Roller Chain Sprockets
Roller Chain Sprockets
Roller chain sprockets are toothed wheels that engage the rollers of ANSI chain to drive or be driven by it. Texas Belting stocks 9,300+ sprockets from #25 through #240 pitch in A-plate, finished bore, QD, taper-lock, and idler styles through our BlackStar line, shipping from Houston, TX.
Shop roller chain sprockets by type
On this page: Part numbers · Chain sizes · Hub styles · Measuring · Bushings · Teeth & wear · Houston · Mistakes · FAQ
How do I read a sprocket part number?
Sprocket part numbers stack three codes: chain size, hub style, and tooth count. 40A30 is an A-plate sprocket (no hub) for #40 chain with 30 teeth. 60BS17 is a #60 B-hub sprocket with a stock finished bore and 17 teeth. 50SDS20 is a #50 QD sprocket taking an SDS bushing, with 20 teeth.
| Example | Chain (pitch) | Hub / bore style | Teeth |
|---|---|---|---|
| 40A30 | #40 (1/2 in) | A-plate: flat plate, no hub | 30 |
| 60BS17 | #60 (3/4 in) | B-hub, finished bore with keyway and set screws; bore follows the number (60BS17 1-1/8) | 17 |
| 50SDS20 | #50 (5/8 in) | QD hub bored for an SDS bushing (sold separately) | 20 |
QD sprockets swap the hub letter for the bushing series (SH, SDS, SK, SF); taper-lock sprockets carry the bushing number (1610, 2012). Multi-strand sprockets add a strand count.
Which sprockets fit my chain size?
Match the sprocket to the ANSI chain number stamped on the chain's side plates. The leading digits give the pitch in 1/8 in steps: #40 is 4/8 = 1/2 in, #60 is 6/8 = 3/4 in, #120 is 1-1/2 in. A sprocket cut for one pitch will not run any other chain size.
| Chain size | Pitch | Roller dia. | Matching sprockets |
|---|---|---|---|
| #25 | 1/4 in | 0.130 in (rollerless) | #25 sprockets |
| #35 | 3/8 in | 0.200 in (rollerless) | #35 sprockets |
| #40 | 1/2 in | 5/16 in | #40 sprockets |
| #41 | 1/2 in | 0.306 in (narrow) | #41 sprockets |
| #50 | 5/8 in | 0.400 in | #50 sprockets |
| #60 | 3/4 in | 15/32 in | #60 sprockets |
| #80 | 1 in | 5/8 in | #80 sprockets |
| #100 | 1-1/4 in | 3/4 in | #100 sprockets |
| #120 | 1-1/2 in | 7/8 in | #120 sprockets |
| #140 | 1-3/4 in | 1 in | #140 sprockets |
| #160 | 2 in | 1-1/8 in | #160 sprockets |
| #200 | 2-1/2 in | 1-9/16 in | #200 sprockets |
| #240 | 3 in | 1-7/8 in | #240 sprockets |
The last digit gives the construction: 0 is standard roller chain, 1 is narrow light-duty, 5 is rollerless bushing chain (#25 and #35, where the listed diameter is the bushing). To identify the chain first, see our ANSI roller chain guide.
A-plate vs B-hub vs C-hub vs idler: which style?
Hub style determines how the sprocket mounts and how much shaft grip it has. A-plate sprockets are flat plates with no hub, B-hub sprockets have a hub on one side, C-hub sprockets have hubs on both sides, and idler sprockets carry their own bearing so they spin freely without being keyed to a shaft.
| Style | Construction | Typical bore | Best for |
|---|---|---|---|
| A-plate | Flat plate, no hub | Small plain bore; often welded to a hub | Low cost, light loads, fabricated assemblies |
| B-hub | Hub on one side | Finished bore with keyway and set screws, or plain bore | Most common replacement style |
| C-hub | Hub on both sides | Larger plain or finished bores | Bigger sprockets and bores; more grip |
| Idler | Runs on its own ball bearing, on a stud or bolt | Not keyed; free-spinning | Taking up slack, guiding chain, adding wrap |
Finished-bore B-hub sprockets are the fastest replacement: match bore and keyway and bolt on. For anything that comes on and off the shaft repeatedly, use a bushed sprocket – see the bushing section below.
