CMI Arborist Rigging Block, 1"

The CMI arborist rigging block in the 1 inch size is a full-size block for heavy removal rigging, made to accept rope up to the large diameters crews use for blocking down big wood. It hangs from a sling at the rigging point and gives the lowering line a smooth, strong path.

Where a full-size block fits

A rigging block takes the lowering line through a strong, large sheave at the rigging point so the load comes down under control and friction is managed at the porta-wrap instead of on the tree. A 1 inch block is made for heavy rigging where crews run big rope and block down large wood.

Hang it with a sling rated for the job, high and close to the stem, and keep the line running straight into the sheave. Compare sizes in our rigging blocks before choosing.

A block also protects the rope. Running a heavy lowering line over a bare crotch burns the bark and the rope, while a sheave lets the line move cleanly and puts the friction where the ground worker can control it.

Ratings and inspection

Read the block's marked rating and remember the force on a rigging point can be close to double the load on the line when the rope runs back down the tree. Plan with that in mind and use slings, rope, and lowering devices that match.

Before each job, check the sheave for smooth spin and wear grooves, the side plates for cracks or bends, and the axle and bushings for play. Retire the block if it has taken a severe shock load. Rigging should follow ANSI Z133.

Keep a record of the block's service history, especially any big shock loads, so the crew knows its condition.