Roller chain sprockets

Overview

Draw a roller-chain sprocket in CadCraft from a chain number and a tooth count. The table covers 38 chains: the 14 ANSI numbers 25 to 240, the 11 ISO 606 A-series chains and the 13 ISO 606 B-series chains. Each chain's pitch, roller diameter, width between inner plates and (where the catalogues agree) inner plate height was read from public manufacturers' catalogues and kept only where at least two of them print the same number. The sprocket is drawn tooth by tooth: the seat arc around each roller and the flank leaving it, with the pitch circle, centre lines and bore, and the command line checks that the chain it was made for seats on it.

Who it’s for

• Machine designers and drafters who need a sprocket outline for a chain drive in a drawing.
• Makers who cut sprockets on a laser, router or waterjet and want the outline from the chain's own pitch and roller size.
• Anyone who wants the standard roller-chain dimensions with the catalogues they come from listed beside them.

What you can do

• Type SPROCKET (SPR), give a chain number such as 40, 80, 08A or 10B, the number of teeth (6 or more), the bore and a centre point: the outline, pitch circle, centre lines and bore are drawn on their own layers in one undo step.
• Type CHAINS to list every chain in the table with its dimensions and how many catalogues agree.
• Type CHAINSOURCES to see every catalogue the numbers were read from, with its address.
• Read the same table as data in lib/chain/chain-table.json in the source, with each number's agreeing and disagreeing catalogues.

Methods and standards

The rollers sit one pitch apart on the pitch circle of diameter p / sin(180 / N). The root diameter is the pitch diameter less the seat diameter (roller diameter plus 2 % clearance). Each tooth gap is the seat arc around a roller centre, swept 80 degrees either side of the line to the sprocket centre, then the straight flank tangent to it, meeting on the tooth's centre line or cut by a tip circle 0.35 pitches above the pitch circle. The check wraps the chain on the sprocket and confirms that every roller seats and clears the outline, and that the next roller can swing out of its seat and first touches the flank, not the tip edge.

Data and sources

Dimensions in millimetres: pitch p, roller diameter d1 (the bushing diameter for chains 25 and 35, which have no rollers), width between inner plates b1 (ISO: minimum; ANSI: nominal roller width) and inner plate height h2. Read on 2026-11-06 from: PTI Europa's A-series table; the Diamond Chain (Drives & Drives) ISO 606 and ANSI B29.1 catalogue; Sedis Delta's BS/ISO 606 table; mm-intercom's series B data sheet; BEP's ISO 606 stainless chain table; Industrial World's British Standard chart; Tsubaki's US catalogue; the Sprocket Engineering Datasheet's ANSI table; and Engineers Edge's ASME B29.1M table. A number is kept when at least two catalogues print it within 0.06 mm (0.1 mm for plate height); inches are converted with 25.4. Where catalogues disagree the disagreement is kept in the table. The numbers are not copied from ISO 606 or ANSI/ASME B29.1, which we do not hold, and the catalogues name no edition.

Verification

tools/chain/test-chain-table.mjs (3326 checks): every row has its agreeing catalogues; the stored numbers are printed by those catalogues; pitch follows the chain number (ANSI number / 8 inch, ISO number / 16 inch); roller, inner width and plate height stay in proportion to the pitch; ANSI chains and their ISO A-series twins have the same pitch, roller and plate height; and every chain draws and seats its own chain at every tooth count from 9 to 80. tools/chain/test-chain.mjs (298 checks) tests the geometry on made-up rows against closed forms. The add-on's own test in CadCraft's engine passes 14 checks. Real chain on real sprockets has not been measured.

Limits

Not in the table: ISO 04C, 06C and 36A (only one catalogue prints their inner width), and the plate height of several chains (the catalogues disagree), shown as not available. The plate height is not used to draw the outline. The tooth form (2 % seat clearance, 80 degree seat half angle, tip 0.35 pitches above the pitch circle, tooth width 0.9 of the inner width) is this add-on's own, not the standard's tooth form, and the sprocket has not been compared with any catalogue sprocket. Hub, keyway, strength, wear and chain length are not part of it. Draws in CadCraft only for now.

Files and formats

Draws ordinary entities (a closed polyline, circles and lines) on layers SPROCKET, SPROCKET-CENTER and SPROCKET-BORE; they save as DXF and DWG like any drawing. Nothing is stored apart from your last chain and tooth count.

Get started

1. Add Roller chain sprockets.
2. Type SPROCKET, answer 40, then 17 teeth, accept the bore and click a centre.
3. Type CHAINS to see the other chains, CHAINSOURCES for where the numbers come from.

Languages

The text is available in:

• Afrikaans (af)
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Works in

Comes with

Nothing else.

Permissions

• Adds commands
• Adds settings

From its manifest. Shown again when an update changes them, and the update waits for your yes.

Versions

Licence and maker

CadCraft (CadCraft, first-party). Licence: Apache-2.0. Dependencies carry their own licences, listed on their pages.