Thread: Dust Extraction for Lathes

It's almost a done deal. I'll be ordering the ClearVue Maxi tonight. Installation problems to follow no doubt, then some tricky work with the metal ducting. I've got some cupboards to move in the meantime and a wall to line with yellow tongue. Apparently I can use an existing 15 amp circuit which will save me my last circuit on the board. I think that means only one more machine to go, but which one? I don't have a drum sander yet...

Jefferson,
Just discovered the CFM figures on the CV page ... where one might expect ... under "specifications".

An 1800 is rated at 1,442 CFM and a Max is rated at 1,935 CFM. These figures will vary depending on duct length, number and type of fittings, hoods/shrouds and etc. But they do what I wanted. They give us a delta. The max pulls 34 % more air than the 1800 ... that's a lot of air.

If you look at the static calculator at Bill pentz's page, you will see that good straight ducting does not do too much damage in terms of losses. That is certainly my experience with a CV. Bill's static calculator says each foot of 8 inch duct costs 0.039" of WC. So, 10 ft of pipe loses 0.39" WC and even 50 ft of pipe only loses 1.96" WC. Each 8 " wye costs 0.42" WC. The losses for 8" bends are:
R/D of 1.5 ... 0.61" WC each.
R/D of 2.0 ... o.41" WC each,
R/D of 2.5 ... 0.34" WC each.

In this case, three bends at an R/D of 1.5 costs almost the same losses as 50 ft of ductwork. My only 90 degree bend has an R/D of about 3.5. If you go with metal ducting and can get wide radius bends, go for it.

So, if you can keep the number of fittings down, and in particular if you can use wide radius bends ... and because a good bell mouth provides quite low resistance, you could likely expect to pull over 1,500 CFM through an 8 inch pipe. That's about four times the maximum air a 4 inch pipe will pull. In fact the difference between an 1800 and Max is more than the maximum for a 4 inch pipe.

The static calculator also indicates you will have no trouble staying at a velocity above 4,000 FPM, in fact it says that for a CFM between 1,500 and 1,600 velocity will be between 4,300 and 4,600, so you have a bit to play with. You get the same velocity through a 4 inch line pulling the maximum of 400 CFM.

Jefferson, this is what its about for me; a good combo of volume and velocity.

Thanks for the data, John. I won't know exactly what the ducting will do to the airflow, but I have 3 lathes to hook up, an open vent to flush the air, plus two ports on the bandsaw. So plenty of wyes and bends. I'll have to get my finger out and stop turning for a while and get onto the installation.

Originally Posted by John Samuel

Peter,

If possible, would you please post a pic of your flexible arm? Also, Can you (or anyone else) point me at a supplier of such arms where the arm is stiffer than a flexible lamp arm? I am trying to find something that will not droop when holding up a piece of 6 inch flexy and PVC bell mouth. My attempts with a lamp arm were OK when holding up to 4 inch flexy, but I need to put the arm on viagra if it is to hold up bigger flexy.

Thanks,

John

John,

Here are the photos of both the flexible arm and the adjustable arm scavenged from desk lamps.

The first two are of the flexible type which I have sitting on the bench onto which the lathe I use for spindle work is bolted. I can twist and move the arm and hose along as needed to capture the dust. I have used this now for about 2 years without any problems.


Attachment 294810 Attachment 294811

The next two photos show the set up for the lathe on which I do only bowl turning. The fairly stiff and heavy hose is clamped onto the adjustable arm of the type of lamp seen in the photos and the fitting is screwed onto the bench. This one can also be twisted and turned along the section of the lathe bed that I use. I'm sure it is strong enough to take a 6" hose for your future setup.

Attachment 294812 Attachment 294813

The lamp on the black stand in the photo could also be removed and the hose fitting can be put into that one, which may be the way to go for Jefferson.

All these lamp fittings came from my kerbside shopping so they were free. Hope that helps.


Peter.

John,

Some observations on these photos.

Originally Posted by John Samuel

Whilst the plastic fitting and hose will collect the sanding dust it won't pick up the heavier chips and curlies as is clearly evidenced by the marks on the paint of the wall behind it where they hit the wall.

