How to choose the right spring: a buyer's guide

If you’ve never specified a spring before, the language is intimidating. Free length, solid height, OD, ID, music wire, ASTM grade, closed-and-ground ends. All you wanted was a coil that pushes back when you press on it.

Most spring orders aren’t actually that complicated. Once you know which of the three main types you need, the rest is filling in numbers. Here’s a guide that walks you through the decisions, in roughly the order you should make them.

Step 1: pick the type

Springs come in dozens of geometries, but 90% of orders fall into three buckets.

Compression spring. A coil that pushes back when you compress it. Loaded along the axis of the coil. The most common spring in industrial machinery — automotive suspensions, valves, presses, mattresses, almost any mechanical device that needs a “push.” If you’re not sure, this is probably what you want.

Extension spring. A coil that pulls back when you stretch it. Has hooks or loops on the ends. Loaded in tension along its axis. Used wherever a mechanism needs to spring closed or retract — garage doors, exercise equipment, weighing scales.

Torsion spring. A coil that twists rather than stretching. The legs at each end rotate against each other, storing rotational force. Used in mousetraps, clothespins, garage door counterbalances, hinge returns — anywhere something needs to spring back to a position rotationally.

If your application doesn’t fit any of those, ask. There are also tapered springs (compression springs that collapse flat, used where stack height matters), constant-force springs (a flat steel strip on a drum that delivers the same force across long extensions), die springs (heavy-duty rectangular-wire compression springs for stamping presses), and disc springs (washer-shaped springs that stack for huge force in tiny spaces). Browse spring types →

Step 2: measure the existing one (or specify the new one)

If you’re replacing a broken spring, the easy path is to bring it to us — we can usually replicate the geometry on the spot. If you’re designing a new mechanism, you need to specify these dimensions:

Dimension	What it means
Wire diameter	Thickness of the wire the spring is wound from. The single most important number — most other specs depend on it.
Outer diameter (OD)	Across the outside of the coil, edge to edge.
Inner diameter (ID)	The hole through the middle. ID = OD − 2 × wire diameter.
Free length	How tall the spring is when no force is applied.
Solid height	How short it gets when fully compressed (compression springs).
Number of coils	Active turns that contribute to the spring rate.

If you only have one of these — say, the OD and the wire diameter — that’s often enough to start. We’ll come back with questions.

Step 3: specify the load (if you can)

The load is what the spring has to do. Two questions:

1. How much force does it need to push (or pull, or twist) at the working position? Measured in newtons or kilograms.
2. How much travel does the spring see between rest and load? Measured in millimeters of compression or extension.

These two numbers, combined with the wire diameter and OD, determine the spring rate. You don’t have to calculate the rate — that’s our job — but if you can give us the force and the travel, we can verify the geometry will actually do what you need.

If you can’t easily measure the force (most engineers can’t without a load cell), describe the application in plain terms: “It has to hold a 2-kg lid open against gravity” or “It returns the lever to neutral after the operator releases it.” That’s enough for an experienced spring engineer to spec something.

Step 4: pick the material

Daichi stocks two grades for general spring work:

• Stainless spring steel — for corrosion resistance, food contact, medical, marine, outdoor applications. Slightly lower fatigue strength than carbon, slightly higher cost. Default choice if any moisture, chemicals, or sterilization is involved.
• High-carbon spring steel — for indoor mechanical applications. Higher fatigue strength, lower cost. Default choice for industrial machinery, fasteners, hardware.

For die springs specifically, we use chrome silicon and chrome vanadium (industry-standard die-spring grades, color-coded by load class). These hold up to millions of cycles in stamping presses where standard carbon springs would fatigue.

For urethane springs (a non-metal alternative for shock damping or corrosive environments), we cast in polyurethane elastomer.

Specialty alloys — Inconel for high temperature, phosphor bronze for electrical contacts, exotic high-performance — can be sourced for production runs. Tell us the application and we’ll suggest the right grade.

Step 5: think about ends and finish

Compression springs have four common end styles:

• Closed-and-ground — flat, perpendicular to the axis. Best for stability and load distribution. Most common.
• Closed-not-ground — flat but not machined. Cheaper, used where stability is less critical.
• Open or open-and-ground — open coil at the ends. Used for specific clearance or geometry needs.

Extension springs need an end form too — German hook (one full bend up), English hook (a side loop), screw-in plug, swivel hook, or a custom-formed end to your drawing.

Finish is usually plain steel for indoor applications, zinc-plated for mild corrosion resistance, black oxide for low-glare aesthetic, or passivated stainless for sterile applications.

Step 6: figure out the order

Now the easy part:

• How many do you need? Anywhere from one piece (we have no minimum) to 100,000+. Different volumes get different prices per piece — we’ll quote both single-piece and run pricing.
• When do you need it? Stock items ship in 2–5 days. Production runs of custom geometries take 1–3 weeks depending on material availability and complexity. Walk-in single-piece custom is often coiled in under an hour at our Valenzuela factory if the geometry is straightforward.
• Where does it ship? Anywhere in the Philippines via partner couriers. International shipping by request.

What to send us when you ask for a quote

The shorter answer: whatever you have. The most useful inputs:

1. A sample of an existing spring (even a broken one with a coin for scale)
2. A drawing or sketch with the dimensions you know
3. A photo of the assembly the spring goes into
4. The application in plain English (“retaining a battery in a remote control”)

If you have all six steps from this guide answered, you’ll get a quote in minutes. If you have one or two, it might take a back-and-forth. Either way, send us a quote request — we’ll come back within 24 hours, usually much sooner.

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Daichi Springs has been manufacturing custom and standard springs in Valenzuela, Metro Manila since 1976. 35,000+ designs in stock. Walk-ins welcome. Get a quote →