Working with Mainsprings

Working with mainsprings

     To Purchase mainsprings through us you'll need the following information: the width in mm, the thickness in mm, and the approximate length in inches of the existing spring. Then determine if the mainspring is a hole end or a loop end. It is easy to tell what style a mainspring is, some mainsprings have a cover around them, and these covers are called barrels. Mainsprings that are in barrels are always hole end mainsprings.

  The loop end mainsprings are the type that are visible from the back of the clock and they have a loop at the end of them.  This loop goes around the pillars that hold the movement together. For this reason, a clock with a broken loop end mainspring must come completely apart to replace the spring. 

    Replacing mainsprings involves letting the power out of any other mainsprings in the movement, so they wont fly out of control and damage you or the rest of the clock. This is done with a mainspring let down tool, do not attempt to use the clock key, this could cause an injury. 

    As the power is being released from the spring, it is desired to keep the mainspring small and harmless, so the power of the spring is released into a mainspring clamp with a mainspring let down tool.

    One of these clamps goes over the mainspring after you wind the clock up, then the power of the spring is released slow until the spring is harmless in the clamp. Mainsprings are serious business, they pack a punch, so please do not take them too lightly and end up getting smacked by one. If you use these tools as suggested you will be fine and have nothing to worry about. As far as the mainsprings in the barrels go, they sometimes can be removed from the clock without taking the movement completely apart, but still needs the power released first.

    After the barrel is in your hand, with the mainspring inside, it is time to take the cap off the barrel. The cap is the only part of the barrel that comes off, so it is pretty easy to find. Pop off the cap off with a appropriately sized screwdriver inserted into the slot provided and you will see the broken mainspring. The arbor that connects to the center of the spring is only connected by a nub hooked inside the hole at the beginning of the mainspring. Just turn the arbor the opposite way of the spring winding direction, and you will see the nub pop out of the mainspring hole. Then the arbor will be loose and able to come right out of the barrel. Now all you have is a barrel with a broken spring in it. 

   I have used this method when a winder is not available to remove an old spring: I hold the barrel tight with a towel wrapped around it, with only a small opening in the towel to get a pair of needle nose pliers to the mainspring. I hold the entire operation as far from my body as possible, then yank the spring out with the pliers. Of course the spring goes wild when this is done and its moderately dangerous. I have never gotten injured doing this and hope you won't either. Just take control of handling mainsprings with precaution and confidence, and you will find that they are an easy obstacle to conquer. Oh, by the way, I am not liable for anything and you are at your own risk. Sound encouraging? If you do not like this style of removing a mainspring from a barrel, we offer various books with other techniques. We also offer the hole end mainspring winder. 

    To put the new spring into a barrel is easier because the new springs come already wound up. It is held in position by wire, and you simply push the spring into the barrel. As the mainspring is pushed into the barrel, the wire slides up and off the spring, until -snap- it goes in completely. The hole end mainspring winder will again make this safer and easier. The risk of doing it without the spring winder is some barrels are made of metal that will shatter on impact from the released spring.

    To insert a unwound spring back into the barrel is trickier. This can be done by hand, but is again, moderately dangerous. Start with the outer hole of the spring hooked to the barrel hook and curve the spring from outer to inner until the spring pops in. This takes strong hands and alot of guts, if the spring gets the best of you, it could hurt. I can tell you I have done it this way many times and have never gotten smacked by a spring. Wear a full suit of armor doing this. Mainsprings can do alot of damage to a clockmaker. If you do not have confidence in doing this, buy a new spring (they do not cost much) or get a hole end mainspring winder tool from us here at Clockworks. 

    The cap of the barrel can be put back on easily with a vise. Start putting the cap on the barrel with the fingers until it wants to go in, but needs that 'snap' to get it into place. Just apply just enough pressure to see it snap into place. Give the movement a visual check over to see if anything was damaged due to the mainspring breaking. It is quite an impact on the clock when a mainspring lets loose and it is good to check the following: See if the click, the part that keeps the mainspring winding in only one direction, is okay and not to loose. See if there are any bent gears. See if there are any bent pivots.

