Axial flow fans.

[JDarvall]

Decided to buy a fan to mount in the wall. right next to my lathe to pull out the dust.......Hoping for some advice on types, prices etc.

Like from this site....here.
http://www.fanpro.com.au/index1.html...FSQqagodSD-UVQ

or any other ideas be appreciated.
Thanks .

[Chipman]

That is an excellent idea... at a guess, I would suggest a spray booth fan

I have thought about doing this kind of thing too but I still haven't decided how to handle the dusty air when it gets outside...I don't want to annoy the neighbours or have it get sucked back into the shed... maybe some kind of filter?

If anyone has got any good ideas, lets share them as dust is our number one enemy!

Chipman

[JDarvall]

sounds like its worth doing. I was thinking of buying a couple.

Got the idea from BobL here. Thankyou kindly.

Just unsure of speed, size, expense to run etc.

[QC Inspector]

The idea is a great one and works well if you don't live close to anyone. A bit loud for some and the dust will bug neighbors if you live in the suburbs.

When the company was replacing some big ceiling mounted gas furnaces, I took off the backs of a couple with 2, 18 inch fans in each (approx 1/3 or 1/2 HP). I matched up the best pair and took them to my father's place and we mounted them in the wall below the window that his Nova lathe sat in front of.

With both fans on, all the fine dust and a lot of the coarse stuff too, was sucked out and blown into the woods. They also blew away the loose dirt on the ground outside for a few yards. There was the benefit of standing in the cool breeze when working, but the downside was that in the winter with the snow on the ground the shop was a little too cool.

To keep out the weather my father attached an old door from a small refrigerator over the fans to the wall outside and opened it when he wanted to do any turning. He isn't one to spend if he doesn't need to.

Since big furnaces are not a common commodity in Australia, you could look for some of the fans used to ventilate poultry barns, greenhouses etc. They might be cheaper and have enclosed motors so the dust doesn't get inside them.

[JDarvall]

With both fans on, all the fine dust and a lot of the coarse stuff too, was sucked out and blown into the woods. They also blew away the loose dirt on the ground outside for a few yards. There was the benefit of standing in the cool breeze when working, but the downside was that in the winter with the snow on the ground the shop was a little too cool.

Thanks for sharing that with me. reasuring that I'm doing the right thing. This is exactly what I'm after.

[BobL]

Decided to buy a fan to mount in the wall. right next to my lathe to pull out the dust.......Hoping for some advice on types, prices etc.

Like from this site....here.
http://www.fanpro.com.au/index1.html...FSQqagodSD-UVQ

or any other ideas be appreciated.
Thanks .

Jake,
I looked on that website and the cheapest fans are ~$500 for 1 cubic metre per second. Sure you can get 5 cubic metres per second for about double those $ but it's going to be very noisy with a 12.5 m/s linear air speed and it's going to suck up anything loose in it's vicinity.

If you are going to spend this much on a fan I reckon better off getting a 2HP DC which will give you about the same flow rate and putting the DC outside. That way you can at least catch the big bits with having them scattered all over your back yard.

[JDarvall]

Jake,
I looked on that website and the cheapest fans are ~$500 for 1 cubic metre per second. Sure you can get 5 cubic metres per second for about double those $ but it's going to be very noisy with a 12.5 m/s linear air speed and it's going to suck up anything loose in it's vicinity.

If you are going to spend this much on a fan I reckon better off getting a 2HP DC which will give you about the same flow rate and putting the DC outside. That way you can at least catch the big bits with having them scattered all over your back yard.

thanks Bob being patient with me. I'm dragging this on a bit I know.

I'm not too concerned about the big bits to be quite honest. I noticed when I use the lathe, chips go every which way anyway. I don't know how anything machine could collect it. and it doesn't matter about the backyard getting chips in it. Actually it probably end up on the road side.

All I'm concerned is the dust particularily when sanding. I want that dust pulled immediately off the spindle and gone, like was mentioned before. Before it floats up around my head.

Would a 1 cubic Metre per second fan be sufficient to pull it out in that way?

