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How to Use Parallels in a Vise
Guide · Updated October 28, 2026
Parallels lift a part in the vise so the top is above the jaws and the bottom stays clear of cutters and drills. Done right, the part sits flat and parallel to the table. Done wrong, it rocks, lifts and comes out tapered.
Check your parallels
Matched pairs should agree within a few tenths. Compare them on a surface plate with an indicator, or stack gage blocks with the free Gage Block Calculator.
Step by step
- Clean everything: Wipe the vise bed, jaws, parallels and part; one chip ruins the setup.
- Pick the height: Choose a matched pair that puts the cut above the jaws with enough part in the jaws to hold, usually at least 1/8–1/4 in of grip.
- Place the parallels: Set them against each jaw, clear of drill or cutter paths.
- Snug the vise: Close the vise lightly on the part.
- Seat the part: Tap the part down with a dead-blow or soft mallet while tightening.
- Check the parallels: Try to slide each parallel; both should be pinched tight. If one moves, the part is lifted.
- Final tighten: Tighten to working pressure and recheck that the parallels are still tight.
Worked example
Facing the top of a 0.75 in tall plate in a 6 in vise with jaws 1.75 in tall: use 1.25 in parallels so 0.25 in of the plate is above the jaws and about 0.5 in is gripped. Seat it, check both parallels are tight, face it, then flip and repeat. Mic the thickness in four corners; a good setup holds within about 0.0005 in.
Part lifts or rocks
Movable vise jaws lift as you tighten. Tap the part down while tightening, use a round bar between the movable jaw and the part for rough stock, and check that the fixed jaw is square to the bed. A part that rocks on one parallel usually has a burr or bow on the bottom; deburr it or shim with paper and indicate the top.
Thin and narrow parts
Use thinner parallels or step parallels, or hold the part on a sacrificial plate. For very thin work, a vacuum plate or double-sided tape on a fixture plate can beat a vise.
Tips
- Basics: parallels and setup blocks.
- Vise setup: setting up a milling vise.
- Jaws: soft jaws.
FAQ
Why do my parallels come loose?
The part lifted as the movable jaw tightened; tap it down and check them again.
What height parallel should I use?
The shortest pair that puts your cut above the jaws while keeping solid grip.
Do parallels need to be matched?
Yes, use pairs ground to the same height.
Can I use 1-2-3 blocks as parallels?
Yes, for taller parts, as long as they are a matched pair.
How do I stop parts lifting in a vise?
Clean everything, tap down while tightening and use a round bar on rough stock.
Related guides and calculators
- Parallels and Setup Blocks Basics
- How to Set Up a Milling Vise
- How to Indicate a Vise True
- Soft Jaw Basics for Vises
- How to Check a 1-2-3 Block
- How to Face Mill
- How to Use a Keyway Broach
- How to Counterbore on a Mill
- How to Use a 5C Collet Block
- How to Use Adjustable Parallels
- How to Use 1-2-3 Blocks for Setups
- All free machinist calculators
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