This is a work of art, it matches the lathe paintwork beautifully but the pity is that it wouldn't work. The hose connection seem to far away and coming from the wrong direction for it to work effectively and the bottom tray part would collect the chips etc. It would help if a second hose was connected to the bottom part to remove the chips. I started of with a box type like that and it failed to do both well.


Peter.

Originally Posted by Sturdee

John,

Here are the photos of both the flexible arm and the adjustable arm scavenged from desk lamps.

The first two are of the flexible type which I have sitting on the bench onto which the lathe I use for spindle work is bolted. I can twist and move the arm and hose along as needed to capture the dust. I have used this now for about 2 years without any problems.

The next two photos show the set up for the lathe on which I do only bowl turning. The fairly stiff and heavy hose is clamped onto the adjustable arm of the type of lamp seen in the photos and the fitting is screwed onto the bench. This one can also be twisted and turned along the section of the lathe bed that I use. I'm sure it is strong enough to take a 6" hose for your future setup.

The lamp on the black stand in the photo could also be removed and the hose fitting can be put into that one, which may be the way to go for Jefferson.

All these lamp fittings came from my kerbside shopping so they were free. Hope that helps.

Peter.

Ahhh ... good stuff. Thanks Peter. I might do a little kerbside shopping myself.

Cheerio!

John

Originally Posted by Sturdee

John,

Some observations on these photos.

Whilst the plastic fitting and hose will collect the sanding dust it won't pick up the heavier chips and curlies as is clearly evidenced by the marks on the paint of the wall behind it where they hit the wall.

This is a work of art, it matches the lathe paintwork beautifully but the pity is that it wouldn't work. The hose connection seem to far away and coming from the wrong direction for it to work effectively and the bottom tray part would collect the chips etc. It would help is a second hose was connected to the bottom part to remove the chips. I started of with a box type like that and it failed to do both well.

Peter.

Peter,

Exactly! Thank heavens you commented. I wanted to let the more experienced blokes respond first, but when I saw the location of the inlet on the pretty blue box I nearly fell out of my tree. Even a complete lathe novice like me would not do that. I'd be afraid to ... BobL would spank me ... and so would Soundman ... and I'd deserve it.

Soundman got that right ... keep the inlet close to the work. A good bell mouth will give an improved bubble shape, and help the negative pressure bubble reach out a bit. That blue beast seems exactly the opposite of the old saying, "It ain't purty, but it works".

Thanks!

John

Some of the Vicmarc lathes (at least the VL 300s) funnel the chips down the back of the lathe. Gets a lot of the rubbish off the lathe, but you've got to get down and dirty to suck the chips up. With my new set-up, I'm thinking about putting floor sweeps down the back of the lathes. Dunno whether it will work but I'll give it a go. At least on the 175 stand, I can sweep the chips up without getting down too far

Originally Posted by John Samuel

Strolled around the CV forum site and grabbed a couple of pics.



It seems from the discussion so far that lathes require different pick-ups depending on the type of work being done (Peter suggests platters and spindle work need differing approaches, and that makes intuitive sense). The clear plastic shroud in the first pic looks better than a big gulp, but it also looks like it would not project the negative pressure bubble quite as far forward as a bell mouth. But perhaps there are good reasons for the wider opening.

Cheerio!

John

I also have observations on these pictures.

On the first picture.......rip the translucent rectangular thingy off and both the air flow and the dust capture will improve...even better fit a bell mouth.

The second picture is a Typical pointless hood that places inlet far away from the work and dramatically increases thcrossectional arear thus reducing air flow.

As for the idea of floor sweeps......well...unless you have a huge waste receptical hooked to your dust collector.... what ever that may be....or it drops straight onto your compost heap....all you will be doing is making work for you self.

Its far more efficent to use a broom and a wide mouth shovel to pick up the bulk shavings......or if ya workshop is on stumps...cut a hole in the floor and put a wheel barrow or wheely bin under it.

cheers

Originally Posted by soundman

....or it drops straight onto your compost heap....

