Bushing Selection Guide
Bushing Selection Guide
Every QD sheave, many timing belt sprockets, and some couplings require a bushing to mount to the shaft. The bushing is the critical link between the shaft and the drive component. Get the wrong bushing type, wrong size, or wrong installation procedure and the drive will slip, vibrate, or fail. This guide walks through bushing selection and installation in order, covering both QD and Taper Lock systems.
1 Identify Your Bushing System
The first step is determining whether your equipment uses QD or Taper Lock bushings. The two systems are not interchangeable. Look at the hub of your existing sheave or sprocket:
| Feature | What You See |
|---|---|
| QD Hub | Flat flange face with 2 or 3 cap screw holes arranged around a smooth, tapered bore opening. No visible split in the hub body. The bushing is a separate piece that sits inside this bore. |
| Taper Lock Hub | A visible split (slit) running along the hub body. Draw screws on the flange face. The hub itself has a tapered bore, and the bushing compresses into it. The split is the key visual identifier. |
If the sheave or sprocket has a part number visible, you can also look it up in the manufacturer's catalog to confirm the bushing type. Or send us a photo of the hub and we will identify it for you.
2 Determine the Bushing Size
QD Bushing Sizing
QD bushings are identified by a letter code (SH, SDS, SD, SK, SF, E, F, J, M, N, P, W, S). The sheave or sprocket determines which letter size it accepts. You then select the bushing with that letter and the bore matching your shaft diameter.
Where to find the letter size: Check the sheave/sprocket part number, product listing, catalog page, or markings stamped on the hub. Example: a sheave marked "Requires SD bushing" or a part number containing "SD" means you need an SD bushing.
| QD Size | Bore Range |
|---|---|
| SH | 3/8" to 1-1/8" |
| SDS | 1/2" to 1-5/8" |
| SD | 1/2" to 2-1/8" |
| SK | 3/4" to 2-7/16" |
| SF | 3/4" to 3-3/16" |
| E | 1" to 3-15/16" |
| F | 1-3/16" to 4-15/16" |
| J | 1-7/16" to 5-15/16" |
| M | 2-1/16" to 7-7/16" |
| N | 2-15/16" to 8-15/16" |
| P, W, S | Up to 12"+ |
Taper Lock Sizing
Taper Lock bushings use a four-digit series number (1008, 1108, 1210, etc.). The sheave or sprocket determines which series it accepts. Select the bushing in that series with the bore matching your shaft.
| Series | Bore Range |
|---|---|
| 1008 | 1/2" to 1" |
| 1108 | 1/2" to 1-1/8" |
| 1210 | 1/2" to 1-1/2" |
| 1610 | 1/2" to 1-5/8" |
| 2012 | 1/2" to 2" |
| 2517 | 5/8" to 2-1/2" |
| 3020 | 3/4" to 3" |
| 3525 | 1" to 3-1/2" |
| 4040 | 1-1/4" to 4" |
| 4545 | 1-1/2" to 4-1/2" |
| 5050 | 1-3/4" to 5" |
Both QD and Taper Lock are available in metric bores. Specify your shaft diameter in millimeters when ordering.
3 QD vs. Taper Lock: Which System to Use
If you are replacing a bushing on existing equipment, use whichever system the equipment already has. If you are specifying bushings for new equipment or have a choice, use this guide:
| Factor | Recommendation |
|---|---|
| North American equipment | QD is the standard. Most sheaves and sprockets sold in North America have QD hubs. |
| European equipment | Taper Lock is the standard. Most imported European machinery uses Taper Lock hubs. |
| Metric shafts | Taper Lock has broader metric bore availability. Preferred when metric precision matters. |
| Stainless steel needed | Taper Lock. Stainless steel QD bushings are generally not available. Taper Lock stainless is standard for food, pharma, and washdown. |
| Largest bore range | QD. Bores up to 12"+ vs. Taper Lock up to 5". |
| Fastest maintenance | Both systems are fast. QD's push-off removal is slightly simpler. Either is far faster than press-fit or fixed bore. |
4 Installation Procedures
QD Bushing Installation
4a. Clean the shaft, bushing bore, bushing taper, and hub taper. Remove all dirt, rust, burrs, and old lubricant.
4b. Do not apply any lubricant to the taper surfaces. QD bushings rely on dry metal-to-metal friction to grip. Oil, grease, or anti-seize on the taper will cause slippage.
4c. Place the bushing into the hub with cap screw holes aligned. Slide the assembly onto the shaft at the correct position for belt alignment.
4d. Insert the cap screws into the tapped holes and tighten alternately in quarter-turn increments until all reach specified torque.
4e. Re-torque after 2 to 4 hours of operation.
Taper Lock Installation
4a. Clean the shaft, bushing bore, and hub taper. Remove all dirt, rust, and burrs.
4b. Apply a light film of oil to the outer taper surface of the bushing. This helps the taper seat evenly and eases future removal. Use light machine oil, not heavy grease.
4c. Insert the bushing into the hub with half-holes aligned to form complete screw holes. Slide the assembly onto the shaft.
4d. Insert the draw screws and tighten alternately in quarter-turn increments until all reach specified torque. The bushing will compress onto the shaft as the taper seats.
