I'd like to bore a hole approx 2.75", I have a boring head from APT
which will do it, but cranking the slide over far enough to use either
of the vertical bar mounts leads to significant vibration on my Sieg X3.

Can I use a horizontally mounted boring bar in order to reduce the
rotating offset mass? .500 inch round shanks in a 2.5" head.

Louis Ohland wrote:

I'd like to bore a hole approx 2.75", I have a boring head from APT
which will do it, but cranking the slide over far enough to use either
of the vertical bar mounts leads to significant vibration on my Sieg X3.

Can I use a horizontally mounted boring bar in order to reduce the
rotating offset mass? .500 inch round shanks in a 2.5" head.

The vibration is more likely from tool chatter / rigidity issues than
from the off balance boring head, unless your are running it excessively
fast.

On Nov 12, 6:11*pm, "Pete C." wrote:
Louis Ohland wrote:

* *I'd like to bore a hole approx 2.75", I have a boring head from APT
which will do it, but cranking the slide over far enough to use either
of the vertical bar mounts leads to significant vibration on my Sieg X3..

Can I use a horizontally mounted boring bar in order to reduce the
rotating offset mass? .500 inch round shanks in a 2.5" head.

The vibration is more likely from tool chatter / rigidity issues than
from the off balance boring head, unless your are running it excessively
fast.

I recently cut some panel meter holes that way, after roughing them
out with the nearest undersized hole saw. The feed outward was 0.010
per pass, more than that caused trouble. Speed was 180 RPM, the
slowest pulley setting, and still somewhat too fast.

jsw

Machine shakes, RPM is past 500.

Pete C. wrote:
Louis Ohland wrote:
I'd like to bore a hole approx 2.75", I have a boring head from APT
which will do it, but cranking the slide over far enough to use either
of the vertical bar mounts leads to significant vibration on my Sieg X3.

Can I use a horizontally mounted boring bar in order to reduce the
rotating offset mass? .500 inch round shanks in a 2.5" head.

The vibration is more likely from tool chatter / rigidity issues than
from the off balance boring head, unless your are running it excessively
fast.

Louis Ohland wrote:
Machine shakes, RPM is past 500.
That's your problem, the machine doesn't have a back gear,
does it?
When you get up to larger diameters, you need to slow down.
500 RPM at 2.75" diameter is 360 SFPM. Not insanely high
for Aluminum, definitely a problem for steel.

Jon

Jon Elson wrote:
Louis Ohland wrote:
Machine shakes, RPM is past 500.
the machine doesn't have a back gear, does it?
When you get up to larger diameters, you need to slow down.
500 RPM at 2.75" diameter is 360 SFPM. Not insanely high
for Aluminum, definitely a problem for steel.

It does have a low range. I need to re-mount the large boring head after
I unmount the rotary table and mount the workpiece to the table.

"Louis Ohland" wrote in message
...
I'd like to bore a hole approx 2.75", I have a boring head from APT
which will do it, but cranking the slide over far enough to use either of
the vertical bar mounts leads to significant vibration on my Sieg X3.

Can I use a horizontally mounted boring bar in order to reduce the
rotating offset mass? .500 inch round shanks in a 2.5" head.

What cutter are you using? A HSS with the right grind and light cuts should
do it.