On Feb 28, 5:44 pm, RichD wrote:
Andrew,
you didn't actually say, but I suspect you changed out the boring head
for other
tooling then put it back in for finishing the other pieces, etc.
That's where the error lies. Don't expect R8 tooling in a worn mill
spindle to
repeat position precisely. Won't happen. The boring head has to be
redialed in
each time it's replaced.
RichD KT4IZ

Rich, that sounds quite plausible....it is an old machine, its got
"Adcock and Shipley" cast in the side rather than being plastered with
American flags like the 2 new ones they have. And while its got an X-Y
digital readout, theres no Z axis readout like the new ones ( which
dont need to be periodically whacked to stop the display
flickering...) And it is R8 - I think (and correct me if I am wrong)
that the new ones use MT3 - it took the storeman a while to find a R8
to MT2 adapter for the 14.5mm drill. There was only one in the store,
and is apparently only used on this particular machine. Drill fell out
of the adapter the first time I used it - was told, "yes, its worn -
wack it in with the copper headed hammer.." The boring head was also
marked "Bridgeport" so it would have been the same vintage as the
machine....

I had marked out the hole locations in the two end blocks using a
vernier height gauge and the marking out table and an angle plate and
layout blue to ensure correct alignment of the shaft - even so, they
were out of alignment. I had put it down to doing something stupid on
my part. (yes, I had centre drilled, then pilot drilled, then final
size to 14.5 - it was a bloody tedious process I can assure you, lots
of tool swapping...)

I did do 2 practice bores, and got good results each time - maybe I
fluked the correct positioning....???

I am a relative novice at his, have a mini-mill at home, and its no
comparison as far as rigidity and precision (or sheer grunt) compared
to the mill I was using at school. Would gladly swap if given the
chance...

I was swapping tooling between the drill and the boring head - by the
end of the day, my arm was sore from raising/lowering the table, and
the bloody boring head had got me fingers a few times when it released
- I could spin it in/out from the bottom rather than struggle with the
stiff drawbar at the head end. The newer machines have some sort of
guide pin so you cannot do that - (Yes, I did pack it out with rags
underneath so as not to damage the cutter) That, and the speed changes
each time from drilling to milling - the high/low range thing where it
also changes direction of rotation is a pain, especially as it didnt
want to lock in all the time - only crunched it once, then realised
that in high range you could rotate the boring head by hand till it
engaged properly....

So, I will have another go next week on one of the new machines - (get
in early, be first in line at the tool store for the milling kit for
one of the new ones.) See if that makes a difference.

The problem for me, as I said, is my sheer inability to measure the
tiny tolerances involved in boring the holes - the only way to check
was to remove the job and then take it over to the arbor press and see
if it worked - but this meant that you lost tool registration so
couldn't put it back in the machine to try again - maybe there is some
"easy" way of doing this - any old hands got any helpful hints here?

BTW - noticed your callsign - the project is for going to be the
rotary optical chopper for the "PICASTAR" DDS DSP transceiver. The
bearing housing machining is the tightest tolerance thing I have
attempted to date...the actual PICASTAR is in the same category of
complexity as far as HB radio goes....

Regards,

Andrew VK3BFA.