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How to Use a Fixture Plate
Guide · Updated October 28, 2026
A fixture plate is a flat plate with a grid of tapped holes and precision dowel holes. Parts and vises locate on dowels, so setups go back in the same place every time and work offsets stay valid.
Check the grid
Verify dowel spacing with gage blocks or a mic over pins. The free Gage Block Calculator builds the stack.
Step by step
- Clean and mount: Stone the table and plate bottom, then bolt the plate down.
- Indicate it straight: Indicate a dowel row or edge parallel to X within a few tenths.
- Pick a datum bore: Choose one dowel bore as the origin.
- Set the work offset: Sweep the datum bore with a test indicator and set G54 to its center.
- Locate with dowels: Place dowel pins in the grid and push parts or vise keys against them.
- Clamp evenly: Use toe clamps or tapped holes without distorting the part.
- Record the setup: Note which holes and dowels you used so the setup repeats.
Worked example
A plate has dowel bores on a 1.000 in grid. Sweep bore A1 and set G54 X0 Y0 there. A part is located against dowels in B1 and B3, so its edge sits at Y = 1.000 in minus the dowel radius: with 0.250 in pins, Y = 1.000 − 0.125 = 0.875 in. The program uses that value, and the next part lands in the same place.
Why fixture plates save time
Instead of indicating each part, you indicate the plate once. Multiple fixtures can share the grid, and setups can go back on later with the same offsets.
Common problems
Parts that shift between loads mean dirty dowels or uneven clamping. Offsets that drift usually mean the plate moved on the table; check the bolt torque and re-indicate.
Tips
- Offsets: work offsets (G54–G59).
- Indicating: indicating a fixture.
- Bores: indicating a bore true.
Second worked example: checking grid position with a 3-4-5 diagonal
On a plate with holes on a 1.000 in grid, pick a hole as origin and the holes 3.000 in along X and 4.000 in along Y. The diagonal between those two holes should be √(3² + 4²) = 5.000 in. Measure it with pins and a caliper or height gage; a reading of 5.003 in means the grid or your pins are off by about 0.003 in over that span.
For dowel location, use one round pin and one diamond (relieved) pin spaced as far apart as the part allows. With pins 6.000 in apart and a 0.0005 in hole clearance, angular play is roughly 0.0005 ÷ 6 ≈ 0.00008 rad, about 0.005°.
Quick shop check
Common problems: dowel pins that are too tight wear the plate. Use slip-fit pins for locating and only snug the clamps.
FAQ
What is a fixture plate?
A grid plate with tapped and dowel holes for repeatable setups.
How do I set a work offset on a fixture plate?
Sweep a datum dowel bore and set the center as X0 Y0.
Do fixture plates need indicating?
Once, when they go on the table.
What dowel size is common?
1/4 in, 3/8 in or 8–10 mm pins on a 1 in or 50 mm grid.
Can I put a vise on a fixture plate?
Yes, with dowels or keys so it repeats.
Related guides and calculators
- Work Offset Basics (G54–G59)
- How to Indicate a Fixture
- How to Indicate a Bore True
- How to Set Up a Milling Vise
- Soft Jaw Basics for Vises
- How to Cut a Hex on a Mill
- How to Use a Corner Rounding End Mill
- Torque Wrench Basics for Machinists
- All free machinist calculators
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