Reversing-groove drum Ø30 × 90: crossed right- and left-hand grooves, pitch 30, 5 wide — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/reversing-groove-drum-30x90-p30/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
Catalog version: 2026-10-20

Overall (mm): length 30.0, width 30.0, height 90.0
- Ø30 × 90 cylinder (Ø5 bore) with two 5 mm wide, 3 mm deep grooves cut over the middle 60 mm: one right-hand and one left-hand helix of 30 mm pitch (two turns each), crossing each other at 180° and meeting at 0°. Each groove is 5 mm wide measured square to its path at the bottom (5.38 mm axially; helicoid flanks, 0.17 mm wider at the surface). A Ø5 pin in the groove runs 60 mm up in two turns of the drum, turns the corner and runs 60 mm back in the next two.
- The level-wind (fishing reel, winch) drum: the turn-around is drawn as the sharp meeting of the two helices; a real traverser carries a keel-shaped shoe that is steered round it.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

dimension  value
drum  Ø30 × 90 mm
grooves  RH + LH, pitch 30, 2 turns each
groove  5 wide × 3 deep
traverse  60 mm per 2 turns
bore  Ø5

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala
- 507movements.com: Brown's movement No. 108: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_108.html
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/reversing-screw-traverse-mechanism/

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/reversing-groove-drum-30x90-p30/index.json
API: https://xemstudio.com/api/geometry?object=reversing-groove-drum-30x90-p30