? Like some sort of shaddow board on steroids.

- I currently use a zero clearance insert for each blade, but noticed (!!) the dust collection was terrible. I drilled 3 holes, each 12mm dia at common points along the now-cut kerf at the most likely heights of the blade (blade heights: ~10mm, ~20mm and ~50mm) . Each about 20mm apart. A HUGE amount of the dust gets sucked down these holes as the gullet of the blade centres on the holes. I don't loose the zero-kerfness-loose-my-offcut-into-the-cabinet capacity (better known as the ZKLMOITC) ... ive not seen this before. Is there a reason others don't do this?

- Lastly, WHY does the the dust extractor hood have to be so wide? Why not 1cm?

I can sense your frustration -- I do find the whole "proper" dust extraction to be quite difficult to get right. At first I thought just throwing lots of money at it would fix the problem. Not so! At first I wasn't willing to take up the advice of BobL and others here on the forum because I thought it wasn't necessary, or was too much work, or that I knew better... But now that I have spent several years trying to improve my dust extraction installation, I've found that the advice given on this forum works, and I have often regretted not listening to said advice in the past.

For the latest mod on my overhead guard, I haven't lifted a finger yet, or made a single cut into any polycarbonate. I've made the mistake of trying to go it alone only to find that what I thought was going to work really well didn't work really well at all!

Thanks to the thread you alluded to, I think I have a pretty good idea of what I want to do for my blade guard and I think it has a good chance of success, thanks to some very generous guys on this forum. And if it doesn't work, this is the first place I'll come to, in order to find solutions!

Good luck mate!

My overhead guard does not get in the way.

IMAG0227.jpgIMAG0226.jpgIMAG0229.jpg

You are right, the guard does not need to be very wide, but it need to be wide enough to allow sufficient air flow. The limiting factor on my guard is the riser, which has the same cross-sectional area as a three and a half inch pipe (sizing from Bill pentz's site). Any smaller and the air flow is killed. The "shoe" of the guard is 40mm wide (internal) and 60 mm wide externally. Were I to make it again I would make it 50 mm internal, to improve visibility of the job.

Did you mop the floor before taking the photos john ?? )


Sent from my iPad using Tapatalk

Glen,

If only you knew.

A couple of years ago my shop was ankle deep in sawdust. It was an unmitigated disaster. Not only were the horizontal surfaces coated in dust, but so too were most of the vertical surfaces. Then the ClearVue was installed. As I speak it is about six weeks since I cleaned the shed. Most of the stuff on the floor is leaf litter than has blown in.

Generally, the shop stays clean. Nowadays if I do something that produces some dust (mostly from hand tools/sanding) I grab it immediately with the shop vac because it takes seconds. Most days I can walk out of the shed, wash my hands and sit at the dinner table. In the old days I would strip off in the shed and walk into the shower before entering the main house.

So if I seem a little enthusiastic about the ClearVue, it's because it has transformed the shop. The overhead guard on the table saw was a big improvement, but one day it will be better.