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Dust filter project and Trend Vari-Jig

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RogerS

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Inspired by DaveL's dust filter I've been meaning to build one myself and finally it made it up the TUIT list.

Like DaveL I'm using the Axminster fine dust filter and coarse filter.



and my fan is this one



It moves about 2000 m3/hour which should be large enough for my workshop.

Scanning the offcut pile I found some 19mm ply for the sides. Didn't have enough for the two ends so found some old carcassing. It's going to be a long beast (about 3ft) as I want to make sure that the filter can expand down its' full length and the fan is also quite long. Maybe ply is a bit OTT but it's there to be used.

Design criteria are the ability to replace the two filters relatively easily and also to be able to remove the fan if need be. Nothing rocket science so far. A fingerguard would be good as well.

Sides cut and the two ends marked up.



Now how to cut a nice circle and a square?

Circle first. The quick and dirty solution would be the jigsaw but I felt I wanted a proper circle. No trammel to attach a router to but thinking upside down, there's the router table which is built around a Festool MFT. (The original idea of combining the two was to be able to quickly remove the Incra fence when I wanted to use it as an MFT. That was three years ago and the Incra fence has never been removed!). But the one advantage is that you don't worry too much about screwing things into the top.

So I drilled a hole in the ply to match the router cutter

and screw a pivot through the centre of the ply.


The Incra fence has been pushed back as far as it will go as I really didn't want to unbolt it.

As you can see, the idea being to gradually wind up the cutter and rotate the ply so creating a circular cut. Just have to remember when the cutter breaks through not to have the fingers in the way.

It worked although for one hairy moment, I'd let go of the ply to get underneath to raise the cutter a bit more and was too lazy to turn the router off. The rotating cutter acted on the ply like a miniature gearwheel and promptly set the ply spinning with the high possibility of the fixing screw coming undone. My very own 'flying saucer'.

Taking things a bit more steadily, produced the hole



To be honest, I have to ask myself was it worth it as the quality of the shuttering ply left the cut line pretty manky.

Now for the square hole. I'd remembered that I wanted some mechanism to hold the filters in place but something that would be easy to undo when the time came. I thought about it a lot and over-engineered as usual..thinking about homemade camlocks etc. In the end, I came to the conclusion that a second ply rectangle cut slightly undersized and located using threaded rod was about as simple and foolproof as it got.

Still got to cut those neat squares tho'. I cut one side with the jigsaw and thought that it lacked finesse. I then remembered that I'd bought a Trend Varijig for another project but that it had gone unused and unwrapped to this day.

The Trend Varijg. Allows you to cut square or rectangular holes using a router and guide bush. Took me ages, it seemed, to work out how it assemble it. Then I was faced with the problem of how to clamp it down especially when there wasn't going to be much meat left around the periphery of the ply. Trend do sell clamps for this purpose but in my case even they wouldn't work.

MFT to the rescue. The MFT comes with clamps that fit through the holes in the top of the MFT.


That worked for one end of the Varijig but, still resolutely refusing to remove the Incra fence, there were no convenient holes to clamp the front and so I resorted to a normal clamp and fixed the front of the Varijig to the MFT frame.



All the time I'm saying to myself, you'd have had this done by now if you'd use the jigsaw.

So started cutting and the first light cut fouled the Incra fence and so bowing to the inevitable I unbolted it. :cry: Why didn't I use a jigsaw?

Made the next pass only to realise too late that the ply had slipped underneath the Varijig.


Not that impressed with the Varijig by this time. Nice idea but using it in earnest leaves a lot of unanswered questions re workpiece clamping. It also begs the question about the whole idea of the Varijig. Great if you're going to use it day in/day out but in reality, it's a pipper to store assembled..long arms jutting out everywhere and so the only sensible solution is to undo it all and put it back in the box until the next time.

Back to the box. Two square holes cut later and still thinking about that jigsaw, I started gluing and pocket-holing.


Tapped the ply for the threaded rod but Araldited them in place just for the hell of it. Installed the filter and by pure chance stuffed my hand down inside each sock to tease it down inside the box only to discover that each pocket is prevented from opening and doing its' job because there are two threads per pocket keeping them closed. Useful to know that.



Crimped up the cable ends nicely as I didn't want the cables coming loose over time. Besides it's the proper way to do these things.


And fitted the fan.



That's it.

