The Crosby Q-681-Z is a galvanized bronze bushed steel sheave block assembled with a bolt-type anchor shackle. It combines the weight of a regular oval block with the strength of an extra-heavy oval block, and runs on a self-lubricated bronze bushing fed by a pressure lube fitting in the center pin. Part of the Q-681-Z / Q-682-Z / Q-683-Z (single / double / triple sheave) line.
Key Features
- Galvanized steel construction
- Self-lubricated bronze bushing
- Pressure lube fitting in the center pin
- Assembled with bolt-type anchor shackle
- Side plates rounded to add stiffness and reduce rope wear/chafing
- Working Load Limit (single sheave): 3 short tons (6 in block) up to 4 short tons (8 in / 10 in blocks)
- For 3/8 in to 5/8 in wire rope depending on block size
- Ultimate load is 4 times the Working Load Limit (4:1 design factor)
Common Applications
- General wire rope rigging and rope-handling
- Block-and-tackle systems requiring single, double, or triple sheaves
Safety & Standards
Every product we carry is individually marked with Working Load Limit (WLL), manufacturer traceability code, and country of origin. Inspection and mill certificates are available on request — email sales@slingcenter.com with your order number.
Governing Standards
- ASME B30.9 — slings (web, round, wire rope, chain) inspection and use
- ASME B30.26 — rigging hardware (shackles, eye bolts, links, turnbuckles)
- ASME B30.10 — hooks
- OSHA 1910.184 and 1926.251 — general industry and construction sling safety
- WSTDA WS-2 and RS-1 — web and round sling design
- 49 CFR 393.102 to 393.130 — DOT cargo tie-down
- NACM — welded steel chain grade specs
Inspection & Safety
Before every use: visual check for cracks, corrosion, distortion, wear, and illegible markings. Annually (minimum): documented periodic inspection by a trained inspector. Remove from service at first sign of damage. Never repair rigging hardware by welding, heating, or bending.
WARNING: Improper use of rigging can cause death or serious injury. Never exceed the rated Working Load Limit. Apply derating for side-loading, elevated temperature, or chemical exposure. Final application decisions must be made by a Qualified Person per OSHA 1926.32(m).
Specifications — Full Dimensions by Size
Request datasheet
| Size (in)(mm) | WLL (t)(t) | Design Factor | Weight (lb)(kg) | Stock # |
|---|---|---|---|---|
| 6152.4 | 3 tons | 4:1 | 156.8 | 760441 |
| 6152.4 | 3 tons | 4:1 | 167.26 | 760452 |
| 8203.2 | 4 tons | 4:1 | 2913.15 | 760463 |
| 10254.0 | 4 tons | 4:1 | 3817.24 | 760474 |
Dimensions and ratings sourced directly from manufacturer catalog pages. SlingCenter does not derive or restate ratings.
Order Sheet — 4 variants
Search below or click column headers to sort. Add any quantity per row to your cart.
| Option ▴▾ | SKU ▴▾ | Price ▴▾ | Stock | Qty | Add |
|---|---|---|---|---|---|
| BLK Q-681-Z 6 IN OL GL SEA LP 3T 3/8 L | 760441 | $888.00 | ✓ In Stock | ||
| BLK Q-681-Z 6 IN OL GL SEA LP 3T 1/2 L | 760452 | $888.00 | ✓ In Stock | ||
| BLK Q-681-Z 8 IN OL GL SEA LP 4T 5/8 L | 760463 | $1,272.00 | ✓ In Stock | ||
| BLK Q-681-Z 10 IN OL GL SEA LP 4T 5/8 L | 760474 | $1,605.00 | ✓ In Stock |
Bulk order? Email sales@slingcenter.com with your list — we'll build a single quote.
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