On 13 February 2012 20:59, gene heskett <[email protected]> wrote: > On Monday, February 13, 2012 11:53:57 AM Bruce Klawiter did opine: > > > I do a ton of work with small cutters and in aluminum, I use a coolant > > mister with alcohol, I use as much air as possible and just enough > > alcohol to keep the part wet. The parts feel like they were in the > > freezer when I am done. As Jon said keep the work cold. > > > > Bruce > > Guy's, maybe I don't understand cutting alu as well as I thought. > > All along, I have believed that it was more important to keep the oxygen in > the air away from the cutting surface in order to slow the formation of alu > oxide on the surface, which in normal air, not blown, can get a good start > in 0.001 seconds or less behind the cutting tools edge as alu is a VERY > active metal, oxidizing (rusting of ferrous material is exactly the same > reaction at a rate millions of times slower than the alu rate) very > rapidly, and its this thin film of oxide that is its own protective > barrier, putting out the fire so to speak. This oxide is also the 2nd > hardest substance known to man and can take the edge off a carbide tool > that has to cut thru it in seconds under the right set of wrong cutting > params, which my slow feed made worse. Dig cutting being worse in this > regard. > > Sealing the cut surface against the air and its oxygen, blown or otherwise, > that causes this instant alu oxide film with its subsequent wear on the > cutting tool has always been the reason for my use of a cutting oil, deep > enough to flood and seal the surface, or misted, particularly when I don't > have the spindle rpms to throw it away from the cut. Misting works better > because it blows the cut chips away, preventing recut damages on the > surface. But my air compressor is outside and I didn't want to throw off > the tarp and open the shop door so I could plug it in. > > Consider also that the higher rpm spindles put the cutting edges past the > cut surface so fast that the only alu oxide they see is on the original > surface before the cut and doesn't have much of a chance to reform before > the cutting tool has moved on. > > The majority of the heat you are referring to is not the heat of the tools > cutting action, but is the result of the chemical reaction that forms this > alu oxide film so rapidly. So my theory has always been to seal the oxygen > away from the cut surface as well as you can with whatever you can that is > not oxygen bearing. Some oils, including the particular cutting oil I > used, can have quite a bit of available oxygen & therefore will not be as > effective as one would think at slowing this 'rusting' reaction. >
..snip I would imagine... that the oxide layer is way way thinner than a micron in thickness, and while tough as you say, in climb milling the cutter tip will hit the metal and with the eggshell effect, simply push past the oxide layer. I think that if this was a general problem, it would recieve more alerts in industry, although some shopfitting sections which are already anodised, do take their toll on the saw blades. Regards Roland ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
