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Ball Knob Dimensions (DIN 319, 16 to 50 mm)
Guide · Updated October 28, 2026
DIN 319 covers ball knobs for levers and handles, ball diameter 16 to 50 mm, thread M4 to M12. Ball diameter, thread, height h and Form C thread depth t1 agree across the fasteners.eu DIN 319 table, the Adfast DIN 319 table and the JW Winco / Ganter DIN 319 metal ball knob sheet. Form E depth t3 agrees across fasteners.eu, Adfast and the Elesa+Ganter DIN 319 catalog. Skipped: the 50 mm hub diameter (27 vs 28 mm), the 10, 12, 30 and 35 mm sizes, t2, press-on Forms L and M, and weights. Check the current edition or your supplier for critical work.
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Step by step
- Pick the ball size: Choose ball diameter d1 from 16 to 50 mm to suit the lever or handle.
- Match the thread: Standard pairing: 16 mm M4, 20 mm M5, 25 mm M6, 32 mm M8, 40 mm M10, 50 mm M12.
- Pick the form: Form C has the thread cut straight into the knob; Form E has a molded-in tapped metal bushing.
- Check the depth: Minimum thread depth t1 (Form C) or t3 (Form E) sets the longest stud you can thread in.
- Check clearance: Height h and hub diameter tell you how much room the knob needs.
- Order it: Designate as DIN 319 C 32 M8 (form, ball diameter, thread), plus material code.
DIN 319 ball knob dimensions (mm)
Columns: ball diameter d1, thread d2, height h (approx.), hub diameter (approx.), minimum thread depth t1 for Form C and minimum thread depth t3 for Form E.
- d1 | Thread d2 | h | Hub dia. | t1 min (C) | t3 min (E)
- 16 | M4 | 15 | 8 | 7 | 6
- 20 | M5 | 18 | 12 | 9 | 7.5
- 25 | M6 | 22.5 | 15 | 11 | 9
- 32 | M8 | 29 | 18 | 14.5 | 12
- 40 | M10 | 37 | 22 | 18 | 15
- 50 | M12 | 46 | — (27 or 28) | 21 | 18
Worked example: 32 mm knob on an M8 lever
DIN 319 C 32 M8 is about 29 mm tall on an 18 mm hub with at least 14.5 mm of thread. Cut the lever stud to about 14 mm so it does not bottom out. In Form E the bushing gives at least 12 mm of thread.
Common problems
- Knob cracks when tightened: plastic Form C overloaded; use Form E with a metal bushing.
- Knob spins loose: add thread locker or a jam nut under the hub.
- Stud bottoms out: stud longer than t1 or t3; shorten it.
FAQ
What is a DIN 319 ball knob?
A round ball knob for levers, handles and machine controls, traditionally phenolic plastic, also offered in steel, aluminum and stainless.
Form C vs Form E?
Form C has the thread cut straight into the knob. Form E has a molded-in tapped metal bushing that holds the thread better in plastic knobs.
Why is the 50 mm hub diameter blank?
The standard tables list 28 mm and the metal-knob catalogs list 27 mm, so we left that cell out rather than guess.
What else was skipped?
The 10, 12, 30 and 35 mm sizes, the t2 dimension, press-on Forms L and M and weights, because sources disagree or only one source lists them.
Plastic or metal?
The DIN sheet covers plastic. Metal versions with the same main sizes exist but are catalog items, not on the official sheet.
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