Compression Spring Ordering Checklist: 7 Steps That Would Have Saved Me $3,200

I'm not going to start with a dictionary definition of a compression spring. If you're reading this, you probably already have a machine down, a quote on your desk, or a prototype that doesn't feel right. I've been in all three situations.

The mistakes I made while ordering springs cost me roughly $3,200 in wasted material, rework, and expedited freight. Most of that was avoidable. This is the checklist I keep next to my keyboard now. It's written for compression springs, but the logic applies to extension and torsion springs too. Seven steps. Do them in order.

Who should use this checklist

Use it when the part number is gone, when an old spring has no drawing, or when a supplier says “the dimensions look close enough.” That phrase should put you on alert.

• You're replacing a worn spring and the old part number is missing.
• You're trying to match a spring that another supplier stopped stocking.
• The spring is being redesigned for a new application or a new load requirement.

If you have a traceable OEM number and the original manufacturer still supports it, skip the detective work and buy that part. This checklist is for the rest of the world.

The seven-step pre-order checklist

Step 1: Say what the spring does when the machine runs

“I need a spring about 50 mm long” isn't a spec. It's one dimension. A spring that holds a detent in place and a spring that returns a heavy guard can have the same free length while needing completely different rates.

Before measuring anything, write one sentence: this spring pushes [part A] against [part B] with about [force]. If you don't know the force, start with a load measurement from the old assembly. Don't skip this because you're busy. It's the step that prevents the rest of this list from being guesswork.

Step 2: Measure the space around the spring, not only the spring

Most failed replacements I've been involved with started when someone measured outside diameter and wire diameter, then ordered the same dimensions without checking where the spring travels. Draw the installed condition and record three numbers:

• Maximum outside diameter: the smallest bore, slot, or housing the spring must fit into.
• Minimum inside diameter: the largest rod, pin, or post the spring slides over.
• Minimum clearance length: the shortest space available between spring seats at the end of the stroke.

If you're copying an old spring, don't assume its current free length is original. It may have taken a permanent set after years of service. Treat free length as information, not gospel.

Also check whether the spring might buckle. If free length is more than about four times the mean diameter, ask whether the spring needs a guide rod or sleeve. Long, slender compression springs can buckle before they reach their rated load.

Step 3: Convert heights into forces

Spring rate is force per unit deflection. If you say, “at 45 mm compressed, the spring should push with about 120 N,” a supplier can work with that. If you say, “make it look like this old one,” you're leaving the important part of the spec to luck.

The online calculators at lee-spring.com are free, and I still use one for a second opinion before I request a custom quote. Enter wire diameter, outside diameter, free length, and active coils. The calculator will at least tell you whether the combination makes sense.

I didn't learn this from a textbook. In 2019, I ordered fifty replacement springs with the same outside diameter, wire diameter, and free length as the original part. They fit. They were about 25% stiffer because I hadn't specified load at operating height. The vendor met the dimensions. My drawing didn't meet the function. That mistake cost about $860 in scrap plus a weekend changeover.

Step 4: Check solid height before you approve any drawing

Every compression spring has a length where the coils physically touch. That's called solid height. If your required compressed height is lower than that point, the spring will bind, the load will spike, and the next failure might not be the spring.

Your drawing should show a compressed height and a required load at that height. Ask the supplier to confirm solid height on their drawing. If a catalog page doesn't list solid height, ask before ordering. This is the step most people ignore because a spring on a bench looks fine at free length.

The question buyers usually ask is, “how long is the spring?” The better question is, “how short can it go before the coils touch?”

Step 5: Pick the end type on purpose

The ends aren't decorative. A plain-cut compression spring can be unstable when the load isn't perfectly centered. Closed ends are the default for many industrial springs. Closed and ground ends give a flat bearing surface and are common when the spring sits in a pocket or needs to stand square.

Don't leave the end condition blank. If you do, a supplier will use their default, and their default might work. The point is to know before the parts arrive, not after.

Step 6: Choose material and finish based on the environment

What looks like a simple spring can be made from music wire, stainless steel, chrome silicon, or beryllium copper. Each has different fatigue properties and corrosion resistance.

If a supplier says “music wire” and the application is outdoors, ask for a corrosion-resistant material. If they say “stainless steel,” ask which grade. 302 is common. 316 offers better corrosion resistance, but it isn't a drop-in for every high-stress spring. Chrome silicon can handle repeated impact better than many stainless grades. If the spring will be washed, exposed to salt, or stored in a humid area, say so in the RFQ.

Finish also matters. Zinc plating can add enough thickness to affect a tight outside diameter tolerance. Material selection is not the place to let the price sheet make the decision for you.

Step 7: Verify the first batch and treat small orders seriously

Ask for load tolerance at the installed height, free length tolerance, and a material certification when the spring matters. The manufacturer's test report is not an upgrade; it's standard. If a distributor doesn't have it, they can usually get it from the factory.

This is true for small orders too. I started with low-volume repair orders and prototypes. The suppliers who answered a $200 question with more questions were the ones who got bigger orders later. Small doesn't mean unimportant. It means potential.

If you're buying through a Lee Spring distributor, the part number from the lee-spring.com catalog is the cleanest way to communicate. Distributors keep local stock, but they can't read your mind from a photo of a rusty spring.

Warnings from the expensive file

Don't use an old spring's color as a spec. Plating colors vary, and many springs are oiled at the factory. Two identical parts can look different.

Don't replace half of a matched pair. When garage door torsion springs are involved, replace both sides. A new spring carrying more than its share will fail early, and the door can become dangerous. That's not a theory.

Don't assume the supplier knows the application. A rusty sample spring from a garage door opener doesn't tell anyone the required torque.

Don't approve drawings after looking only at dimensions. Check that the load at height is printed on the drawing.

This reflects standard spring specification practice as of April 2026. Material availability and lead times change; verify current part numbers before ordering.

The bottom line

Most wrong spring orders are not caused by bad suppliers. They're caused by incomplete specs that no supplier could have fixed. State the job, measure the envelope, convert height into force, check coil bind, choose end condition and material, then verify the first batch.

That list has caught more than a dozen mistakes for us. It takes about fifteen minutes. Use it before you send the next RFQ, not after you need the springs yesterday.