I Started Using a Lovejoy Coupling Checklist After Ordering the Wrong L110 Spider

About seven years ago I started handling Lovejoy-brand coupling requests for an industrial equipment supplier. Since then I have made enough ordering mistakes to write this down. The one I remember most clearly was a $900 reorder that happened because I typed the name of the insert instead of the complete coupling. If that sounds familiar, this checklist is for you.

I use it when someone sends a photo of a failed jaw coupling, says they need a Lovejoy coupling spider L110, or pastes an old line item like a Lovejoy AL-100 x 7/8 coupling. It is not a full engineering guide. It is a basic stop-and-check list that has saved me from repeating my own errors.

Check 1: Identify whether you need a complete coupling, hubs, or only the spider

A jaw-type Lovejoy coupling is a two-hub assembly with an elastomeric insert between the hubs. The insert is often called a spider. When someone says L110, the first thing to confirm is which of those parts they are asking for.

The phrase Lovejoy coupling spider L110 is normally an insert-only request, because the spider is the part that wears out. But if the motor shaft and gearbox input shaft are still bare, you need two hubs and a spider. I made the mistake of assuming that every L110 request in our system included hubs, and I overstocked spiders for a machine that did not have them yet.

Check 2: Read an existing part number as a clue, not as a complete spec

One line item that used to trip me up was the old purchase-order text Lovejoy AL-100 x 7/8 coupling. It looks useful, and it is not useless, but it does not tell me everything I need to know.

AL-100 describes a coupling part family, and 7/8 tells me at least one shaft diameter. It does not tell me whether both hubs need a 7/8 bore, whether the bore needs a keyway and set screw, or whether the customer expects a spare spider in the box as well. I now ask for the left side and right side separately, in writing, even when I am in a hurry.

Check 3: Do not skip the keyway and set screw details

Bore size is half the story. A Lovejoy hub can be supplied as a plain bore or a machined bore with keyway. On a 7/8 inch shaft, the keyway width is usually 3/16 inch, but that still depends on the hub size and whether the bore is standard or custom. If I do not verify this, the hub arrives either with no way to transfer torque or with a sloppy fit.

Set screw location matters too. Some hubs have a set screw aligned with the keyway, and some have two set screws at different angles. When maintenance installs the coupling without looking at that detail, the hub can shift during reversing loads. This is one of those checks that takes thirty seconds but prevents a second phone call.

Check 4: Look at the driver and driven equipment before choosing size

The part number has to match the shaft, but the coupling size also has to handle the torque. If I stop at bore size, I can end up with a coupling that fits physically and still is not big enough for the motor's locked-rotor torque or peak starting torque.

For a simple motor-to-pump application, the catalog service factors are usually enough. I still confirm the actual motor frame and the driven equipment from the nameplate before I pick the coupling family. A coupling that is too small is easy to spot because it fails fast. A coupling that is wildly oversized creates another problem: extra mass on the shaft that makes acceleration slower and adds load on the motor bearings.

One specific case I pay attention to is a stepper motor driving a small belt conveyor or a rotary index table. A stepper motor can have a rapid acceleration profile, especially when it is used without an external gearbox. The coupling should be selected with that stop-start pulse in mind, not as if it were a smooth induction motor. Oversized hubs can add enough inertia to make a stepper motor miss steps at high index rates.

Check 5: Ask which gear stage is on the driven side

This sounds like a gearbox question, not a coupling question, but it changes the installation geometry.

The direct answer to the common question — which gear is most likely to use a spur gear? — is usually the gear between two parallel shafts. A spur gear is simple and efficient when the shafts are parallel. But that does not tell you what happens if a reducer has a worm gear stage. Worm gears are compact, high-ratio, right-angle drives. They have more sliding contact and more heat than a comparable spur stage, and they often position the motor input shaft perpendicular to the slow-speed output shaft.

Why does that matter for a coupling? When someone tells me their coupling connects a motor to a worm gear reducer, I check the direction of the input shaft. If I order a complete Lovejoy jaw coupling by catalog number without knowing whether the motor must sit above, beside, or inline, I can miss the shaft orientation problem. That is the kind of mistake that costs a custom bracket and several days of downtime.

Check 6: Confirm the material and environmental limits

One caveat: I have mostly worked with dry industrial machinery, not food washdown or high-temperature ovens. If your line has caustic washdown or heat near the upper limits of standard rubber, the spider material changes everything.

Standard Buna-N spiders work for a lot of normal applications, but they are not a universal answer. Oil, ozone, high temperature, and chemical washdown all affect the service life of the insert. When I replace a Lovejoy coupling spider L110 in an outdoor conveyor or a washdown area, I look up the material compatibility before clicking order. The same size spider can be made from different materials, and they are not interchangeable in every environment.

The final check: know what you are actually paying for in an emergency

When a machine is down, I stop looking for the cheapest option and start asking one question: can the supplier confirm the exact part is on the shelf, or will it ship later from a warehouse? A fast-shipping quote is only useful if the person on the other end can verify the Lovejoy part number against the hub and spider design.

I have paid extra many times for same-day shipment. The extra cost buys certainty, which matters more than speed. A delayed shipment can shut down a line for a day. The part number that shows up wrong also shuts down the line, which is why I still run this whole checklist even when I am in a rush.

It is not the most exciting part of maintenance work, but it is the part that prevents the most embarrassing phone calls. Write the coupling assembly down clearly, confirm the bore and keyway on both ends, and do not assume that every L110 spider is the same material. That has been enough to keep me out of the reorder queue for the last three years.