Thread: Dust Extraction for Lathes

John,

There is a thread in the General Turning Forum that discusses dust and shows some interesting hoods.
https://www.woodworkforums.com/f8/dus...urners-177866/

It really depends on what you are doing on a lathe and whether you are concerned about collecting chips or health impacting fine dust.

For short small (e.g. spindle) work my dust particle testing shows that 1000 CFM and a bell mouth hood is used close to the work is sufficient to prevent very fine dust moving into the space occupied by the operators nose and mouth. However some chip loss appears unavoidable..

As the diameter of the object was increased,there is even greater chip loss, and increasing amounts of fine dust moving into the operator position. The amount of dust observed was usually low and variable, and dependent on many things, e.g.: the type of chisel and the way the chisel was being used, and how many breaks one took. One thing I remember was it did not appear to increase significantly over long time periods or escape into the rest of the shed.
When I stopped turning and left the DC running any fine dust in the operator position was vented by the DC in less than a minute.

1000 cfm is equivalent to a hemispherical bubble of air ~2ft in diam per second being pulled from the vicinity of the inlet. However, a hemispherical shape is poor approximation of the profile of the air being sucked into any port. For a naked pipe the shape is more like a flat mushroom with substantial air being drawn from behind the hood, while for a bell mouth it is more of a taller mushroom shape which enable it to draw more air from directly in front of the inlet.

I have not tested anything systematically above about 6" in diameter and as my lathe is limited to objects of 12" in diameter although it would make sense that large bowls etc would require more CFM and more strategically placed hoods. I like the idea of an additional hood being located directly underneath the banjo.

Thanks, Bob.

I would like to catch chips etc, but it is the fine dust that I would want to be sure to catch. Its a bit like my press, when big chips fly out occasionally, I ignore them. Currently fooling around with changes there. Thinking about using a couple of feet of flexy with a PVC bell mouth at the end. The idea is to be able to pull the inlet closer to the work when needed; to ensure the inlet is always at optimal height relative to the cutter/sanding drum, and to change the shape of the negative pressure bubble, as you indicated in your post.

But the day will likely come when I get a lathe, so I am trying to get ahead of the game and gather some good info now.

Thanks,

John

I have seen first hand, on forums and in magazines, quite a number of dust extraction ideas for lathes.

The problem is by far the majoity of them fail because they fly in the face of the laws of phsycs.

First we have to establish that for effective dust extraction and especially removal of airborne dust, air velocity is required. Air must move at a sufficient rate to take the dust with it into the duct before it falls to the ground or goes elsewhere.

Second we have to understand that in free air you can blow air a great deal further than you can suck it.

In fact you can't suck it very far at all.

This is because when air exits a duct or hose, the duct or hose controlls it and directs it in a particular direction, where under suction air comes from all directions to fill the low presure void left by the air sucked away.

Under pressure the shape of the duct, hose or nozzle exerts quite a lot of influence on the flow and direction of the air flow, where under suction it exerts very little..........for those with problems understanding, this is in free air.....the end of the duct into open space.

Once you get much more than the diameter of the duct away from its opening the air velocity drops dramatically.


We see quite a lot of funnels offered for sale, for the purpose of dust extraction.

Funnels will provide some influence on the "shape" of the sucked area, but their effectiveness is very poor.....all they do is transition the diameter of the duct and thus lower the air velocity.

If the sucked area is increased the air velocity decreases...and this is a squared relationship.

So if we start with a 100mm ( nominal) round duct with an area of 7850mm2...we then fit a square plastic shute (the common small shute) 100 x 250mm an area of 25000mm2 we have reduced the air velocity at its opening to arround 1/3.

If we fit a big gulp dust shute of 330 x 400 mm we have an area of 132000mm2, we have reduced the air velocity at its opening to 1/16.

Then you have the issue of getting these larger orifices close enough to the work to be effective.
Especially when the air velocity right at the opening of these shutes is marginal or insufficient to suspend the dust you want to collect.

I have seen large shutes in operation and most of what goes down them was either going that way at velocity or fell into them due to gravity.

My recommendation is to keep the opening the same size as the duct or hose feeding it, and get it close to the job, if you possibly can.

If you have some sort of stand or arm to mount it on great, you can direct the suction where it is required.

As its stands, I just have a piece of bent wire hook, that allows me to hook the dust hose to my side of the tool rest or to the bed of the lathe.

It keeps the opening pretty close to the work.especially when I am sanding.