How would I setup a dust extractor so that it pulls it out in a similar way. One of those big gulp plastic things from carbatec ? Don't the hoses from a DC provide only localised sort of suction. I don't want to have to move a hose around right up close to the spindle to where ever I'm sanding at the time. Too fiddly. Feel like its going to get in the way. I like to work fast.

I was thinking of putting the fan about this height in the wall(picture)...so I've still got my shelf in front of me for my copy details and spindle and tools.

[BobL]

Jake,

It's not just flow rate but also air speed that will determine satisfactory capture of dust off the spindle.

- At 500 rpm a 10 cm diameter object on a lathe has a linear circumference speed of ~2.5 m/s and this is the maximum speed the air/very fine dust/sawdust are flung off with. It doesn't continue at that speed of course as it interacts with other air a slows down very quickly. Nevertheless higher rpm's of course means higher speed.
- Ignoring the sawdust chips, the air speed needed at the spindle to capture the fine stuff will need to be at greater than this or some of it will enter the shed.
- Bear in mind that any object being turned in the presence of a one way air flow partially shields itself, so almost irrespective of air flow there will be some fine dust flung off.
- you can increase the airspeed of collection by reducing the area of the intake. Bearing in mind that if the collection area is smaller than the object being turned then it's a bit of a waste of time.
- A 1 cubic m/s flow with an air speed of 2.5 m/s means a maximum of 0.4 m^2 - that's about a 0.6m by 0.6m collection area.
- You could make a rectangular air intake box shaped to suit the lathe dimensions and place that behind the lathe that concentrates the air flow directly off the turning object.
- You would have to box up the back of the lathe for the fanpro unit anyway, as the air speed drops pretty quickly as you move away from the fan
- NB this is all the above is for only 500 rpm turning speed. 1500 rpm means you need 7.5 m/s air speed to catch the fine dust.

The reason I'm recommending an external 2HP DC is that they too can move about the same amount of air, (well a bit less ie 1500 cfm/0.7 cubic metres per second) and usually come with two intakes. If you made a box connecting the 2 intakes immediately behind the turning object that would work pretty well. The DC sitting outside also reduces the noise.

Another alternative would be buy two of the cheaper/budget units (1200 cfm) for $300 each and get 2400 cfm or 1.2 cubic m/s for $600, throw away the bags and just use the flexy ducting etc.

I'd be looking to just get the DC blower units themselves - pretty noisy though, maybe the fanpro fans are better from a noise point of view.

[JDarvall]

Thanks again Bob.

How much reduction in performance would a 2hp dust extractor have do you think as the hose gets longer? I thinking about having a hose near 9metres long.

[rsser]

For numbers like these google for Bill Pentz website on dust extraction; lots of good info there AT.

FWIW for a while I just had an old kitchen extractor fan mounted in an exterior wall and attached to some 8" flex duct. That could be positioned right behind the bowl or spindle and sucked most of the dust out.

Since then the main extraction is a carba-tec big gulp mounted on a stand and feeding a 2 hp dusty. V. good primary protection IMO.

[Chris Parks]

Jake,
I'd be looking to just get the DC blower units themselves - pretty noisy though, maybe the fanpro fans are better from a noise point of view.

Bloody hard to find in Oz, readily available in the US. Why is it so?

[BobL]

Thanks again Bob.

How much reduction in performance would a 2hp dust extractor have do you think as the hose gets longer? I thinking about having a hose near 9metres long.

As much as length I would expect too many corners or bends to be as significant.

All I can really give you is a result of an experiments of the effect of corrugated hose length on flow rate. A straight 3 m and 1 m long x 100 mm diam hose have less than 5% flow difference between them at 300 cfm. I have not measured it above that flow rate that but I expect it will be significant.

I also could not measure any difference @ 300 cfm between a 3m length of 100 mm diam corrugated hose and a straight piece of 100 mm diam Polypipe, but once again I expect at higher CFMs that this will be significant.

To try and answer your question I would guess it will be about 25%? for a corrugated pipe

To reduce this effect for a 2HP/1200 cfm unit you could run 2 x 100 mm diam hoses or a 125 mm or 150 mm ($$$$$) pipe