The chain specification defines the sprocket interface. First identify whether the installation uses an ANSI, DIN, ISO, BS or JIS chain system. These systems use different designations and may differ in the dimensions that control engagement. A similar pitch alone is not enough to confirm compatibility.

Record the following information from the chain marking, chain documentation or a sound section of chain:

• Chain standard: ANSI, DIN, ISO, BS or JIS.
• Chain number or series: the complete designation, not only a nominal pitch.
• Pitch: the distance between adjacent chain pin centers.
• Roller diameter: required for the tooth pocket and roller seating.
• Chain width: normally the relevant inside width or the width required by the sprocket row.
• Strand configuration: simplex, duplex, triplex or another specified multi-strand arrangement.

The sprocket tooth profile must match the chain series as well as the pitch. Confirm the chain number before reviewing bore or hub options. For roller chain sprocket selection, treat the complete chain designation as the starting point, not an estimate based on outside diameter. Do not select a sprocket by measuring its outside diameter and then guessing the chain size. For replacement work, a worn chain can make measurement less reliable, so a clear chain marking, a new chain section or a confirmed chain drawing is a better reference.

If those details are already known, browse All Chain Sprockets or Standard Roller Chain Sprockets.

Sprocket type is selected by the chain arrangement, shaft mounting, load path and maintenance method. The same chain size may be available in different body, hub and bushing configurations. Choose the product family first, then check the dimensions that control fit.

Type A plate sprockets

A Type A sprocket is a flat plate sprocket without an integral hub. It is considered when the sprocket will be mounted to a separate hub, flange or fabricated component, or when axial space is limited. A pilot or plain bore may be appropriate when the final mounting feature will be machined or supplied separately.

See Type A Plate Sprockets for the product-specific options.

Type B and Type C hub sprockets

A Type B sprocket has a hub on one side. It is commonly considered for direct shaft mounting where the bore, keyway and fixing arrangement are part of the sprocket. A Type C sprocket has hubs on both sides and may be considered when the assembly needs additional support around the bore or a different hub arrangement.

The correct choice depends on shaft position, chain line, available axial space and the required hub dimensions. Use Type B & Type C Hub Sprockets for the detailed product selection.

Transmission sprockets

Transmission sprockets transfer power between a driving and a driven shaft. Confirm the chain, tooth count relationship, operating speed, load, shaft arrangement, alignment and bore before selecting the sprocket. Detailed transmission options are covered on Transmission Sprockets. This section only identifies when that product group is the right starting point.

Conveyor chain sprockets

Conveyor sprockets move a chain carrying products, pallets, fixtures or bulk material. Selection depends on the conveyor chain, tooth count, chain pull, speed, shaft layout, chain line and environment. The application-specific range is covered on Conveyor Chain Sprockets.

Idler and tensioner sprockets

An idler or tensioner sprocket guides the chain, maintains wrap or controls slack rather than transmitting the main drive torque. Bearing or shaft arrangement, mounting position, chain alignment and access for lubrication can therefore be as important as the tooth count. See Idler & Tensioner Sprockets.

Double pitch sprockets

Double pitch sprockets are selected for the matching double pitch chain. They are not interchangeable with a standard roller chain sprocket simply because the outside diameter appears similar. Confirm the chain series and tooth form before choosing Double Pitch Sprockets.

Other planned product groups, including Split Sprockets, Weld-On Sprockets, OEM Sprockets and Replacement Sprocket Assemblies, are selected when installation, fabrication, original-equipment or replacement requirements control the design.

Tooth count affects the speed ratio, sprocket diameter, chain articulation, smoothness of engagement and wear. For a simple chain drive, the relationship between the teeth on the driving and driven sprockets determines the speed change. Confirm the required ratio before fixing the tooth count.

For sprocket size selection, review tooth count together with chain pitch, center distance, chain wrap, operating speed, load and available installation space. A smaller tooth count gives a smaller pitch diameter for the same chain pitch, but the chain articulates through a sharper angle and the drive may show more chordal action, vibration or noise. A larger tooth count generally gives a larger pitch diameter and smoother chain engagement, but it requires more space and may change the available ratio or rotating mass.

Tooth count also affects how the chain seats and shares contact around the sprocket. A tooth count that is unsuitable for the speed, load or chain arrangement can increase tooth and chain wear even when the bore is correct. For replacement work, chain number and tooth count are usually more useful than outside diameter alone.

For a replacement sprocket, count the teeth and identify the driver or driven position if the part is part of a transmission. If the tooth tips are heavily worn, use an unworn reference and verify the mating chain. Do not treat a worn outside diameter as the original design dimension.

The sprocket must match the actual number of chain strands. Select a simplex sprocket for a single-strand chain, a duplex sprocket for a double-strand chain and a triplex sprocket for a triple-strand chain, subject to the complete chain specification.

Check more than the number of rows. Confirm the strand arrangement, row spacing, overall chain width, tooth alignment and the available clearance around the sprocket. A sprocket with the correct pitch and tooth count can still be wrong if its row configuration does not match the chain.

