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Silica hazard from grinding wheel.

K

KEW

Joined
Jun 9, 2005
Messages
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Location
North Metro Atlanta
The thread on truing grinding wheels is causing me to wonder how safe my practices are. Whenever I dress a wheel, I put on a respirator. However, unless I have fans agitating the air, I typically only wear the respirator about 2 minutes after I'm finished or take it off immediately if I walk across the shop. My logic (right or wrong) is that the silica particles are substantially heavier than air and will drop out of suspension fairly quickly (unlike wood dust!).
Does anyone actually know (or know where to look up) how long these particles would hang in the air.
TIA
 
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My guess is that the silica will not travel more than 4-5' from the grinder. If the air is still and you walk that far away from the grinder before you remove your respirator, you should have nothing to worry about. On the other hand, if you use compressed air to clean the area around your grinder as well as your clothing, you are spreading silica over a sizeable portion of your shop. Best not to do that.
 
Here's something else to think about...

M2, M4, and probably some of the other tool steels contan molybdenum. I was doing some reasearch on tool steels and ran across this on Wikipedia:

Precautions

Molybdenum dusts and fumes, as can be generated by mining or metalworking, can be toxic, especially if ingested (including dust trapped in the sinuses and later swallowed). Low levels of prolonged exposure can cause irritation to the eyes and skin. The direct inhalation or ingestion of molybdenum and its oxides should also be avoided. OSHA regulations specify the maximum permissible molybdenum exposure in an 8-hour day to be 5 mg/m³. Chronic exposure to 60 to 600 mg Mo/m³ can cause symptoms including fatigue, headaches, and joint pains.

Here's the URL:

http://en.wikipedia.org/wiki/Molybdenum
 
I sketched out a dust extraction unit to put on the back of my grinder station which would use the small Shopvac that I bought to clean up after my metal lathe. I haven't built it yet but probably will when the weather gets warmer.
 
Assuming that the fractures of the wheel were the size of the grit, then 60-120 grit would indeed drop fast.
Since you can't be sure of it and silica is well known to be an irritant, I wear a mask,
 
It definitely makes sense to wear a mask.
If I am sanding wood, I will keep my mask on until I leave the shop.
How long do you keep your mask on once you have finished at the grinder?
 
KEW said:
How long do you keep your mask on once you have finished at the grinder?
Click to expand...

Usually take it off as I walk away. Not that this should be the safety standard for all...
 
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