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T-Slot Nut Dimensions (DIN 508, 5 to 54 mm Slots)

Guide · Updated October 28, 2026

DIN 508 covers nuts for T-slots made to DIN 650. Tenon width a, nut width e, overall height h and tenon height k agree across the fasteners.eu DIN 508 table, the J.W. Winco DIN 508 sheet and the McMaster-Carr DIN 508 listing for 5, 6, 8, 10, 12, 14, 18, 22, 28, 36, 42, 48 and 54 mm slots; the Elesa+Ganter DIN 508 sheet also matches 5 to 28 mm. The 16, 20 and 24 mm rows come from the Winco and Elesa+Ganter sheets, which agree; no standard thread is shown for them. Skipped: 30 and 32 mm slots (only one source). Thread column follows the fasteners.eu and McMaster tables. Check the current edition or your supplier for critical work.

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Step by step

  1. Measure the slot: Measure the narrow throat of the T-slot. That width is the slot size a and the nut size: a 14 mm slot takes a 14 mm DIN 508 nut. DIN 650 slot widths are what the nut is made to fit.
  2. Check the tenon: a is the width of the upper tenon that rides in the throat. It is made undersize (about -0.3 to -0.5 mm) so it slides freely.
  3. Check the body: e is the width and length of the square lower body that sits under the slot lips; k is the tenon height and h the overall height.
  4. Pick the thread: The DIN 508 table pairs each slot with one standard thread: 14 mm slot with M12, 18 mm with M16, 22 mm with M20. Catalogs also sell smaller threads in a given slot.
  5. Add the stud and collar nut: Thread a DIN 6379 stud into the T-nut, put the strap clamp on, and finish with a DIN 6331 collar nut on top.
  6. Tighten correctly: Do not let the stud bottom out on the slot floor; it can lift the nut and crack the table lips. Keep the stud flush with or just above the nut base.

DIN 508 T-slot nut dimensions (mm)

Columns: slot / tenon width a (nominal), standard thread, nut width e (square body), overall height h, tenon height k. a, e and k are made slightly under nominal so the nut slides.

Worked example: 18 mm table slot

A mill table with 18 mm slots takes an 18 mm DIN 508 nut: M16 thread, 28 mm square body, 20 mm tall with a 10 mm tenon. With a 25 mm strap clamp and an M16 DIN 6331 collar nut (24 mm tall), the stud needs about 20 + 25 + 24 + 3 = 72 mm of length above the slot floor, so an 80 mm stud set flush with the bottom of the T-nut leaves a little spare.

DIN 508 vs DIN 6331 vs a square nut

Common problems

FAQ

What is a DIN 508 T-slot nut?

A square-bodied nut with a narrow raised tenon that slides into a machine table T-slot. It anchors a stud for clamping workpieces and fixtures.

How do I know what size T-nut I need?

Measure the slot throat width. That number (for example 14, 18 or 22 mm) is the DIN 508 nut size.

What thread goes with a 14 mm T-slot?

The DIN 508 table lists M12 for a 14 mm slot. Some catalogs also offer M8 and M10 in that slot size.

Why are 16, 20 and 24 mm slots missing a thread?

The sources we cross-checked list body dimensions for these slots but do not agree on one standard thread, so it is left blank. Catalogs sell several threads for them.

Can the stud go through the T-nut?

Only if the stud does not touch the bottom of the slot. A stud bearing on the slot floor pushes the nut up and can break the table lips.

How is DIN 508 different from DIN 6331?

DIN 508 sits inside the T-slot. DIN 6331 is the tall collar nut on top of the clamp strap, threaded onto the same stud.

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General shop information only — follow your drawing, tool maker's data and your quality system.