Do not replace a duplex or triplex sprocket with a simplex part because the outside diameter looks close. Multi-strand chains require the corresponding sprocket tooth paths and spacing. Detailed product choices are available at Simplex, Duplex & Triplex Sprockets.

Bore and mounting details often decide whether a sprocket can be installed without rework. Confirm the shaft interface before treating a catalogue part as interchangeable.

Pilot bore

A pilot bore is a starting bore that may be machined to the required shaft size. It can be considered when the final shaft diameter and keyway will be finished during the project or by the buyer. Confirm the amount of material available for machining and the final mounting specification before ordering.

Finished bore

A finished bore is machined to the specified shaft interface. Confirm the bore diameter, fit requirement, keyway and any set-screw arrangement. The bore should be checked against the actual shaft, not only against an old part number.

Keyway

The keyway transfers torque between the shaft and sprocket when a keyed mounting is used. Confirm the keyway width, depth, orientation and applicable inch or metric standard. A correct bore with the wrong keyway is still an installation problem.

Set screw

A set screw may be used to secure a finished-bore sprocket to the shaft. Confirm whether it is required, where it must be positioned and how it relates to the keyway, shaft shoulder and surrounding clearance. Do not assume that a set-screw position from another sprocket will suit the current shaft.

Taper Lock and QD mounting

Taper Lock and QD sprockets use matching bushing systems for shaft mounting. Confirm the bushing series, shaft bore, key arrangement, sprocket hub and the space needed to install or remove the bushing. They can simplify removal during maintenance, but the sprocket and bushing still have to be specified as a matched assembly.

See Taper Lock & QD Sprockets for the relevant mounting options.

Hub dimensions

Record hub outside diameter, hub length, side orientation, offset and the resulting chain line. Check the hub against shaft shoulders, bearings, guards, spacers and adjacent sprockets. A hub that is too long, too short or positioned on the wrong side can create misalignment even when the chain size and tooth count are correct.

Material and treatment should follow the actual load and environment, not a generic material preference. Review load, wear, shock, corrosion, washdown, dust, speed, lubrication and operating hours together with the chain and mounting design.

• Carbon steel can be considered for general industrial applications when the load and environment support that choice.
• Alloy steel may be reviewed for applications with higher load, shock or wear demands, subject to the drawing and service conditions.
• Stainless steel may be considered where corrosion resistance, moisture or washdown conditions are important.
• Tooth hardening may be reviewed where tooth wear is a significant design concern.
• Surface treatment may be considered for corrosion or wear requirements when it is compatible with the material, dimensions and assembly process.

A material name alone is not a complete specification. Confirm material, heat treatment and surface treatment against the load, chain engagement, machining requirements, welding or assembly steps and operating environment. Do not infer a fixed grade, hardness or surface treatment from a photograph. Put those requirements on the approved drawing or mark them for confirmation before quotation.

The industry or machine type provides useful context, but it does not replace chain and dimensional data. Use the application to identify the conditions that can change the sprocket selection.

Application	Selection factors to review
Material Handling & Conveyors	Chain pull, continuous movement, alignment, conveyor speed, wear, shaft layout and whether the part is a drive, conveyor, idler or tensioner sprocket.
Agricultural Machinery	Dust, moisture, shock loads, seasonal operating conditions, mounting strength and the material or treatment appropriate to the actual service.
Packaging Equipment	Start-stop cycles, indexing, speed, chain engagement, timing, available space and alignment between the drive components.
Mining & Building Materials	Abrasive dust, heavy loads, impact, long operating hours, tooth wear, hub design and the required material or treatment review.
Food Processing	Washdown, moisture, corrosion, cleaning method, material selection and any surface-finish requirements defined by the equipment or process.
Woodworking	Dust, chips, chain alignment, wear, maintenance access and the space available for the hub and guard.
Bucket Elevators	Vertical conveying, chain pull, operating speed, shaft arrangement, chain engagement, bore, hub and installation access.
OEM / MRO	OEM drawing control, repeatability, replacement fit, equipment space, available sample or photos, quantity and the information needed for a controlled quotation.

For the industry-specific pages, see Industries. Use the industry to describe the operating conditions, not as a substitute for the chain specification.

A standard sprocket is usually the practical choice when the chain standard, chain number, tooth count, strand, bore or bushing, keyway, hub and installation space match a planned catalogue configuration. Start with All Chain Sprockets or Standard Roller Chain Sprockets when the main dimensions are already known.

Consider a custom sprocket when one or more of the following controls the purchase:

• A special bore, keyway, bushing or set-screw arrangement.
• A special hub, offset, length or mounting face.
• Unusual dimensions or restrictions around the shaft, guard, bearing or frame.
• An OEM replacement that does not match a current standard catalogue part.
• A drawing-based part with controlled dimensions or revisions.
• A physical sample, worn part or clear photos when the original drawing is unavailable.
• A split, weld-on or assembled structure required for installation or maintenance access.

A custom order does not necessarily mean a new tooth design. A standard chain interface with a non-standard bore or hub can still require a custom part. Use Custom Chain Sprockets for drawing and sample-based requirements, and OEM Sprockets when the part is controlled by an equipment design or repeat production specification.

