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Spur gear, module 1, 21 T, profile shift -0.46, Ø6 bore (meshes a 30 T at 25 mm)

What is a negatively shifted 21 tooth gear? · Modern device · basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance

Also called: profile shifted gear, 21 tooth gear, engranaje de 21 dientes corregido, Zahnrad 21 Zähne mit Profilverschiebung

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

length
22.0 mm
width
22.06 mm
height
8.0 mm

Notes

  • Module 1, 20° involute, 21 teeth with a negative profile shift of -0.46 m: thinner teeth, tip at Ø22.08, so that it meshes with an unshifted 30-tooth gear at 25 mm instead of its natural 25.5 mm. Below the base circle (Ø19.73) the flank is radial; the mating idler's tips are shortened to stay clear of it. 8 mm face, Ø6 bore.
  • Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

Spur gear, module 1, 21 T, profile shift -0.46, Ø6 bore size chart

dimensionvalue
module1
teeth21
profile shift-0.46 m
tip Ø22.08 mm
centre distance with 30 T25 mm
boreØ6

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. 504: figure, his text and an animationwebPublisher's page; dimensions are facts
Xem StudiodrawingwebPublisher'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

spur-gear-m1-21t-xm046-b6gear, z 0..8, a tooth centred on +XSTEP · 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=spur-gear-m1-21t-xm046-b6

Spur gear, module 1, 21 T, profile shift -0.46, Ø6 bore (meshes a 30 T at 25 mm), isometric render of a generated part
Render of spur-gear-m1-21t-xm046-b6 from the free STEP; not to scale.

Fits with

Ferguson's mechanical paradox (19 / 20 / 21 tooth wheels on one pin), isometric render of a generated part
Ferguson's mechanical paradox (19 / 20 / 21 tooth wheels on one pin)5 sizes★ 1 file

Questions

What is a negatively shifted 21 tooth gear?

Module 1, 20° involute, 21 teeth with a negative profile shift of -0.46 m: thinner teeth, tip at Ø22.08, so that it meshes with an unshifted 30-tooth gear at 25 mm instead of its natural 25.5 mm. Below the base circle (Ø19.73) the flank is radial; the mating idler's tips are shortened to stay clear of it. 8 mm face, Ø6 bore.