Shaft Couplings: Jaw, Chain & Spacer
Shaft Couplings: Jaw, Chain & Spacer
Shaft couplings join a motor or reducer shaft to a driven shaft, transmitting torque while absorbing minor misalignment. Texas Belting stocks 520+ couplings and components in Houston, TX: BlackStar L-type jaw couplings from L035 to L276, replacement spiders, roller chain couplings, spacer couplings, weld-on hubs, and set collars.
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On this page: Types · Identify · L-jaw chart · Spiders · Chain · Sizing · Houston · Mistakes · FAQ
Jaw, chain, or spacer coupling: which type do you need?
Jaw couplings cover most motor-to-pump and motor-to-gearbox drives: they run dry, need no lubrication, and the elastomer spider is the only wear part. Chain couplings carry more torque for the same shaft size and disconnect by pulling one duplex chain. Spacer couplings add a drop-out center section so a pump seal can be serviced without moving the motor.
- L-type jaw couplings - iron hubs driving an elastomer spider in compression; quiet, greaseless, and the jaws still interlock if the spider fails. Sizes L035-L276.
- Chain couplings - hardened sprockets wrapped by duplex roller chain, 4012-12022; compact for the torque, needs grease and a cover.
- Spacer couplings - a drop-out center bridges the pump shaft gap so seals come out with feet untouched; spec by torque plus DBSE (distance between shaft ends).
How do I identify a jaw coupling size?
Measure the spider outside diameter first - that single measurement identifies an L-jaw size. A 1.75 in spider is an L075, 2.54 in is an L099 or L100, 3.75 in is an L150. If the spider is destroyed, measure hub OD and overall length instead; bore and keyway then confirm which hub to order.
- 1. Spider OD. Pop the spider out and caliper across the lobes; match it in the chart below. A chewed-up spider usually keeps its OD.
- 2. Hub OD + overall length. No spider left? Hub OD tracks spider OD within a few hundredths; overall length splits the look-alike pairs.
- 3. Bore and keyway. Inch hubs use standard ANSI/ASME B17.1 keyways, so bore plus keyway fully specs each hub - the two halves can differ.
L-jaw coupling size chart (L035 to L276)
The L-jaw line covers 13 standard sizes, from L035 (0.375 in max bore, 3.5 in-lb nominal torque) to L276 (2.875 in max bore, 4,716 in-lb with an NBR spider); the wider jaw family runs to 7 in bores and 170,000 in-lb. Below: industry-standard L-series envelope dimensions and typical published ratings.
| Size | Spider OD (in) | Overall Length (in) | Max Bore (in) | Torque, NBR Spider (in-lb) | Max RPM |
|---|---|---|---|---|---|
| L035 | 0.62 | 0.81 | 0.375 | 3.5 | 31,000 |
| L050 | 1.07 | 1.71 | 0.625* | 26.3 | 18,000 |
| L070 | 1.38 | 1.98 | 0.750 | 43.2 | 14,000 |
| L075 | 1.75 | 2.13 | 0.875 | 90 | 11,000 |
| L090 | 2.12 | 2.15 | 1.000 | 144 | 9,000 |
| L095 | 2.12 | 2.51 | 1.125 | 194 | 9,000 |
| L099 | 2.54 | 2.84 | 1.188 | 318 | 7,000 |
| L100 | 2.54 | 3.48 | 1.375 | 417 | 7,000 |
| L110 | 3.31 | 4.22 | 1.625 | 792 | 5,000 |
| L150 | 3.75 | 4.50 | 1.875 | 1,240 | 5,000 |
| L190 | 4.50 | 4.86 | 2.125 | 1,728 | 5,000 |
| L225 | 4.98 | 5.34 | 2.625 | 2,340 | 4,200 |
| L276 | 6.19 | 7.82 | 2.875 | 4,716 | 1,800 |
* L050 max bore is without a keyway. Torque is the published nominal rating with a solid-center NBR spider; urethane raises it 1.5x, Hytrel-type roughly 2-3x. Hytrel-type is limited to 3,600 rpm, bronze to 250 rpm.