Replacement work should begin with the mating chain and the installation interface. A heavily worn tooth profile should not be copied directly as the manufacturing geometry. Wear may have changed the tooth tips, tooth pockets, bore, keyway or hub faces.

Before requesting a replacement, confirm as much of the following as possible:

• Chain standard, chain number, pitch, roller diameter and chain width.
• Tooth count and whether the sprocket is driving, driven, idling or tensioning the chain.
• Strand configuration: simplex, duplex or triplex.
• Bore diameter and shaft size.
• Keyway dimensions, set-screw details or bushing system.
• Hub outside diameter, length, side orientation and offset.
• Outside diameter, recorded as a reference rather than the only identification dimension.
• Photos of both sprocket faces, the shaft area, chain path and surrounding installation space.
• A drawing, CAD file, part number, equipment reference or physical sample if available.

If the old part is the only reference, compare it with a sound section of chain and measure from unworn surfaces. A sample can show the mounting arrangement, but it cannot prove the original tooth geometry after wear. A clear photo helps with the first review, but it may not show the dimensions that control chain engagement or shaft fit.

For the measurement sequence, use How to Measure a Sprocket. For assemblies or legacy parts that need a fit review, see Replacement Sprocket Assemblies. If no catalogue part matches the confirmed dimensions, the next step is Custom Chain Sprockets.

Selecting by outside diameter alone

Outside diameter does not identify the chain standard, tooth count, roller diameter, bore or hub. It can also be reduced by tooth wear. Use the chain and tooth count as primary references, then confirm the dimensions that control installation.

Ignoring the chain standard

A pitch that appears similar does not prove that an ANSI, DIN, ISO, BS or JIS chain and sprocket are compatible. Confirm the complete chain designation and the engagement dimensions.

Matching pitch but not roller diameter or chain width

The chain must seat correctly in the tooth pockets and fit the sprocket row. Pitch-only selection can produce poor engagement, noise and accelerated wear.

Choosing the correct teeth with the wrong bore or keyway

Tooth count does not solve a shaft-interface problem. Check the bore, keyway, set screw, bushing and hub before approving the part.

Ignoring mounting space and chain line

A sprocket may have the correct chain and bore but still fail to fit because the hub, offset, guard, bearing or removal path was not considered. Check the installed position, not only the loose part.

Copying worn geometry

A worn sprocket is evidence of the existing assembly, not necessarily a reliable manufacturing template. Verify the chain, tooth count and unworn reference surfaces before reproducing the part.

Choosing material without considering the environment

Dust, moisture, corrosion, washdown, shock and continuous operation can change the material and treatment review. Select the material after defining the operating conditions, not before.

Mixing strand or bushing configurations

Simplex, duplex and triplex sprockets require the matching chain arrangement. Taper Lock and QD options also require the correct bushing system, shaft bore and installation clearance.

Use this checklist before comparing a product or sending an RFQ.

Item	What to confirm
Chain	Standard, chain number or series, pitch, roller diameter and chain width.
Teeth	Number of teeth and driver or driven position when applicable.
Strand	Simplex, duplex, triplex or another specified multi-strand arrangement.
Bore	Pilot bore, finished bore, Taper Lock or QD; shaft diameter and bushing details where applicable.
Keyway	Keyway size, standard, orientation and whether a set screw is required.
Hub	Hub type, outside diameter, length, offset, side orientation and chain line.
Material	Carbon steel, alloy steel, stainless steel or another project-defined material; treatment if required.
Application	Transmission, conveyor, idler, tensioner, OEM or replacement use; load, speed, shock, dust, corrosion or washdown.
Quantity	Required quantity and whether the order is a one-time, repeat or OEM requirement.
Drawing / Sample	Drawing, CAD file, part number, equipment reference, photos or physical sample.

A quote request should identify the dimensions that control chain engagement and shaft fit. Send the chain standard and number, tooth count, strand, bore, keyway, hub dimensions, material or treatment requirements, application, quantity and any drawing or sample.

For a transmission, add the driver and driven positions, speed or ratio requirements, shaft arrangement and available space when known. For a conveyor, include the conveyor type, chain path, operating conditions and any chain pull or speed information available. For a replacement, add the old part photos, shaft and keyway measurements, hub dimensions, outside diameter and a sample or drawing if available.

If a dimension is unknown, identify it as unknown rather than treating a worn measurement as exact. This makes the specification review more useful and separates confirmed dimensions from items that need verification.

Browse relevant sprocket products

When the chain standard, tooth count, strand and mounting method are confirmed, use All Chain Sprockets, Standard Roller Chain Sprockets or Drive & Conveyor Sprockets to compare the relevant product family. The product pages cover the part itself; this guide covers the decision before purchase.

Send Your Drawing

When the bore, hub, tooth count or mounting arrangement is unusual, or when the part is an OEM or replacement item, send the drawing, CAD file, photos or physical sample. For a YZEFY Sprockets enquiry, use Custom Chain Sprockets, Replacement Sprocket Assemblies or OEM Sprockets as appropriate.