The Replacement-Part Checklist I Use Before Ordering Martin Sprocket & Gear Components

I handle replacement-parts orders for a small maintenance crew. For about eight years now. In that time I've personally made—and written down—14 significant mistakes, totaling roughly $5,600 in wasted budget and a lot of lost credibility with the shop floor. So I built a checklist. This is that checklist.

It's for anyone who needs to order components like sprockets, gears, bearings, or linear motion parts and wants to avoid the stupid errors I've already made. It's not a substitute for reading the catalog. It's what I do before I read the catalog.

Step 1: Confirm you're on the official website

I know this sounds basic. But the first time I looked for Martin Sprocket & Gear, I ended up on a reseller site that looked almost identical. The logo was there. The product photos were there. What wasn't there was support when I got the wrong part.

Now I go directly to the Martin Sprocket & Gear official website: martinsprocket.com. If you search for 'martin-sprocket' or 'martin sprocket & gear official website,' you'll get a mix of ads, third-party catalogs, and the real link. The real link is the one with martinsprocket.com in the address. Per FTC guidelines, advertising claims have to be truthful and not misleading, but I'd rather check the URL myself than trust a logo.

If you're in Texas, the Martin Sprocket & Gear branch in Arlington, TX has a counter. I've picked up same-day orders there twice. (Should mention: I'm not against resellers—I use them when their stock is tighter. But for checking part numbers, the official site's catalog is the least confusing.)

Step 2: Get the exact part number from the catalog, not from memory

The part number is not a product name. 'Sprocket' is not a part number. 'Heavy duty linear actuator' is not a part number. I've tried all of those, and the result was never good.

On the official website, find the product family and write down the alphanumeric part number. Then check the specs underneath. For a chain sprocket, you need the number of teeth, chain pitch, bore size, keyway size, and set screw arrangement. If you're replacing a roller-chain sprocket, the tooth profile follows ASME B29.1 for stock parts, so match the chain pitch to the same standard.

I skipped the keyway once. I ordered 25 sprockets with bores that were technically correct but the keyway wasn't cut for the shaft. That was a $1,150 mistake plus a week of downtime. This was back in 2021, and I still remember the mechanic's face.

Step 3: Don't ask 'Which is better, ball bearing or roller bearing?'—ask what your machine needs

That phrase is one of the most common searches in the maintenance world, and it's the wrong question. Neither bearing type is 'better' by itself. They're better at different things.

In general, ball bearings handle lighter radial loads, run at higher speeds, and can take some axial load. Roller bearings handle heavier radial loads but are usually happier at moderate speeds and don't like much axial load. That's the simple version. The real answer depends on load, speed, alignment, lubrication, space, temperature, and contamination.

I once ordered ball bearings for a shaker screen because the old ones were ball bearings. I didn't check the load rating. They failed in about a month. Our mechanic pointed out the housing was set up for a spherical roller bearing. That mistake cost $410 plus a 3-day production delay. The lesson: bearing type is a design decision, not a preference. It took me three years and around 60 orders to understand that.

If you're on Martin's bearing pages, use the load ratings and speed limits, not the photo. And if the application has vibration or shaft deflection, a cylindrical or spherical roller bearing is often the right starting point. Verify with the vendor before trusting a random internet checklist writer.

Step 4: Separate motion control from linear actuators

Another thing I see a lot is people mixing up a heavy duty linear actuator with a stepper motor system. They're not interchangeable. A linear actuator turns rotary motion into push/pull and has a load rating, stroke, speed, and duty cycle. A stepper motor moves in precise increments and needs a driver/controller. It does not push anything by itself.

If you're prototyping with an Arduino stepper motor, that's a perfectly good way to learn stepping control. But I've seen a project fail because someone tried to lift an industrial door with an Arduino stepper motor assembly. It had enough static torque on paper, but the driver overheated and the motor lost position. What they needed was a heavy duty linear actuator with a suitable screw jack or gearmotor.

Before ordering, define the job in numbers: load, speed, how long it runs each cycle, and total stroke. Then check the actuator's duty cycle. 'Heavy duty' on the label doesn't mean it runs forever. The duty cycle percentage is the most overlooked spec in that whole category.

(I should add: for precise positioning at low torque, a stepper-based system is a great tool. For a 2,000-lb push application, a heavy duty linear actuator is the starting point. Different tools.)

Step 5: Verify shaft, bore, keyway, and mounting before you approve anything

This step sounds like common sense, but it's where I've spent the most money. The part number looked right. The description said '1-inch bore.' Then I misread the spec and ordered a 1-1/8-inch bore because I was in a hurry.

Write down the actual dimensions from the old part or the shaft. Compare them to the specs on the product page. For a gear or sprocket, check bore, hub diameter, hub width, keyway size, and face width. For a bearing: shaft diameter, housing bore, width, and fit. For a linear actuator: stroke, mounting clevis/pin size, and bolt pattern. Don't rely on the part number alone—the same part number family can cover multiple bore sizes. (ugh, they do that.)

Step 6: Download the CAD or drawing from the product page

This is one of those steps that feels like extra work but saves the most time. On the Martin Sprocket & Gear product pages, as of January 2025, most items include drawings and CAD files. Download the drawing and look at the dimensions. If the outside diameter of a sprocket is 5.82 inches and your available space is 5.5 inches, you just caught a problem before you paid for it.

I started doing this after I ordered a chain guard that was too small. The dimensions were right there in the drawing, but I didn't check. The part cost $180, shipping back cost another $40. Now I download the file first. If you have a CAD person, import the step file into your assembly. It catches a surprising number of obvious mistakes.

Step 7: Add a buffer to the lead time

This one is not technical, but it's the most expensive thing on this list. The worst order I ever placed was for a standard part I needed 'yesterday.' I paid expedited shipping on a part that would have arrived in time if I'd checked the catalog lead time in the first place. The express fee was about three times the part cost.

Check the product page for lead time. If it says 'ships in 2 weeks,' don't let a verbal 'should be faster' change your plan. Add a few days to whatever the screen says. If you're near Dallas/Fort Worth, ask about will-call at the Martin Sprocket & Gear Arlington, TX location. They've saved me once or twice.

The short list I still use before every order

Here's the condensed version:

• Is the site really martinsprocket.com, or a look-alike?
• Did I copy the part number from the correct product family?
• For ball vs. roller bearings, did I verify load rating and speed for the actual application?
• For a heavy duty linear actuator, is the duty cycle enough for the cycle rate?
• For an Arduino stepper motor or positioning project, do I have a load calculation or just a guess?
• Bore, keyway, shaft diameter, mounting pattern, stroke—written down and compared?
• Did I download the drawing, and did I actually open it?
• What's the lead time, and what's the backup plan?

I still make mistakes. In Q3 2024, I ordered a coupling with the right bore sizes but the wrong keyway orientation. I blame metric vs. inch, but really it was me being in a hurry. The checklist got me closer, not perfect. But it's a lot cheaper than using my memory.

Take the parts of this that fit your job and leave the rest. At least, that's been my experience with the last 14 mistakes. (Hopefully you'll make fewer.)