CNC Machined Aluminum Fixture Clamp Plate
Fixture clamp plates machined from 6061-T6, with the clamping face flat to 0.02 mm and parallel to 0.03 mm, locating bores from Ø20 to Ø80 mm at H7 and round to 0.015 mm, dowel holes reamed to position within 0.03 mm and relief pockets between them.
- Clamping Face Flat to 0.02 mm
- Bores H7, Round to 0.015 mm
- Dowel Pattern ±0.03 mm
- Stress Relieved Before Finishing
*Send the part drawing and the machine table pattern. The bore positions come from the part datums, not from the plate edges, and a plate that is 0.05 mm out will clamp every part with the same error.
Fixture Clamp Plate Overview
A fixture plate holds a part in the same place for every cycle. Its accuracy is in the relationship between the locating bores and the clamping face, and that relationship is lost if the plate moves after machining.
The plate is faced, roughed with 0.8 mm left, stress relieved overnight, then finished in a single set-up with the bores bored and the dowels reamed from one datum before the edges are broken.
6061-T6 Aluminium Plate
6061-T6 is used because a fixture plate is large and thin, and it stays flatter after stress relief than a harder alloy. It is also light enough for one operator to lift on and off the table.
7075-T6 or Cast Tooling Plate
7075 is chosen for a small, highly loaded fixture. Cast tooling plate is used for large plates where flatness matters more than strength, since it is stress relieved by the supplier.
A plate thinner than 15 mm will deflect under clamp load and spring the part; the cure is a thicker plate or support pillars underneath, not more clamp pressure.
Fixture Clamp Plate Specifications
Facing and boring data for fixture plates, with the flatness, bore and pattern values that keep a part clamped in the same place.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Fixture Clamp Plate / Locating Plate | Machining Process | 3-Axis CNC Milling, Boring, Facing |
| Material | 6061-T6 Aluminium Plate | Envelope | Up to 400 × 300 × 40 mm |
| Plate Thickness | 15 – 40 mm | Clamping Face | Flat 0.02 mm, Parallel 0.03 mm |
| Locating Bores | Ø 20 – 80 mm, H7, Roundness 0.015 mm | Bore Position | ±0.03 mm |
| Dowel Holes | Ø 6 – 12 mm, H7, Reamed | Mounting Slots | 18 mm, ±0.10 mm |
| Counterbores | Depth ±0.05 mm, Square Seat | Edge Break | 0.5 mm, No Burr in the Bores |
| Relief Pockets | Depth ±0.10 mm | Plate Weight | 2.8 – 14 kg |
| Customization | Quick-Change Pattern, Air Ports, Sensor Slots, Handle Holes | Lead Time | 6 – 8 Days Sample, 12 – 18 Days Batch |
| Inspection | CMM Bore Positions, Granite Flatness, Dowel Pin Fit | Packing | Face Protection, Wooden Crate |
Key Features of Our Fixture Plates
Rough, relieve, finish, then gauge — flatness that survives a week on the table.
Rough, Relieve, Finish
The plate is roughed with 0.8 mm of stock, released from the vice overnight and finished afterwards, which is the only way a 400 mm plate stays within 0.02 mm after machining.
Bores and Face From One Datum
Locating bores, dowel holes and the clamping face are all cut in the final set-up, so the relationship between them holds at 0.03 mm instead of drifting between operations.
Reamed Dowels, Bolted Clamping
The dowels take the location and the bolts take the clamp load, so the plate can be removed and refitted without losing its position on the table.
Relief Pockets Between Bores
Material is removed where it does not carry load, which cuts weight by a third and lets the plate sit flat without rocking on a table that is not perfectly level.
Fixture that has to hold the same position?
Surface Finishes for Fixture Plates
The clamping face and the bores are geometry; the rest is protection against coolant and handling.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| Clear Anodizing | Corrosion resistance, bores visible | Hard Anodizing | Wear surface on a production fixture |
| Masked Bores | Keeps H7 fits after coating | Bead Blasting | Even matte on the outside edges |
| Chromate Conversion | Conductive face for part earth | Laser Marking | Fixture number and datum arrows |
| Anodizing Build | 10 – 20 µm, Sealed | Face Masking | Keeps the clamping face flat |
| Edge Sealing | Stops dye bleed at the slots | Bore Plugs | Fitted Through Coating |
| Assembly Oil | Light film to stop corrosion | Crate Packing | Face Down on Foam |
*Anodizing on a fixture face wears through in weeks under clamps and chips at the bore edge; most plates are left bare or hard anodized only on the outside edges.
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Machining Process for Fixture Plates
The plate is roughed, relieved and then finished, so the clamping face is still flat to 0.02 mm a week after it comes off the machine.
01. Part and Table Review
Check the part datums, the machine table pattern and the clamp positions, then set the bore positions and the plate thickness from the clamp load.
02. Face and Rough
Face both sides, rough the bores and pockets with 0.8 mm of stock, and mark the plate number before it leaves the machine.
03. Stress Relief
Release the plate from the fixture and let it settle, then re-face the back so the finishing cut starts from a flat, stress-free blank.
04. Finish Face, Bores, Dowels
Finish the clamping face, bore the locating holes to H7, ream the dowels and check bore positions on the CMM before unclamping.
05. Deburr, Mark, Crate
Break every edge, blow out the bores, mark the datum arrows and crate the plate face down on foam.
Send the part drawing and the table pattern, and we will quote a plate finished after stress relief and checked on the CMM.
Fixture Clamp Plate FAQs
0.02 mm when it leaves us, and typically 0.04 mm after a year of clamping, because aluminium relaxes slowly. Plates that must stay under 0.02 mm are re-finished annually or made from cast tooling plate.
Yes, from the old plate or a CMM report. The bores are the datum, so any wear in the old plate is measured and compensated rather than copied.
Yes, M6 to M12 clamp holes are added on the pattern you specify, with counterbores if the screws sit below the face.
Bare 6061 stains in water-mix coolant within weeks. A chromate conversion coat protects the surface without changing the bore size, and it stays conductive for part earthing.
Up to about 14 kg at 400 × 300 × 40 mm, which is a one-man lift. Above that we add handle holes or split the plate into two sections.
Yes, up to 2 mm can be faced off before the counterbores get too shallow. Each re-face moves the bores relative to the face, so the plate is re-marked with its new height.
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