Roller chain sprockets and their hubs · Type A plate, B hub one side, C hubs both sides, D detachable hub, Taper-Lock and QD bushed · finished bore, keyway and set screws, maximum bore, length through bore · chain number and pitch, number of teeth, multi-strand · chain drive selection · crawler track drive sprockets compared
A sprocket hub is the boss that carries a chain sprocket on its shaft: it holds the bore, keyway and set screws that transmit torque, and its length and diameter limit how large a shaft the sprocket can take. Ask three things first: the chain number (pitch) and strand count, with the number of teeth set by the drive's speed ratio; the hub style — plate, one-side hub, two-side hub, detachable or bushed; and the bore — finished to the shaft size with keyway and set screws, or plain for machining, within the maximum bore.
Roller chain sprockets for ANSI-numbered and metric (BS/DIN, ISO-coded) chain, single and multi-strand, with Type A, B, C and D hubs, finished, plain, Taper-Lock and QD bores, and the chain drive selection that sets chain size and tooth counts — including buyers searching for sprockets and gears or chain drives. Drive sprockets (tumblers) for crawler track undercarriages are compared briefly; engineering-class conveyor chain sprockets, timing belt pulleys, gears and the chain itself are outside this page except where compared.
01
Sprocket nomenclature names four standard styles: Style A, a flat plate with no hub on either side; Style B, a hub extending on one side; Style C, hubs extending on both sides; and Style D, a plate with a detachable bolt-on hub. QD (quick detachable) sprockets take a tapered bushing bolted into the bore that compresses onto the shaft, taper-bushed sprockets carry designations such as TL, BTL or CTL, shear-pin hubs act as an overload device, and split sprockets install without disturbing the shaft. The maximum bore is set by the hub wall thickness needed for strength, with allowance for keyway and set screws; the length through bore must allow a key long enough for the shaft torque; and the hub diameter must not exceed the inside of the chain sidebars. Part numbers give the chain pitch, then the hub style, then the tooth count, with a prefix for multi-strand (D double, E triple, F four-strand) and an H suffix for hardened teeth. [1]
Tsubaki's No. 100 (1.250 in pitch) B-style, 25-tooth sprocket 100B25F-2 lists a 2.000 in finished bore, 3.000 in maximum bore, 4.500 in hub diameter, 2.000 in length through bore, 10.650 in outside diameter, 9.974 in pitch diameter, 9.204 in caliper diameter, 0.692 in tooth width, hardened teeth and 18.400 lb weight; its dimensions allow for a standard keyway with a set screw at 90°. [3] Tsubaki's stock sprockets are 1045 cold-rolled carbon steel with no powdered metal, hardened to RC35–50 on ANSI 35–80 pitch sizes, bored, chamfered and de-burred, black-oxide coated, and finished-bore sprockets come with set screw placement directly over the keyway and at 90°. Its finished-bore codes use a letter for the fraction, so a -1B bore is 1.125 in, and its interchange chart lists examples such as 40B17 (B hub, 17 teeth), 60A21 (A plate), 41BTL26 (Taper-Lock B hub) and 80SK17 (QD hub). [2]
Give the supplier the chain number or ISO chain code and strand count, number of teeth, hub style, bore type (finished, plain or bushed), bore size and tolerance, keyway and set screw requirements, hub diameter and length through bore limits, tooth hardening, material and finish, and quantity.
02
Tsubaki's roller chain selection starts from the power source, driven machine, horsepower, shaft speeds and diameters, and center distance. A service factor from 1.0 (smooth load, electric motor) to 1.7 (large impact, internal combustion engine without hydraulic drive) multiplies the horsepower to give design horsepower; the chain number and small-sprocket teeth come from the rating tables at the high-speed shaft rpm. More than 15 teeth on the small sprocket is suggested and the large sprocket should have fewer than 120; the large sprocket's teeth equal the small sprocket's teeth times the speed ratio; and the sprocket must be checked against space limits and shaft diameter. Multi-strand chain is rated with factors of 1.7 for two strands, 2.5 for three, 3.3 for four, 3.9 for five and 4.6 for six rather than by multiplying single-strand ratings. Chain speed is S = P·N·n/12 ft/min, chain tension T = 33,000·HP/S lb, and chain length in pitches L = (N1+N2)/2 + 2C + ((N2−N1)/6.28)²/C, with any fraction counted as one pitch. The ratings assume 15 °F to 140 °F, horizontal shafts, the suggested lubrication and steady load; at 100 pitches of chain under those conditions, a service life of approx. 15,000 hours can be expected. [4]
Editorial calculation: with Tsubaki's length formula, a 17-tooth and 51-tooth pair at 40 pitches center distance gives L = 34 + 80 + (34 ÷ 6.28)² ÷ 40 ≈ 114.7, rounded up to 115 pitches; a No. 100 (1.250 in pitch) 25-tooth sprocket at 100 rpm runs at S = 1.25 × 25 × 100 ÷ 12 ≈ 260 ft/min, so 10 hp gives T = 33,000 × 10 ÷ 260 ≈ 1,270 lb. [4]
Editorial calculation: the nomenclature formula PD = pitch ÷ sin(180°/N) gives 1.25 ÷ sin 7.2° ≈ 9.973 in for a 25-tooth No. 100 sprocket, and OD = pitch × (0.6 + cot 7.2°) ≈ 10.645 in, consistent with Tsubaki's listed 9.974 in and 10.650 in. [1] [3]
03
A crawler undercarriage sprocket, also called a tumbler, drives an endless track of articulated chain links, each with an engagement cam, rather than a roller chain. A Terex (now Tadano Demag) patent describes a sprocket with 9 teeth formed in one piece on a central disc and arranged in three identical segments of 120° each — 120° being described as an advantageous wrap-around angle — against prior art with 10 teeth in two five-tooth segments over 180°; reducing the sprocket diameter increases propulsive force, so the travel drive torque can be smaller. The patent names caterpillar cranes and excavators as uses. [5]
Editorial note: track sprockets and segments are ordered by machine model, track pitch, tooth and bolt count rather than by ANSI or ISO chain number, so treat them as undercarriage parts when requesting quotations.
