Hi Steve
Need to wait and see if Russell explains his reasoning. I think it will depend on his type of Camvac maybe? Perhaps his reasoning was to prevent the filters clogging up in the Camvac earlier than they would do - if he didn't use a cyclone. Did he have the Camvac and then discover that the filters gradually got clogged up so it lost suck? Then added in the cyclone as a way around that problem?
My take is this.
Any sort of dust/chip extraction/collection has to output its' air back into the room (or outside through a vent). The latter is not a good idea in winter as it will suck out all your warm air as well. So most people's equipment will have some sort of filtration. It can be as simple as the filter inside an Earlex type vacuum cleaner, a 0.5 micron drum filter as fitted to some extractors or the triple filtration system fitted to some Camvacs. The better the filtration (ie how fine is the dust that it filters out) the quicker it will eventually get clogged up and so your extraction suck will go down. That is why many extractors (I use the term in its' broadest sense) have multiple layers of filtering starting from a coarse filter and going down through ever decreasing fine filters.
One benefit of the cyclone in the path is that much of the dust and debris will drop out at that point and not end up going through the filtration system. So the filters will last longer before they need to be replaced or cleaned.
To get all this extraction to work, you need suck. Some woodworking machines need more suck volume rather than velocity. For example, a hand-held orbital sander chucks out a lot of fine dust. You need velocity.
A thicknesser will chuck out less dust but larger chippings/shavings (and lots of them) so you need suck volume to lift these chippings and suck them away. Which is why the output ports on thicknessers and similar machines are 4" diameter.
A spindle moulder will chuck out even more.
So what is my own experience?
I bought an Earlex vacuum cleaner - one of the wet'n'dry ones. Tools that I had at the time were a planer, a thicknesser, an orbital sander and a cheapie Ryobi router table. And a small Ryobi cheapie table saw. It coped fairly well but I was forever having to take the filter out and clean all the dust from it. And the capacity was a bit low and so I had to keep emptying it.
So I bought the mini-cyclone as previously mentioned. Built an air-tight box for it to sit on, mounted the box/cyclone unit onto a wheeled base and to power it I used an Earlex vacuum cleaner. The whole lot was remotely turned on/off. The difference was fantastic. The filter in the Earlex very rarely got blocked as most of the chips and dust ended up in the cyclone. Indeed, I used to find myself watching it all spiral down into the box.
That has worked well for me for several years. Then I upgraded the router table and fitted an Incra fence which has very good extraction built-in and also a larger table saw. The cyclone unit still coped well.
Then I bought a spindle moulder and also started doing a lot more 'production' work - running off architraves etc - and the cyclone unit struggled to keep sufficient air flow through the 4" pipe from the spindle moulder that it kept blocking up. Even when it did work, the cyclone collection box filled up way too quickly.
So I bought a twin engine Camvac 386 on ebay. I like the filtration feature but it's not wheeled which is a pain. But I was a bit disappointed with the air volume - it didn't seem any better than the vacuum cleaner. And you can't easily see when it's full. I did toy with the idea of fitting an intermediate chip collector box - sort of like a cyclone but without the spiral - but never took it much further because I could see my woodworking (hopefully) moving up a notch and so I decided to invest in a much larger 'normal' extraction unit from Axminster -
this one.
It works well. I think that perhaps it's not quite as good as the cyclone/vacuum at extracting the router table and so I was thinking about hanging on to this unit. I'd already decided to sell the Camvac. But now I'm thinking that I may well sell my beloved cyclone unit as well.
The downside of the Axminster unit is that the standard bag doesn't filter out the very fine dust and so I will be fitting one of those (not from Axminster, I might add) 0.5 micron drum filters. And after a TUIT, one of the home-made dust filtering units a la DaveL.
So not sure if that helps or hinders?
Oh yes, lathes are notoriously difficult to extract. Most of us who use one have a full face guard.
