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How to Use an Angle Plate
Guide · Updated October 28, 2026
An angle plate is a precise 90° block that holds work vertically, at right angles to the table. It lets you machine or inspect a face square to another without a fancy fixture.
Know it is square
Check your plate against a square and gage blocks before trusting it. Check it with a mic you've verified against gage blocks; the free Gage Block Calculator builds the stack.
Step by step
- Check the plate: Verify the plate is square and the faces are free of dings and burrs.
- Clean the table: Wipe the table and plate base and stone off any high spots.
- Mount it: Set the plate on the table and bolt or clamp the base, snug but not tight.
- Indicate the face: Sweep the work face with an indicator along the X axis and tap it straight.
- Tighten and recheck: Tighten the base clamps evenly and indicate again.
- Clamp the work: Clamp the part to the face with clamps near the cut, using a parallel under it for height.
- Support overhang: Add a jack or support under long overhanging work before cutting.
Worked example
Squaring the end of a 4 in tall plate on a mill: bolt the angle plate down, sweep its face over 6 in of X travel and tap it until the indicator moves 0.0003 in. Clamp the part to the face, resting on a 1 in parallel. After milling, check the end on a surface plate against a square: a 0.0002 in gap over 4 in means the face is within 0.00005 in per inch of square.
Spring and sag
A tall part clamped high on the plate can deflect under cutting force. Keep clamps close to the cut, take lighter finishing passes, and support the overhang.
Box parallels and slotted plates
Slotted plates take T-bolts through the face. A box parallel or 1-2-3 block works like a small angle plate for little parts.
Tips
- Verify it: checking an angle plate.
- Square checks: checking squareness.
- Small parts: parallels and setup blocks.
- Angles other than 90°: setting up a sine plate.
FAQ
What is an angle plate used for?
Holding work at 90° to the table for machining, grinding or inspection.
How do I indicate an angle plate?
Sweep its face along the table axis and tap it straight before tightening.
How square is an angle plate?
Precision plates are often within 0.0001–0.0002 in per 6 in; check yours.
Can I use an angle plate on a surface grinder?
Yes, a small precision plate on a magnetic chuck is common.
Angle plate vs vise?
A plate holds large or odd parts a vise cannot, and keeps them square to the table.
Related guides and calculators
- How to Check an Angle Plate
- How to Check Squareness
- How to Check a Machinist Square
- Parallels and Setup Blocks Basics
- How to Set Up a Sine Plate
- How to Use a Surface Plate
- How to Indicate a Vise True
- How to Use a Surface Grinder
- How to Use a Faceplate on a Lathe
- How to Use 1-2-3 Blocks for Setups
- How to Use Box Parallels
- All free machinist calculators
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