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Double-helical (herringbone) gears, 20 : 30, helix 20°

Why use double-helical (herringbone) gears? · Hardware · basis: Xem Studio design following Brown No. 41 (1868)

Also called: herringbone gears, double helical gears, chevron gears, engranajes bihelicoidales, Pfeilverzahnung

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

sizes
5 in table

Notes

  • Each gear has two rows of oblique teeth of opposite hand meeting at the middle of the face: like single helical gears the teeth engage gradually and several are always in contact, but the two axial thrusts cancel, so no thrust bearing is needed.
  • Here normal module 1.5, 20 and 30 teeth, helix 20° each way, 16 mm face; centre distance (r₁ + r₂) = 39.91 mm with the transverse module 1.6. Every transverse section is an exact involute spur mesh.
  • Brown's No. 41 shows a second pair of oblique-toothed wheels; this page draws the double-helical form, the answer to the end thrust of No. 40.
  • Parts (each has its own page): double-helical-gear-mn1-5-20t-beta20-bore6, double-helical-gear-mn1-5-30t-beta20-bore8, linear-shafts-h6.
  • Brown's movement No. 41 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

Double-helical (herringbone) gears, 20 : 30, helix 20° size chart

parametervalue
normal module1.5
teeth20 / 30
helix20°, both hands on each gear
face16 mm
centre distance39.91 mm

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. 41: 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

double-helical-gears-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.
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Plain text: sheet.txt · JSON: /api/geometry?object=double-helical-gears-mechanism

Double-helical (herringbone) gears, 20 : 30, helix 20°, isometric render of a generated part
Render of double-helical-gears-mechanism-assembly from the free STEP; not to scale.

Fits with

Double-helical (herringbone) gear, normal module 1.5, 20 teeth, helix 20° , face 16, Ø6 bore, isometric render of a generated part
Double-helical (herringbone) gear, normal module 1.5, 20 teeth, helix 20° , face 16, Ø6 bore34.93×34.93×16.0 mm★ 1 file
Double-helical (herringbone) gear, normal module 1.5, 30 teeth, helix 20° , face 16, Ø8 bore, isometric render of a generated part
Double-helical (herringbone) gear, normal module 1.5, 30 teeth, helix 20° , face 16, Ø8 bore50.89×50.89×16.0 mm★ 1 file
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

Why use double-helical (herringbone) gears?

Each gear has two rows of oblique teeth of opposite hand meeting at the middle of the face: like single helical gears the teeth engage gradually and several are always in contact, but the two axial thrusts cancel, so no thrust bearing is needed.