Dodge SK QD Bushing, Keyed, Three-Bolt Flanged, Ductile Iron

Genuine Dodge SK series QD bushings in ductile iron, supplied with keyseat. The SK is the workhorse QD size on compressor and industrial V-belt drives: a three-bolt flanged bushing rated 7,000 lb-in, with a 4 degree tapered bore that pulls tight onto the shaft as the three cap screws are drawn down. It mounts and dismounts without a puller and holds the sheave dead concentric.

Three stock bores are listed here: 1-3/8 in. (Dodge 120427), 1-5/8 in. (Dodge 120431) and 1-7/8 in. (Dodge 120435). Pick the bore that matches your shaft.

Key specifications

• Series: Dodge SK, QD standard
• Torque rating: 7,000 lb-in
• Hardware: three 5/16-18 x 2 in. cap screws, supplied with the bushing
• Installation torque: 180 lb-in. Do not exceed it. Over-torquing a QD bushing cracks the sheave hub
• Flange outside diameter: 3.88 in.  |  Flange thickness: 0.50 in.  |  Bolt circle: 3.31 in.
• Barrel diameter: 2.81 in.  |  Length through bore: 1.88 in.
• Minimum hub diameter: 4.75 in. in class 30 cast iron, 4.50 in. in steel
• Bore range for the series: 1/2 in. minimum. In ductile iron, 2-1/2 in. maximum with a full or shallow keyway and 2-5/8 in. unkeyed
• Taper: 4 degrees. Mounts conventionally or reversed
• Material: ductile iron

Bore, keyway and weight by size

• 1-3/8 in. bore (120427): keyseat 5/16 x 5/32 in., 5/16 in. square key. 3.12 lb
• 1-5/8 in. bore (120431): keyseat 3/8 x 3/16 in., 3/8 in. square key. 2.86 lb
• 1-7/8 in. bore (120435): keyseat 1/2 x 1/4 in., 1/2 in. square key. 2.50 lb

Note that catalogs often print the keyseat dimension and the square key size interchangeably. They are different numbers. The keyseat is the slot cut in the bushing bore; the key is the square stock that fills it together with the shaft keyway.

Fitment

SK bushings fit any sheave, sprocket, timing pulley or coupling hub bored for the SK QD size. They are not interchangeable with the smaller SD bushing, nor with the two-screw Type H bushing used in bushed fractional-horsepower sheaves, even though all three are flanged tapered bushings. Check what your hub is bored for before ordering. SK is called SK by every major maker, so there is no cross-brand letter to translate.

Installation

Wipe the taper and the hub bore clean and dry. Do not use anti-seize, oil or any lubricant on the mating taper surfaces, which makes the bushing over-advance and crack the hub. Line up the keyways, start all three cap screws, then tighten them in rotation to 180 lb-in. Recheck after a few hours of running, and again after the first belt re-tension.

QD is a registered trademark of Emerson Electric. Not sure which bushing your sheave takes? Send us the sheave part number or a photo of the hub and the Warthog Air Compressor Store team will confirm before you order.