Industrial Chain Drives: Sizing, Selection and Maintenance: Types of Transmission Chains

The Complete Engineering Guide to Roller Chain Drives, Sprockets, and Power Transmission

What You Will Learn in This Guide

This is not a surface-level overview. This is the reference guide you keep bookmarked for the next decade. Here is exactly what we will cover:

• Every type of transmission chain and when each one belongs in your design
• The anatomy of a roller chain — every component, every dimension, every tolerance
• ANSI chain numbering decoded — so you never misorder again
• Sprocket types, classes, and materials — including the tolerance tables engineers actually need
• Every critical diameter — pitch, bottom, caliper, outside — with the formulas and lookup data
• Sprocket proportions for cast, bar-steel, single-strand, and multiple-strand configurations
• Power ratings for every standard chain size from No. 25 through No. 120
• Service factors and multiple-strand factors that prevent the failure the practitioner experienced
• Center distance formulas, chain length calculations, and idler sprocket placement
• Tooth form geometry — the ANSI standard seating curve, pressure angles, and profile data
• Hob design and space cutter specifications for sprocket manufacturing
• Lubrication types that directly determine your chain's rated life
• Installation, alignment, and a complete step-by-step design procedure

Let's begin where the practitioner began — with understanding what a transmission chain actually is.

Types of Transmission Chains

Before you can select the right chain, you need to understand the full landscape. Roller chains get most of the attention, but they are one member of a larger family. Each type exists because it solves a specific problem that the others cannot.

Detachable Chains

The links of a detachable chain are identical — each has a hook-shaped end in which the bar of the adjacent link articulates. Available in malleable iron or pressed steel, the chief advantage is the ease with which any single link can be removed without special tools or disassembly of the entire chain.

Best for: Low-precision conveyance applications where field maintenance speed matters more than power transmission accuracy.

Cast Roller Chains

Cast roller chains are constructed wholly or partly from cast metal parts. The rollers and side bars are accurately made castings without machine finish. Links are connected by forged pins secured by nuts or cotters.

Best for: Slow speeds and moderate loads where the precision of standard roller chains is not required, or where cost constraints prohibit machined components.

Pintle Chains

Unlike the roller chain, the pintle chain is composed of hollow-cored cylinders cast or forged integrally with two offset side bars, with each link identical. Links are joined by pins inserted through the side bar holes and cored holes in adjacent links. Lugs prevent pin rotation in the side bars, ensuring articulation occurs between the pin and the cored cylinder.

Best for: Heavy-duty, low-speed conveyor and elevator applications where ruggedness matters more than precise pitch accuracy.

Standard Roller Transmission Chains

This is the workhorse of power transmission — and the focus of this guide.

A roller chain is made up of two kinds of links: roller links and pin links, alternately spaced throughout the chain length. The rollers are evenly spaced, and the outstanding advantage of this design is the ability of the rollers to rotate when contacting the sprocket teeth. This rolling contact — rather than sliding contact — dramatically reduces wear and improves efficiency.

Two arrangements are in common use:

• Single-strand type — a single chain for moderate power transmission
• Multiple-strand type — two or more chains joined side by side with common pins that maintain roller alignment across strands

Standard Double-Pitch Roller Chains

These are like standard roller chains except their link plates have twice the pitch of the corresponding standard-pitch chain. They conform to ANSI/ASME B29.3M-1994.

Best for: Low speeds, moderate loads, or long center distances where the reduced weight and cost of double-pitch chains become significant advantages.

The Anatomy of a Roller Chain — Every Part, Named and Defined

Understanding chain nomenclature is not academic — it is the difference between ordering the right replacement part and shutting down a line for three days while the wrong one ships back.

Per ANSI/ASME B29.1M-1993, the standard nomenclature is:

Critical Insight: The connecting link is often the weakest point in a chain. It is the first place to inspect when diagnosing premature wear or unexpected failure. the practitioner found that the connecting link on his failed No. 80 chain showed signs of fatigue cracking that predated the catastrophic failure by at least 2,000 hours.

ANSI Roller Chain Dimensions — The Master Reference Table

Every dimension on a standard roller chain is proportional to the pitch. This single principle governs the entire design system and makes it possible to scale chain selection across the full range of sizes.

The following relationships apply across all standard series chains:

• Roller Diameter $D_r \approx \frac{5}{8}P$
• Chain Width $W \approx \frac{5}{8}P$ (distance between link plates)
• Pin Diameter $D_p \approx \frac{5}{16}P$ or $\frac{1}{2}$ of the roller diameter
• Link Plate Thickness (Standard Series) $LPT \approx \frac{1}{8}P$
• Link Plate Thickness (Heavy Series) ≈ that of the next larger pitch standard series chain
• Maximum Height of Roller Link Plates = $0.95P$
• Maximum Height of Pin Link Plates = $0.82P$
• Maximum Pin Diameter = nominal pin diameter + 0.0005 inch
• Minimum Hole in Bushing = nominal pin diameter + 0.0015 inch
• Maximum Width of Roller Link = nominal width of chain + (2.12 × nominal link plate thickness)
• Minimum Distance between Pin Link Plates = maximum width of roller link + 0.002 inch

ANSI Roller Chain Dimensions (ANSI/ASME B29.1M-1986)

* Bushing diameter — these size chains have no rollers.