Still thinking about the fingerguard.
 

oddsocks

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looks the business Roger - what was the total cost of fan & filter compared to buying the axminster unit? The axminster spec is 600cum per hour so your fan is shifting 3 times that!

Dave
 

p111dom

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Very nice. May I suggest a speaker grill from maplin for guarding? They sell large PA bits and bobs and some of their grills have a lattice with gaps of about 8mm. More than enought for good airflow but small enough for adequate protection. You don't give the size of the fan but grills are available in 8, 10 and 12 inches.
 

RogerS

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p111dom":3oax6t6y said:
Very nice. May I suggest a speaker grill from maplin for guarding? They sell large PA bits and bobs and some of their grills have a lattice with gaps of about 8mm. More than enought for good airflow but small enough for adequate protection. You don't give the size of the fan but grills are available in 8, 10 and 12 inches.
Thanks for the suggestion. For clarity, the fan is about 325mm square. When running the air is blown out at the periphery of the fan blades ...almost in a plane at right angle to the box horizontal axis and so whatever I use doesn't want to impede that flow as that's what's needed to stir up the air.
 

wizer

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Sorry Roger, I giggled when I saw the router jig cock up. That's exactly the thing that happens to me. All. The. Time. ;)
 

RogerS

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wizer":2ydceo2l said:
Sorry Roger, I giggled when I saw the router jig cock up. That's exactly the thing that happens to me. All. The. Time. ;)
LOL. I think that the Varijig needs a row of screw holes down all the limbs so you can secure the work underneath. That or faff about with double-sided tape maybe.
 

Fergus

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Very neat solution. Have mentally added one of these on the list of things to have a go at making (eventually lol) as I have a few extractor fans kicking about at work. :)
 

planetWayne

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Hi Roger,
If its not too cheeky - could you post up links for the filter and fan units please?

Looks like a good plan - might be able to get something set up in the garage between the joists to help keep the air moving and filtered.

Cheers
Wayne.
 

RogerS

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Wayne

This is the link for the two filters.

The fan I bought from another forum member. I do have a tangential blower that I bought off eBay going spare. It came from an old computer equipment rack.

Roger
 

DaveL

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Roger,

Well done, you have made a much more sturdy unit compared to mine. Should last for years. 8) Mine is still going strong and it was made from thin ply and second hand hardboard. :roll:

This type of air cleaner is well worth buying/making, the amount of dust collected is quite surprising and if it ends up in the filters, its not in your lungs. :D
 

RogerS

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matt":2w812fpc said:
I'm curious to know about noise level? What sort of speed does the fan turn at?
Not sure, Matt...the label is on the fan inside the unit!

I'll measure the sound level and let you know. Think it's more a question of what sort of spectrum the noise is. It's a brushless motor and so that avoids particular peaky noise associated with brush motors. Besides, the main aim is to leave it on for a couple of hours when one leaves the workshop so it will scrub the air clean. Mind you, I'll probably keep it running when I'm in there as well.
 

matt

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I keep thinking about getting an dust filter but my main reason would be to allow me to remove my face mask sooner. However... how do you know when the air is "clean" enough to breathe?
 

RogerS

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Matt

This is the spec for the currently available model. Not sure how similar mine is to the spec as the model number is EMP252M. Looks as if the volume might not be quite as high as I was led to be believe but good enough for my workshop.

E Range Low-Pressure Industrial Axial Extract Fan. 250mm (10")diameter 230V. 1500m3/hr (416.7l/s). IP44. 71dB(A)

If you're using a totally enclosed face mask then I'd say keep using it. The dust filter circulator is more a long term solution (long as in hours). Efficient dust/chip collection/extraction at the point of creation is the nirvana we all aspire to.
 

planetWayne

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Interestingly, there was a recent 'wood whisperer' episode (87 or 88 I think) on about health and safety - and respirators and air filters came up.

His humble opinion (and it seems to make reasonable sense) was to always use a face mask whenever doing anything that produced dust or fumes (sanding through to finishing) and to use the air filter when leaving the shop of an evening - say on a 3 hour timer. That way, when you come back in the morning the air should be cleared ready for the days work - which actually may not involve kicking up more dust (catching up on paper work - designs etc).

The thought process being that most air filters are up high and although they would eventually clear the air, the real nasty stuff is still most concentrated at bench high, where your working, so not having a mask and just relying on the shop filter is a no no.

Anyways - it made sense to me :)

Wayne.
 
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