Compression spring end types: a simple guide

The ends of a spring are the two turns of wire right at the very tips — one on top and one on the bottom. They look like a small detail, but they make a big difference. They decide whether the spring stands nicely on its base, whether it pushes straight, and whether it fits neatly into the place where it works.

In this guide we will explain, in plain words, how the ends of a compression spring are shaped, what the four most common types are, and how to pick the best one for your job. No complicated math — just what you need to order the right spring with confidence.

What the spring's ends are

Picture a compression spring as a spiral staircase made of coiled wire. Most of those turns sit in the middle and do the pushing: they squeeze together and spring back when you let go. The ends are the first and last turns, and their job is different. Instead of pushing, they act as a base — like the feet of the spring.

The way those last turns are shaped changes everything. A well-made end lets the spring rest firmly and straight. A poorly finished end can leave the spring leaning to one side, so it pushes sideways instead of straight up. That is why it pays to know your options before you order.

It is a simple detail, but it shows up every time the spring touches a surface. And since every spring has two ends, this care counts twice.

The four most common end types

There are four common ways to finish a compression spring. They range from the simplest and cheapest to the neatest and most precise. Which one you choose depends on how much you want to spend and how straight the spring needs to sit. Here is each one and when to use it:

• Open (or plain) ends: the wire simply stops, following the same slope as the other turns, like the end of a spiral staircase. This is the cheapest option. The spring may sit a little crooked. Good for simple, rough or low-cost jobs, when the finish is not so important.
• Closed (or squared) ends: the last turn is bent inward until it touches the neighboring turn, forming an almost flat base. The spring sits much straighter. It is a great everyday choice, because it balances price and quality.
• Closed and ground ends: after the end is closed, it is sanded down until smooth and flat, much like sanding a piece of wood. The spring sits perfectly straight and pushes right along its axis. This is the best option for precision and higher loads, but it costs a bit more.
• Plain ground ends: these are open ends that are also sanded flat. They land in the middle: flatter than plain open ends, yet without the full finish of closed and ground ends.

Why ground ends matter

Grinding is just the technical word for sanding the end of the spring until it is flat and smooth. Think of it as giving the spring a steady foot. With a nicely flat base, it stands up on its own, does not tip over, and spreads the load evenly across the whole resting surface.

When the end is not ground, it usually finishes at a single point, leaving a small bit of leftover wire. That makes the spring rest crookedly, like a table with one short leg. Over time, that tilt can wear the spring unevenly and even make it push sideways, slipping out of place. For jobs that need precision, a ground end avoids these problems.

How the ends change the spring's size

The turns at the ends do not push like the turns in the middle — they only form the base. On closed and ground springs, about two turns are used up this way, one at each tip. So when making the spring, the factory usually adds a few extra turns to make up for it and deliver the force you need.

The ends also change the spring's size when it is fully squeezed. When you press the spring all the way, every turn touches its neighbor and the spring reaches a minimum height, called the closed height (or solid height). A very simple sum gives you a rough idea of that height:

In other words, the thicker the wire and the more turns the spring has, the taller that minimum height. Ground ends, because they are sanded, leave the spring a touch shorter when fully squeezed. You do not need to memorize the formula: it is just there to show that the ends affect the final size of the spring.

How to choose the right end

The good news is that choosing is easier than it sounds. Just think about two things: how much you want to spend and how straight and precise the spring needs to sit. Here is a quick guide to steer you:

• Needs to be cheap and the finish does not matter much: choose open ends.
• Everyday general use with good seating: choose closed ends.
• Needs precision, a nice flat base and to handle more load: choose closed and ground ends.

Where you see this in everyday life

You are around compression springs all the time, even without noticing. The spring in a click pen, the one in a shock absorber, the one in a valve, or the one behind a machine button — they all rely on their ends to work well.

In a simple pen, an open end does the job. In equipment that needs steady force and precise alignment, like a valve or a machine part, closed and ground ends make sure the spring always pushes straight and in the right spot. Noticing this difference helps you ask for exactly what your project needs, without overpaying or cutting corners where you should not.

On molas.app.br, choosing the end type is simple and visual. You pick the end you want and watch the spring update instantly in 3D, while you follow the price adjusting on its own. So you can spin the spring on screen, compare the options, and see exactly how each end type changes the look and the fit — all before you place your order.