Pololu 20D 100:1 metal gearmotor 6 V (#3454): body, Ø4 shaft and M2.5 face-plate holes — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/pololu-20d-metal-gearmotor-100-1-6v/  (sheet CC BY 4.0)
Basis: Pololu product page #3454 and the Pololu '20D mm Metal Gearmotors' dimension drawing; hole spacing cross-checked with the Pololu 20D bracket #1138 drawing.
Catalog version: 2026-10-20

Overall (mm): length 62.1, width 20.0, height 20.0
- Datum: motor axis along z, rear of the motor can at 0, output shaft toward +z.
- Motor can Ø20.0 × 25.1; gearbox Ø20.0 × 19.0 (L for 100:1), face plate at 44.1 from the rear.
- Output shaft Ø4.0 D-shaft extending 18.0 from the face plate (the D-flat is not dimensioned; drawn round).
- Two M2.5 threaded holes in the face plate, 15.0 apart on a line through the shaft (±7.5); maximum screw engagement 3.5 (modelled Ø2.5 × 3.5 deep).
- Gearbox length by ratio: 16.0 (25:1, 31:1), 17.5 (63:1, 78:1), 19.0 (100:1 to 195:1), 20.5 (250:1 to 488:1); 12 V, CB and extended-shaft versions share the face plate and shaft. Not modelled: rear motor terminals.
- Dimensions are exact nominal (true size), no tolerance added.

feature  x (mm)  y (mm)  size
face-plate hole 1  −7.5  0  M2.5, 3.5 max engagement
face-plate hole 2  +7.5  0  M2.5, 3.5 max engagement
output shaft  0  0  Ø4.0 D, 18.0 long

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Pololu: 100:1 Metal Gearmotor 20Dx44L mm 6V (#3454) — web — Publisher's page; dimensions are facts — https://www.pololu.com/product/3454
- Pololu: 20D mm Metal Gearmotors dimension drawing — web — Publisher's page; dimensions are facts — https://www.pololu.com/file/0J1242/20d-metal-gearmotor-dimension-diagram.pdf
- Pololu: 20D gearmotor bracket #1138 dimensions — web — Publisher's page; dimensions are facts — https://pololu.com/file/0J724/1138-bracket-dimensions.pdf

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