    Pivots are the part of the gear arbor that stick through the plate of the clock. It is really an arbor, but the skinny end of the arbor that sticks throughout the plate is called a pivot in clock world. If these get bent, then it will create to much resistance in the gear train to let the clock run.

Mainspring Breakage

    When a mainspring breaks it can cause a lot of damage to the rest of the clock. After letting the power of any other springs so they are harmless in  the clamps, disassemble the movement. Now check for bent pivots and arbors, pivot holes that are opened larger from the shock, and broken teeth on the gears.

    Arbors are the first to be straightened with whatever means you have. A steel block and a hammer would work. Then attempt to straighten the pivots. Use your judgment on the method to straighten out the pivot, a vise is an option and so isn’t flat nose pliers with no ridges. Make sure there are no ridges on the pliers because if you mare up the pivot then when its back in the clock it will eat away at the brass plate. You have about one shot at straightening the pivot, if the pivot is bent this way or that way too much it will break. This would call for re-pivoting and that is a whole different topic to be covered later.

    Now you have the arbors and pivots straightened it is time to inspect the pivot holes. If the pivot holes are oval instead of round then it is time for bushings. Again this is a different topic and shall be covered later.

    Time to look at the gears (AKA wheels) and see if the teeth are bent or worse, BROKE.  If they are bent, bend them back and then use emery cloth to make them smooth again. If they are broke then there is still hope. If the movement is still made, its time for a new one, check with us to find out. If the movement is an antique and no longer in production, then you may still be able to get a movement (that is not the quality of the new one) that is made in Korea. There is also an option of looking on for a junk movement that will match yours and the last option is to fix the gear with new teeth. Replacing teeth is covered later on.

Cleaning the mainspring

If the mainspring is not broken and does not seem visually bad or gummy then best to do nothing with it. That is not to take it out of its clamps or barrel at all during the cleaning process. Even then, if a spring seems bad enough to clean, replacing the spring is less dangerous, cleaner and it comes pre lubricated. Sometimes the spring is not made or is a unusual size so it costs more, in this case the spring can be cleaned. A mainspring can be cleaned by using solution if it is built up with old oil. The solution goes on some cloth and then rubbed on both sides of the spring. If the unwound spring is a foot or more in diameter (in a American 8 day time strike movement taking a ¾ x .018 x 96 spring) than it should be good to use after it is cleaned. The purpose of cleaning the spring is so when it is wound up it won’t stick to itself. When a mainspring sticks to itself then it can’t put out the power it used to because of the friction. The answer is not WD 40. This stuff makes a mess, after awhile it turns into blue goo although from the start it seems to do the trick perfect. When your done with wiping the mainspring down with the cloth soaked with solution its time to rinse it with something, preferably clockmaker rinse, but if none is available try denatured alcohol or warm water if it comes down to it. Then blow dry with a hairdryer on low heat. And I mean low heat, if you get this sucker to hot it will break when you wind it and that would be a lot of wasted effort. On the flip side if you use the warm water and it is not dried all the way, you risk it rusting. When it is done with the cleaning and drying, its good to go over it with steel wool to polish it. Now you have a mainspring that will not stick to it self and that is the goal. Lubricating with mainspring grease is optional. 


Click rivets that have come loose happen for a variety of reasons. If you have the clock movement out of its case, and you see the clicks rivet is loose, best to do something about it. Let the power down from the mainspring into a clamp, then replace the rivet. If the rivet hole is oblong instead of round, make the hole round again with a broach or file. The installed rivet should be tight and secure but at the same time letting the click move back and forth freely before the click spring's pressure is reapplied. Clicks and Rivets are on the Hardware Pages of the Clockworks website.

Mainspring over-wind myth

Clocks can’t be over-wound. I do not mean to say this to prevent you from over winding a clock, but to release the myth of over winding from your mind. Over winding is not possible on clocks, the myth started with some pocket watches that could be over wound and has been feared of ever since. The mainspring does have less power sometimes when it is fully wound then it does say ¾ of the way wound. This is because the mainspring with old oil built up on it will stick to itself and not be able to give the power it should. If a clock has a mainspring in good condition it should be able to be wound all the way up with no problem. Clocks that are “over wound” most likely need to be cleaned..

