Compare the old opening with the final bore envelope
A centered final bore can remove material around a smaller opening when that entire opening lies inside the final bore's removal circle. It cannot add material back where an earlier opening protrudes outside that circle. Setting the boring head to the drawing diameter does not erase the earlier geometry.
Open Milling Operations and choose Job 4 / Boss and bore. From View, choose 2D sections. Before each case, choose Start this job over, then Sure? Start over, so each comparison begins with a fresh block. Use the Move to X, Y and Z inputs and Move. Keep tool and boring-head changes at Z +20 by using Raise to Z +20.
| Fresh-block case | Illustrative simulator moves | Individual bore inspection |
|---|
| Previous opening stays inside | Load the drill Ø10. At X 50.5, Y 30, move the tip to Z −24. Raise to Z +20. Load the boring head Ø20.00, move to X 50, Y 30, then bore to Z −21. | The modeled Ø20 bore contains the earlier opening. Its row reports measured Ø20.00 through, with no diameter-too-big, centre-position or CUT TOO FAR failure; the unfinished whole job does not need to pass. |
| Previous opening extends outside | Load the drill Ø10. At X 52, Y 30, move the tip to Z −24. Raise to Z +20. Load the boring head, enter 18 in Boring Ø and choose Set; bore at X 52, Y 30 to Z −21. Raise, set Ø20, then bore at X 50, Y 30 to Z −21. | CUT TOO FAR — Bore Ø20.00 ±0.05 through reports about Ø20.41, 0.41 too big, with the fitted centre about 0.38 from target. THRU also fails because inspection tests a full allowed diameter around the fitted irregular opening; it does not mean the centered boring-head move stopped short. The centered final pass cannot replace the material removed outside its circle. |
- In the first case, where is the edge of the Ø10 opening relative to the centered Ø20 removal circle?
- In the second case, which individual checks show that the result is not simply a centered Ø20 hole: diameter, position, overcut, or all three?
- Why does a final DRO of X 50, Y 30 not undo the earlier off-axis removal?
These coordinates, depths, offsets and fitted/grid inspection numbers belong only to this idealized simulator. They are not acceptable cleanup allowance, safe boring offset, rework instructions or physical gauge results. The model does not predict boring-bar entry or interrupted-cut behavior, rigidity, deflection, chatter, force, finish, alignment uncertainty or workholding. Geometric containment is necessary here, not sufficient for a real process: use the drawing, measured hole, complete setup, tool-maker guidance and responsible process authority.
The top, boss and chamfers remain unfinished in both cases, so the overall feature row or job may still be incomplete. Read the bore's diameter, position and overcut checks for this comparison.
