PM2.5 readings at my local Men's Shed.

**NeilS** · 23rd November 2021, 10:58 AM

Originally Posted by BobL

You probably don't need me to say this but any newbies reading this should know that measuring the dust from a couple of cuts or a few minutes use of a machine can be misleading since the fine dust rapidly dilutes into a the shed. Results will differ considerably for longer uses as well as taking much longer to reduce afterwards.

Yes, monitoring each workshop space over a shed session will be a second stage in this exercise.

Each of the workshop spaces has multiple machines in it so as a first stage I'm taking readings at each of the machines that are likely to be the main sources of fine dust. Having a means of measuring this will identify the main offenders and indicate whether attempts at improving capture at source is working.

Background to all of this was the addition of a 4^th workshop at the Shed and the need for DE in that. One option was to run a bigger impeller on our existing 5HP cyclone and upgrade the main duct from 150mm to 225mm all the way through to the fourth workshops. Given the length of that run and the cost of 225mm pipe and fittings that was not going to be such a cheap solution and would also be very disruptive.

The other option that is favoured is to install a second cyclone (probably a CV1800) in the 4^th workshop and extending that back into the 3^rd workshop and leave the existing cyclone and ducting for just the first two workshops. Dust level measurements before and after implementation will be good to have.

Originally Posted by BobL

I saw this at a mens shed where two blokes were turning - thing was they were often pausing and happily chatting away - the dilution of the fine dust was matching their chat pauses. Dust levels never got about 35 µg/m^3 over the half hour I was monitoring them. One other thing they had going was they had super sharp turning tools and there was not a lot of scraping going on.

Power sanding at the lathe is the one thing that bumps up the readings in my own workshop, especially on larger diameter pieces. Rarely, if ever, had them go up as high as 35 µg/m³ on my economy particle counter. Anything above 10 µg/m³ has me adjusting the position of the bellmouth intake to optimise extraction... the optimum position for any one piece or speed can be quite precise and not always intuitive. Before getting the counter I was only guessing.

**NeilS** · 1st December 2021, 10:13 AM

Took some readings at the belt and disc sander on Monday. This is the worst culprit at the Shed.

As Bill Pentz points out; "Power sanding, routing and shaping generate the most dust".

The belt/disc sander has been moved to the new workshop area where there is no ducted DE as yet. Someone hooked up a donated dinky DE to it... no rude comments please!

Baby DE.jpg

So, the results were not completely unexpected...

Pre-use PM2.5 6 μg/m³

With the so-called DE on and using disc for 2mins - 143 μg/m³With the so-called DE on and using the belt:

At 1mins - 34 μg/m³

At 19mins - 41 μg/m³

At 20mins - 62 μg/m³

Turned off sander and left DE running:

At 23mins - 29 μg/m³

At 24mins - 19 μg/m³

Elsewhere in workshop:

At 24mins - 19 μg/m³

At 25mins - 12 μg/m³

At 27mins down to 9 μg/m³ back at sander.

There is a lot to be solved there in terms of connection to an adequate DE and capture at the source, but I now have a before set of readings against which to measure any improvements.

**QC Inspector** · 2nd December 2021, 02:40 AM

You could do another test without collection on just to show doubters how bad it gets when someone "just has a little bit to do".
Thanks for posting your results.

Pete

**NeilS** · 2nd December 2021, 09:32 AM

Originally Posted by QC Inspector

You could do another test without collection on just to show doubters how bad it gets when someone "just has a little bit to do".

Yes, Pete, the "just has a little bit to do" without opening up the blast is a risk. Bye and large the crew at the Shed are pretty good at always opening up first and closing up after use.

I would have to do any 'without collection' for comparisons at a time when there isn't a session at the Shed as there is too much uncontrolled activity going on for me to do that when the Shed is operating. Perhaps when the Shed goes into its break over the end of the year.

Easy enough to load up the air in a workspace with fine dust but quite a task to subsequently purge it without a room exhaust system installed, which we only have in one of our four workshop spaces.

