In this video, we'll go over
the necessary steps to square the tool head to the table on a Bridgeport mill.
The head of the mill has to be square. This is very important.
If it isn't square, you won't be able to mill your pieces square,
and you will drill holes at an angle.
You'll need a table stone, a 3/4 inch wrench, a tramming ring, a finger indicator, and
something to hold the indicator.
We'll be using a Zero-It indicator holder.
Begin by making sure the table and the ring are free of burrs, dirt, and chips.
Clean the table and tramming ring with a cleaner and then stone the table and tramming
ring using the table stone.
When stoning the table, make sure you're always using a figure-8 pattern.
After stoning, wipe off the table and the tramming ring.
Put the tramming ring on the table.
Clamp the Zero-it indicator holder into a drill chuck, collet, or solid holder.
Place the indicator into the holder and clamp it.
Put the spindle into neutral, so that it's easy to turn.
Rotate the spindle by hand.
Make sure the indicator will stay on the
top surface of the tramming ring.
You may have to adjust the holder to achieve this.
Now, bring the table up until you have 10 to 20 thousands of pressure.
Clamp the knee.
Loosen the front toolhead clamping bolts one at a time and then lightly
re-tighten them to ensure there is some drag.
Move the indicator to the three o'clock position as you're looking down at the ring.
Zero out the indicator by rotating its
face until the zero lines up with the needle.
Rotate the spindle until the indicator is at the nine o'clock position and read
how far the indicator moves.
Divide this number by two.
This is how far you'll need to move the head
using the swivel bolt.
Move in the direction that the needle is
moving back towards zero.
Once you've moved it, zero out the indicator again
and rotate it to the three o'clock position.
Take a reading on the indicator.
If it's within one thousandth of an inch, you can
tighten the front toolhead bolts.
Check that the head didn't move while you were tightening the bolts.
If the indicator reads more than one thousandth of an inch, you'll need to make more
adjustments before tightening the front toolhead bolts.
Always double-check your
readings on the indicator after tightening the bolts.
Once you've tightened the front toolhead bolts, relieve the pressure on the swivel bolt.
Next, perform the same procedure for the 12 o'clock and the 6 o'clock positions.
This uses the tool head side clamping bolts.
Loosen the side toolhead clamping bolts one at a time and
lightly retighten them to ensure that there is some drag.
Rotate the indicator to the six o'clock
position and take the indicator reading.
Move the head with the swivel bolt until the indicator is back to zero.
Once the indicator is at zero, rotate it to the 12 o'clock position and ensure that
it's reading within one thousandth of an inch.
Tighten the side toolhead clamping bolts.
Relieve the pressure on the swivel bolt.
Check that the indicator is still reading within one thousandth of an inch
all the way around the tramming ring.
If the reading is less than one thousandth of an inch,
then the head is square and you're ready to mount your workpiece.
If the reading is more than one thousandth of an inch, you'll need to repeat the
prior steps until it reads within one thousandth of an inch all the way around.
Once you've determined that the head is square, lower the table.
Remove the tramming ring, remove the indicator from the holder and remove the
holder from the spindle.
You've now finished squaring the head on a Bridgeport Milling Machine.
You're ready to mill your pieces and drill your holes.