In general flood with a water based coolant will shift more heat than a mist system. Flood also usually shifts the chips better. On the down side it is very messy and can actually reduce the life of carbide tooling.
Carbide tooling can take a lot of heat but it hates thermal shock. The cutting edges of a milling cutter operating in flood coolant will get heated rapidly while they are actually cutting then suddenly cooled as they hit the coolant. This can cause cracking and chipping. Oil has a much lower thermal capacity and conductivity than water so it doesn't cause as much thermal shock. To a large extent you can get around the problem by using high pressure flood coolant to make sure the cutter does not get a chance to heat up. So why are mist systems still fairly rare in industry? Two main reasons spring to mind. 1) flood keeps the work and machine at an even temperature so you don't need to allow for thermal expansion. 2) Flood has always been used. If it works, why change it? In my experience carbide works well with oil misters, HSS needs flood or a heavy mist of water based coolant. Les John Harris wrote: > Hi All, > Back in the late 50s when, as a young apprentice, I was turning > knobs on a milling machine as part of my education, the shop foreman replaced > the flood system on the mill with a new-fangled mister. The mister feed tank > was filled with the same stuff that was used for the flood system. That is > water with 15(?) percent soluble oil. > > The foreman told me that the mist cooled the part and the tool by evaporating > the water, and the oil gave some lubrication to the cutting action. Also > misting greatly aided the water evaporation compared to the flood system. > > As the foreman is by now no longer with us, I feel safe in raising the > question, was what he told me true? If it was, why are you now using only oil > that is much less efficient in absorbing heat by evaporation than water? > > Regards all. I love reading the chat. > ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
