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.
Related guides: V-Belt Drive Design
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
Before starting: Shut down and lock out the equipment. Support heavy or vertical assemblies against falling. Use the current instructions for the exact bushing and mating component; this overview does not replace them.
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. Keep the bore and shaft dry as well. Lubrication can cause hub fracture; prepare the cap screws only as the exact product instructions specify.
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. Use the manufacturer's installation-hole pattern for conventional or reverse mounting. Tighten the cap screws alternately, check alignment, and stop at the specified torque. Do not tighten further to close the designed flange-to-hub gap.
4e. Follow the product manufacturer's run-in and torque-check schedule, with the equipment locked out.
Taper Lock Installation
4a. Clean all oil, dirt, paint and burrs from the shaft, bushing bore, outside taper and hub bore.
4b. Keep the bushing taper, hub taper, bore and shaft clean and dry. Oil, grease and anti-seize on these surfaces can cause hub or bushing breakage.
4c. Match the half-hole pattern and use the installation holes shown in the product instructions. Prepare the screws only as that manual specifies; Dodge MN4044 and the Gates PowerGrip GT3 Taper-Lock procedure specify lightly oiling the screws, not the mating surfaces.
4d. Fit the specified key, position the assembly, allow for axial movement during tightening, and check alignment. Tighten screws alternately with a torque wrench to the exact product specification.
4e. Complete any seating and re-torque steps required by that manufacturer. Check torque after initial run-in and at the specified maintenance intervals, with the equipment locked out.
5 Torque Specifications
Use the current torque specification for the exact assembly. A bushing series alone is not enough to choose a safe value. Identify the manufacturer, bushing part number, mating sheave/sprocket/coupling and supplied screw size and grade.
| Before tightening | What to confirm |
|---|---|
| Correct manual | Match the bushing and mating component, including any application-specific instructions. |
| Torque and units | Read the installation screw torque, not the assembly's torque capacity. Confirm whether the value is in lb-in, lb-ft or N·m. |
| Screw condition | Use the specified screws and preparation. A value for one lubrication condition is not automatically valid for another. |
| Final checks | Follow the prescribed tightening, seating, alignment and run-in checks. Do not exceed the specified torque. |
Unverified universal torque values are not provided here. If the instructions are missing or disagree, stop and contact us with the exact part numbers before installation.
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. Use the threaded removal holes identified in the exact product's mounting diagram; do not confuse them with clearance holes.
6c. Tighten alternately. The screws push the bushing out of the hub taper.
6d. Support the released assembly and remove it from the shaft according to the product instructions.
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.
With the equipment locked out and the assembly supported, use the manufacturer's specified jacking holes and removal sequence. If it will not release, stop and seek product-specific help. Do not improvise with heat, pry bars or direct hammer blows. Any approved removal treatment must be cleaned off before reinstallation.
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. |
| Oiling Taper Lock mating surfaces | Lubricant on the taper, bore or shaft can cause hub or bushing breakage. Keep these surfaces clean and dry. |
| 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. Follow the manufacturer's run-in and periodic torque checks. |
| 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?
Keep QD and Taper Lock mating tapers, bores and shafts clean and dry. Screw preparation is product-specific: follow the exact manufacturer's instructions. A direction to lightly oil screws does not mean oiling the taper.
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?
With the equipment locked out and the assembly supported, use the manufacturer's specified jacking holes and removal sequence. If it will not release, stop and seek product-specific help. Do not improvise with heat, pry bars or direct hammer blows. Any approved removal treatment must be cleaned off before reinstallation.
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?
Use the current manufacturer instructions for your exact bushing and mating component. Confirm screw specification, preparation and torque units. Do not substitute a generic series-based value. Contact us with the part numbers if you need help.