There's been a bit of discussion on metal dust in other fora so I thought I would do a simple experiment.
125 mm Angle grinder, thin kerf cut of wheel, 100 mm long cut in 6 mm thick steel.
Measure dust levels in shed before and over time thereafter.
Mass of wheel used up is 1.53 g, Mass of metal grit/dust generated is 16.45 g.
Dust particle sensor is held at operators head height.
The graph shows the numbers of dust particles per litre of air for specific size ranges of particles.
Note how the large particles (>5 microns) falls rapidly while for the fine particles it takes a couple of minutes to reach a maximum - another demo that fine particles behave like a gas.
For comparison purposes sanding a 300 mm long 25 mm diameter hardwood rod in a lathe generates about 1/3 to 1/2 of the dust generated in this experiment.
In other words metal cutting is a filthy grubby process that generates a lot of fine dust.
The grinding dust does precipitate out a bit faster than wood dust.
For sanding dust the time taken for the finest dust to fall to half it's previous level is around 22 minutes, for metal grinding dust its 17 minutes.
For the coarsest dust (>5 microns in size) it takes around 1.5 minutes for the metal dust to settle out while for the wood it takes around 12 minutes. Interestingly the ratio of these two times is 8 which is the approx ratio of the density of wood to metal! Remember that the coarse particles probably won't hurt you as much as the finer ones because thy hang around for hours.
Does it represent a danger? I will need to do some more maths but in the meantime crank up your dust extractors. If you wear a mask you need to keep it on for some time after you are done cutting.
125 mm Angle grinder, thin kerf cut of wheel, 100 mm long cut in 6 mm thick steel.
Measure dust levels in shed before and over time thereafter.
Mass of wheel used up is 1.53 g, Mass of metal grit/dust generated is 16.45 g.
Dust particle sensor is held at operators head height.
The graph shows the numbers of dust particles per litre of air for specific size ranges of particles.
Note how the large particles (>5 microns) falls rapidly while for the fine particles it takes a couple of minutes to reach a maximum - another demo that fine particles behave like a gas.
For comparison purposes sanding a 300 mm long 25 mm diameter hardwood rod in a lathe generates about 1/3 to 1/2 of the dust generated in this experiment.
In other words metal cutting is a filthy grubby process that generates a lot of fine dust.
The grinding dust does precipitate out a bit faster than wood dust.
For sanding dust the time taken for the finest dust to fall to half it's previous level is around 22 minutes, for metal grinding dust its 17 minutes.
For the coarsest dust (>5 microns in size) it takes around 1.5 minutes for the metal dust to settle out while for the wood it takes around 12 minutes. Interestingly the ratio of these two times is 8 which is the approx ratio of the density of wood to metal! Remember that the coarse particles probably won't hurt you as much as the finer ones because thy hang around for hours.
Does it represent a danger? I will need to do some more maths but in the meantime crank up your dust extractors. If you wear a mask you need to keep it on for some time after you are done cutting.
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