Extension Springs. A Guide To the Manufacturing Process

As part of our continuing series to simplify some of the concepts around spring manufacture we look at the manufacture of the extension springs. It is helpful to consider the process from the perspective of creating the product manually so as to better visualise the process and concepts involved. It goes without saying that at Transworld Engineering we have the tools and machines to automate this process for you. If you would like to learn more, then why not book a visit to our showroom.

The following section will explain how to manufacture extension springs

Wire Length

When creating individual springs for testing There is little need to calculate the precise length of wire required per spring for manufacturing short extension springs with wire up to approximately 0.250" or light wire. However, it would help if you had a sufficient buffer of extra length. To estimate the wire length, you can take the actual measurement of the spring's length. Divide the wire length by wire size to calculate the estimated number of coils in the spring. Multiply that figure by 3.3 (an exaggerated Value of Pi). It will result in a wire a little longer than your requirement, which should not be an issue as you can use the first few springs in the loop making setup.

Coiling the First Trial

You are now ready to manufacture the extension spring.

Cut a piece of wire in the correct length. In the case of light wire, you can undo the wire and put it in front of the winding machine or lathe. To avoid tangling of wire, start by taking the wire end inside the coil as your starting end. You may coil multiple springs simultaneously by cutting off a longer wire length if you want to coil short springs.

You can now fire up the oven while ensuring that other people in the area remain out of danger while completing the rest of the process.

You need to put the wire into this setup and bring the wire guide to the left side near the pickup pin.

Begin the coiling process. Move the chuck carefully while ensuring that the wire rests on the pickup pin, which in turn should be seated on the wire guide. You can now allow a few coils to lay down on the finishing plate.

Once you lay down a couple of first coils on the finishing plate, you can proceed to the next step. At this point, you need to ensure the functioning of the following two processes simultaneously.


1. Move the wire guide slightly to the left side. You should ensure a gap between the two initial coils while laying down the wire over the finishing plate. At the same time, you should not let the wire run over itself when you turn the finishing plate.

The idea of keeping a gap controls the "initial tension." Such initial tension is the vital force in the wire, which applies some pressure on the spring to break the coils apart. For example, there is enough initial tension in Garage door springs. However, there is hardly any initial tension in slinky toys, which are essentially extension springs without any loops.

2. You have to discontinue winding if you notice any of the following two events

a. You have got to the point beyond which you can't approach your lathe machine's "off" switch.

b. You don't have any more wire left.

Now, the wire guide has comes closer to the endpoint of the finishing plate.


Back off the chuck to allow the spring to remain loose on the finishing plate. In case you are using a light wire, you may hold the spring body close to the chuck and pull the dogleg out. It will loosen your grip to allow the coils to unwind slowly. Finally, move the wire guide by sliding it and spring off the finishing plate.

Now you can put the spring into the oven to relieve the stress. Please note that springs manufactured from stainless steel will expand slightly with the heat. On the other hand, springs made from music wire will contract a little.

After you have completed this process, you should allow the springs to air cool. Afterward, you can check the diameter for accuracy. If you have followed it properly and ensured the setup as explained, you should get the exact diameter you had planned.

Now observe the coils of the extension springs. All those coils must lay flat against each other up to the end of the spring body. If you notice any gaps in the spring body, it implies that you had allowed the wire guide to slide to the right side at the time of coiling.

If we consider the manufacturing of extension springs as a manual process, which isn't the usual case here at Transworld Engineering of course, it is easier to highlight the differences between the manufactured level of tension in an extension spring, and the typical and reasonable operating tension.

In the manufacture of an extension spring, there are things that we need to consider. One of these is the initial tension of the extension springs and how it relates to the working tension of the springs in their daily uses. The probability of there being a difference is high. The loops at the end of your spring’s end may or may not cross or line up with each other. Where your spring is long enough, you can opt to twists these loops to make them cross or align with each other. They will remain held in that position due to the initial tension.

It is essential to assume the loop position.

Loop Making

Below, we are going to discuss the process of making a basic type of loop that has no frills and will work with most springs. You can make other types of spring loops that are stronger, more efficient, and prettier. However, there are specific tools that you must have for you to make these types of loops.

Step by Step Procedure of Making a Simple Loop

1. Cut and get rid of the spring’s end. It is crucial as you will leave the coils that are in contact with each other all the way around.

2. Mount and firmly your spring in a vice between the two looping plates.

3. Using your looping rod, reach into the spring’s centre and hook your rod’s tip under the first coil.

4. Push the rod downwards to apply pressure that will bend the rod upwards. Let go of the rod when the coil top is directly above the spring’s centre.

5. Reach under the already bent coil using a looping rod and using the tip’s rod, snag up the end of the wire.

6. To align the coil’s end with the spring’s body, apply pressure to bend it.

After performing this procedure, you will have made one end of the spring. The next step in creating a simple loop is figuring out the length of wire that you need to get rid of on the other end to achieve the desired length. If you wish to make it a little short, extend your hooks. All you need to do is straighten out the wire once you take it off the body of your spring.

Where you aim to make just one short spring from your coil, count the coils you have and depending on the number you need, add or remove to remain with the number of coils you need. If you have wound a long coil when you are making a short spring, repeat the same thing. Using your wire cutters (or a cut-off-wheel where you are working with a heavier wire), from the main body, detach the first spring.

Cut off some parts of the whole coil for you to achieve the right length. However, keep in mind that you are only needed to add to each end of spring “just shy of a full coil” for you to achieve a high-quality product.

Alternatively, where you have a long spring (or where you do not wish to waste your time counting the number of coils), all you need to do is measure the coil’s body and make an addition of about 1 coil.

Once you trim the body of the coil to size, proceed to make the second loop. The procedure for making the second loop is similar to that of making the first loop. To ascertain if you have come up with the desired length of, double-check the spring inside one hook to the inside of the other. Checking in this manner allows you to get the best and accurate results.

Where the length of the spring you have made is very short, there are several options for you to correct it. You can choose to either make the next spring with a fancier loop type or with more coils.

Loops and Hooks

For most extension springs, loops are the most convenient and ideal. However, there are times that you will need to use hooks for efficiency. For instance, you need to use a hook when you want to slip your spring onto a pin.

Swivel Hooks

There are times where hooks that swivel are ideal for making extension springs, but if you do not have kick press tooling, it is a challenging task. For you to be on the safer side, ensure you purchase a commercially made one.

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