On 5/3/20 4:32 AM, Nicklas Karlsson wrote:
On Sat, 2 May 2020 at 16:29, N <[email protected]> wrote:
Did not check check then moving but expect a lot less accuracy then at move,
Bear in mind that when the tool position matters the tool is often
stationary in the important direction.
Then it will be more than good enough for drilling, I do not have to do
measurements by hand anymore then drilling/threading for example hole for
cooling fins. Searched manual and did not immediately found how to control
movement in (X,Y) plane with good position accuracy while less is required in Z
direction.
Regards Nicklas Karlsson
Hi Nicklas,
As the owner of an aging (1960's vintage) BP size mill one
develops habits which tend to minimize offsets from wear. To wit: holes
are always approached from -X +Y. Reference position is upper left of
the fixed jaw on the vise.
For openings for cooling fans, etc I simply helix into the hole. I start
just above the surface and climb cut where Z = depth and P defines the
number of passes for full depth. Nice pretty holes are helped by a
couple of skim passes. Accuracy is always defined by the application
e.g. good enough!
I would like to think I can hold sub thou tolerances but I know better.
I once made a bunch of 1018 CD pillow blocks for a robotics club. I
bothered to measure them afterward just for grins. They were -.003 in X
and Y with a std dev of 0.001". Those were done on my Mazak which had a
long history machining aluminum parts. I would not expect anything close
to that on my small mill.
However, being careful with hole placement I can drill holes that
machine screws will go thru and match the threaded hole. Bear in mind
that machine screws are often -.003" so that helps. Normally one can
tune following error to be much less than the backlash so backlash and
lack of rigidity are probably major contributing factors to off
tolerance. Just thinking out loud. Sorry for the length of post but ...
Have fun and stay safe.
Dave
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