Decoding Standard Roller Chain Numbers

the practitioner's first lesson in his deep-dive was embarrassingly simple: he had been ordering chains for years without ever understanding what the numbers actually meant. Once you know the code, you will never misidentify a chain again.

The ANSI Numbering System

• The right-hand digit tells you the chain type:

  • 0 = roller chain of usual proportions
  • 1 = lightweight chain
  • 5 = rollerless bushing chain

• The digits to the left of the right-hand figure denote the number of 1/8-inch increments in the pitch

• The letter "H" following the chain number denotes the heavy series

• A hyphenated number suffix denotes the strand count:

  • -2 = double strand
  • -3 = triple strand
  • -4 = quadruple strand

Decoding Examples

Key Chain Variants

Heavy Series (H): Made in 3/4-inch and larger pitches with thicker link plates than the regular standard. Their value is only in the acceptance of higher loads at lower speeds.

Lightweight Machinery Chain (No. 41): A 1/2-inch pitch chain, 1/4-inch wide, with 0.306-inch diameter rollers and 0.141-inch pin diameter. Minimum ultimate tensile strength is 1,500 pounds.

Multiple-Strand Chain: Essentially an assembly of two or more single-strand chains placed side by side with pins extending through the entire width to maintain alignment.

Chain Length Tolerances and Measuring Loads

• Tolerances for chain length: New chains, under standard measuring load, must not be underlength. Overlength tolerance = $\frac{0.001}{(\text{pitch in inches})^2} + 0.015$ inch per foot
• Measurements must be taken over a length of at least 12 inches
• Measuring load: Equal to 1% of the ultimate tensile strength, with a minimum of 18 lb. and a maximum of 1,000 lb. for both single and multiple-strand chains
• Minimum ultimate tensile strength (single-strand): $\geq 12{,}500 \times (\text{pitch in inches})^2$ pounds
• Multiple-strand tensile strength: Single-strand strength × number of strands

What this means in practice: A No. 80 chain (1-inch pitch) has a minimum ultimate tensile strength of $12{,}500 \times 1^2 = 12{,}500$ lb. A No. 80-2 (double strand) doubles that to 25,000 lb. But remember — ultimate tensile strength is not your working load. It is the point where the chain breaks. Your working load should be a small fraction of this number.

Types of Sprockets

Sprocket selection is half the equation in chain drive design. Four standard designs exist, each suited to different mounting and load conditions.

The Four ANSI Sprocket Types

Additionally, shear pin sprockets and slip clutch sprockets are available for drives where overload protection is critical — designed to prevent damage to the drive or downstream equipment caused by overloads or stalling.

Attachments — Adapting Chains for Conveying, Elevating, and Timing

Standard chain components can be modified with attachments to adapt the chain for conveying, elevating, and timing operations. Two components are commonly modified:

• Link plates — provided with extended lugs that may be straight or bent
• Chain pins — extended in length to project substantially beyond the outer surface of the pin link plates

Straight and Bent Link Plate Extensions and Extended Pin Dimensions (ANSI/ASME B29.1M-1993)

All dimensions in inches.

Sprocket Classes — Commercial vs. Precision

ANSI/ASME B29.1M-1993 provides for two classes of sprockets: Commercial and Precision. The selection between them is a matter of drive application judgment.

When to Use Each Class

Commercial Sprockets are adequate for:

• Moderate to slow speed drives
• Applications requiring Type A or Type B lubrication
• General industrial machinery without critical timing requirements

Precision Sprockets may be required for:

• Extreme high speed combined with high load
• Fixed center distance drives
• Critical timing or register problems
• Close clearance with outside interference
• Applications requiring Type C lubrication

Rule of thumb: If your drive requires oil stream lubrication (Type C), consult the manufacturer about whether Precision sprockets are needed.

Keys, Keyways, and Set Screws for Sprocket Mounting

To secure sprockets to the shaft, both keys and set screws should be used. The key prevents rotation; the set screw prevents longitudinal displacement.

Critical installation practice: Keys should be fitted carefully in both the shaft and sprocket keyways to eliminate all backlash, especially on fluctuating loads. A set screw should be located over a flat key to secure it.

Recommended Set Screw Sizes (American Chain Association)

Sprocket Diameters — The Four Critical Measurements

Every sprocket has four diameters you must understand. Getting any one of them wrong during inspection, ordering, or design will cost you time and money.

. Pitch Diameter (PD)

The pitch diameter is the diameter of the pitch circle — the circle that passes through the centers of the link pins as the chain wraps on the sprocket.

Because the chain pitch is measured on a straight line between adjacent pin centers, the chain pitch lines form a series of chords of the pitch circle.

$$\text{Pitch Diameter} = \frac{P}{\sin(180° \div N)}$$

Where $P$ = pitch and $N$ = number of teeth.

