MartinSF-2-13/16QD Split Taper Bushing, SF Size, 2-13/16 in Keyed Bore, Flanged

Product Description

What this part is

A Martin SF-2-13/16 QD split taper bushing — SF bushing size, 2-13/16 in finished bore with keyway. A QD bushing is the taper adapter that clamps a sheave, sprocket, coupling or drum onto a shaft: the bushing barrel is tapered and split, and drawing it into the mating tapered bore squeezes it onto the shaft so the drive component runs concentric and can be removed again without a press.

Decoding the designation

SF – QD bushing size designation, which sets the taper envelope, flange diameter and bolt circle
2-13/16 – finished bore, 2-13/16 in, keyed
Split flange and split barrel, the defining feature of a QD bushing

What these specs mean in practice

The bushing size and the bore are two separate matching problems. The SF size has to match the bushing bore of the sheave or sprocket — an SF bushing does not fit an SK, SD or E bored component, whatever the shaft size. The 2-13/16 in bore has to match the shaft. Because the barrel is split, tightening the capscrews closes the split and produces a genuine clamp on the shaft rather than relying on a setscrew, so the drive holds torque without marring the shaft, and the whole assembly comes off again by moving the capscrews into the pull-off holes.

Published specifications

Bushing size: SF (QD system)
Bore: 2-13/16 in (71.44 mm), finished with keyway
Construction: flanged, split barrel and split flange
Mounting system: QD (Quick Detachable) tapered bushing
Material: cast iron / steel bushing body

Quantity and configuration

Sold as 1 Pc. The bushing only. No sheave, sprocket, coupling, drum or shaft key is included.

Fitting notes

The bushing goes into the tapered bore of the driven component and the capscrews pass through the flange into the component, drawing the taper up. Threads and taper faces are cleaned dry, since lubricant on the taper causes overtightening and can split the hub. Tightening is done progressively and evenly around the bolt circle, and the bushing is re-checked after the first run under load. Removal reverses the process: the capscrews move into the tapped pull-off holes and jack the taper apart.

Interchange guidance

The direct equivalent is any SF-size QD bushing with a 2-13/16 in bore — the QD system is a common industry standard, so Martin, TB Wood’s, Browning, Dodge and Gates SF bushings of the same bore interchange. Adjacent QD sizes such as SK, SD, E and F share the system but have different taper envelopes and bolt circles, so those are different parts, not alternatives. A taper-lock bushing (1610, 2012, 3020 series) is a different clamping system altogether and does not fit a QD-bored component.