ASME B29.3-1994 — Steel Bushed Rollerless Chains, Attachments, and Sprockets

28 10 月, 2026
ASME Standards

🛤️ ASME B29.3-1994 is the American National Standard for steel bushed rollerless chains and their attachments and sprockets. A rollerless chain is the simplest family of chain drives: it is made of alternately assembled bushing links (roller/bushing links) and pin links, with the pins articulating inside the bushings, and the sprocket teeth engage directly on the outside diameter of the bushings — there are no rollers on the chain. Compared with roller chain, the rollerless chain omits the roller components: construction is simpler, chain weight is lower, and manufacturing cost is less, but the bushing-to-sprocket-tooth contact is sliding friction, so operating speed and life are below those of roller chain. It is therefore particularly suited to low-speed, heavy-duty conveying and elevator duties in demanding environments. The Standard establishes the dimensional limits needed to ensure chain interchangeability on sprockets (pitch, bushing diameter, link plate width, pin diameter, measuring load, and minimum ultimate tensile strength) and also provides attachment and sprocket matching requirements.

💡 The core advantages of a rollerless chain are simplicity and economy: no rollers cuts per-unit cost and chain weight substantially, which is why grain elevators, drag conveyors, bucket elevators, and agricultural machinery use them widely for low-speed, high-load service. The trade-off is poor high-speed suitability, so speed must be kept within the applicable range.

1. Scope and Construction Principles 📌

The Standard (whose lineage traces to ASA B29.3-1952 and ANSI B29.3-1977) applies to steel bushed rollerless chains, their attachments, and mating sprockets. Basic chain construction:

Inside link (bushing link): two bushing link plates plus two bushings pressed into the plate holes.
Outside link (pin link): two pin link plates plus two pins that pass through the bushing bores and are riveted or secured at the ends.
No rollers: sprocket teeth contact the bushing outside diameter directly, and the bushing slides over the tooth face during engagement.

⚠️ Distinguish “bushed chain” from “roller chain”: a roller chain has rollers over the bushings — rolling friction and good high-speed performance; a rollerless chain has no rollers and the bushing engages directly. B29.3 is the latter; never apply roller-chain high-speed criteria to it.

2. Dimension Series and General Parameters 📏

The Standard lists a general dimension table by chain number, including:

Pitch: the distance between adjacent joint centers, defining the size grade.
Bushing diameter and overall width: determine contact and load-carrying width with the sprocket teeth.
Pin diameter and link plate thickness: determine joint strength and wear life.
Measuring load: the specified tension applied when measuring chain length.
Minimum Ultimate Tensile Strength (M.U.T.S.): the static acceptance criterion.

Parameter	Function	Typical Notes
Pitch	Size grade and sprocket pitch basis	Preliminary selection by load and space
Bushing diameter/width	Load-carrying and engagement width	Sets sprocket face width
Pin diameter	Joint shear/wear strength	Check with M.U.T.S.
Measuring load	Standardized chain length	Basis for assembly and elongation checks
Ultimate tensile strength	Strength acceptance	Apply safety factor for selection

💡 Interchangeability dimensions are given as limiting dimensions rather than single nominal values, so chains built to the Standard by any manufacturer engage standard sprockets correctly; as in other B29 standards, link-level interconnectability is generally guaranteed only within one manufacturer and chain number.

3. Attachments 🧩

To adapt to conveying operations, the Standard provides dimensions and mounting requirements for common attachment types:

K-type attachments: one-side or two-side bent plates for scrapers and pusher plates.
A/D-type straight plates: with mounting holes for buckets, hangers, or cross beams.
Extended-pin attachments: extended pins for cross-rods or wheels.

Attachments usually replace ordinary link plates with special plates; hole positions and dimensions are standardized so products from different manufacturers remain interchangeable.

🚨 Fitted attachments change the link stress state and introduce bending moments; check the attachment holes, plates, and pins for strength including a shock/impact factor — do not merely divide the base chain strength by a safety factor.

4. Sprocket Engagement and Lubrication ⚙️

Rollerless chain sprockets contact the bushings in sliding engagement; tooth count, pitch circle, and tooth form follow pitch and tooth count calculations. To avoid interference and loss of engagement, the sprocket face width and tooth thickness must match the bushing outside width and link plate spacing. For lubrication:

Method: at low speed, periodic grease application or drip oiling is typical; both journal pairs — bushing/pin and bushing/sprocket tooth — need lubrication.
Speed limit: speeds are generally far below roller chain; at higher linear speeds bushing wear and temperature climb steeply.
Tension: maintain a moderate slack-side sag to prevent disengagement and impact.

💡 Lubrication is the cheapest way to extend rollerless chain life: the sliding contact between sprocket teeth and the bushing outside diameter wears several times faster when unlubricated; establish a periodic lubrication routine for low-speed heavy-duty service.

5. Engineering Practice Essentials 🛠️

Selection workflow: determine conveying rate/lift height → compute chain tension including acceleration and shock → select the chain number from M.U.T.S. with a safety factor → verify speed is within rollerless-chain range → match attachments and sprockets.
Length verification: pre-stretch and measure under the measuring load; twin parallel strands must be equal in length to avoid uneven loading.
Installation: align sprocket faces and keep shaft parallelism within tolerance; secure connecting-link locks.
Maintenance: periodically check bushing wear (pitch elongation), link plate cracking, pin bending, and attachment bolt looseness.

6. Frequently Asked Questions ❓

❓ Q: What is the essential difference between B29.3 rollerless chain and roller chain?
A: In a rollerless chain the sprocket teeth slide directly on the bushing outside diameter, and there are no rollers; construction is simpler, cost and weight lower, but speed and life are below roller chain — ideal for low-speed heavy conveying.

❓ Q: How should the top linear speed of a rollerless chain be controlled?
A: Keep it within roughly 1–3 m/s depending on size and lubrication; outside that range, switch to roller chain or bushed roller chain and re-check.

❓ Q: Why must chain length be measured under the measuring load?
A: A chain’s length differs by several pitches between no tension and measuring tension; only measurement under the specified load makes length acceptance and elongation checks comparable.

❓ Q: Can attachment links be mixed with ordinary links from another manufacturer?
A: The Standard guarantees only interchangeability dimensions on sprockets; interconnectability between manufacturers is not assured — use the same manufacturer and chain number for the whole chain for consistent wear and fitting.