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Soft Jaw Basics for Vises
Guide · Updated October 27, 2026
Soft jaws are aluminum or mild steel jaws you machine to fit a part. They grip odd shapes, protect finished surfaces and make second ops repeatable.
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Step by step
- Mount the jaws: Bolt them on clean and seat them.
- Clamp a spacer: Clamp a spacer or parallel between the jaws so the pocket is cut under clamping pressure.
- Cut the pocket: Cut it to the part profile, slightly oversize for clearance.
- Add a stop: Add a part stop or locating step.
- Label: Mark the jaws with the part number and the setup.
Tips
- Aluminum cuts fast and doesn't mark parts.
- Steel jaws last longer for production.
- Indicate the vise first: see indicating a vise.
Related: indicating a vise, parallels.
Worked example: boring soft jaws for a 2.000 in part
Clamp a stop or a piece of round stock between the jaws behind the area you will cut, so the jaws are loaded as they will be in use. Tighten to the normal clamping force. Mill a 2.000 in pocket, or slightly smaller, such as 1.998 in, so the jaws grip firmly instead of just touching. Leave a step at the bottom about 0.10 to 0.25 in high to locate the part height.
Mark the jaws with the part number and which side is fixed, and use the same stop every time you recut. Aluminum jaws are easy to cut and gentle on finished parts; steel jaws last longer for production. Each recut removes metal, so start with jaws thick enough for several pockets. Check the first part with a micrometer and indicator before running the batch; a pocket that is too big lets parts shift and cut oversize.
Quick shop check
Machine a step in soft jaws to locate a 2.000 in wide part about 0.002 in oversize (2.002 in) for easy loading. Machine the jaws clamped on a spacer under about the same clamping force used in production. Number jaw pairs so they go back on the same vise.
FAQ
Why clamp a spacer when cutting soft jaws?
So the pocket is cut with the jaws under the same pressure as when clamping the part.
Aluminum or steel?
Aluminum for most work. Steel for long runs or high clamp force.
How deep should the pocket be?
Enough to locate and grip, often 0.100 to 0.250 in.
How do I check pocket size?
Use calipers or pin gages, checked against gage blocks. Build any reference size free with the Gage Block Calculator at gageblockcalc.com.
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General shop information only — follow your gage manufacturer's instructions and your quality system.