Toolpath is not written without knowing how the part is held. Until datum and setup count close, the program inflates both time and measurement.
Measurement lives in the grip.
At first glance the job is machine selection. The question on the table is different: which surface is reference, how many times it will be removed and re-clamped, which face closes in a single setup.
Without this note, the operator sees a new part at every setup. Position and concentricity live on the same reference. If reference is re-established, measurement is rewritten.
What sits on the note.
A workholding note does not have to be a full fixture drawing. A short record is enough. Unwritten grip stays as "easy mill" on the quote; in the shop it becomes a second operation.
- Which surface is datum, which is left free.
- Jaw, pin, or vacuum surface.
- Pocket and face that close in a single setup.
- Vibration or thin wall to avoid.
- Three dimensions to check on first part.
Datum is chosen once.
Assembly surface is often reference on most jobs. Free wall is not opened to clamp marks. If datum is not on the drawing, the workholding note writes it — the machine does not assume.
Setup count divides tolerance.
When the part is clamped a second time, that reference is re-established. If there is a second operation, why it stopped is one sentence. "Let us flip it" is not sufficient justification.
5-axis is not opened for every geometry.
5-axis is sometimes chosen for single setup, not toolpath. Flat body and single face close on three axes with the right vise. The cost of second setup is written then.
Undercut, angled pocket, or mutually visible position pushes 5-axis. The cell is chosen by geometry — not by catalog line.
The note closes before the first part.
Program does not reach the machine until the workholding note is approved. First part is measured against this note. A surface showing deviation questions grip — not the tool.
If the note changes, the card stops. It is not passed with "let us try one more pass." Approved grip is also the grip of serial repeat.
When grip is written, the program opens.
If datum, setup, and first-measurement note stand, toolpath is written. Otherwise the program machines an assumed part. Delivery does not carry that assumption.