Lovejoy, Martin, TB Woods - the L-series crosses brands. A Lovejoy L100, Martin ML100, TB Woods L100, and Browning or Maurey equivalent share the same envelope and accept the same spider; TB Woods publishes its L-jaw line as 100% interchangeable with industry-standard designs. Send us any brand's hub number for a BlackStar match.
Interchange references are based on manufacturer-published equivalents. Verify dimensions before ordering.
Which coupling spider material should you use?
Match the spider to torque, temperature, and damping. NBR rubber is the default: best vibration damping and -40 to +212 °F service. Urethane carries 1.5 times the torque of NBR. Hytrel-type elastomer carries roughly 2 to 3 times NBR torque and runs to 250 °F, but published angular misalignment drops by half. Bronze is for slow, high-torque shafts only.
| Material | Torque vs NBR | Temp Range | Damping | Misalignment (Parallel / Angular) | Use It For |
|---|---|---|---|---|---|
| NBR (SOX) rubber | Baseline (1x) | -40 to +212 °F | Best | 0.015 in / 1° | Default: pumps, fans, blowers, gear drives |
| Urethane | 1.5x | -30 to +160 °F | Moderate | 0.015 in / 1° | Torque headroom on moderate-shock drives |
| Hytrel-type | ~2-3x | -60 to +250 °F | Low | 0.015 in / 0.5° | High torque plus heat; 3,600 rpm cap; align carefully |
| Bronze | Matches Hytrel-type rating per size | -40 to +450 °F | None | 0.010 in / 0.5° | Slow-speed only - 250 rpm max - heat and debris |
What do chain coupling numbers mean? (4012 to 12022)
A chain coupling number encodes chain size and tooth count: the leading digits are the ANSI roller chain size and the last two digits are the teeth on each sprocket. A 5016 coupling is two 16-tooth hardened sprockets joined by #50-2 duplex chain; a 4012 runs #40-2 chain over 12-tooth sprockets.
| Coupling | Chain | Teeth / Sprocket | Max Rebore (in) | Max RPM | OD (in) | Length (in) |
|---|---|---|---|---|---|---|
| 4012 | #40-2 | 12 | 0.875 | 5,000 | 2.41 | 2.53 |
| 4016 | #40-2 | 16 | 1.313 | 5,000 | 3.03 | 2.53 |
| 5016 | #50-2 | 16 | 1.688 | 4,000 | 3.78 | 3.25 |
| 5018 | #50-2 | 18 | 2.000 | 3,600 | 4.19 | 3.75 |
| 6018 | #60-2 | 18 | 2.438 | 3,000 | 5.00 | 4.19 |
| 6020 | #60-2 | 20 | 2.750 | 2,500 | 5.50 | 4.44 |
| 6022 | #60-2 | 22 | 3.000 | 2,500 | 5.95 | 4.69 |
| 8018 | #80-2 | 18 | 3.125 | 2,000 | 6.66 | 5.33 |
| 8020 | #80-2 | 20 | 3.563 | 2,000 | 7.30 | 5.52 |
| 10018 | #100-2 | 18 | 3.875 | 1,800 | 8.33 | 6.22 |
| 10020 | #100-2 | 20 | 4.625 | 1,800 | 9.13 | 6.97 |
| 12018 | #120-2 | 18 | 4.688 | 1,500 | 10.00 | 7.88 |
| 12022 | #120-2 | 22 | 6.125 | 1,200 | 11.89 | 8.88 |
Values are typical published dimensions; max rebore is the largest recommended plain bore with a standard keyway. A complete assembly is two sprocket hubs, one strand of duplex coupling chain, and grease.
How do I size a shaft coupling?
Size a coupling from torque, not horsepower alone: torque in in-lb equals 63,025 times HP divided by RPM. Multiply that by a service factor for the driven load, then pick the smallest coupling whose published nominal torque meets the result and whose max bore fits both shafts.
Step 1 - Torque. A 5 hp motor at 1750 rpm loads the coupling with 63,025 x 5 / 1750 = 180 in-lb.
| Driven Load | Typical Service Factor |
|---|---|
| Even torque: centrifugal pumps, blowers, fans | 1.0-1.25 |
| Moderate shock: conveyors, agitators, machine tools | 1.5 |
| Heavy shock or reversing: reciprocating compressors, crushers | 2.0-2.5 |
Step 2 - Service factor. Typical elastomeric-coupling factors; use the equipment maker's value where specified. The 5 hp agitator example: 180 x 1.5 = 270 in-lb design torque.
