Loss of extraction 'suck'


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Established Member
20 Feb 2004
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In the eternally wet North
I mentioned in another thread my impression that I was losing suck in my Axminster 2200 extractor. I have a fine filter from RB Industrial fitted in place of the standard bag and my usual practice is to whack it a few times each time I change bags...just to loosen up and let fall any fine dust from it into the bag. I even went as far as to use my SDS hammer drill beating against a piece of wood against the side of the filter.

Last weekend I bit the bullet and donning a respirator removed the filter and took it outside. Looking inside I saw it totally covered in fine dust which would explain the loss of suck. I cleaned out about a bucket full of fine dust and now the extractor is breathing easier.

But it does raise a few questions:

1) Maybe there is something about those cyclones after all!

2) Presumably there is a 'life' of these filters?

3) I've read somewhere that for the filters to 'work' then they need a fine coating of dust inside..but wonder if this is a 'woodworking' myth?

4) The Axminster fine filter has a paddle which in hindsight seems like a good idea.

5) I wish I'd 'calibrated' the suck when I first bought it as a reference point.

Any thoughts?

As background, I rarely use MDF or man-made boards - use primarily oak.
I've just bought the same extractor Roger and it came with the cloth fine filter bag. I'm not that impressed - it does a decent enough job on the P/T, but on the t/s it's a bit pants. And i'm cutting up loads of MDF at the mo.

Out of interest, how much was your filter from RB? I'm wondering whether a cartridge filter will perform better than the cloth filter.


My cyclone filter was treated to a cleanout a few months back after 3-4 years of use. I got a couple of mugfuls of dust followed by a good cloud produced by the airline in the garden. The pigeons were coughing a bit but the b'stards are still alive enough to be eyeing up my newly planted cabbages. :evil:

My cyclone is the Barry Burgess/Ikea flowerpot design which lurks on this forum archive under Barry's name and can be seen here in my workshop.

As it turned out, my lack of suck turned out to be a piece of paper towel over the blower inlet!
Filter blinding has certainly always been the cause when I've slowly lost airflow, and that was on the bog stock coarse filter bag system I had until recently.

I'm mid install of a Pentz cyclone system.

The Pentz view is that you can't run a filter fine enough to stop the fine dust that is the prime cause of health problems (e.g. one to HEPA 15) without a cyclone unless you have shares in a filter factory, and a rather large bank balance. This because not only do they blind far too quickly, they also get damaged and leak back into the shop and choke airflows down to levels that prevent decent collection.

Which is why he developed his cyclone based system. He sets out his views on the situation and on what's needed for effective dust collection and separation in summary in the introduction to this section: http://www.billpentz.com/woodworking/cy ... yclone.cfm, and in more detail here: http://www.billpentz.com/woodworking/cy ... Basics.cfm He's not the most concise writer, but 1000s of his systems have been built, and they seem to work very well. He licensed these guys in the US to sell the design commercially: http://www.clearvuecyclones.com/index.php

It takes a fairly well optimised cyclone design to drop out the very fine dust, and some reputedly don't. He says in the first link above that the methods needed to cost effectively do this were sorted out by the sellers of certified systems to regulated industry many many years ago - and that his design is based on this information.

He also reckons that most of the sellers of low end systems to unregulated private users have continued to offer filtration that plain doesn't work - that the fabric is purposely selected to release fines back into the air, but to catch chips so that it doesn't blind too quickly. i.e. that they amount to dust distribution systems....