How do I measure a sprocket for replacement?
Identify a sprocket with four checks: count the teeth, get the chain pitch from the chain itself, note the hub style, and measure bore and keyway. Diameter is a cross-check, not an identifier – use the pitch diameter formula PD = P / sin(180°/N), where P is pitch and N is tooth count.
Outside diameter for a standard tooth form is close to OD = P × (0.6 + cot(180°/N)). Calculated diameters in inches:
| Teeth | #40 PD | #40 OD | #50 PD | #50 OD | #60 PD | #60 OD |
|---|---|---|---|---|---|---|
| 15 | 2.405 | 2.652 | 3.006 | 3.315 | 3.607 | 3.978 |
| 20 | 3.196 | 3.457 | 3.995 | 4.321 | 4.794 | 5.185 |
| 25 | 3.989 | 4.258 | 4.987 | 5.322 | 5.984 | 6.387 |
| 30 | 4.783 | 5.057 | 5.979 | 6.321 | 7.175 | 7.586 |
| 40 | 6.373 | 6.653 | 7.966 | 8.316 | 9.559 | 9.980 |
QD vs taper-lock sprockets: which bushing system?
Bushed sprockets clamp to the shaft with a split tapered bushing instead of a fixed bore, so one sprocket covers many shaft sizes and comes off without a puller. QD bushings are flanged, taper 3/4 in per foot on the diameter, and mount standard or reverse. Taper-lock bushings are flangeless with an 8 degree included taper, sitting flush inside the hub.
QD bushing bore ranges
| QD series | Bore range (std keyway) | Max bore (shallow / no keyway) |
|---|---|---|
| JA | 3/8 – 1 in | 1-1/4 in |
| SH | 1/2 – 1-3/8 in | 1-11/16 in |
| SDS | 1/2 – 1-11/16 in | 2 in |
| SK | 1/2 – 2-1/8 in | 2-5/8 in |
| SF | 1/2 – 2-1/4 in | 2-15/16 in |
Taper-lock bushing bore ranges
| Bushing | Bore range | Length thru bore |
|---|---|---|
| 1210 | 1/2 – 1-1/4 in | 1.00 in |
| 1610 | 1/2 – 1-5/8 in | 1.00 in |
| 2012 | 1/2 – 2 in | 1.25 in |
| 2517 | 1/2 – 2-1/2 in | 1.75 in |
| 3020 | 15/16 – 3 in | 2.00 in |
Ranges are typical published manufacturer bore listings. Choose QD for reverse-mount flexibility and easy removal; choose taper-lock when space is tight and the bushing must sit flush. Shop QD bushings and taper-lock bushings, or read the full QD vs taper-lock guide.
How many teeth, and when is a sprocket worn out?
Published selection guides recommend at least 17 teeth on a drive sprocket at moderate to high speed, a driven sprocket under 120 teeth, and a single-reduction ratio of about 7:1 or less. Below 17 teeth each link articulates through a larger angle, raising speed pulsation and roller impact.
- Drive sprocket: 17T+ preferred at speed; slow drives can run smaller counts.
- Ratio: at or under about 7:1 single-reduction for adequate wrap; two-stage beyond that.
- Odd tooth counts: an odd-tooth sprocket with an even-link chain spreads wear – a long-standing practice.
- Idlers: mount on the slack side with at least three teeth engaged, per manufacturer guidance.
Diagnose wear by tooth shape and chain elongation. Worn teeth hook into a shark-fin profile as an elongated chain rides up the tooth face. The standard replacement threshold is 3 percent elongation; for sprockets over 67 teeth it tightens to 200/N percent (a 100-tooth sprocket allows only 2 percent). On #40 chain, 12 pitches pin-to-pin measure 6.000 in new, 6.180 in at 3 percent. If the chain measures long or the teeth are hooked, replace chain and sprockets as a set – either worn part quickly chews up the new one.