**NeilS** · 13th July 2022, 12:14 PM

I'm still working away at the ducting and machine port connections at our local Shed...

I was about to tackle the thicknesser and not looking forward to that after reading two relevant threads...

The generic 2HP 10" planer/thicknesser dust control issues

6" port upgrade for a 15" Thicknesser

The one on the dedicated 15" thicky being most relevant as it is almost identical in design to ours.

I recently had the dust cover off ours to rotate the TC cutters (that was quite a task with about 100 inserts to rotate!) and could see while doing that that there was very little clearance between the tips on the cutter head and the housing to provide infeed airflow for the current 4" dust port, let alone an upgrade to 6".

Thicky - min gap.jpg Thicky - max gap.jpg
Min gap - 5/8" .... Max gap - 3/4"

Thicky - out.jpg
As it should be, no
gap on out-feed side

Sitting behind the cowling around the cutter head there are rollers, etc, so opening up anywhere there would be of minimal value in terms of increased air flow and potentially counterproductive by allowing some of the sawdust to escape out of the cowling and back onto the work piece.

The other option would be to open up some vent holes at the rear back of the top dust cover. This would involve creating vents in both the outer cover and in the infeed deflector (attached to the cover) that is positioned above the cutters. By my calculations, an additional 17^2" of vent would be needed to supply a 6" duct. Looking at the both the deflector above the infeed side of the cutter head and the outer dust cover I could not see how that could be done in the available space across the 15" width, both physically and safely... the cover is made of quite heavy gauge metal to provide a safety barrier above the cutter head.

My concern with the 4" port on the thicknesser is more to do with air speed in the 6" ducting than fine dust as my
PM2.5 readings sat between 3 and 5μg/m³after half an hour of running Oregon and Jarrah through it. That was about the same as the background reading outside.

The issue with air speed in the ducting is that the thicknesser produces a large volume of shavings that can plug inside the 6" ducting runs if the air speed is not maintained. That can also result in poorer separation in the cyclone.

I am thinking of just adding an additional open air intake with about 18^2" capacity next/near to the thicknesser port to provide the necessary speed in the 6" ducting.

**NeilS** · 15th July 2022, 08:12 PM

I completed the upgrade to the ducting for the drop saw a little while ago.

It involved...

adding a flexible hose from the drop saw dust 'port' takeoff and connecting it directly to the main 6" duct.

takeoff for drop saw.jpg Drop saw.jpg

eliminating the flexi duct section of the 6" ducting with rigid ducting all the way to the saw enclosure.

Chamfering the inlet from the enclosure to the 6" ducting

Routed port inlet.jpg

Extending the enclosure to minimise dust escape to the sides

Replacing the blast gate at the saw with a rocker gate up near the Y that feeds into the main duct. The ring pull can be seen above the enclosure in the above photo.

The chaps at the Shed are far more chuffed with the rocker gate than the considerable reduction in fine dust that has been achieved with the above measures, but I'm very happy with the outcome...

Reading after ducting upgrade.jpg

**Chris Parks** · 16th July 2022, 12:01 AM

Neil, I added a bell mouth to duct entry on mine which according to theory can only help, it would be interesting to compare a straight cut duct entry to a chamfered entry to a bell mouth.

**NeilS** · 16th July 2022, 11:34 AM

Originally Posted by Chris Parks

Neil, I added a bell mouth to duct entry on mine which according to theory can only help, it would be interesting to compare a straight cut duct entry to a chamfered entry to a bell mouth.

Yes, Chris, I would have used an appropriately dimensioned bell mouth if I had enough space to do everything below the bench that I needed to fit in there, so it was a compromise.

I have no doubt that an appropriately radiused bell mouth would have been much better and I expect the benefit from that small radius on the chamfer is minimal (it was the largest router bit we had at the Shed), but it was easy enough to do while I had the dust enclosure apart, so I just did it.

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