What a taper lock bushing actually does
A taper lock bushing is the interchangeable hub between a shaft and a driven component. The bushing has an 8-degree tapered outside diameter and a straight bored inside. Two or three screws pull it into the mating taper of a pulley, sprocket or coupling, and that wedge action clamps the shaft without any machining, keyway cutting or press fit.
The practical benefit is serviceability. One bushing size accepts a range of shaft bores, so a stock pulley can fit several different shafts, and a worn or damaged component can be swapped without touching the shaft. That is why almost every fractional-horsepower through heavy-duty drive you will find on a plant floor is bushed rather than bored-to-suit.
How the four-digit number works
Bushing sizes run from 1008 up to 7060, and the number is a shorthand rather than a part code.
- The first pair of digits loosely tracks the maximum bore in inches.
- The second pair tracks the bushing length in tenths of an inch.
So a 1008 is roughly a 1-inch-maximum, 0.875-inch-long bushing, and a 5050 is a 5-inch-maximum, 5-inch-long bushing. Treat this as a memory aid, not a formula. The 3030 is the clearest warning against leaning on it: its standard-keyseat maximum bore is 2.750 inches, not 3.000 inches. The chart below is the authoritative reference.
Taper lock bushing size chart, 1008 through 7060
Bore ranges, torque capacity, length and mounting screws by bushing size.
| Bushing | Min bore (in) | Max bore, standard keyseat (in) | Max bore, shallow keyseat (in) | Torque capacity (lb-in) | Length B (in) | Mounting screws |
|---|---|---|---|---|---|---|
| 1008 | 0.500 | 0.875 | 1.000 | 1,200 | 0.875 | 2 × 1/4 x 1/2 |
| 1108 | 0.500 | 1.000 | 1.125 | 1,300 | 0.875 | 2 × 1/4 x 1/2 |
| 1210 | 0.500 | 1.250 | — | 3,600 | 1.000 | 2 × 3/8 x 5/8 |
| 1215 | 0.500 | 1.250 | — | 3,550 | 1.500 | 2 × 3/8 x 5/8 |
| 1310 | 0.500 | 1.375 | 1.438 | 3,850 | 1.000 | 2 × 3/8 x 5/8 |
| 1610 | 0.500 | 1.500 | 1.688 | 4,300 | 1.000 | 2 × 3/8 x 5/8 |
| 1615 | 0.500 | 1.500 | 1.688 | 4,300 | 1.500 | 2 × 3/8 x 5/8 |
| 2012 | 0.500 | 1.875 | 2.125 | 7,150 | 1.250 | 2 × 7/16 x 7/8 |
| 2517 | 0.500 | 2.250 | 2.688 | 11,600 | 1.750 | 2 × 1/2 x 1 |
| 2525 | 0.750 | 2.250 | 2.500 | 11,300 | 2.500 | 2 × 1/2 x 1 |
| 3020 | 0.875 | 2.750 | 3.250 | 24,000 | 2.000 | 2 × 5/8 x 1-1/4 |
| 3030 | 0.938 | 2.750 | 3.250 | 24,000 | 3.000 | 2 × 5/8 x 1-1/4 |
| 3525 | 1.188 | 3.250 | 3.938 | 44,800 | 2.500 | 3 × 1/2 x 1-1/2 |
| 3535 | 1.188 | 3.250 | 3.938 | 44,800 | 3.500 | 3 × 1/2 x 1-1/2 |
| 4030 | 1.438 | 3.625 | 4.438 | 77,300 | 3.000 | 3 × 5/8 x 1-3/4 |
| 4040 | 1.438 | 3.625 | 4.438 | 77,300 | 4.000 | 3 × 5/8 x 1-3/4 |
| 4535 | 1.938 | 4.250 | 4.938 | 110,000 | 3.500 | 3 × 3/4 x 2 |
| 4545 | 1.938 | 4.250 | 4.938 | 110,000 | 4.500 | 3 × 3/4 x 2 |
| 5040 | 2.438 | 4.500 | 5.000 | 126,000 | 4.000 | 3 × 7/8 x 2-1/4 |
| 5050 | 2.438 | 4.500 | 5.000 | 126,000 | 5.000 | 3 × 7/8 x 2-1/4 |
| 6050 | 3.000 | 6.000 | — | 282,000 | 5.000 | 3 × 1-1/4 x 3-1/2 |
| 7060 | 3.000 | 7.000 | — | 416,000 | 6.000 | 4 × 1-1/4 x 3-1/2 |
Three things to read carefully in that table. Min bore matters as much as max bore: a 3020 will not hold a 1/2-inch shaft, so a small shaft can force you down a size even when torque is not the constraint. Shallow keyseat is what unlocks the larger bores, and it costs some key bearing area. And pairs share a bore — 1210 and 1215 both take up to 1.250 inches, 1610 and 1615 both take up to 1.500 inches. The difference is length, not capacity, which is the single most common ordering mistake we see.
Which key goes with which bore
The keyseat is determined by the bore, not by the bushing size, so the same bushing number can need a different key at each bore.
| Bore range (in) | Keyseat, width × depth (in) |
|---|---|
| 0.500 – 0.563 | 1/8 × 1/16 |
| 0.625 – 0.875 | 3/16 × 3/32 |
| 0.938 – 1.250 | 1/4 × 1/8 |
| 1.438 – 1.750 | 3/8 × 3/16 |
| 1.813 – 2.250 | 1/2 × 1/4 |
| 2.313 – 2.750 | 5/8 × 5/16 |
| 2.813 – 3.250 | 3/4 × 3/8 |
| 3.313 – 3.750 | 7/8 × 7/16 |
| 3.813 – 4.500 | 1 × 1/2 |
A key is furnished with every bushing that has a shallow keyseat. If you are buying a bushing for an existing hub, give us the bore along with the bushing number so the key and keyseat are matched on the first pass.