If you can tolerate a 70% drop in air velocity, by all means use one of the small rectangular shutes.....I baught one and found it unsatisfactory.

The big gulp dust shutes in my opinion are neither use nor ornamant, unless they are under the job and you rely on gravity....because these devices will result in a 94% drop in air velocity at its opening.

Like any dust collection, if you get the opening close to the work you need a hell of a lot less suck to get the job done.

cheers

Originally Posted by soundman

My recommendation is to keep the opening the same size as the duct or hose feeding it, and get it close to the job, if you possibly can.

If you have some sort of stand or arm to mount it on great, you can direct the suction where it is required.

Agreed. That is also what Bob recommended and it is exactly my intention. The short piece of flexy will allow me to pull the inlet closer when I need, and to make small adjustments to the height, depending on the job.

For the press I imagine the bell-mouthed inlet being attached to the stand, but flexible. A prototype made with a flexible lamp base worked well, but I am looking around for an even better solution.

Cheerio!

John

I note in some designs an inlet has been placed under the banjo. However, one aspect BobL alerted me to some time ago was the tendency of many machines to create dust in such a way that much of it tended to rise. This was the case for the drop saw and the spindle moulder, but in my shop that was solved with shroud design.

Does anyone have data/experience as to whether this is an issue with lathes? It seems to me that the operator's face will be higher than the work, and that rising dust could be an issue.

Cheerio!

One problem with lathes, is the work piece acting as a fan.

It tends to thorw the waste down at the front, but straight at the operator comming over the top.

Depending on the size, shape and the type of cut waste can be propelled in almost any direction.......I have once or twice had chips bounce off the back of my hand, behind the visor and fair up my roght nostril .....hence the need for a dust inlet that can be positioned where it is needed.

I find quite often my simple hose hooked on the front of the bed, encourages waste to keep comming over the top and down the spout.....the suction hose being between me and the lathe often works well.

There was a bloke a few years ago who tried marketing a a roughing gouge made from tube....a vacuum hose was attached to the but end of the gouge.......seemed like a good idea at the time but the diameter of the tube was not sufficient & it clogged frequently and then there was the weight of the hose on the back of the gouge.

I have seen dust spouts mounted on a second banjo comming in from the rear.

But anything that works has to put the inlet close to the work.

cheers

A bit peed off, as the power went off as I was halfway through a reply.

First up, disregard most if not all that Soundman says. I urged / challenged him to show his wares and explain his set up but he declined. I much prefer to listen to Bob L and get the right advice.

My experience?

I have 5 lathes, but only three in operation at one time. So I need lots of HP. At least I did last Friday. And most of the Thursdays before....

Vicmarc VL 175

I have a cheapie 3/4 HP single bag DE connected to this one. With some 4 inch flexi duct. Works well enough when sanding with the head stock parallel to the bed. (Not so sure about the fine dust escaping in the air, or from the bag) Not so when I rotate the head and hollow boxes. Dust everywhere. If this is your only lathe, shape of the DC chute will be less important than how you position it. Especially if you turn platters etc and use the outrigger.

Vicmarc VL 300 long bed.

I have two banjos for this lathe and a long twin-post 600mm rest. Required? A rectangular chute. But I also turn finials on this lathe, it's so stable. Same as the 175, a cheapie 3/4 HP DC with a 200 Micronair overhead. This one gets very dirty. A blind corner in the 9m x 6.5m area.

Stubby S 750

This lathe causes me more grief than the others. Bigger platters etc, that vary in size and the chips and fine dust go everywhere. I currently run a 2 hp DC to this lathe without success. Gulp chute. Small CT air filter overhead. The A/C helps but not over winter.

I've heard some say that they can capture lathe dust at source. Crap! Absolute crap. Put a strong light on and take a look at what you can actually see. Never mind the finer stuff. I watched a mate turns some osage orange the other day and the fine dust that I could see went everywhere. In spite of the DC.

What I need to know is how often the ClearVue Max will cycle the air. And will it get to the dead spots. I'll find out soon hopefully. My turning end of the shed is 9m x 6.5m, 2.7 walls, 3.9 ceiling. And yes, I turn well enough and have been taught by the best.

Probably unlike Soundman who refuses to give us a brief assessment of how much actual turning he's done. Or what he turns. And how good. Or how he sharpens his tools. I rest my case.

I really doubt if any dust extraction is going to be capable of catching all chips. They fly every which way. And at increasing speed as your skill improves. I have hit in his office 20 feet away and around a corner. ( ) Sanding dust maybe, because the area that goes is more controlled. But a face shirld duty thing would work best. (But you get a cold face in winter from the blowing air).

