The 6-Part Power Transmission Buying Checklist I Run Before Signing Any PO

I manage procurement for a mid-size automation company. For the past six years, I've tracked about $180,000 in power transmission spending, and the most expensive mistakes were rarely the part cost. They were the small things: wrong chain type, skipped elongation check, actuator speed specified for the wrong load, or a 'cheap' quote that didn't include freight. This checklist is what I run through before signing a PO for a chain or an industrial linear actuator. It's not a fancy engineering guide. It's the practical version.

When This Checklist Helps

I use it when:

• Replacing a chain and the old part is still in front of me.
• Comparing quotes for a chain, actuator, or sprocket kit.
• Investigating why a chain fails earlier than expected.

Skip it if you're only forecasting next year's budget. That's a different spreadsheet.

The Checklist

1. Measure chain elongation before you compare prices

Most buyers look at a chain and ask, 'does it look worn?' The better question is, 'has it reached the elongation limit?' Chain wear on a roller or leaf chain is not always visible. Pins and bushings wear slowly, the pitch gets longer, and that's what the gauge measures.

Clean the chain where it is loosest. Place a Tsubaki chain wear indicator on the side plates over a fixed number of pitches, usually 6 to 12 depending on the gauge. Compare the reading to the limit. For many standard roller chains, 2% elongation is the replacement threshold. For some conveyor applications, it's 1.5%. The Tsubaki catalog states the limit for each series, and ANSI/ASME B29.1 treats pitch elongation as the main wear signal.

If the chain is stretched, order the replacement. If it's inside the limit, clean it, re-lube it, and put it back. Don't feel guilty about the hour spent. It's cheaper than replacing a chain that wasn't the problem.

2. Know whether you need leaf chain or roller chain

Leaf chain looks like a roller chain in a photo, but it's not. Roller chain has rollers and runs on sprockets. Leaf chain doesn't have rollers, so it is narrower and better for lifting, counterweight, and balancing applications. Tsubaki leaf chain is commonly specified in AL or BL series and follows ANSI/ASME B29.8.

Buy the wrong one and you'll pay twice. If you order roller chain for a leaf chain mast, it may not fit. If you order leaf chain for a sprocket drive, it will wear fast and probably fail early. Write down the number stamped on the side plate. If the side plate is worn, measure the pitch and the plate width. That gives you enough to verify the part before you send out a request for quote.

3. Check linear actuator speed before you pick a model

'How fast can a linear actuator move?' is the first question most people ask. The answer is, 'which one?' There is no single speed. For a screw-driven actuator, the math is:

linear speed (mm/min) = (motor RPM ÷ gear ratio) × screw lead (mm/rev)

Example: a motor spins 3,000 rpm, the gearbox is 10:1, and the screw lead is 10 mm. Output speed = 300 rpm, so linear speed = 300 × 10 = 3,000 mm/min, or 50 mm/s. If the screw lead is 5 mm, the speed drops to 25 mm/s.

Belt-driven linear actuators work differently, and they can be faster, sometimes several m/s. But speed and load are usually opposites. Ask for the speed-thrust curve before you buy. A spec that says 'max speed 500 mm/s' and 'max thrust 300 N' in separate rows does not mean both happen at the same time. That's a deal-breaker in a new build.

4. Don't let a timing belt search turn into a chain order

One of the stranger searches that lands on chain pages is 'Volvo timing belt replacement.' I understand why: timing belts and timing chains both use the words timing and belt/chain. But a Volvo timing belt is a rubber belt. If the engine was designed for a belt, you need a belt replacement kit, not a chain. A chain won't fit, won't tension the same way, and probably won't sync the cams.

Timing chains exist, and Tsubaki makes engine and motorcycle chains too. But those are also specific. If you need an engine timing chain, order the exact engine kit. Don't grab an industrial roller chain with a similar pitch. Bottom line: know which component is actually in the machine before you use the search bar.

5. Compare total cost, not unit price

Supplier A quotes $290 for the Tsubaki chain. Supplier B quotes $245. Unit price says B. I've been burned by that math. One order on paper was $245, but after freight and a connector link, the invoice landed at $335. Supplier A was $305 with freight included. That swung $30 in the opposite direction from what the quote suggested, before adding the extra week of lead time.

Put every quote through a simple TCO table:

• Part price
• Freight
• Handling or transaction fees
• Tax
• Extra connectors or attachment links
• Cost of delay if the part doesn't arrive on time

Then add one line-stop cost. If a stop is $220/hour, a 30-minute delay is $110 before you open the box. The lowest unit price is not the lowest cost. It never is once you add the other stuff.

6. Replace the sprockets when the chain is worn

This is the counterintuitive step. Replacing only the chain can be the more expensive option. Once a chain has reached 2% elongation, the sprocket teeth have likely worn into a hooked profile. A new chain on that sprocket will not seat properly. It will wear fast and can skip under load.

Inspect the sprocket teeth before ordering. If the teeth look hooked, replace them. If the tooth profile is still flat on the flank and there's no visible hook, you can probably reuse them.

I went back and forth on chain-only vs full-kit for one rebuild. The kit cost 45% more upfront. The chain-only side failed 14 months later. The kit was still running at 24 months. That's the kind of math that doesn't show up on the PO but shows up on the maintenance log.

What Usually Bites People

Overlooking the environment

Standard roller chain is not the same as washdown chain, high-temperature chain, or corrosion-resistant chain. If a replacement fails in the same month as the old one, look at the environment before blaming the brand. Tsubaki offers different grades for a reason. Choosing the correct grade is cost control.

Skipping the part number check

Chain numbers look similar. Tsubaki RS80 is not automatically the same as 80B or 16B. Pitch matters, but so do pin width, plate width, and ultimate strength. When in doubt, measure. A 1 mm difference in pin width can make a connector impossible to fit.

Ignoring alignment

Misalignment shows up as edge wear on one side of the chain. A new chain on a misaligned drive will wear quickly, and no brand will fix that. Check the sprockets for side loading before you order parts.

Where This Checklist Doesn't Apply

I'm a buyer, not a design engineer. I don't use this checklist to design a new machine. For that, use Tsubaki's engineering catalog, actuator sizing tools, or the OEM specification. This is for people who have an existing machine and want to replace components without creating a new problem.

The same logic goes for brand preference. I generally trust Tsubaki chain and wear indicators because the catalog data has been reliable for our orders. But that doesn't mean it's the right answer for every application. If a machine needs a timing belt, buy the belt. If it needs an engine timing chain, buy the engine kit. If it needs a high-speed roller chain, buy a high-speed roller chain. No brand is always best. Saying so is how bad procurement decisions get made.

Bottom Line

Run through these six points before you sign the PO. It takes about an hour. That hour is cheaper than a reorder, a wrong part sitting in receiving, or a production stop. If you're here from a Volvo timing belt replacement search, leave with a belt kit. If you're replacing a chain, use the wear gauge, compare TCO, and don't reuse hooked sprockets. That's the checklist.