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Tommy Screw with Loose Bar Dimensions (DIN 6306, M6 to M20)

Guide · Updated October 28, 2026

DIN 6306 covers tommy screws with a loose, sliding bar for jigs and fixtures, thread M6 to M20, Form D (no pad) and Form E (with a DIN 6311 thrust pad, steel only). Every value below agrees across the Ganter DIN 6306 catalog sheet, the JW Winco DIN 6306 sheet and the Elesa+Ganter DIN 6306 catalog. Skipped: the z dimension (sources conflict at M6 and M8) and weights. Check the current edition or your supplier for critical work.

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Step by step

Pick the thread: Choose M6 to M20 to suit clamp force and the tapped hole in your fixture.
Pick the length: Each thread has two or three standard lengths l1; pick one that reaches the part with thread still engaged.
Read the bar: The loose bar has diameter d3 and length l3 and slides through the head, so you can shift it for clearance or leverage.
Check the point: Thrust point d4 (h11) with pin length l2 accepts a DIN 6311 thrust pad on Form E.
Choose Form D or E: Form D has no pad; Form E comes with a DIN 6311 thrust pad fitted (steel only).
Order it: Designate as DIN 6306 D M10 x 40 (form, thread, length l1).

DIN 6306 tommy screw dimensions (mm)

Columns: thread d1, standard lengths l1, head diameter d2, bar diameter d3, thrust point d4 (h11), bar length l3, and lengths l2, l4, l5 (approx.), l6 and l7 as lettered on the DIN 6306 drawing in the Ganter, JW Winco and Elesa+Ganter sheets.

Thread d1 | l1 | d2 | d3 | d4 | l2 | l3 | l4 | l5 | l6 | l7
M6 | 20, 30 | 14 | 6 | 4.5 | 30 | 60 | 2.5 | 2.1 | 15 | 45
M8 | 30, 40 | 14 | 6 | 6 | 30 | 60 | 5 | 3 | 15 | 45
M10 | 40, 50 | 18 | 8 | 8 | 32 | 80 | 10 | 3.6 | 17 | 63
M12 | 50, 60 | 20 | 10 | 8 | 35 | 100 | 10 | 4.5 | 19 | 81
M16 | 55, 70, 90 | 24 | 13 | 12 | 40 | 120 | 10 | 5.3 | 23 | 97
M20 | 55, 70, 90 | 30 | 16 | 15.5 | 45 | 140 | 10 | 5.6 | 28 | 112

Worked example: M10 fixture clamp

DIN 6306 D M10 x 40 has an 18 mm head with an 8 mm loose bar 80 mm long and an 8 mm h11 thrust point. If 40 mm does not reach the part with at least 1 to 1.5 x d of thread engaged, step up to the 50 mm length. Need a pad? Order Form E for the DIN 6311 pad.

Loose bar vs fixed bar

DIN 6306 loose bar: slide the bar to clear nearby clamps or to get more leverage on one side.
DIN 6304 fixed bar: no moving parts, nothing to rattle, same thread range.
DIN 6332 thrust screw: same idea with no bar, add your own knob or lever.

Common problems

Bar slides on its own: the spring is weak or missing; replace the screw.
End cap lost: bar can fall out; refit caps before use.
Pad falls off: check the snap ring and h11 point size.

FAQ

What is a DIN 6306 tommy screw?

A hand clamping screw whose bar slides through a cross hole in the head. End caps keep the bar from falling out and a small spring holds it where you leave it.

DIN 6306 vs DIN 6304?

DIN 6304 has a bar fixed in the head. DIN 6306 has a loose, sliding bar, handy when the bar would hit the fixture in one position.

Form D vs Form E?

Form D has a bare thrust point. Form E is supplied with a DIN 6311 thrust pad (steel versions only).

What material?

Typically steel property class 5.8, blackened, hardened thrust point; also stainless AISI 304 in Form D. End caps are plastic.

Why is the z dimension missing?

Catalogs disagree on z for M6 and M8 (5.4 and 6.8 vs 6 and 7.6 mm), so we left that column out rather than guess.

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