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Black oxide steel sprocket, 21 teeth, 5/8 inch bore

Tsubaki

Tsubaki 40B21 Sprocket 40 Chain 5/8 Bore 21 Teeth collectible

SKU CH-QBK1-DA0BW

Steel chain sprocket with 21 teeth, 5/8 inch bore, and black oxide finish

  • TypeBearings, V-belts & Power Transmission Equipment
  • ColorTransparent
  • Precision 21-tooth profile engages chain cleanly
  • 5/8 in plain bore with keyway fits shafts securely
  • Grade 1045 steel resists wear under load
  • Black oxide finish protects against corrosion
  • Includes set screws for immediate installation

Tsubaki 40B21 Sprocket for Chain Drive Systems

The Tsubaki 40B21 is a steel sprocket designed for number 40 roller chain with a 1/2 in pitch. It features 21 teeth, a 5/8 in plain bore and a black oxide finish. This component suits maintenance teams and machinery builders replacing worn drive parts on conveyors or industrial equipment.

Includes Set Screws and Keyway for Secure Mounting

The sprocket ships with set screws and a machined keyway measuring 3/16 in wide by 3/32 in deep. These features lock the hub to a keyed shaft without additional machining. The one-sided hub projects .716 in and measures 2 3/4 in in diameter, keeping the assembly compact.

Plain Bore Limits Shaft Compatibility to 5/8 in

The 5/8 in plain bore fits only shafts of that exact diameter; larger or smaller shafts cannot be used. Maximum bore capacity is 1 7/8 in, but the supplied bore is fixed. Grade 1045 steel construction handles typical chain loads, yet the single-strand design excludes multi-strand drive configurations.

Highlights

  • Precision 21-tooth profile engages chain cleanly
  • 5/8 in plain bore with keyway fits shafts securely
  • Grade 1045 steel resists wear under load
  • Black oxide finish protects against corrosion
  • Includes set screws for immediate installation

Specifications

BrandTSUBAKI
TypeBearings, V-belts & Power Transmission Equipment
ColorTransparent

Questions about this item

How often will the 1045 steel sprocket need replacement under continuous operation?

The 1045 carbon steel construction resists wear on the 21 teeth, but replacement timing depends entirely on chain tension, lubrication schedule, and load cycles in your specific drive.

What limits the 40B21 sprocket first during sustained high-speed use?

The 3.355 in pitch diameter and 1 in length through bore define the contact area; tooth fatigue or chain stretch will appear before the 2 3/4 in hub reaches its stress limit.

Does the black oxide finish on the 3.62 in outside diameter reduce heat buildup during all-day running?

Black oxide mainly prevents corrosion; it does not significantly change thermal dissipation, so heat will follow chain speed, tension, and ambient airflow rather than the finish.

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