How sensitive are the grindstones to frost?

[Vetten]

It's winter and minus degrees here in Denmark and the same in the workshop at night. Do i have to take the grindstone in at night?

[jeffs55]

Not unless it has water in it. Water expands when frozen and thus cracks the stone. Just make sure it is BONE dry. Do not use any form of antifreeze in your water either, it is bad for the stone. Good luck.

[Herman Trivilino]

I've noticed that moisture can stay in the grindstone for several hours or even days, but that shouldn't be an issue.

[Vetten]

So the conclusion must be when I have used it I should take it in to dry out...

[Herman Trivilino]

Only if you're using it in below-freezing temperatures.  And if you're doing that, I wonder how you keep the water in the trough from freezing.   

[Jeff Farris]

Well, some people heat their shop while working, but don't heat it when not there. In that case, in very cold temps, there is some danger. I would take the stone (or the whole machine) into a heated area for a day or two after use if the shop is going to get below freezing.

[RobinW]

i take my wheel into the house during the winter if I have been using my T7. The temperatures in the last couple of weeks have been just above freezing (2 to 5 degree C)  when I have been in my garage. For those who remember their physics, the anomalous expansion of water occurs at 4 degrees C (for the non-physicists, water shrinks with falling temperatures, and then at 4 degrees C it starts expanding again!).

From the following link on this forum, you can see the difference in weights for a wheel both dry and wet, and using the difference and convert weight to litres shows how much water the wheel typically absorbs.

http://forum.tormek.com/index.php?topic=1417.msg4456#msg4456

[Rob]

spot on.  In fact if water didn't expand from 4 deg down to zero (causing ice to be less dense than cold water and hence to float....life could never have evolved since the seas (where life began) would have frozen from the bottom up :-)

[Herman Trivilino]

Plus, the ice layer that forms on the surface of both fresh water lakes and the seas serves as an insulator, protecting life below.  If the freezing began at the bottom there'd be no layer of insulation.

If you cool a sample of room-temperature water down microscopic slush starts forming at about 10^oC.  These microscopic ice structures force the water molecules further apart than they would be if the water were warmer.  There's the competing effect of the molecules getting closer together as you cool the water, simply because they are moving slower.  At about 4^oC the former effect starts to dominate, and it continues to do so down to 0^oC when the water is still a liquid.

These effects are all dwarfed by the enormous increase in volume that occurs when the water freezes at 0^oC.

It's this last expansion that might damage the grindstone.

[Ken S]

Excellent comment, Robin.  I don't think my Ohaus scale can quite handle the weight of a stone.  I would be curious to know if there is any difference in weight if the wheel is run momentarily with no water to hopefully allow some water to evaporate due to centrifugal force.

Ken

ps I don't suppose using sea (salt) water, which has a lower freezing point, would be such a brilliant idea.

[Rob]

Plus, the ice layer that forms on the surface of both fresh water lakes and the seas serves as an insulator, protecting life below.  If the freezing began at the bottom there'd be no layer of insulation.

If you cool a sample of room-temperature water down microscopic slush starts forming at about 10^oC.  These microscopic ice structures force the water molecules further apart than they would be if the water were warmer.  There's the competing effect of the molecules getting closer together as you cool the water, simply because they are moving slower.  At about 4^oC the former effect starts to dominate, and it continues to do so down to 0^oC when the water is still a liquid.

These effects are all dwarfed by the enormous increase in volume that occurs when the water freezes at 0^oC.

It's this last expansion that might damage the grindstone.

Mists of time clearing......bringing back some lessons from long ago Herman.  I now recall a lecture when I was at University called "the unique properties of water"......fascinating.

[Ken S]

I am curious:  Has the Tormek engineering department done any research on the impact of cold temperatures on the stones?  (Surely Sweden is as cold as Denmark.)

Ken

[Jeff Farris]

Don't know how much research is needed, Ken. If it is saturated and it freezes, it's going to crack. I've seen a bunch of them. In every case temperatures were extreme (sub-zero Fahrenheit) and the heat was turned off after a day of working in the shop. If temps are below freezing and your stone is saturated, take it into a heated area to dry out.

[Ken S]

Good plan, Jeff.  (Cost effective, too!)

Ken

[RobinW]

I tried a little experiment this afternoon.

My stone has been in the house a couple of days since I last used it. It still felt a touch damp when I held it. I weighed it 'dry' at 5.08Kg in a room temperature of 20 degrees C.

I then used it for a couple of hours in 6 - 8 degrees C and then weighed it at 5.25Kg.

Following KenS suggestion above, I then dropped the water trough and left it running for 45 minutes and then reweighed it at 5.24 Kg.

The 10gm reduction after 45 minutes is so small that the change in weight is probably below the accuracy of the scales. Evaporation at that low temp is also too slow to be noticeable in the time.

At 90 rpm I doubt there is any centrifugal force big enough to shed any water. It might be interesting if the stone was fixed to the washing machine and put on a fast spin cycle at 1000 rpm!!!! Don't know if my wife would be too impressed if I tried that test. She's had to put up with many things over the years!

Anyway it is quite clear from all of the above posts that the Tormek stone is at risk in temperatures where the water is liable to freeze, so enough on this subject.