CNC Workholding and Fixture Plan Template
Most dimensional problems on CNC parts trace back to how the part was held. A workholding plan forces you to decide datums, locators and clamping before cutting, and gives the setup person a reference.
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CNC Workholding and Fixture Plan Template
Workholding and Fixture Plan
Company: Acme Precision Machining Part: HSG-3300 Rev B Operation: OP20 mill back side features Machine: Okuma MB-46VAE Plan owner: M. Verma Date: 2026-10-20
Workholding Device
Device: Soft jaws Parts per setup: 2
Datums and Locating
Primary datum A on the machined bottom face resting on parallels. Located against fixed jaw.
Clamping
Hydraulic vise at 40 bar. Soft jaws bored to the casting profile. Pull-down clamp at the rib.
Risks and Cautions
Thin wall near the flange may deflect under clamping. Check flatness after release. Clear the jaw edge with the 20 mm endmill.
Verification
| Check | Method | Result |
|---|---|---|
| Part seated on locators | Feeler gauge or visual | |
| Clamp force or torque set | Gauge or torque wrench | |
| Tool clearance to clamps | Dry run or simulation | |
| Part held without distortion | Indicator before and after clamping |
Approvals
This is a planning document, not a fixture design calculation. Clamp forces and fixture strength must be confirmed with your own engineering practice and the workholding maker's limits.
Link fixtures and tooling assets to routings
Optional: a review of how fixture and tooling records could connect to ERP routings.
Optional. The tool and every export work without this. No spam.
How to use the template
Start from the print: identify the datums that the operation's features reference. Describe the workholding device, how the part locates against those datums, and how it is clamped. Note risks such as thin walls, tool access to clamped areas or known distortion. Add verification checks and sign. Export to PDF for the traveler. Use one plan per operation, since each operation usually holds the part differently.
The 3-2-1 locating principle
A rigid body has six degrees of freedom. The classic 3-2-1 approach constrains them with three points on the primary datum, two on the secondary and one on the tertiary. Clamps then hold the part against the locators without moving it. Extra locating points over-constrain the part, which can distort it or make location depend on casting variation.
- Locate first, then clamp; clamps should not do the locating
- Clamp over a supported area to avoid bending thin sections
- Keep datum surfaces clean of chips before each load
- Check tool and holder clearance to clamps and jaws
Common mistakes
Teams often clamp harder than needed, deflecting the part so that it springs back out of tolerance when released. Another common issue is loading a part on chips or burrs and getting a different zero each time. Plans also skip the second operation: if OP20 needs to find a feature machined in OP10, say which feature, and check it. Keep the plan with the setup sheet and revise it after any crash or fixture change.
Frequently Asked Questions
Do I need a plan for simple vise setups?
A short plan still helps, especially for second operations, where datum transfer matters most. For routine parts, keep it to a few lines.
How do I choose clamp force?
It depends on cutting forces, part stiffness and the device. Use the workholding maker's guidance and your own engineering practice. This template records the decision but does not compute it.
What is a datum in this context?
A datum is a reference feature on the print that features are measured from. Workholding should locate on the datums that the operation's tolerances depend on.
Should fixtures be tracked in the ERP?
Many shops do, as tooling assets linked to the routing. It helps with maintenance and finding the right fixture, but small shops can start with a log.
If fixtures and workholding assets are tracked in your ERP or PLM, Netray can help link them to routings. The template works independently.
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