Drilling Aluminum Dry - RPM Speeds with HSS

Typically, I tell people who *need* to drill aluminum dry to run at about 70% of the RPM shown on my charts (http://www.multi-drill.com/drill-speed-chart.htm ).
In other words, a 1/2" hole in aluminum run dry would be run at around 1000 RPM rather than 1500 or so...
We are relatively conservative with our numbers because when it comes to drilling, most people don't need CNC-type speed. ...So don't slam me for being so slow and out of touch! :)
I'm wondering if there is a rule of thumb any of you follow for such procedures?
Regards, Joe Agro, Jr. (800) 871-5022 01.908.542.0244 Automatic / Pneumatic Drills: http://www.AutoDrill.com Multiple Spindle Drills: http://www.Multi-Drill.com Production Tapping: http://Production-Tapping-Equipment.com / Flagship Site: http://www.Drill-N-Tap.com VIDEOS:
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