Lovejoy Coupling L-095 or L-100? How to Choose (And What VFD Compatibility Actually Means)

Let me save you a phone call: there's no single “best” Lovejoy coupling. The right one depends on the motor, the driven shaft, the space between them, and the torque the job actually requires. I handle purchasing for a 110-person repair and manufacturing company, which means I'm the one who gets asked to “just order the same thing we got last time.” Sometimes that works. Sometimes it doesn't.

Last month, my morning started with a request for an L-100 Lovejoy coupling for a conveyor motor, then a Fanuc servo motor for a retrofit, then a fitness gear rack for the training room. Those three items don't have much in common, but they're a good reminder that every order starts with a person—ideally a clear spec.

If you're reading this because you're about to buy a Lovejoy coupling and you're not an engineer, here's how to think about it.

Start by figuring out which scenario you're in

There's no one-size-fits-all answer, but there are a few common situations:

• You're replacing a failed coupling on an existing machine.
• You're building or retrofitting a motor drive (VFD or servo).
• You're a small buyer or a first-time customer and want to avoid getting it wrong.

Each one has a slightly different path. Let's go through them.

Scenario A: You're replacing an existing Lovejoy coupling

If the old coupling is already worn out, your first instinct might be to order the same model number. Do that only after you check the bore and keyway. Yes, this sounds obvious. It's not.

The Lovejoy L-095 and the L-100 are both L-type jaw couplings. They look similar from across the room. The L-100 is the larger one, with a larger bore range and a higher torque rating. But “the old coupling was an L-095” doesn't tell you the bore size of the old hub. A previous repair could have re-bored a bigger hub to fit a smaller shaft. That happens more than it should.

Take a caliper and measure the two shaft ends. You need:

• Motor shaft diameter
• Driven shaft diameter
• Gap between the shaft ends, so you can confirm hub spacing
• Keyway width and depth, if it's keyed

Do not use a tape measure for this. A half-millimeter difference changes the fit. I've seen a coupling ordered with a “close enough” measurement, and “close enough” led to a vibration that loosened the keys and ruined a two-week schedule.

According to the Lovejoy catalog we use for ordering (May 2025 version), the L-095 and L-100 are both current L-type sizes. They're not the same part with different labels. Honestly, I'm not sure why these two particular sizes show up on so many machine tags. My best guess is they cover the shaft sizes that are common in light industrial equipment.

In my first year in purchasing, I made the classic beginner mistake: I ordered an L-095 from a photo because the old hub “looked like” an L-095. It was actually an L-100 re-bored down, hidden under years of grease. The new coupling didn't fit. We paid an extra $96 in emergency freight, and the maintenance lead did not let me forget it. Now I measure first and order second. The extra ten minutes is free.

If the old coupling has a model stamped on the hub, that's useful—but only half useful. Use it as a starting point, not the answer. The model tells you the coupling frame. The bore tells you what will actually mount on the shaft. A good distributor will ask for both.

Scenario B: You're dealing with a VFD or a servo motor

This is where the “what motors are compatible with VFD?” question usually comes up. The short answer: not every motor is a drop-in VFD motor.

For a general-purpose VFD application, you want an inverter-rated motor, often called vector-duty or inverter-duty. These are built to handle the voltage spikes and extra heating that come from variable-frequency drives. A standard three-phase induction motor might work in a basic fan or pump application, but it's a gamble if you need a wide speed range or continuous low-speed operation. NEMA MG-1 Part 31 covers inverter-fed motor design, and it's a good reference if you want more than a salesperson's opinion.

Servo motors are a different story. If you have a Fanuc servo motor, you need a servo amplifier—not a VFD. A Fanuc servo motor is a closed-loop component designed to work with Fanuc control systems. It's not a general-purpose AC motor that you can wire to a cheap VFD and expect it to behave. I once got an internal request to run a spare Fanuc servo motor with a VFD “just to turn it.” Senior maintenance shut that down fast. Different motors use different drives. Don't force it.

The coupling part comes after the motor-drive question. Once you know which motor and which driven component you're connecting, the coupling is sized from shaft diameters and torque. A VFD can change torque characteristics across the speed range, so keep a little margin instead of picking the smallest coupling that technically fits.

Scenario C: You're a small buyer or a first-time Lovejoy customer

Maybe you need one Lovejoy coupling L-095 to get a machine running again, and you're worried that a supplier won't care because the order is small. That fear is real. Some suppliers treat a single coupling like it's a waste of their time. In my experience, the ones who help the small orders are the ones who deserve the bigger orders later.

When I took over purchasing in 2020, I was getting quotes for $200 orders, and one vendor treated us like a serious customer. I remember the exact quote because it included the bore size confirmation. They didn't just send “L-095: $42.” They said, “I need the shaft diameter to confirm the bore.” That's the sign of a person who cares about details.

Today, that vendor gets the bigger orders too. I've also had a vendor tell me to “just check the model number” and then send something that wouldn't fit. That was a fun conversation. You don't need to be a brand-loyal customer to ask for a simple confirmation. If they won't confirm the bore with you, that's a red flag.

Small doesn't mean unimportant. It means potential.

How to tell which scenario you're in

If this is already starting to sound like work, here's a simpler way to decide:

• Failed part on a working machine? Go with Scenario A. Measure, verify, then order. Add a replacement spider since they wear out faster than hubs.
• New motor or variable-speed setup? Go with Scenario B. Sort out the VFD-compatible motor first, then size the coupling to the shafts.
• One-off order and not sure who to trust? Go with Scenario C. Ask questions. If the supplier doesn't take you seriously, find one that will.

Our process works because we control the purchasing side. If you're a maintenance lead with multiple locations and an engineer who sources his own parts, your process will look a little different. The measurements don't change.

And if you got here from a search like “fitness gear rack,” this wasn't the page you meant—unless you're actually working on a piece of fitness equipment with a motor and a coupling. In that case, the same measuring steps apply. A Lovejoy coupling won't store dumbbells, but it might be the quiet, reliable part between a motor and a gearbox that you didn't know you were looking for.

The bottom line: Lovejoy couplings look simple, but the details matter. The L-095 and L-100 are different sizes for a reason. VFD compatibility is a motor issue, not a coupling issue. And good service shouldn't depend on how many units you're ordering.