Step 3 - Map into the chart. 270 in-lb lands on an L099 (318 in-lb with NBR); a 1-3/8 in shaft forces the L100, and an L095 with a urethane spider (291 in-lb) also clears 270 where the envelope is tight. Bores pick the size more often than torque - check bore first, then confirm torque.
Shaft coupling supplier in Houston, TX
Texas Belting stocks BlackStar jaw, chain, and spacer couplings plus spiders in Houston. Most stocked sizes ship same day from our Houston, TX warehouse, and cross-reference quotes typically come back within one business day. We serve the Texas Gulf Coast and ship nationwide - call (888) 203-2358 to confirm availability.
Common shaft coupling selection mistakes
- Sizing by bore alone. A 1 in bore fits anything from L090 up; only spider OD or torque identifies the size.
- Confusing the look-alike pairs. L090/L095 and L099/L100 share spider ODs - check overall length before ordering.
- Masking misalignment with a stiffer spider. Hytrel-type carries more torque but publishes half the angular misalignment of NBR. Realign the shafts instead.
- New spider, hammered hubs. Jaws that ran metal-to-metal are peened; a fresh spider pounds out in weeks. Inspect jaw faces first.
- Mistaking metric curved-jaw (Rotex-style) hubs for L-jaws. Similar look, non-interchangeable geometry - match the spider profile.
When to call us first
- Taper-bushed or QD-style chain couplings - bushing series and bore must match
- Spacer couplings for process pumps - we quote from torque plus your DBSE
- A hub with no legible markings - send photos with a caliper in frame
- Torque beyond the charts, high-speed balanced drives, or hostile chemical service
- Metric or curved-jaw replacements where the interchange is not obvious
Call (888) 203-2358 or send us what you have - part numbers, photos, or measurements.
Frequently asked questions
How do I measure a jaw coupling to identify its size?
Pull the spider and measure its outside diameter - that one number identifies the size: 1.75 in is an L075, 2.12 in is L090 or L095, 2.54 in is L099 or L100, 3.75 in is an L150. Split the shared pairs by overall length, then measure bore and keyway.
Are Lovejoy and other L-jaw couplings interchangeable?
Dimensionally, yes. The L-series is an industry-standard design: published interchange charts map Lovejoy L, Martin ML, TB Woods L, Browning, and Maurey size for size, and TB Woods states its L-jaw line is 100% interchangeable with industry-standard designs. Verify dimensions before ordering.
Can I replace just the spider in a jaw coupling?
Yes - the spider is the sacrificial wear element. Slide the hubs apart, seat a new spider of the same size and material, and reset the hub gap. If the jaws are peened, cracked, or thinned from metal-to-metal running, replace the hubs too.
When should a coupling spider be replaced?
Replace the spider when permanent set has reduced the legs' original thickness by about 25%, or at the first cracking, glazing, or missing chunks. Elastomer dust inside the coupling guard is the classic early symptom. Most plants change spiders on a PM schedule instead of running them to failure.
What do the numbers on a chain coupling mean?
The leading digits are the ANSI roller chain size and the last two are the tooth count on each sprocket: a 4012 is two 12-tooth sprockets on #40-2 duplex chain, a 5016 is 16-tooth sprockets on #50-2, a 6018 is 18-tooth on #60-2, and the pattern runs through 12022.
What chain does a 5016 chain coupling use?
A 5016 coupling uses #50-2 duplex (double-strand) roller chain sized to wrap its two 16-tooth sprockets, joined with a connecting link so the drive separates without moving either machine. Replacement coupling chain comes as a ready-to-fit strand with the link included.
Related products and guides
Need help matching a shaft coupling?
Send the hub numbers, a spider photo, or two caliper measurements - we cross-reference L-jaw, chain, and spacer couplings and ship most stocked sizes same day from Houston.
Request a Quote Call (888) 203-2358Last updated: July 2026