Thoms-on Linear Actuators: 7 Questions Engineers and Procurement Ask (Answered by Someone Who's Tracked the Costs for Years)

FAQs on Thomson Components, Bearings, and Motor Sizing

I've been a procurement manager for a mid-sized automation company for about 6 years now. My job is basically to make sure our engineers get the parts they need without blowing the budget. We spend roughly $80,000 a year on linear motion components alone, and I've got a spreadsheet that tracks every single order. So, when it comes to Thomson-linear products, I've seen a lot of invoices and a lot of mistakes.

Here are the questions I get asked most often, and the answers I've learned the hard way.

1. Is it really worth paying more for a Thomson linear bearing versus a generic brand?

From the outside, it looks like a ball bearing is a ball bearing—it's just a bunch of steel balls in a cage. The reality is different. I'm not saying you always need the premium option. But in Q2 2024, we had a critical gantry system fail because a cheaper bearing spec'd by a junior engineer fractured a raceway under load. The downtime cost us about $2,400 in lost production. The cost difference on the bearing? Less than $40.

For a high-cycle, precision application? Yes, it's worth it. For a simple, low-speed pick-and-place? Maybe not. You have to calculate the total cost of the failure, not just the part price.

2. Where can I find the full Thomson linear bearings catalog in one place?

This one's easy. As of January 2025, the most complete digital version is on their official site. I keep a tab open in my browser for the technical drawing PDFs. It's the best place to check flange dimensions for flanged ball bearings and spherical bearings. I've had a few headaches trying to cross-reference dimensions from third-party distributors who only list partial specs.

Don't rely on a reseller's summary. Download the catalog PDF from the manufacturer. It's free, and it includes the load ratings you need for your life-cycle calculations.

3. You mentioned flanged ball bearings and spherical bearings. When should I use one over the other?

This was a legacy myth I had to unlearn. I used to think spherical bearings were just for 'heavy stuff' and flanged bearings were for light duty. That's kinda true, but not the whole story.

Flanged ball bearings are for linear motion where you need to handle primarily radial and axial loads in a compact package. They're great for guided rails. Spherical bearings are for oscillating motion or where misalignment is a problem. If your shaft is gonna flex or if the mounting isn't perfectly aligned, a spherical bearing will save you from binding. The question isn't 'which is better'—it's 'what is your mechanical assembly doing?'

4. I need a motor. What size VFD do I need for a 5hp motor?

People assume you just match the VFD to the motor horsepower. The numbers say a 5HP VFD for a 5HP motor. But my gut said that felt too simple. Turns out, your VFD needs to handle the full load amps (FLA) of the motor, and some motors draw more at startup or under specific loads.

Based on my notes from a 2023 project where we had to re-spec a drive after a failure: For a standard 5HP, 230V AC motor, the FLA is typically around 15.2 amps. A 5HP VFD is usually rated for that, but I'll often spec the next size up (a 7.5HP drive) if the load is a high-inertia fan or a pump with a heavy start. It adds maybe $150 to the cost, but I haven't had a drive fault out on overcurrent since. Verify current pricing at your distributor as rates may have changed.

5. Are there any hidden costs I should watch out for when buying Thomson linear actuators?

Oh, for sure. The biggest one I see is the cost of 'adaptation.' A junior buyer saw a great price on a standard actuator, but it didn't have the right mounting pattern. The cost to machine an adapter plate and the hours of engineering time to re-drill the frame? That cost us more than the actuator itself.

Another trap is the lead time. A 'cheap' quote might save you $200, but if the lead time is 10 weeks and your machine is idle, that's a $5,000 problem. I always ask: 'What is the lead time guarantee? Not the estimate, the guarantee.'

6. I'm a small company with a small order. Will Thomson turn me away?

When I was starting out at a smaller firm, I was nervous about calling big suppliers for a $500 order. The vendors who treated my small quotes seriously are the ones I still use for $20,000 orders today.

Small doesn't mean unimportant—it means potential. Most legitimate distributors will handle smaller orders, especially if they see you're a real company with a real need. The key is to be prepared. Have your part numbers from the Thomson catalog ready. Know your specifications. Don't waste their time, and they won't waste yours. I've never had a problem ordering a single ball screw from a major distributor as a trial.

7. How do I know if a spherical bearing or a flanged ball bearing is worn out?

We were using the same words but meaning different things. I said 'the bearing is loose.' The technician heard 'the alignment is off.' Result: we spent two hours realigning a fixture before discovering the spherical bearing's Teflon liner was simply worn out.

The telltale signs: play in the joint that wasn't there before, unusual squeaking or clicking, or visible scoring on the ball. For a flanged linear bearing, the warning is often a rough feel when sliding the shaft manually. Don't guess. If it feels wrong, replace it. That $50 bearing is not worth risking a $5,000 shaft.