Dust Extraction AGAIN (Sorry Guys!)

[gregmcateer]

Having read loads of threads here and elsewhere, the (general) consensus seems to be to use as large a bore as possible.

Having said that, SunnyBob (IIRC), reduces from 100mm to 63mm almost straight out of the vac and still achieves satisfactory suck, (if I can say such a thing without censure ).

My proposed setup is;

1. Bandsaw (which has a 100mm exit.
2. Lathe with whatever I want, ending in a hood/hopper type thing
3. Either another hose or use disconnect from lathe to use as shop floor vac
to;
Extractor (a secondhand Woodstar with a 100mm inlet)
via;
A Cyclone of some sort (yet to be bought), dropping into a 60 litre barrel.

Should I just pipe into the barrel side, then back out the top, or should I;
a) Make / buy (if they exist at minimal cost) a 100mm inlet and outlet cyclone, or
b) reduce down to 63mm and get a 20 quid cyclone?

OR, (just thought of this), reduce bandsaw down immediately and pipe whole setup in 63mm?

Answers on a postcard in *****-proof format, if you please.

Many thanks in advance

Greg

 

[dzj]

I don't think you'll be able to catch the finer particles at the source with 63mm piping.
You'll need some kind of additional air filtration.

 

[gregmcateer]

Thanks, dzj.

I do have a jet air filtration unit. I was wondering more about the pipe sizing throughout. Mike Pentz seems to indicate that anything less than 4" diameter is sacrilege in the extraction world.

Although it is only a hobby workshop and max distance from machine to collection 2.5m, I don't want to under-do it and regret it.

Greg

 

[gregmcateer]

Been thinking about this a bit more overnight, (Really must learn how to sleep without workshop-based dreams).

Can anyone advise - Is it good / bad / irrelevant to reduce the pipe from 100mm to 63mm, (either immediately out of the bandsaw, or later on near the cyclone) then back up to 100 at the vac?

TIA

Greg

 

[CHJ]

For entraining the dust produced when sanding a reasonable sized item on the lathe you need the maximum airflow past the turned piece possible.

I'd aim for 100mm with the maximum airflow rate possible and some form of cowling/funnelling to ensure the air drawn in is coming across the work piece as much as possible and not just bypassing behind the work.

Do not rely on shop air filtration to protect your lungs, it keeps the shop cleaner in the long run but if it's collecting dust then your lungs are doing the same in parallel.

Bandsaws are notorious for spraying the dust around, albeit the bulk of it in the lower compartment, once again the more extraction airflow volume you can achieve the more chance you have of collecting it.

Re. stepping ducting size down and then back up, If you reduce the size of ducting and restrict the airflow rate, it will hold the dust in suspension in the smaller duct but the moment it opens out into a larger bore it is likely to drop the dust out of suspension and leave it lying in the larger duct, (it may also leave dust in the larger collecting duct because flow rate was not high enough for the bore to entrain the dust.

Large systems often have an air bleed system in the far end of the systems larger ducting to maintain the air volume flow to stop this happening if smaller feed ducts restrict the flow rate.

 

[gregmcateer]

Thanks Chas, for the detailed reply.

For lathe area, I'm planning a cowl as you describe. Plus I wear a 3M powered mask like yours.

Regarding your para:
"Re. stepping ducting size down and then back up, If you reduce the size of ducting and restrict the airflow rate, it will hold the dust in suspension in the smaller duct but the moment it opens out into a larger bore it is likely to drop the dust out of suspension and leave it lying in the larger duct, (it may also leave dust in the larger collecting duct because flow rate was not high enough for the bore to entrain the dust."

If the 100mm duct goes to the barrel / cyclone, (stepped down or not), then out to the 100mm pipe on the vac, is it likely to have dropped the majority of the dust in the barrel, before it reaches the larger pipe?

TIA

Greg

 

[dzj]

Thanks Chas, for the detailed reply.


If the 100mm duct goes to the barrel / cyclone, (stepped down or not), then out to the 100mm pipe on the vac, is it likely to have dropped the majority of the dust in the barrel, before it reaches the larger pipe?

TIA

Greg

Yes, this is what a cyclone is for.
Finer dust will not drop in the barrel, but a further filtration step is needed.
Some people skip such a step and vent it directly outside. Works well in the warmer months, but not so when your shop is heated.

 

[gregmcateer]

dzj,
Gotcha. I hadn't realised the finer dust won't have dropped, but it's obvious when I thin about it. Is the filter in the vac sufficient, or am I then blowing the worst dust into my workshop?

