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Reversing-screw drum and traverser (uniform to-and-fro traverse)

How does a level-wind drum move a pin back and forth? · Hardware · basis: Xem Studio design following Brown No. 108 (1868)

Also called: level wind, reversing screw, diamond thread traverse, double helix drum, husillo de doble rosca cruzada (nivelador), Kehrgewindespindel (Kreuzgewinde)

Exact dimensions. True size, with no printing tolerance added.

sizes
5 in table

Notes

  • A drum carries a right-hand and a left-hand helical groove that cross: a pin held in a block on a guide rod follows one groove up the drum and, at the end, is turned into the other and brought back. Uniform rotation gives uniform straight-line travel in both directions with no reversal of the drive.
  • Here pitch 30 mm, two turns each way: 60 mm of travel per two drum turns. Drawn with the pin 150° into the right-hand groove, 12.5 mm up its traverse, in the 5 mm groove with its end 0.5 mm off the bottom.
  • Brown's No. 108 (uniform reciprocating rectilinear motion from uniform rotary motion, by a cylinder with reversed threads); the same pair driven from the rod is his No. 167.
  • Parts (each has its own page): reversing-groove-drum-30x90-p30, traverser-block-16x28-pin5-guide6, dowel-pins-metric, linear-shafts-h6.
  • Brown's movement No. 108 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

Reversing-screw drum and traverser size chart

parametervalue
drumØ30 × 90, Ø5 bore
groovesRH + LH, pitch 30
traverse60 mm per 2 turns, each way
pinØ5 dowel
guide rodØ6 × 150

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Henry T. Brown (1868, public domain)Five Hundred and Seven Mechanical Movements — scan on archive.orgwebPublisher's page; dimensions are facts
507movements.comBrown's movement No. 108: figure, his text and an animationwebPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json

reversing-screw-traverse-mechanism-assemblyAssembled mechanism, all parts placed at one pose (STEP keeps each part separate)STEP · STL
Let your AI pull this. Add https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.
Set it up →

Plain text: sheet.txt · JSON: /api/geometry?object=reversing-screw-traverse-mechanism

Reversing-screw drum and traverser (uniform to-and-fro traverse), isometric render of a generated part
Render of reversing-screw-traverse-mechanism-assembly from the free STEP; not to scale.

Fits with

Reversing-groove drum Ø30 × 90: crossed right- and left-hand grooves, pitch 30, 5 wide, isometric render of a generated part
Reversing-groove drum Ø30 × 90: crossed right- and left-hand grooves, pitch 30, 5 wide30.0×30.0×90.0 mm★ 1 file
Traverser block 16 × 28 × 16: Ø5 pin hole (radial) and Ø6 guide-rod bore, isometric render of a generated part
Traverser block 16 × 28 × 16: Ø5 pin hole (radial) and Ø6 guide-rod bore16.0×28.0×16.0 mm★ 1 file
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325), isometric render of a generated part
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)5 sizes★ 23 files
Linear shafts Ø3 to Ø25 mm (h6), 100 to 1000 mm long, isometric render of a generated part
Linear shafts Ø3 to Ø25 mm (h6), 100 to 1000 mm long10 sizes★ 70 files

Questions

How does a level-wind drum move a pin back and forth?

A drum carries a right-hand and a left-hand helical groove that cross: a pin held in a block on a guide rod follows one groove up the drum and, at the end, is turned into the other and brought back. Uniform rotation gives uniform straight-line travel in both directions with no reversal of the drive.