Thread: Saw Table Dust Extraction Improvement

Gday Bob, I have the same saw that Carbatec sells with the sliding table and like you have found the dust extraction from new was woefull if not non existant.

I got rid of the supplied dust guard and replaced it with the deluxe suva guard and now dont have a problem at the top of the machine but below is still a problem, while most of the dust goes out the extraction pipe, alot of it ends up on the floor.

Who ever decided extracting dust from the edge of the blade at 90% to the blade needs their furry head read, IMHO.

Have you modified the blade guard next to the blade to better extract the dust or are you just collecting it at the bottom of the cabinet?

I think what you've done is great and look forward to hearing more about it.

Regards, Ross.

G'day Ross, I have looked at the Suva but thought I would try to keep the overhead guard attached to the riving knife so that the tilt, up, down would remain the same.

Your comment re the extraction at 90% I think refers to the internal blade guard/collector which had that useless concertina hose which caught more than it passed - replace it and there should be an improvement as there was with mine.

No, I haven't modified the internal guard except for the hose - With regards the "spillage" from this guard - that's where the sloping floor and bottom extraction comes into play - the election poster [plastic posterboard], I had 2, had to be cut into 2/3 and 2/3 and overlapped otherwise you couldn't get them in. The gap at the front of the machine has been left so that some air is drawn in and passes over the sloping floor into the sweep at the bottom. This works quite effectively at the moment but I intend to "play" with the gaps underneath the cast iron top to see if that has any effect.

Regards,
Bob

Hi Bob, good mods if I might make a suggestion for an improvement, I am making an assumption at this point which is that your 3 into 1 feeds into a ~100mm main pipe, Is this the case? the problem with this (if it is) is that u end up not really getting 3x lots of suck into your one main pipe, what u really end up with is a reduced suck at each pickup point in some proportion based on the restriction of each pickup
From the maths we need a main of 173mm to pick up 3-100mm pipes 141 for 2-100 and 200 for 4-100mm pipes

something like this....this is 2 of 2x120 into 200 main line
multiple branches into main line.jpg
The outside of 100mmDWV(?) pipe fitting fits quite snug into a 120mm inlet

An alternative is to reduce the hose size to the pickup points that dont require as much flow as off the blade, say 50mm to the blade guard 80 for the cabinet pickup and stay with the 100 from the blade, this way u need 137mm main, this is not a practical size so I would suggest 150 as a main even if u have to reduce down at your DC, flow losses are reduced for a larger size pipe and I reckon u would see a further improvement in dust collection

Pete

I would agree with PJT's suggestion. I don't have a ducted workshop, but I now run a 125 mm hose from my 2 HP DC to the saw. The hose run is about 8 meters and I have noticed an increase in suction from when I was just running 100mm all the way through. I would imagine you would get a decent benefit with bigger pipe sizes , even if you didn't run more than one machine at a time.

Put a hole in the cabinet behind the blade and put a proper 150mm line into it. I looked at mine after I cleaned the cabinet and had used it for a short time and the pattern of dust would indicate that it gets thrown in that direction. Remember also that if you cannot supply the air going into the cabinet at the same rate as the extractor is removing it the air flow slows down. I left the original air extraction port open for this reason. We will see what happens when it is hooked up.

Bob, where did you get the clear flex hose from?

Originally Posted by Mini

Remember also that if you cannot supply the air going into the cabinet at the same rate as the extractor is removing it the air flow slows down. I left the original air extraction port open for this reason. We will see what happens when it is hooked up.

Yep, I agree with Mini here as well, if the air can't get in it can't get out either, before my current ducting mod I just poked the end of a 10m long piece of 100mm flex hose into the end of the 200 main pipe, that was way too much restriction and reduced flow dramatically into the DC

Pete

Lots of good advice here.

If you want to go further into the theory, and the numbers, make a cuppa and sit down with Bill's Cyclone & Dust Collection Research - Ducting

Thanks for the suggestions.

Chris - the clear pipe came from Carba-Tec - it is the "special" super flex pipe where 3m concertinas into 1m - current catalog [2010], p 94, CAT Hose 43B. If you are replacing the hose inside the table, ensure you tilt the blade fully to 45 degrees before cutting the length. This hose has made a great difference inside the saw as it stretches and retracts.

With regards upgrading the main line - this has been a thought for a while but currently the state of play is that I have plumbed a 4" line through the wall to get the extractor outside - as I'm in the process of looking at upgrading the top bag of my extractor to a pleated cartridge [with claims of 700% increased filter area which also increases the CFM rate] I thought I would wait until this was in place.

Currently if I only have 1 line open to the extractor the chips in the collection bag only circulate half way up the collection bag - if I open 2 lines then the chips circulate right to the top of the bag and the machine seems to run smoother - not scientific I know but anecdotal. When using the current setup the collection has been vastly improved in all aspects - inside the blade guard there is a restriction form 4" to 3" which is then channeled into a rectangular configeration - this restriction is possibly working a little like a crevice tool on a vacuum cleaner hose - I had considered adding blast gates to the floor sweep and the internal blade collector but at this stage it does not appear to be overly necessary as the collection seems to be working. The air flow at the moment is getting in via the large slot for the tilt mechanism as well as around the perimeter under the cast iron top - I have not needed to play with blocking this area at this time but it is a possibility.

I'm sure that this config can be improved but I will need to wait until after the Bris wood show as I'm hoping that C'tec will be doing a good deal on the cartridge filters.

Again, thanks for your interest and comments.

Regards,
Bob

Thanks Bob, mine does not have any hose within the cabinet. I reckon that hose is polyurethane, I was thinking of bringing some in from the US as I could not find it anywhere in Oz.

Originally Posted by Bob38S

Thanks for the suggestions.
Currently if I only have 1 line open to the extractor the chips in the collection bag only circulate half way up the collection bag - if I open 2 lines then the chips circulate right to the top of the bag and the machine seems to run smoother - not scientific I know but anecdotal. Regards,
Bob

Anecdotal can be good, I look at the way my chips build up in my collection box and this gives me a good idea of how much flow I am achieving, from what Bob describes I would suggest that the 4" main line is capable of carrying the flow from the 2 lines, but only because of the restrictions on each of the 2 lines attached to the machines, (hose, fittings, air entry)
Sounds like improvements r being made and this is

Pete