 

[sunnybob]

My system appears to not work according to most here.
Strangely, my system works extremely well.
At least 95% of ALL dust is collected and seperated by the 63 mm cyclone into the hopper, leaving the main drum empty. There is a truck type filter over the fan motor, which of course gets blocked by fine dust and has to be brushed out once every month or so.

The last time I emptied the plastic bucket it was 3/4 full, and the only thing inside the main extractor drum was a pair of plastic gloves that I (forgot) to remove from the bench.
By the way, those 20 quid cyclones are NOT 63 mm, they are mostly 50 mm and are fairly useless if you have a 100mm outlet machine.

 

[gregmcateer]

Thanks for that, Bob.
(btw, your photos have disappeared from your original post)
Greg

 

[dzj]

As Bob says, a cyclone will catch 95% of the larger particles. Catching the smaller than 1 micron dust requires
a good second stage filter. Google 'dust collector canister filter'.
I send these particles into the atmosphere, something I can get away with as my shop is surrounded by gardens and such.

 

[CHJ]

My lathe extraction is arranged with very coarse filtering to maximise airflow, (it will happily take a 75mm cube of wood as far as the extractor fan along about 3 metres of 100mm duct and a 100mm polishing mop all the way through to the bin). The fine and not so fine dust is vented to the external extractor shed and outside air.

My Bandsaw, Chopsaw, Bench Top Thicknesser and 300mm Disk Sander is now looked after by a cheap 100mm inlet drum extractor from Rutlands, (switched between appliances.) this has a fine Cartridge filter and paper intermediate filter bag reducing the filter load. It's the most effective collection of the fine dust I've had to date after several incarnations of chip extractor setups with drop bins etc.

Don't know how long the cheap unit will last but it sure sucks a lot of air.

 

[sunnybob]

Thanks for that, Bob.
(btw, your photos have disappeared from your original post)
Greg

yeah, have you read the photobucket threads? They now want to go from a FREE hosting site, to a £400 a year subscription site. That would mean me paying about a tenner everytime I posted a pic EVERY YEAR i want the pic to be visible.
No way Jose.

Untill I find something else... no pics.
If there is a specific thing you want a pic of I'm happy to attach it to a pm for you.

 

[gregmcateer]

Thanks, Bob.

I think I've sussed your setup by looking at it last time, before they held you to ransom.

If I'm stuck I'll PM you

Greg

 

[sunnybob]

anytime

 

[yanky]

Do check noise levels.
It seems the cyclones are noisier than the standard dust extractors - even if they have induction motors. If you look at Axminster, they rate some of their cyclones at xxdB (at 3m), because they don't sell well due to the noise they make.
If you work alone, it's fine with ear defenders, but not if you want to talk to someone while you work.

 

[CHJ]

Following on the comments above about noise, with my setup:-

Chip extractor on lathe (positioned outside shed) is in itself not noisy but the airflow rate achieved generates enough noise to render open listening to radio a no go.

Cheap Dust extractor used elsewhere is at the 'really should use ear defenders' level. Acceptable for the occasional use I require.

 

[yanky]

That's very good to put it outside.
I have a Jet extractor, with a micro filter. I'm struggling with the noise issue more than the dust. An air filter will help pick up the micro particles, but I don't have anywhere to move the extractor outside of the workshop. If you come across anything quiet, do let me know. Some noise might be inevitable, but there must be guys here that can advise you on that.

 

[gregmcateer]

If you come across anything quiet, do let me know. Some noise might be inevitable, but there must be guys here that can advise you on that.

Yanky,

I'll disclaim any practical (and theoretical) knowledge, as I'm learning here, too. However SunnyBob put a link to his set up thread. Although access to his photos has been killed by the Photobucket, I did see it before disappearing. He has put the extractor in a sound-insulated box and says it is very satisfactory. When asked about heat, he said no problems, there.

I think I'll go this route, too, as I don't have the space to take Chas' approach and house it outside the workshop.

Am currently searching for sheet material to make a cyclone to take 100mm pipe. Might use printer's zinc sheet or even dismantled paint tins if I can get large enough and achieve a good seal. - Thoughts on this welcome, folks.

Greg

 

[sunnybob]

at great personal expense... (hey, time is money ya know!)

22mmMDF, some old blankets and furniture webbing. and some 12 mm ply sound baffles in the lower section.
Took the sound down from red arrows on display, to next doors vacuum with the windows shut. Cutting on the bandsaw makes more noise than the extraction does. In fact sometimes I finish bandsawing only to realise I forgot to switch the extraction on.