Martin QD Bushing: Features, Sizes and Replacement | CTS
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- Sep 28,2026
Summary
Martin QD bushings are standard quick-disconnect bushings, not proprietary parts. Learn the features, the JA to S sizes, and how to cross reference and replace a Martin QD bushing.
About Browning Split Taper Bushing
Martin is one of the names maintenance teams in the United States reach for when they order a QD bushing, and a Martin QD bushing is a standard flanged bushing rather than a proprietary part. If the bushing in your machine is stamped Martin and carries a type letter such as SK or SDS, the part that has to come out is a stock QD bushing of that letter and bore. This guide covers what a Martin QD bushing is, the features that decide whether a replacement will hold, the full JA to S size range, and how to cross-reference the old part and fit a replacement in a few minutes.
A QD bushing is drawn into the tapered hub bore by its cap screws: the flange stays outside; the taper does the gripping.
What a Martin QD bushing is
QD stands for quick disconnect, and the name describes how the bushing works rather than who makes it. A QD bushing is a short flanged sleeve with a tapered outside diameter and a key-seated bore. Cap screws pass through the flange and pull the bushing into the matching taper in the hub, which closes it onto the shaft and locks the whole assembly together. To release it, the same cap screws are moved into threaded removal holes and the bushing backs itself out of the hub. No press, no heat, no puller.
Martin Sprocket & Gear supplies QD bushings under the same letter codes as the rest of the industry: JA, SH, SDS, SD, SK, SF, E, F, J, M, N, P, W and S. That is the point. The letters are a dimensional standard, not a brand series, so a Martin QD bushing and any other QD bushing of the same letter and bore are built to the same bolt circle, flange diameter, taper, keyseat, and cap screw size.
Features of a Martin QD bushing worth checking
When you replace one, these are the features that matter, because each of them has to match the bushing that came out:
Flanged, quick-disconnect body. The flange carries the cap screws and the removal holes, so installation and removal both happen from the flange side of the hub.
Three to five cap screws. Most types use three; the larger M and N types use four, and the S type uses five. The screw size is fixed by the type letter.
Single split. The split runs along one side of the bushing so the taper can close onto the shaft as the screws are tightened.
Tapered outside diameter. The taper is what creates the grip and the concentricity, and it has to match the taper already machined into your hub.
Keyseated bore. Standard, shallow keyway and no-keyway bores are offered for the same letter, and they are different stock items.
Cast iron or steel. Standard bushings are cast iron; steel is used for higher shock or reversing loads where the specification calls for it.
Inch or metric bores. Stock inch bores cover the common shafts, while metric and special bores are machined to your drawing or to a measured shaft.
Martin QD bushing sizes, JA to S
Every QD type letter carries a fixed bolt circle, cap screw size, and stock bore range, and Martin uses the same letters. In the table below, a Martin bushing of a given letter and bore and a CTS bushing of the same letter and bore are dimensionally interchangeable. The bore ranges shown are the standard keyway stock ranges.
| Type | Stock bore range (in) | Bolt circle (in) | Cap screws |
|---|---|---|---|
| JA | 3/8 – 1 | 1-21/32 | 3 × 10-24 |
| SH | 1/2 – 1-3/8 | 2-1/4 | 3 × 1/4-20 |
| SDS | 1/2 – 1-11/16 | 2-11/16 | 3 × 1/4-20 |
| SD | 1/2 – 1-11/16 | 2-11/16 | 3 × 1/4-20 |
| SK | 1/2 – 2-1/8 | 3-5/16 | 3 × 5/16-18 |
| SF | 1/2 – 2-1/4 | 3-7/8 | 3 × 3/8-16 |
| E | 7/8 – 2-7/8 | 5 | 3 × 1/2-13 |
| F | 1 – 3-5/16 | 5-5/8 | 3 × 9/16-12 |
| J | 1-7/16 – 3-3/4 | 6-1/4 | 3 × 5/8-11 |
| M | 1-15/16 – 4-3/4 | 7-7/8 | 4 × 3/4-10 |
| N | 2-7/16 – 5 | 8-1/2 | 4 × 7/8-9 |
| P | 2-15/16 – 5-15/16 | 10 | 4 × 1-8 |
| W | 4 – 7-1/2 | 12-3/4 | 4 × 1-1/8-11.5 |
| S | 6 – 8-1/4 | 15 | 5 × 1-1/4-15.5 |
Shallow keyway and no-keyway bores extend past the stock range for the same letter, and inch or metric specials are machined to your drawing or to a measured shaft. Wrench torques, weights, and dimension drawings for every type are on the QD bushing page, and the bore and bolt circle data above are the same set published in our QD bushing sizes and series reference.
Is a CTS QD bushing a Martin QD bushing replacement?
What we claim, and what we do not
CTS QD bushings are 100% dimensionally interchangeable with the equivalent QD bushings from Martin, Dodge, Browning and TB Wood's. That claim covers the fit: bolt circle, taper, keyseat, bore and cap screws, so a CTS bushing drops into the hub a Martin bushing came out of. It does not claim the same casting source, the same material grade or the same service life, and no supplier can honestly guarantee a life figure without knowing your load, speed and environment. CTS is an independent manufacturer and is not affiliated with, authorised by or endorsed by Martin. Material and inspection certificates are available on request so you can compare them against your own specification.
What to check before you commit to a replacement
QD bushings are the everyday mounting method for chain sprockets on reducers and drive shafts, V-belt sheaves and pulleys, conveyors, bucket elevators, fans and blowers, mixers and agitators, pumps, packaging and food lines, and agricultural machinery, where a worn bushing is often swapped in the field. CTS supplies them to OEM builds, MRO spares and distributor stock in cast iron and steel, with export packing and rust protection for sea and air freight. If you are replacing a Martin bushing on an existing hub, the type letter and the bore are the whole cross reference, and the rest is a standard stock part.
FAQs
Can I replace a Martin QD bushing with a CTS bushing?
Yes. In the same type and bore, a CTS QD bushing is dimensionally interchangeable with a Martin QD bushing, so it fits the hub the old bushing came out of and comes out again with the same cap screws. Send the part number from the old bushing, and we will confirm the match before you order.
What if the stamping on the Martin bushing is worn or missing?
Measure the outside diameter, the bolt circle and the bore, and count the cap screws. Send those numbers with a photo of the bushing and the hub, and the type can usually be identified from the standard dimensions alone.
Can I buy a single replacement bushing, and is there a minimum order?
Popular types and bores are held in stock and ship with no minimum order, so one replacement bushing is a normal order. Sizes that are not on the shelf are machined to your drawing, sample or shaft dimensions, including inch and metric bores and special keyways.
Trademarks: Martin®, Dodge®, Browning®, TB Wood's® and Taper-Lock® are trademarks of their respective owners. CTS is not affiliated with, authorised by, sponsored by or endorsed by these companies. Brand names and part numbers of other manufacturers are used only to identify the equipment that our products are dimensionally interchangeable with. All other trademarks are the property of their respective owners.