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Jim Wilkins[_2_] Jim Wilkins[_2_] is offline
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Default Gun Drilling - Again - Expanded

"Larry Jaques" wrote in message
...
On Tue, 7 Jan 2020 16:45:55 -0500, "Jim Wilkins"
wrote:

wrote in message
. ..
On Tue, 7 Jan 2020 00:26:50 +0000, David Billington

wrote:

On 06/01/2020 21:46, wrote:
On Mon, 6 Jan 2020 13:15:59 -0700, Bob La Londe

wrote:

On 1/5/2020 10:50 AM, Bob La Londe wrote:
Ok, my previous deep drilling operations went off pretty well.
Carbide
3 flute drills worse used on a couple of them. One to start
holes for a
hand ground split point, and the smaller hole with just a
carbide jobber
drill. Both actually met up in the middle close enough. One
for a
hinge pin and the smaller one for an injection cavity feature.
They
worked. Didn't actually do any gun drilling.

Now I am looking at an application that will need to drill
straight
(size is not highly critical), for from 20 to 28 inches for a
water
jacket.
The only machine i have I think would be suitable for it is
the
14x40
engine lathe. Throwing a 20x30 inch piece of plate on the
chuck
is
obviously not the answer. LOL. I was thinking to use some
sort
of tool
holder in the spindle, and make a mount and support for the
plate on the
carriage. After doing a bit of reading gun drilling does not
just use
hydraulic pressurized oil. It is also done with pneumatic air
mist
under pressure. Now the trick I think is to figure out how
to
pressurize a spinning gun drill inside a lathe spindle. I
have
some
ideas, but they are kind of vague at this point.

The thought of buying and setting up a dedicated machine down
the road
is not out of the question. Right now I am looking for the
shade tree
get it done short term solution.
I think I have most of it figured out if using the lathe is the
answer.
Just the details of the actual fluid delivery and recovery to
work out,
and you guys have given quite a lot of information to help
figure
that
out.

I figure I can mount a big right angle plate (I have one) in
place of
the compound, stand the plate on edge, and clamp it to it. I
can
stack
blocks to get height if needed, and adjust with the cross
slide.
By
putting the plate on edge it will virtually eliminate any
material sag
(a concern at 30 inches long) from over hang as long as the
clamps do
not slip.

The whole thing gives me ideas for solving some of my other
deep
drilling issues as well. Making them easier. Next is a stop
switch on
the carriage, so I can walk away for a minute without fear of a
crash
because I got distracted. I think the same kind of roller
micro
switch
as is on the chuck safety cover. Maybe with a mag lock mount
for
rapid
positioning. Allow it to over travel as it comes to a stop of
course.

If only I could easily automate peck drilling with it. LOL.
I just set up an air cylinder to release the half nut on the
carriage.
I used a proximity switch to sense the carriage and thereby
close
a
relay which powers a solenoid air valve. It works very well and
allows
overtravel of the carriage past the switch. The system repeats
within
.003"
Eric

An interesting modification but I wonder how fail safe it is in
the
case
of power failure, the lathe would coast to a halt so I guess it
depends
how close the stop point is to the chuck. The reason I mention it
is
that a guy I used to work with mentioned operating a lathe with an
air
chuck and they had a power failure and the air supply turned off
and
jettisoned the part narrowly missing the guy, they fitted a UPS to
that
circuit shortly afterwards.


It's plenty safe because I'm at the lathe ready to stomp on the
brake.
I suppose I could connect the setup like all my other air operated
clamping stuff so that when the power is off the part is clamped.
So
on the lathe power off would mean half nut disengaged.
Eric


You may already know, but this is a good place to show the motor
control circuit that prevents the machine from starting unattended
when the interrupted power returns.
https://www.ecmweb.com/content/artic...circuit-primer


JPGs not available. Keywords: magnetic contactor, right?


"3 wire control"