Roller chain sprocket supplier in Houston, TX
Texas Belting stocks 9,300+ roller chain sprockets, #25 through #240, plus the QD and taper-lock bushings to mount them. Most stocked sizes ship same day from our Houston, TX warehouse, serving the Texas Gulf Coast and shipping nationwide. Call (888) 203-2358 to confirm availability.
Common sprocket selection mistakes
- Ordering by tooth count alone. A 30-tooth sprocket exists in every pitch. Confirm the chain number first.
- Reading outside diameter as pitch diameter. Catalog PD runs through the roller centers and is always smaller than the OD.
- Treating #40 and #41 as the same chain. Same pitch, different width and roller – each needs its own sprockets.
- Replacing the chain on hooked sprockets. Worn teeth destroy a new chain in short order. Inspect and replace as a set.
- Mixing bushing systems or series. QD and taper-lock never interchange, and each sprocket accepts one series only.
When to call
Call us when you have:
- Double, triple, or double-single strand sprockets
- Stainless, plastic, or hardened-tooth needs for washdown or abrasive service
- Plain-bore sprockets needing custom bore and keyway work
- A Martin, Browning, Tsubaki, or Dodge part number to cross-reference
- No readable markings at all – just measurements and photos
Call (888) 203-2358 or send us what you have.
Frequently asked questions
What size sprocket fits #40 roller chain?
Any sprocket cut to ANSI #40 dimensions: 1/2 in pitch with teeth sized for a 5/16 in roller. Tooth count and bore are set by your drive: count the teeth on the old sprocket and measure the shaft. #41 chain shares the 1/2 in pitch but is narrower with a smaller roller, so it takes its own sprockets.
How do I measure a sprocket to find its size?
Count the teeth, then identify the chain pitch by measuring pin-center to pin-center on the chain. Record hub style, bore, and keyway. Cross-check diameter with PD = P / sin(180 deg / N). Calipers resting in opposite tooth gaps read the caliper diameter, about one roller diameter under PD, so compare against caliper diameter, not PD.
What does the B in 40B18 sprocket mean?
Hub style. A is a flat plate with no hub, B has a hub on one side, and C has hubs on both sides. So 40B18 is an 18-tooth sprocket for #40 chain with a hub on one side. A BS number is a B-hub sprocket supplied with a finished bore, keyway, and set screws, ready to mount.
What is the difference between a QD bushing and a taper-lock bushing?
Both are split tapered bushings that clamp a sprocket to a shaft. QD bushings have a bolt flange, taper 3/4 in per foot on the diameter, and mount standard or reverse. Taper-lock bushings are flangeless with an 8 degree included taper and sit flush in the hub. The systems never interchange, and each sprocket accepts one series.
How many teeth should a drive sprocket have?
Published guides recommend at least 17 teeth at moderate to high speeds, because fewer teeth increase chordal speed variation and roller impact. Slow, light drives can run smaller sprockets. Keep the large sprocket under 120 teeth and single-reduction ratios at or below about 7:1.
How do I know if my sprocket is worn out?
Worn teeth lose their symmetric profile and hook over like shark fins, and the chain starts riding high, whipping, or jumping teeth. Check the chain too: at 3 percent elongation, or 200/N percent on sprockets over 67 teeth, the pair is due. Hooked teeth mean replacement, not adjustment.
Should I replace the chain and sprocket at the same time?
In most cases, yes. A stretched chain re-cuts new sprockets to its worn pitch, and hooked sprockets rapidly wear a new chain. If the teeth still show a symmetric profile and the chain is only lightly worn, a chain-only swap can be acceptable.
What is an idler sprocket used for?
An idler takes up chain slack, increases wrap, or guides the chain around an obstruction. It runs on its own ball bearing on a stud or bolt, so it is never keyed to a driven shaft. Mount idlers on the slack side with at least three teeth engaged.
Related products and guides
Need help matching a sprocket?
Send the part number, tooth count, chain size, and bore – or just photos of the worn part. We will identify it and quote the replacement, bushing included.
Request a Quote Call (888) 203-2358Last updated: July 2026