"jon_banquer" wrote in message
...
On Tuesday, April 14, 2015 at 4:11:50 PM UTC-7,
wrote:
I bought my Bridgeport mill new in 1981. Today I just finished
power
tapping a bunch of 5/16-18 through holes in .5 thick 7075 aluminum.
With the mill in low range at 250 RPM. I just put the tap in the
drill
chuck, turn the spindle on forward till the tap is through and then
plug reverse the motor and back the tap out. I can't even begin to
count how many holes I have tapped this way on this machine. I have
never overheated the motor or switch gear and they are still
original.
The motor has the "tropical insulation" in it so I guess that means
it
can stand hot humid running. I don't know if a new Bridgeport today
would hold up as well, I hope they would. I do know of more than
one
import mill that has cooked a motor and/or the switch gear.
Eric

I'm always amazed when people rave over a Bridgeport. It means they
have no idea what modern CNC machine tools are capable of and they
are completely out of touch with the reality of how machining is
done today.

CNC is little help without a CAD file, which you don't have when
making repair parts.

Segway's experimental parts were mostly made manually, cut-to-fit, on
a CNC Bridgeport and lathe. I rarely saw them running CNC files,
usually an engineer was working from a sketch and inventing the part
on the fly.

The files that castings had been made from didn't help without the
production machining fixtures to position them. I had to reconstruct
their hole patterns relative to locatable reference features, then
locate and center-punch new holes with a height gauge and dividers
while they weren't stressed by clamping. Thin-walled plastic injection
moldings were particularly difficult to clamp securely enough without
distorting them.

Expensive CAD seats were in heavy demand. The only one I could borrow
was for the powerful but quirky circuit board design program which
didn't talk to SolidWorks or the milling machine. It was quicker to
just manually mill a one-time part from the drawing while the machine
was free than to manually translate and enter the G code.

There was a considerable speed advantage in being able to make
non-production stuff in-house rather than cleaning up the drawing
enough to send it out.

-jsw