Originally Posted by jefferson

First up, disregard most if not all that Soundman says. I urged / challenged him to show his wares and explain his set up but he declined. I much prefer to listen to Bob L and get the right advice.

My experience?

I have 5 lathes, but only three in operation at one time. So I need lots of HP. At least I did last Friday. And most of the Thursdays before....

How does what you own prove what you know or can do?

I know plenty of people who own more than one car but couldn't actually drive a sharp nail into hot $h!t.

I own two lathes but I don't call myself a turner. When I get more practice I might call myself a turner, but I know I am a long way off of that. By your reasoning I am just three lathes behind you. That doesn't inspire me to go out and buy them. I need to learn more about using the ones I have.

Soundman was right in not responding to your claims of superiority based on what you own. I see it too often on the forum where someone says "ok but I bet you have never..." only to have a response of "I do it for a living" or something similar. Then the first person either challenges again with another "I bet you have never..." or challenges for proof. I see this time and time again.

I have no doubt that Bob and John know what they are talking about, but Soundman is right - they aren't talking about what I am doing in MY shed. Sure I learn from them, and I have learned a lot from them. I also have reason to believe that they have learned from me too. A couple of years back I had a brief disagreement with Bob in the forum about how much you can do with limited availability of power and he has often since mellowed his responses to reflect that not everyone even has 15 amps to play with.

I dont agree with everything that Soundman says but I see his contributions here as kind of a Devil's advocate, the voice of what can be achieved in practice with limited power, finances and other resources that most of us have to deal with, as opposed to the theoretical utopia that some like to promote.

It is important that the balanced views are all put forward, and all should be respected. I agree with Soundman that too many threads are hijacked by the 3+ horsepower clearvue brigade when all the Op was asking was if he could put a straw in his mouth and blow the dust off the workpiece in his scrollsaw.

Basically, most people who ask a question in the dust extraction forum have read a couple of posts. I bet they already know about clearvue's and 3hp minimum systems from the first thread they read. They read the second thread and find out the same thing, and the third, and the fourth and the fifth. Is it any wonder they make a post, so that they can find out if there is something else they can do that's cheaper or doesnt require a 15 amp power circuit, but might just help a little. And then two posts into their thread (if they are lucky and its not the first response) they get hit with it again.

Doug

Originally Posted by jefferson

What I need to know is how often the ClearVue Max will cycle the air. And will it get to the dead spots. I'll find out soon hopefully. My turning end of the shed is 9m x 6.5m, 2.7 walls, 3.9 ceiling.

I'm sure Shedman can get that info for you. All you need is an estimate of the CFM given the ducting etc you plan to use. I have a CV1800. I love it, but buying it was likely a mistake if I do get a lathe. Should have gone for the Max. Mine turns over an amount of air equivalent to the air in my shed in about 7 minutes. Your area at 9 X 6.5 X 3.9 is 288 cuM. My 1800 is estimated at 1,000 CFM or better, which is at least 1,700 cuM per hr or about 28 cuM per min. At that rate, an 1800 will turn over 288 cuM of air in about 8 minutes. The Max will pull a lot more air, and will do it faster than that. I use mine to clear the shed of fumes when spraying. Works a treat.

If I do get a lathe it will be for furniture components, so I need to be able to turn a table leg. Don't see platters etc in my future yet, so my guess is that at least for a start the biggest diameter I'll be turning is 6-8 inches.

I was thinking that a Max would be the business because it would allow us to have two 6 inch inlets operating simultaneously ... just got to figure out how to configure them.

Anyway, please keep us posted.

Cheerio!

John

Originally Posted by tea lady

I really doubt if any dust extraction is going to be capable of catching all chips. They fly every which way. And at increasing speed as your skill improves. I have hit in his office 20 feet away and around a corner. ( ) Sanding dust maybe, because the area that goes is more controlled. But a face shirld duty thing would work best. (But you get a cold face in winter from the blowing air).

Thanks Tea Lady,

Don't really care so much about the chips. Good chip collection is a bonus I'll aim for if I get a lathe, but mainly because I'm lazy and don't like cleaning up after myself. It's the fine dust that concerns me. My shed used to be disgustingly dusty, and because it is built onto the house SWMBO was never impressed with the dust that found its way into our bedroom. The new dust extraction system keeps the shed and the air we breathe clean and I rarely need to do more than give things a quick swish with the vac occasionally. I like that a lot, and don't want to turn it into a mess again.

