On Mon, 24 Dec 2012 12:07:19 -0500, you wrote:
>Now that makes me wonder, as there are recommend speed rates for cutting
>materials.
>
>I can drill acrylic plastics with a 1/4" drill and at very different rpm
>than nickel, which is at a very different rpm than brass, again, a
>different speed than mild steel.
>Change the bit size more than 10% in either direction and usually the
>speeds for all will need to change again.
>It can be rather a PITA when doing a number of different sized holes in
>one material.
>
>What are the correct rpms for through drilling "virgin" boards and
>different dia holes?
Generally, from about #50 on down, I use at least 20000 RPM, and would
use 30 from #60 on down, if I had something that did it.
For #50 to about #40 I'd use 10K RPM or so, but that's a feel thing
rather than not.
The real thing to calculate is chip load (how much is drilled per
revolution) and SFM (surface feet/minute) which is computed at the
edge of the drill bit and is related directly to drill size (in terms
of RPM).
No idea of what it's supposed to be for FR4, and also needs to be
adjusted for tools used.
Harvey
>
>
>
>On 12/24/2012 2:43 AM, jeremy youngs wrote:
>> also to note when producing boards one is usually using a high speed
>> spindle and turning 15000 or more rpm
>>
>> On Sun, Dec 23, 2012 at 7:43 PM, AlienRelics <alienrelics@...> wrote:
>>
>>> ∗∗
>>>
>>>
>>> Widening a hole is asking a lot less than drilling a hole where none
>>> exists.
>>>
>>> Steve Greenfield AE7HD
>>>
>>> --- In Homebrew_PCBs@yahoogroups.com, Corey Minion <csminion@...> wrote:
>>>> Odd, I have drilled out hundreds if not thousands of undersized holes in
>>>> boards (down to my last 25 boards after 3 years)
>>>> It was my first pcb design and I screwed that up, never occurred to me
>>>> that there were different sized leads on that first one.
>>>> Anyone lubing there bits and tools prior to cutting?
>>>> Also, are you use some sort of cooling?
>>>> I use compressed air when working on boards.
>>>>
>>>> I have used 2 HSS bits over all that time, never noticed them dull much
>>>> more than any tool I may work with on polycarb or acrylic.
>>>> I find it dulls far less than working on ferrous metals, and less than
>>>> non-ferrous as well.
>>>>
>>>> I am a college and real world trained silver(metal)smith since 89.
>>>> I have always been really conscious of tool sharpness
>>>>
>>>> Worst material I have found so far to work with, industrial ceramics.
>>>> EATS tools. nam nam nam.
>>>>
>>>
>>>
>>
>>