On Wednesday 11 November 2009, Jon Elson wrote: >Gene Heskett wrote: >> 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? > >I've been using 4-flute more than 2-flute. You get more cutting edges, >and the core >is supposed to be a little stronger, at the expense of less room for >chip flow. In aluminum, >the problem is the back rake, ie. you can cut so fast the back of the >flute is rubbing on >the work. I have much less experience in steel, and have had problems >with breaking the >bits, and also had to go insanely slow. I once forget to zero the Z >axis and had a 1/8" >carbide end mill plunge fully through a 1/8" aluminum panel and then >start plowing >full-width at 40 IPM! It only broke when I hit Estop. I don't know how >long the cutter >could have withstood that abuse, but it made over an inch of slot before >I stopped it. >Mostly, you want to take as large a cut as the tool, workpiece, fixture, >etc. can handle. >Excessive vibration is to be avoided, as it causes wild fluctuations in >chip load. >You usually can plunge 1/2 the end mill diameter per pass when plowing >full width, >and maybe an engaged length equal to the mill's diameter and half the >diameter >depth on the side. 2500 RPM is pretty slow for 1/8" carbide. In medium >steel, you want >about 250 SFPM, or 7500 RPM. > > >So, the basic rule is take as heavy a cut as you can without causing >tool or workpiece >deflection. For medium steels, .003" chip load per inch of cutter >diameter is recommended. >So, for a 1/8" cutter, that works out to .000375" per tooth. For a >2-flute end mill at >2500 RPM, that is a disappointing 1.9 IPM.
Ouch! And no wonder I'm getting snow flakes. Or in steel, very sharp needles I'm always picking out of my fingers. 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. 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. 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. >--------------------------------------------------------------------------- >--- 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 > -- 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> Knocked, you weren't in. -- Opportunity ------------------------------------------------------------------------------ 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
