On Wednesday 11 November 2009, dave wrote: >On Tue, 2009-11-10 at 22:07 -0700, David Braley wrote: >> Gene Heskett wrote: >> > Greetings; >> > >> > One of the things I have not yet learned is how to get the most swarf >> > from a given milling tool. I have a tendency to go slow, so the swarf >> > is sometimes so thin it settles like snow flakes when it is blown away >> > from the work. >> > >> > Obviously this is wasting the cutting edge of the tool, dulling it >> > prematurely. >> > >> > So when my fresh shipment of 1/8" mills gets here, I would like to be >> > able to have it throw thicker chips and far fewer of them but remove >> > lots more metal before they dull. >> > >> > I'm going to rig me an oil squirter from an in tank auto fuel pump to >> > try and keep the mill wet. With a tuna can under the workpiece I can >> > catch most of the runoff, and maybe even filter & recycle it. Details >> > to be invented yet in the finest of shade tree mechanic methods of >> > course. ;) >> > >> > Assuming I keep the area wet with cutting oil at a high enough flow >> > that I don't wind up with a muddy slurry, but do have enough chips to >> > act as a wick and keep the mill wet from the cutting oil they absorb >> > (or the oil level in the tuna can is high enough), and the 1/8" 2 flute >> > carbide upcut spiral mill is turning 2500 rpms, how fast can I feed it >> > while doing a 0.020" deep cut per pass without breaking it? Slower and >> > deeper, or shallower and faster for best tool life? >> >> Feeds and speeds as you already know is a delicate dance with what >> material you're machining, spindle speed, number of flutes on your >> milling cutter, table speeds and lubrication. And like you discovered >> above, it's better to cut than rub your material off. >> >> It sounds like you are running a smaller machine. If that's the case, >> another factor comes into the equation and that's how stable or rigid >> your spindle is. A spindle that is built with bearings less than ABEC >> 7's is not going to give you the rigidity you will need for long tool >> life. Your small spindle my wind way up, but that'll be useless when you >> start to load it with heavier cutting. Procession is not your friend. >> Even if it's so small, you can hardly detect it. >> >> I like your oil squirter idea for lubricating your cutter, but I want >> you to consider instead using a spray mister. The reason is simply >> because once you start to make bigger chips with those tiny cutters, >> you're going to have a problem with getting them out of the way. The >> smaller cutters are more commonly broken because the chips clog up the >> works. A spray mister will by its nature, blow everything out of the >> slot you're cutting, keeping the system cool, lubed and clean. It's less >> of an issue with larger cutters. The mister does make more of a mess, >> but with simple and carefully placed shielding, you can contain most of >> it. You will also be surprised at how little mist coolant you'll end up >> using when you get it adjusted right. >> >> My worthless two cents. ;-) >> >> David > >Cutting Al is absolutely a can of worms. > >Rule #1 is to use T6 if possible. > #2 is to remove chips so they don't recut. Sometime a shop vac >works well here. > #3 even a bit of kerosene or WD-40 helps at times but the surface >tension may glob up the chips and make a mess. > #4 air and shop vac may do the best job.
My thoughts were to try and get a coat of oil on the cut surface as fast as possible, with the tool swimming in the oil if possible, because that impedes the formation of the alox coating, a factor which may be more responsible for the heat generated then the cutting stress itself. You can get a significant coat of alox on the freshly cut alu in .001 second, yet another factor in running at high spindle & feed speeds, not enough time for a coat of the 2nd hardest stuff in the universe to grow between flutes going by & exposing fresh, VERY active surface to the oxygen in the air. And that sort of speed is a luxury I don't have with my puny spindle. At 2500 rpms, that is 41 revs a sec, so if I didn't screw it up, that is nearly .006 seconds between flutes of a 4 flute mill. And I ordered 2 fluters this time... And the alox reaction is contributing a goodly amount of heat if the air is allowed to get to it. I guess we are damned if we do, and damned if we don't The oil mist, coming in on a 50 psi air stream, may be the best idea of all. Flooding the area with dry nitrogen would also help, but who can afford that? Not me. >If you get the Al to high temps it flows and bonds to the cutter. I once >saw a cutter at Boeing Surplus: probably 1 to 1.5 inch dia and 8" long >with a cone of melted Al on it. Going for cheap if one had a 50 taper >machine to use it on. A couple of pounds of lye would have done a good >job of cleaning it up (and made a decent amount of hydrogen). :-) >Even the experienced guys have problems. ;-) > >It has been my experience that carbide mills don't do well on flexible >(wimpy) spindles. HSS is much tougher and you just live with the slower >speeds. I've wondered about that, thanks for the info. >Most extruded Al is way too soft to cut cleanly and leads to problems. > >Plunge milling to remove material is probably the best approach, just >watch the tip of the mill for fusion of base material. > >Naturally YMMV. > >I'd rather deal with P20 (Rc 30 4140) than Al. > >HTH > >Dave And TBT, if I had my druthers, the only alu in the supply channels would be 7078-T6, it machines NICE. But I'm just a beggar, taking what I can get. :) Thanks Dave. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> "We learn from history that we learn nothing from history." -- George Bernard Shaw ------------------------------------------------------------------------------ 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
