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Roller chain sprockets: #25 (6.35 mm) and #35 (9.525 mm), 10–40 T

Name: Roller chain sprockets: #25 (6.35 mm) and #35 (9.525 mm), 10–40 T dimension sheet
Creator: Xem Studio
License: https://creativecommons.org/licenses/by/4.0/

What is the pitch diameter of a 20 tooth #25 sprocket? · Hardware · basis: ANSI B29.1 roller chain: #25 pitch 6.35 mm, roller Ø3.30, width 3.18; #35 pitch 9.525, roller Ø5.08, width 4.78; #40 pitch 12.70, roller Ø7.92. PD = pitch / sin(180°/N), OD ≈ pitch × (0.6 + cot(180°/N))

Long Earth Society build part. Flywheel-to-alternator drive on the larger LES engines. The engines · all LES parts

sizes: 12 in table

Notes

#25 is the small 'bicycle-chain-looking' chain on printers and robots: 6.35 mm (1/4 in) pitch, Ø3.30 rollers, 3.18 mm inner width. #35 is 3/8 in pitch (go-karts, heavier robots). #40 is 1/2 in (bicycles use 1/2 in pitch too but a narrower #410/#415 width).
Pitch diameter = pitch / sin(180°/N): #25 20 T → 40.6 mm; #35 20 T → 60.9 mm. Centre distance between sprockets must put a whole number of links on the chain: L (links) = 2C/p + (N1 + N2)/2 + (N2 − N1)²p/(4π²C); round to an even number.
Tooth profile here is the simple roller-seat form (ANSI 'standard' profile approximated): printed PETG #25 sprockets run fine at model speeds; buy steel for anything over 50 W.
LES: #25 chain from the flywheel to the generator where a belt would slip on a hot shaft; 10 T on the engine, 30 T on the alternator.

Sizes

chain	teeth	pitch_dia_mm	od_mm	pitch_mm
#25	10	20.55	23.35	6.35
#25	12	24.53	27.51	6.35
#25	15	30.54	33.68	6.35
#25	20	40.59	43.9	6.35
#25	25	50.66	54.08	6.35
#25	30	60.75	64.23	6.35
#25	40	80.93	84.49	6.35
#35	10	30.82	35.03	9.525
#35	12	36.8	41.26	9.525
#35	15	45.81	50.53	9.525
#35	20	60.89	65.85	9.525
#35	30	91.12	96.34	9.525

Where the files are

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

Wikipedia	Roller chain	web	CC BY-SA 4.0 (text)
McMaster-Carr	Roller chain sprockets (free STEP per part, for your own design use; no redistribution)	STEP, PDF	McMaster-Carr site terms verify
Wikipedia	Sprocket	web	CC BY-SA 4.0 (text)
Long Earth Society	Engine and rig builds	web, video	LES site

Free files

★ Free files 12 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

sprocket-25-10t-b8	#25 chain (6.35 mm pitch), 10 T, PD 20.55, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-25-12t-b8	#25 chain (6.35 mm pitch), 12 T, PD 24.53, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-25-15t-b8	#25 chain (6.35 mm pitch), 15 T, PD 30.54, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-25-20t-b8	#25 chain (6.35 mm pitch), 20 T, PD 40.59, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-25-25t-b8	#25 chain (6.35 mm pitch), 25 T, PD 50.66, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-25-30t-b8	#25 chain (6.35 mm pitch), 30 T, PD 60.75, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-25-40t-b8	#25 chain (6.35 mm pitch), 40 T, PD 80.93, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-35-10t-b8	#35 chain (9.525 mm pitch), 10 T, PD 30.82, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-35-12t-b8	#35 chain (9.525 mm pitch), 12 T, PD 36.80, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-35-15t-b8	#35 chain (9.525 mm pitch), 15 T, PD 45.81, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-35-20t-b8	#35 chain (9.525 mm pitch), 20 T, PD 60.89, Ø8 bore hub with M3 set screw	STEP · STL
sprocket-35-30t-b8	#35 chain (9.525 mm pitch), 30 T, PD 91.12, Ø8 bore hub with M3 set screw	STEP · STL