You want as much RPM as you can get. But I found that if you are hand drilling its also important to find one that will stop quickly as it is much easier to locate the drill in the pad hole when the drill is not turning.
I have a little surplus 24V PM DC motor that is about 1" in dia and 1.5" long with a pin chuch coupled to the shaft. I run it about 40V and don't actually know the RPM. It fits real nice in the palm of my hand. Hooked up a foot switch that shorts the motor windings out when released so the back emf stops the motor in about a second.
Photo:
https://picasaweb.google.com/cschaffter/PCB_Stuff#5433062346975752258Don't even think about carbide drills with a hand held drill they are just too brittle and will snap just looking at them cross-eyed. Just use HHS bits and keep a small sharpening stone handy.
To use carbide you need a nice stable sensitive drill press with a low runout spindle. Even better, a CNC setup.
Craig
--- In Homebrew_PCBs@yahoogroups.com, Kamal Shankar <kbshankar2000@...> wrote:
>
> How important is the RPM of the drill we use on a PCB?
>
>
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> What would the difference be between a 1750 RPM vs a 10k RPM drill regarding drilling on a PCB? (I always thought higher RPM -> lower torque to drill a hole, but I read higher RPM is better?)
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> There is a dremel I have been using for sometime using HSS bits that I have used on my FR2 boards.
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> Now that I am going to migrate to a thinner FR-4 substrate, I am looking forward to buying a good minidrill that also has a stand (since I will be using carbide bits)
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> Does anyone have feedback on these:
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> $44 Proxxon 28512 12-Volt Micromot 50 EF Rotary Tool
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> http://www.amazon.com/Proxxon-28512-12-Volt-Micromot-Rotary/dp/B000S5KO3K/ref=acc_glance_hi_ai_ps_t_5
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>
> $59 Proxxon 28606 MICROMOT Drill Stand MB 140/ S
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> http://www.amazon.com/Proxxon-28606-MICROMOT-Drill-Stand/dp/B000209ZAE/ref=pd_cp_hi_4
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>
> They don't seem to make these in the US (they supposedly make them under a different name "Micro-Mark", but I am not sure if they are the same quality)
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> The price looks like $120 incl. shipping which is a good price for a brand new precision "drill press" don't you think?
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> If you have any better tools to suggest, I would be glad to know about them!
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