Me personally, the 1/2" per second or so leaves a large margin even with bits already starting to dull. Someone else with a slower spindle might find the margin not nearly as large as intuition might suggest. Breaking torque was the limit in the FSWizard figures I gave. For 5000 rpm, a seemingly safe and slow feed of 1/8" per second exceeds the recommended feed rate of 7.05 in/min.
Mike.
-------- Original message --------
From: "craigl2@earthlink.net [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
Date: 2/23/2016 11:16 AM (GMT-06:00)
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: drill pcb
Craig
---In Homebrew_PCBs@yahoogroups.com, <mikewhy@...> wrote :
Aside from runout, feeds and speeds can be the culprit. FSWizard Pro
gives the following for a 0.03" 2-flute, uncoated carbide drill in
FR4.
RPM 20k
SFM 150 ft/min
Feed rate: 29 in/min
........
RPM 20k
SFM 150 ft/min
Feed rate: 29 in/min
........