Now there's a brilliant idea. I'm wondering how much extra ducting that'll take. In fact I think that the extra ducting will quite possibly mean less pressure drop than a filter or a cyclone.

Originally Posted by jefferson

Thanks for the data, John. I won't know exactly what the ducting will do to the airflow, but I have 3 lathes to hook up, an open vent to flush the air, plus two ports on the bandsaw. So plenty of wyes and bends. I'll have to get my finger out and stop turning for a while and get onto the installation.

Jefferson,

That's why duct design/layout is important.

Remember that when calculating the losses you include only the duct and fittings etc between the cyclone and the machine in use (plus any mufflers/filters). The trick is to design it in such a way that you get your 1,000 CFM at every machine. It's not really difficult, and there are folks here to help (the brains trust at this board is incredible). Generally speaking, a good approach is to run a main duct through the middle of the shop (8" in your case) and to branch off this to your machines (6" in your case). Talk to Shedman and BobL about the wisdom of running the 8" line all the way to your most problematic lathe. It sounds like a good idea to me because it lifts airflow for that machine by a hefty amount, but I don't have the expertise to recommend it.

When you are installing your system, suggest you do a static test before the ductwork goes up. It's a simple job made easier if you hook up a short length of duct to the cyclone inlet.

I waited until I got the cyclone before doing any detailed planning. That was a mistake. If I'd done the detailed duct design and static calcs in advance, that would have sped things up during installation. The good news for the lathes is that ports will be simple and relatively quick to do. In my shop more time was spent re-building/upgrading hoods/ports to 6" than in installing either the cyclone or the ductwork.

One question. You hinted that steel fittings might be cheaper than 225 mm PVC fittings. Can you give us a feel for the difference?

Cheerio!

John

Joihn, the local club is currently connecting an (inefficient) Carbatec cyclone in the club workshop. One of the guys got some pricing on the wyes for the 225mm and I think he said over $200 each. I've got some work to do ripping some cupboards out and lining a wall, so will come up with some drawings to post on the possible layout. The Clear Vue guy said to run the main line in 200mm, drop lines with blast gates high in 150mm. I have a sheet metal worker mate that can help out too with the hoods. I'll keep you all posted.

Thats not a new idea, many a country saw mill just had a pipe heading off into the paddock....definitely not Bill Pentz approved.

A few lengths of 6 inch PVC may get you far enough away from ya shed for it to not be a problem.....that is if you have some elbow room.

And ya don't want the air flow to be all that good or it blows the stuff around too much.

there have been some imaginitve ideas used to suprepess the dust over the years.

A sprinkler on the end of the pipe.

Old sacks.

The truck inner tube tied on with tiewire is amusing if not effective....people mostly did this to keep the rain out of the end of the pipe...still ammusing......like a 20 horespower whoopie cushion

I met a bloke who just blew his chips into one of those big furtiliser bags ( ya know the 4x 4 x 4 foot ones, the big farmers get)...he reconed when he was on his game with disposal, he just left it on the trailer.



If you blow into your cyclone, you have air flow to spare and the sizes right ( the bottom of the cyclone about 3 inches in diameter and the vertical riser about a foot across for a 6 inch inlet.......you can leave the bottom of the cyclone open....there will be very little air flow out the bottom.......it just drops on the ground or into an open bin....again very common in times past...again not BP approved ( Bill Pentz or Baden Powel).

cheers

Jefferson,

Got all my pipes and fittings from Total Eden ... the prices from plumbing suppliers (when I bought my stuff) was about 40% higher ... sharp intake of breath!

Total Eden's prices are (incl GST):

• 225 mm Pipe ... $133 per length.
• 225 mm 45 Bend ... $40
• 225 mm 90 Bend ... $42
• 225 mm to 150 mm wye ... $133.

I know it about doubles the cost, but you might like to consider using two 45's instead of one 90 bend to reduce losses.

Of course, you only need 225 mm for the main duct. All the rest can be done in 150 mm, which is far cheaper. Again, Total Eden has the best prices I have seen.

How does that compare with steel? It may be the case that you could get a couple of wide radius bends made in steel, and do everything else in PVC. Over to you, Red Leader.

Cheerio!

John