On Wednesday 11 November 2009, Jon Elson wrote: >Gene Heskett wrote: >> Ouch! And no wonder I'm getting snow flakes. Or in steel, very sharp >> needles I'm always picking out of my fingers. > >Yeah, I know about those! But, those numbers were for mild tool steel. >For aluminum, >the strategy is a bit different. > >> But this stuff is alu, the 2" >> wide, 1/8" thick bar stock they sell at Tractor Supply. Petty soft, >> gummy stuff too, but cuts to length on the chop saw nicely, 12" saw. That >> width limits me to 13 teeth if I want full height teeth on all of them. > >The chop saw will cut anything. Gummy aluminum, you DO NOT want! Does >it have >a "striped" appearance?
Not too noticeable Jon, actually pretty clean in that regard. I get the impression it may be rolled rather than extruded, the edges are just slightly rounded and very consistent, so it could be extruded from very new, clean dies. >Most likey something like extruded 6061. You >CAn machine >it, I've done a lot, but you have to take light cuts and keep the tool >moving along. If it >heats up, even a LITTLE, you are in trouble. Humm. >> And I was running at 1.5, and about .033" deep with an already dull bit >> when I broke it the second time. Alu was piling up in front of the mill >> so I knew it was a matter of time, something it wasn't doing when the >> mill was fresher. > >By then, you are in deep doo-doo. Are you conventional milling? That >is where the >material is fed into the cutter opposing the direction the cutting teeth >move? Yes, too much backlash in my table to get away with climb, although at light cuts I might be able to get by with it. >This is >the worst method for surface finish and tool wear. If your machine can >handle it, you >want to do most of your work in the "climb milling" direction. This is >where the >cutting teeth move in the same direction as the material feed. The >advantage is the >teeth bite directly into the uncut material, starting with a full chip >thickness. In >conventional milling, the tooth slides aling the already-cut surface >until enoguh pressure >is developed to force it under the material surface, then the thickness >of the chip >increases. This sliding causes much increased flute wear and welding of >re-cut >chips to the surface. If your machine has a lot of backlash, then the >direction of >cutting forces can cause the work to be pulled into the cutter, breaking >bits. But, >if the friction exceeds the cutting force, or the backlash can be kept >down, you >will get better surfaces and longer tool life. I'll give it a shot at light feeds, and with the brake screw set a bit, as that is a 425 motor its capable of horsing it against some drag. > >> I only had maybe 1/4" of it in the collet at the time, and I expected to >> see alu piled up in the flutes, but amazingly, it was clean, no stuck >> chips. Just apparently dulled by all the alox it had cut already. These >> are TiN coated mills, $5 ea at Hemly, just across the Ohio river from me. > >I wouldn't waste money on the TiN coating for aluminum. I find it reduces the stickyness, lots less alu getting stuck on the mill. And at that size, the price diff is quite low. Thanks Jon. Note to all: One of those days when it wasn't worth it to gnaw thru the straps and get up; In case someone tries to access my web site, which is on this machine, it may not be available for a day or so, my main drive is in the process of dirtying its clothes, a 500GB, less than a year old. I have a 1TB Seagate SATA laying here to put in once I get an rsync recoverable backup made. -- 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> Chisolm's First Corollary to Murphy's Second Law: When things just can't possibly get any worse, they will. ------------------------------------------------------------------------------ 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