Taper lock bushings for pulleys and sheaves
Bushed pulleys are the most common taper lock application. The bushing is what lets a single sheave casting cover a range of shaft sizes, so distributors stock the bushing separately from the pulley and assemble to order.
Selection runs in this order: pick the sheave for the belt section and the pitch diameter the drive calls for, confirm the number of grooves, then pick the bushing by the shaft bore you actually have and the torque the drive has to transmit. Toothed and V-belt sheaves with a bushed hub use the same bushing range as sprockets of comparable torque, so a 2517 or 3020 turns up across several drive types.
Two checks before you order. Confirm the hub length your sheave expects — a 1215 in place of a 1210 will not seat. And confirm the belt section is right for the sheave: if you are converting between fractional-horsepower and classical belts on the same drive, use our 4L and 5L to A and B cross reference before you specify the pulley.
Taper lock bushings for sprockets
Bushed sprockets follow the same logic, with one extra constraint: chain pull. A sprocket carries the chain tension as a side load on the bushing, so the torque capacity that matters is the torque at the shaft including the chain pull component, not just motor torque. On a slow, short-center drive that rarely changes the bushing size. On a long-center drive with a small sprocket it frequently does, and it is the reason a sprocket application sometimes steps up a bushing size compared with the sheave on the same shaft.
The other sprocket-specific factor is that a bushed sprocket lets you change tooth count without pulling the shaft or re-machining. Keep the same bushing and change the sprocket, which is what makes ratio changes on an existing line cheap.
Mounting screw torque
Fastener torque is set by bushing size, not by how tight the drive feels. Overtorquing cracks hubs and bushings, and it is a warranty-invalidating failure that shows up as a cracked hub boss.
| Bushing size | Screws | Size | Type | Torque (lb-ft) | Torque (lb-in) |
|---|---|---|---|---|---|
| 1008 – 1108 | 2 | 1/4-20 | Setscrew | 4.6 | 55 |
| 1210 – 1215 – 1310 – 1610 – 1615 | 2 | 3/8-16 | Setscrew | 15 | 175 |
| 2012 | 2 | 7/16-14 | Setscrew | 23 | 280 |
| 2517 – 2525 | 2 | 1/2-13 | Setscrew | 36 | 430 |
| 3020 – 3030 | 2 | 5/8-11 | Setscrew | 67 | 800 |
| 3525 – 3535 | 3 | 1/2-13 | Setscrew | 83 | 1,000 |
| 4030 – 4040 | 3 | 5/8-11 | Capscrew | 142 | 1,700 |
| 4535 – 4545 | 3 | 3/4-10 | Capscrew | 204 | 2,450 |
| 5040 – 5050 | 3 | 7/8-9 | Capscrew | 258 | 3,100 |
| 6050 | 3 | 1-1/4-7 | Capscrew | 650 | 7,820 |
| 7060 – 8065 | 4 | 1-1/4-7 | Capscrew | 650 | 7,820 |
Installing and removing a taper lock bushing
The process is short, and almost every premature failure traces back to one step being skipped.
To install. Clean the shaft, the bushing bore, the bushing OD and the hub bore, and remove all oil, grease and dirt. Slide the hub and bushing onto the shaft. Oil the screw threads and points only. Never lubricate the hub bore or the outside of the bushing — that is the surface the taper relies on for grip. Turn the screws in loosely, seat the bushing, then tighten the screws alternately and evenly to the torque in the table above. Seat the bushing with a drift against the large end, working around the bushing away from the split and finishing either side of the split, then re-torque. Repeat until the screws stop moving at the specified torque.
To remove. Take out all the screws, oil the threads and points, then thread them into the holes that are tapped in the bushing side. Those are the jacking holes. Tighten alternately and the bushing walks out of the taper. One screw is normally left over and unused on removal. If the bushing is stubborn, tap the face of the hub.
Frequently asked questions
Can I use a smaller bushing to fit a bigger shaft? No. Maximum bore is a hard limit set by the wall thickness of the bushing. Beyond it the taper distorts and the bushing will not hold. If your shaft is larger than the standard-keyseat maximum, check the shallow-keyseat column before assuming you need a bigger bushing.
What is the difference between a 1210 and a 1215? Length, not bore. Both accept shafts up to 1.250 inches. The 1215 is 1.500 inches long against the 1210's 1.000 inches, so it is chosen when the hub is wider. Fitting the wrong one of a pair means the assembly will not seat.
Can I buy the bushing without the pulley? Yes, and that is usually the right answer. Bushings are stocked as separate items in inches and millimetres, and the pulley, sprocket or coupling is what carries the driven-side spec.
Do metric shafts need a different bushing? No. The same bushing sizes are bored to metric dimensions, so a 2517 is a 2517 whether the bore is 50 mm or 2 inches.
Why did my hub crack? Almost always overtorqued screws or a bushing that was lubricated on the taper surfaces. Re-check the fastener torque against the table above for your bushing size.
Need the right bushing today?
Our counter and engineering desk spec bushings, bushed pulleys and bushed sprockets from the shaft bore and torque, not from a guess at the part number. Send us the shaft diameter, the bushing number stamped on the old part, or just a photo of the assembly with a tape measure across it, and we will come back with the exact bushing, the matching key and a firm delivery date.