. Bottom Diameter

The bottom diameter is the diameter of a circle tangent to the seating curve at the bottom of the tooth gap.

$$\text{Bottom Diameter} = \text{Pitch Diameter} - D_r$$

Where $D_r$ = roller diameter.

. Caliper Diameter

This is the measurement you take with a caliper to verify the sprocket — and it depends on whether the tooth count is even or odd.

For even-tooth sprockets: $$\text{Caliper Diameter} = \text{Pitch Diameter} - D_r$$

For odd-tooth sprockets: $$\text{Caliper Diameter} = \text{Caliper Factor} \times P - D_r$$

Where: $$\text{Caliper Factor} = PD \times \cos\left(\frac{90°}{N}\right)$$

Why this matters: When the practitioner was verifying his replacement sprockets, he initially got a measurement that didn't match the table. He was measuring a 63-tooth sprocket (odd) using the even-tooth formula. Once he applied the caliper factor, the numbers matched perfectly.

. Outside Diameter (OD)

The diameter over the tips of the teeth.

For turned sprockets: $$OD = P \left[0.6 + \cot\left(\frac{180°}{N}\right)\right]$$

For topping hob cut sprockets: $$OD = \text{Pitch Diameter} - D_r + 2 \times \text{Whole Depth of Topping Hob Cut}$$

ANSI Roller Chain Sprocket Diameters (1-Inch Pitch — ANSI/ASME B29.1M-1993)

For any other pitch, multiply all values by the pitch.

Caliper factor values are shown only for odd-tooth sprockets. Even-tooth sprockets use Pitch Diameter − Roller Diameter directly.

Tolerances on the Caliper Diameter

Caliper diameter tolerances are minus only — meaning your sprocket can be at or below the nominal caliper diameter, but never above it.

The tolerance formulas are:

Precision Sprockets: $$\text{Tolerance} = 0.001P\sqrt{N} + 0.003 \text{ inch}$$

Commercial Sprockets: $$\text{Tolerance} = 0.002P\sqrt{N} + 0.006 \text{ inch}$$

(Commercial tolerances are exactly twice those of Precision sprockets.)

Minus Tolerances on Caliper Diameters — Precision Sprockets (ANSI/ASME B29.1M-1993)

All values in inches. Commercial tolerances are twice these values.

Sprocket Tooth Section Profile Dimensions (ANSI/ASME B29.1M-1993)

These dimensions govern the cross-sectional shape of the sprocket tooth, including chamfer depth, chamfer width, minimum radius, and the transverse pitch that defines strand spacing for multiple-strand chains.

Maximum flange thickness fillet radius: $r_f = 0.04P$ for maximum hub diameter.

Whole Depth: $WD = \frac{1}{2}D_r + P\left[0.3 - \frac{1}{2}\tan\left(\frac{90°}{N_a}\right)\right]$ where $N_a$ is the intermediate number of teeth for the topping hob.

Sprocket Flange Thickness (ANSI/ASME B29.1M-1993)

All dimensions in inches.

Proportions of Sprockets

Single-Strand and Multiple-Strand Cast Sprockets

The following formulas define the proportions of cast roller chain sprockets per the American Chain Association:

For single-strand and multiple-strand sprockets:

Where $P$ = chain pitch, $W$ = nominal chain width, $D$ = shaft diameter, and $PD$ = pitch diameter.

Sprocket Web Thickness for Various Pitches

Bar-Steel Sprockets

For bar-steel sprockets, the American Chain Association provides:

Where $Z$ varies with pitch diameter:

• PD up to 2 inches: $Z = 0.125$ inch
• PD 2–4 inches: $Z = 0.187$ inch
• PD 4–6 inches: $Z = 0.250$ inch
• PD over 6 inches: $Z = 0.375$ inch

Spoke Design Assumptions

When sprocket wheels are designed with spokes, the usual assumptions are:

• The maximum torque load equals the chain tensile strength × the sprocket pitch radius
• The torque load is equally divided between the arms by the rim
• Each arm acts as a cantilever beam
• Arms are generally elliptical in cross section, with the major axis twice the minor axis

Selection of Chain and Sprockets

This is where the practitioner's education got deadly practical. Selecting the right chain and sprocket combination requires balancing multiple constraints simultaneously.

The Core Principle

The smallest applicable pitch of roller chain is always desirable for quiet operation and high speed. However, short pitch with high working load can often be obtained through multiple-strand chain rather than jumping to a larger single-strand pitch.

Selection Process

Step 1: Select the small sprocket large enough to accommodate the shaft. Check maximum bore and hub diameters against the shaft size.

Step 2: Determine the number of teeth in the larger sprocket based on the desired speed ratio. Do not overemphasize exactness — a minor change in speed of one or both shafts usually produces satisfactory operation without creating a cumbersome installation.

Step 3: Verify the power rating accounts for all three critical factors:

1. Service Factors
2. Multiple-Strand Factors
3. Lubrication Type