Mainspring repair

Hole end mainsprings that break near the outer hole may be able to be repaired by cutting the springs bad section out and making a new hole. The bad section gets cut out with shears. Next the mainspring gets clamped down on a piece of wood and punched to start a hole for the drill to get into. With the spring clamped down good, drill your new hole. Wear eye protection when doing this for sure.

    The mainspring that has been cut down so it is shorter only means the clock will not run as long, if it is an 8 day clock then it might only last 7 days instead. Of course the best thing to do would be just to buy a new one. On rare occasions the clock requires a strange sized spring that is not available. We have a chart of all the Hole End Mainspring sizes available to be purchased new.

    Loop end mainsprings that break are more difficult to remedy. Best to get a new one. If the clock is an American 8 day time strike movement chances are the dimensions of the spring is ¾ x .018 x 96”. We have a chart of all the Loop End Mainspring sizes available to be purchased new.

Mainspring lubrication

Mainsprings are not oiled, they are greased if anything at all  Generally speaking, if it turns then oil it, if it slides then grease it. The mainspring should be greased or nothing at all. If greasing is your option then it should be done when it is out side of the clock movement and uncoiled. The practice of applying a couple of drops of oil onto a wound up spring just does not work and creates a mess in the future, same with WD40. I have heard of people having good luck with carburetor cleaner sprayed on the spring but I have not tried it yet. A clock should be able to run with no lubrication at all anywhere, lubricating just being something to help it work and add some preventive maintenance to reduce pivot hole wear. So when lubricating, only a little is needed in any spot there is friction otherwise it builds up and will be more difficult to clean next time.


Using a Mainspring Winder

    Using a mainspring winder is the safest way to work with mainsprings. They can work with both loop end and hole end springs. It consists of the main winding component that has a switch to flip from wind to unwind. The also come with an assortment of chucks that go into the mainspring barrels when working with hole end mainsprings.

    To remove the hole end mainspring from its barrel, follow these steps. Pop off the cap to the barrel by whacking the end of the arbor with a wood hammer just enough so the cap pops off, but the mainspring stays inside. Then insert the correct sized mainspring let down tool into the end of the mainspring winder. Find the proper sized chuck that is to hold the mainspring and put it over the end of the winder where the let down tool is located, then put the barrels winding stem arbor onto the let down tool that is inserted in the machine. Now you bring the tail stock of the mainspring machine up to the other side of the barrels arbor, set the machine to wind, hold the barrel with your hands (using gloves) and start winding up the spring. When the spring is wound enough to get the holder in place, insert the holder over the spring leaving some of the springs length out of the holder where the hole end is. Then unwind the spring into its holder. Now you can remove the barrel from the spring's end by just turning it the opposite way of the springs direction, just enough to release the barrels hook from the springs hole.  Remove all this from the mainspring winder now, so you can take the barrel out of the way. With the barrel out of the way, you can now put the holder with the spring in it back into the machine. (Leave the springs arbor still in the middle of the spring) Hook up the mainspring to the tool just as it was before with the let down tool on one side and the tail stock on the other side of the arbor. Then insert the winder tool's hook into the hole of the mainspring and wind up the spring until the holder can be removed. Unwind the spring without the holder now until it is completely unwound then it can be cleaned in solution and greased with mainspring grease. To put the spring back into the barrel is self explanatory, just do the reverse process.

    To use the winder on loop end mainsprings is possible also. After removing the spring from the clock with the mainspring clamps on, put the winding stem of the arbor into the let down chuck that is inserted into the headstock of the mainspring winding tool. Then reverse the tailstock so the bar that sticks out of it can be inserted into the loop of the mainspring and the whole thing can be positioned as to secure the other end of the winding arbor. Now the spring can be wound up enough to remove the mainspring clamp, and then unwound completely with out the clamp. Now the spring can be cleaned with solution and dried with a blow drier, then greased with mainspring grease. To put the spring back into the clamp is to do the opposite of the removal.

    See how safe and easy a mainspring winder makes it? It should be called a hole end and loop end mainspring winder and unwinder tool. This tool takes the fear from clock repair. People have lost eyes, cut there gut open, and other horrible things from attempting to wind or unwind mainsprings by hand. This tool eliminates all these catastrophes from happening and is a must have for a clock service center.