“Tramming” or Aligning a Bridgeport Type Milling Head
1) Place the machine spindle about an inch in from the back table edge.
2) Using a bent rod, or an indicator holder like the 1st Word , set the indicator
anywhere from 6″ to 8″ out from the spindle center.
3) Use 1-2-3 blocks, or a similar gage block to slide under the indicator for the reading.
4) Tighten the knee-lock clamp on the saddle.*
5) Adjust the swivel head in the X-axis to get zero readings at
positions #1 and #2. ( at about 1″ in from the table edge )
This will roughly align the head in the X-axis.**
6) Now swing the indicator to the #3 position, and adjust the knuckle joint
in the Y-axis to get zero readings at positions #1 and #3.
7) At this point the head is aligned quite close. Now go back and check
positions #1 and #2, and adjust if necessary. Then check #1 and #3 again
and adjust if needed.
8) When all (3) positions read zero, (or within a total of .001) the head is
aligned in both axes.
With the indicator at the #3 position, loosen the knee-lock clamp and check
the indicator reading. If the reading drops .003 or more, it’s time to snug up
the gib on the knee ways.
( but it’s always a good practice to tighten the knee-lock clamp when machining high
accuracy cuts )
When adjusting the swivel and knuckle, leave a little tension on the clamping bolts.
This will help prevent the head from moving when you fully tighten these bolts.
Author: Sparro Machine Products