So are you saying its impossible to break chips with HSS drills?
Use G73 instead of G81. Adjust you "Q" peck amount to suit. Or, increase the feed.
[/endthread]
It's "Difficult" to break chips with conventional HSS-Jobber drills. A lot depends on your material. Low carbon steel, soft low-strength aluminum alloys, will almost never give satisfactory chip-breaking with conventional HSS-Jobber drills. Cast-iron, certain tool-steels
(D2), brass will give good chip-breaking without any effort. So the material will play a big part in chip-breaking if you're using HSS-Jobber drills.
If you want premium performance, you need to go to specialized drills. Often times these are made from solid carbide, but there's some "premium" drills made from cobalt-HSS and powdered-HSS as well. The one thing that all of these drills have in common, is that they're designed with special attention to the flute shape, tip geometry, etc.. In other words, they're designed from the get-go to be high-performers. HSS-Jobber drills are not, and they never will match the performance of "premium" drills.
Now, HSS-Jobber drills will perform well in aluminum in terms of speed & tool-life just fine. You're not getting bad advice here when people say to run them as fast RPM/feed as possible for your machine. But, understand that these drills were never designed to offer superior chip-breaking in soft aluminum alloys. If so, they would suck for drilling carbon steel using a drill-press. HSS-Jobber drills are designed to be just that - a drill that works OK in every material, in every machine - and they fit that jack-of-all trades role very well. Just understand that they're a master-of-none as well...
If you want to continue using HSS-Jobber drills for your aluminum/volume job, and you want better chip-breaking, you'll have to use a G73 chip-breaking drill cycle to get satisfactory chip-breaking. You can probably also max your machine on RPM & increase feed to match, to compensate for any lost cycle time.
The nice thing about using G73, is that it's EASY. You simply change the
G81 in your program to a
G73 and then add a
Q.25 to that same line. The
Q tells the machine to retract slightly every .25" of drilling-depth in order to break a chip. Alter the "Q" value as needed to suit your needs. The amount of retract/peck is determined by, and can be changed in parameter #5114
(in the case of Fanuc 0i series & similar controls) and every machine I've ever seen has been set around .01" retract/peck distance. See attached for explanation.
If you want to continue to used G81 continuous drilling, then do like others have suggested, and go with a premium drill.