04
The manufacturer cards below state what each reviewed source shows.
When requesting quotations, ask each supplier for the sprocket drawing with pitch, outside and caliper diameters, hub diameter, length through bore and maximum bore, the bore and keyway tolerances, set screw positions, material, tooth hardness, finish, and stock or made-to-order lead time.
05
This is a functional reference built from the sources cited; it is not one maker's design.
| Element | Role | Fix in the order |
|---|---|---|
| Toothed plate | Teeth matched to chain pitch; PD = pitch ÷ sin(180°/N). [1] | Chain number, teeth. |
| Hub body | Style B one side, C both sides, D bolt-on. [1] | Hub style. |
| Bore | Finished, plain or bushed; max bore by wall thickness. [1] [3] | Size, tolerance. |
| Keyway and set screws | Set screw over keyway and at 90°. [2] | Keyway size. |
| Bushing (QD, Taper-Lock) | Tapered bushing compresses onto shaft. [1] | Bushing series. |
| Teeth hardening | RC35–50 on ANSI 35–80. [2] | Hardness. |
06
A sprocket quotation needs values for your project. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Chain number and pitch | No. 100 = 1.250 in pitch example. [3] | ANSI number or ISO code. |
| Strands | Prefix D double, E triple, F four-strand. [1] | Strand count. |
| Number of teeth | More than 15 small, fewer than 120 large. [4] | Teeth per sprocket. |
| Hub style | A plate, B one side, C both sides, D detachable. [1] | Style. |
| Bore type and size | 2.000 in finished bore example; -1B = 1.125 in. [3] [2] | Bore, tolerance. |
| Maximum bore | 3.000 in example, with keyway and set screw. [3] | Max bore. |
| Keyway and set screws | Set screw over keyway and at 90°. [2] | Keyway, screws. |
| Hub diameter and length through bore | 4.500 in and 2.000 in example. [3] | Hub dimensions. |
| Outside and pitch diameter | 10.650 in and 9.974 in example. [3] | OD, PD, caliper. |
| Material and hardness | 1045 carbon steel; RC35–50. [2] | Steel, hardness. |
| Finish | Black oxide. [2] | Coating. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Chain: [ANSI number or ISO code; strands] Teeth: [driver; driven] Hub: [A; B; C; D; QD; Taper-Lock] Bore: [size; tolerance; keyway; set screws] Drive: [hp or kW; rpm; service factor; center distance] Material: [steel; hardened teeth; finish] Quantity: [units]
The manufacturers below list roller chain sprockets on their own websites; each card links to the page reviewed. Confirm ratings, materials and approvals for your order.
Lists ASA, double, finished-bore, taper-bore, idler and EN sprockets.
Product scope checked 2026-10-12
Lists sprockets and plate wheels alongside spur and bevel gears.
Product scope checked 2026-10-12
Lists roller chain sprockets, including custom (non-standard) sprockets.
Product scope checked 2026-10-12
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
Style A is a flat plate without a hub, Style B has a hub on one side and Style C has hubs on both sides. [1]
Tsubaki suggests more than 15 teeth on the small sprocket and fewer than 120 on the large sprocket. [4]
Tsubaki's finished-bore sprockets have set screw placement directly over the keyway and at 90° to keep proper shaft position. [2]
Sources checked 2026-10-11. Three are Tsubaki documents (a selection procedure, a sprocket flyer and a catalogue item page), one a distributor's sprocket nomenclature page, and one a granted US patent on crawler sprockets.
Ask for use case, specification boundaries, supplier type, and RFQ preparation information for this product.
Compare manufacturer profiles with relevant product and process capability.