4e. Re-torque after 2 to 4 hours of operation.
5 Torque Specifications
QD Bushing Torque
| QD Size | Torque (ft-lbs) |
|---|---|
| SH | 6 |
| SDS | 8 |
| SD | 15 |
| SK | 15 |
| SF | 30 |
| E | 50 |
| F | 50 |
| J | 75 |
| M | 100 |
| N | 150 |
| P, W, S | Refer to manufacturer specs |
Taper Lock Draw Screw Torque
| Series | Torque (ft-lbs) |
|---|---|
| 1008 | 5.8 |
| 1108 | 5.8 |
| 1210 | 5.8 |
| 1610 | 9 |
| 2012 | 18 |
| 2517 | 18 |
| 3020 | 31 |
| 3525 | 50 |
| 4040 | 80 |
| 4545 | 80 |
| 5050 | 136 |
6 Removal Procedures
QD Removal
6a. Remove all cap screws from the tapped holes.
6b. Thread the cap screws into the push-off (jacking) holes. These are the unthreaded holes that were empty during installation.
6c. Tighten alternately. The screws push the bushing out of the hub taper.
6d. Slide the assembly off the shaft. No pullers needed.
Taper Lock Removal
6a. Remove all draw screws from the draw holes.
6b. Thread one or more screws into the extraction (jacking) hole(s). These are separate holes marked for removal.
6c. Tighten to push the bushing free from the hub taper.
6d. Slide the assembly off the shaft.
If either bushing type is stuck, apply penetrating oil around the taper joint and allow it to soak for several hours before retrying. Do not use hammers or pry bars on the bushing or hub.
Common Bushing Mistakes
| Mistake | What Happens |
|---|---|
| Oiling a QD taper | Bushing slips on the shaft under load. Sheave spins on the shaft. Belt misaligns and fails. The most common QD installation error. |
| Installing Taper Lock dry | Taper galls (metal-to-metal seizure). Bushing becomes extremely difficult to remove later. May require cutting the bushing off. |
| Wrong bushing type for the hub | QD bushing in a Taper Lock hub (or reverse). Bushing will not seat. Drive cannot be assembled safely. |
| Wrong bore size | Bushing too loose: wobble, vibration, and the sheave may walk off the shaft. Bushing too tight: cannot slide onto the shaft. Always measure the shaft diameter before ordering. |
| Skipping re-torque | Screws loosen during initial run-in. Bushing grip weakens. Sheave shifts on the shaft, causing misalignment and belt tracking problems. Re-torque after 2 to 4 hours. |
| Over-torquing | Can crack the bushing hub or strip screw threads. Always use a torque wrench and follow the specified values. |
| Dirty taper surfaces | Dirt, rust, or old lubricant on the taper prevents proper seating. The bushing may feel tight during installation but slip under load. Always clean both surfaces before assembly. |
| Reusing damaged bushings | Scored, cracked, or deformed bushings will not grip reliably. Replace damaged bushings. They are inexpensive compared to the cost of a drive failure. |
Related Pages
Frequently Asked Questions
How do I tell if my equipment uses QD or Taper Lock bushings?
Look at the hub. QD hubs have a flat flange face with cap screw holes around a smooth tapered bore. Taper Lock hubs have a visible split (slit) along the hub body with draw screws on the flange. If you cannot tell from looking, send us a photo and we will identify it.
Can I switch from QD to Taper Lock (or vice versa)?
Not without replacing the sheave or sprocket. The bushing type is built into the hub design. If you want to switch systems, you need a new sheave or sprocket with the other hub type, plus the matching bushing. Contact us if you need help finding the equivalent component in the other system.
Do I oil a QD bushing or a Taper Lock bushing?
Taper Lock: yes, apply a light film of oil to the outer taper surface. QD: no, install completely dry. This is the most critical difference between the two installation procedures. Oiling a QD taper causes slippage. Installing a Taper Lock dry causes galling.
How do I measure my shaft for the correct bore?
Use a micrometer or caliper to measure the shaft diameter at the point where the bushing will sit. Measure in two directions (90 degrees apart) to check for out-of-round. The shaft should be within the bushing bore tolerance. For keyed shafts, measure the shaft diameter (not including the key) and confirm the key width matches the bushing keyway. Standard English bores increase in 1/8" increments. Metric bores are specified in millimeters.
My bushing is stuck. How do I remove it?
First, make sure the cap screws (QD) or draw screws (Taper Lock) are threaded into the correct jacking/extraction holes. If the bushing still will not release, apply penetrating oil around the taper joint and let it soak for several hours or overnight. Then try the extraction screws again. Do not use hammers, pry bars, or heat on the bushing or hub, as these can crack the casting or damage the shaft.
Can I reuse an old bushing?
Yes, if the bushing is not damaged. Inspect for cracks, scoring on the taper surfaces, deformed keyway, and stripped screw threads. If any damage is present, replace the bushing. Bushings are inexpensive relative to the cost of a sheave or sprocket, so replacing a questionable bushing is always good practice.
Where can I find the torque spec for my bushing?
Torque specs for all QD letter sizes and Taper Lock series are listed in the tables above on this page. They are also printed in manufacturer catalogs and on the bushing packaging. When in doubt, use the values in this guide or contact us for confirmation.