Seems to me that particularly for turning platters etc on a lathe that a ventilated face shield might be a good idea.

Cheerio!

John

Jefferson..maaaate.

You poo poo what I have to say yet you demonstrated that you have no sucsess with what you are doing.

AND,.... I know what you are doing will be unsucessfull....I don't need to see it, I don't need to try it...because the laws of physics say it wont work.......AND you go on and prove the point every day.

So you have spent a bit of money and you still fail to achieve results........but you dismiss what I have to say without even trying it.

Lathes ARE a funny thing to achieve dust capture........you will never captuure all the heavy chips, they are simply too heavy and come off at too high a speed.......they present very little respiratory risk unless you work at the lathe without a face shield and with your mouth wide open......but capturing a very large portion of the fine dust IS possible.....BUT...you must have sufficient air flow close to the workpiece.

I'll say it again...you need to have sufficient air flow close to the work piece.

You keep going on about air exchange........you have heaps of dollars down the drain with air filtration.

As for the 1Hp single baggers............hell even among the single power point brigade, these things are considered nearly useless....bugger all air flow..... and......as far as fine dust......OH HELLl...... The bags on these things are B$#@! poor and work little better than a sieve.......forget the invisable dust...you can see the crap coming out of these filthy little things.

If you don't capture the majority of your dust at source you will need very large ventilation capacity...I mean HUGE.... to exchange the air sufficiently to mantain adequate air quality.....

If you do not want to attempt to capture dust at source you will need to produce similar air velocity thru your ventilation or filtration system to suspend and carry the same dust but over a very much larger area.

You say you do this for a living, and you have spent a few dollars on machines...but ya still pissing arround with the very lowest end of dust extraction equipment.

If you'd spent the money that you have on pointless air filtration on one or two decent dust extractors and put them outside. You would be way ahead of where you are.

AND you seem stubborly resitant to use good personal protective equipment.

There is a very good reason why so many serious turners use forced air full face helmets.

You are doing everything that is well known not to work, but you will not be told about things that have been proven do.

Sorry mate but your reasoning defies logic and phsyics and you cant be helped.

cheers

Originally Posted by doug3030

It is important that the balanced views are all put forward, and all should be respected.
Doug

I agree with Doug on this point. Can we all try to do show a little restraint, please.

I have my opinions, and am not afraid to voice them, nor should anyone else. By all means, disagree, but we are likely wise to avoid slanging matches. In particular, surely it is not necessary to sink the slipper or resort to ridicule or name-calling.

Doug, that is my issue. I care not one whit if Soundman or Sturdee or anyone else disagrees with me. But it is disappointing when a particular forum member seems to follow me around just so he can call me a born again dust messiah ... again ... still. Whatever my faults might be, I am only trying to learn where I need to and help when I can. I have just read these threads again ... https://www.woodworkforums.com/f200/c...action-178328/ ... https://www.woodworkforums.com/f200/g...s-shed-178958/. I invite you all to go over them ... slowly. Sadly, there is no shortage of slanging and name-calling. No matter how strongly we feel about the subject, none of us is entitled to belittle, slander or generally demean others.

Sermon over.

I value experience, but the school of hard knocks has taught me to value knowledge and solid data much more. Does anyone have a link to sites that have good data that indicates the effectiveness of varying dust control approaches for lathes? I am particularly interested in particle counts by size groupings, and in particular, the finer particles.

Cheerio!

John

Originally Posted by jefferson

disregard most if not all that Soundman says. I urged / challenged him to show his wares and explain his set up but he declined. And yes, I turn well enough and have been taught by the best.

and

Probably unlike Soundman who refuses to give us a brief assessment of how much actual turning he's done. Or what he turns. And how good. Or how he sharpens his tools. I rest my case.

and in another thread

Tim, I've lent my E chuck to a mate, so I can't post some pics of recent work.

Jefferson,

The thing that I've noticed that whilst you claim we should ignore Soundman because did not take up your unreasonable challenge to show what he turns or how much, you haven't posted any of your works as your credentials. All you claim that you have 5 lathes. Well so do I, but having more lathes doesn't necessarily make you a great turner, I know because I'm still a learner, so why don't you post some of your works as a credential like you challenged Soundman.

Similarly in the other thread, don't you have any photos for the works you made before you lent out your chuck. If you have post them.

Peter.

Btw anyone would have known that the 3/4 hp single bag units would be a waste of time. The only good thing of them is to use the motor and fan as a booster in the longer pipe runs.