Clock Loop-End Mainspring Replacements

Loop-End MainspringDescriptionDamage AssessmentMeasuring the Mainspring

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Loop-End Clock Mainspring Description

Loop-End Clock Mainspring Description would be a long flat spring with a loop on one end that gets wrapped around a movement pillar. In other words this is the type of mainspring you can see when you look at the movement, it is not contained in a barrel style container. You can see the mainspring wind up when you use the clock key, unless it is broken of course. If broken it will seem like its winding up when you turn the key, only to snap back again, so you end up just winding it forever with nothing happening. When the mainspring is broken they sometimes stick way outside the side of the movement. Sometimes when these break when inside the clock case it will even blow out the side of the wood case. I have seen ginger bread or kitchen clocks where the power of the snapped spring slams against the inside wall of the case and some case work is needed as well.

These mainsprings come wound up with a tie wire around it. Usually they can be installed in the movement just as it comes, wound up. Once the movement is reassembled perfect, you can wind up the mainspring and cut that wire off of it. As mentioned in other sections, treat these things with respect and caution. Wear safety glasses when working with mainsprings and also gloves, seriously these things can punch you, wack you, cut you, and snap at you. I dont mean to scare you away, just use caution because they do pack a punch.

We offer a repair service if you just want us to take care of it for you instead. We do them all day long, it would be part of an overall movement restoration job and not just a mainspring swap out if you send it in. If you choose to go this route please email a picture of the movement so we can quote, to [email protected]

- - The content of this web page and web site was written and copyright by James Stoudenmire of Clockworks.com - It may not be used commercially without permission. - -

Clock Mainspring Break - Damage Assessment

Clock Mainspring Break - Damage Assessment these are the common things to inspect prior to purchasing the spring, so you know what your in for prior to taking on the project.

If the clock has lantern pinions it is possible that a pin on the lantern pinion is bent or broken off completely. It would happen on the next wheel up from the mainspring gear, or main wheel you could call it. The impact of the main wheel from the break jolts the next wheel up with such force the pinion cant withstand the impact often. These are not so easy to repair if the pin breaks, it requires the removal of the pinion and also the pinion dismantled to restore it. The gear or wheel you could say, comes out, the pinion removed via staking set, and repaired with the same steel rod size to make perfect again. If the pin is just bent sometimes it can be straightened again with needle nose pliers for a quick fix.

Clock Mainspring Break - Damage Assessment to the arbor of the next wheel up from the main wheel is also something to check. See if its bent instead of straight, often it will be bent from the impact of the mainspring breaking and would need to be straightened again if possible. It maybe hard to tell if it is in the clock, best to remove it and roll the arbor half of the wheel on the table and see if it rolls straight. Also and just as important check the skinny ends of the arbor known as the pivots. These are the skinny ends of the arbor that stick into the movements outer main brass plates, in the small holes. If these are bent, the clock will not run. They need to be straight or the clock will have too much resistance in the gear train for the clock to function under the power of the new mainspring.

Lastly inspect the teeth of the gears on both the main wheel where the spring was attached, and the next wheel up. Bent teeth are common but not as easy to correct. Bending back and reshaping them with a needle file sometimes works, other times the wheel needs a chunk cut out and replaced with new teeth or dentures you could say i guess, soldered in place.

If this is not in the realm of your interest in learning about and experimenting with, please send us the movement instead. We will take care of everything for a fee. Please email a pic of what is going on to [email protected] so we can quote.

- - The content of this web page and web site was written and copyright by James Stoudenmire of Clockworks.com - It may not be used commercially without permission. - -

Clock Loop-End Mainspring Measuring

Clock Loop-End Mainspring Measuring is explained in this section. Always wear gloves and safety glasses when working with mainsprings as they have a habit of shattering, snapping, expanding rapidly and unexpectedly. It depends on the job of course, but they can wack you, cut you, all these things. Just treat them with caution and respect, protect your hands and eyes. Not to scare you away, just want you to be aware if a mainspring is wound or stretched out, there is some power there and they can pack a punch.

Items needed for this measurement is a tape measure and a digital caliper, these are the best things to use. To get the width of the mainspring is easy, just use the digital caliper in inches and see how wide it is first. When you have the width, find that width section first on the below chart. Next is the thickness, again using the digital caliper. Write these two measurements down and again refer to the chart and narrow down the section even more. Now you have a narrow section of the chart of sizes your working with and only need the length.

The length is sort of tricky, what we do here is put the end of the spring in a vise and stretch it out with a tape measure beside it as we unwind it. Of course the tension of the spring is such it wants to wind back up in a violent manner and if you let go it winds back up with a snap. This is the sort of stuff that I was cautioning about earlier, if no gloves it can cut. If there is a cat sitting by the vise and you let go, the cat may not like you anymore, things like this. The length is the hardest to get but close enough is good enough. Match the closest one to the chart and you are done. The length has not much to do with the function of the clock, only the time in which the clock will run. For example if the mainspring substantially shorter, it may not run the full 8 days.

The most common size loop end mainspring for antique 1900s through 1945 American units is CML304. This size was sort of the industry standard when Seth Thomas, New Haven, Gilbert, Sessions was in full swing with the 8 day time strike units in mass production.

- - The content of this web page and web site was written and copyright by James Stoudenmire of Clockworks.com - It may not be used commercially without permission. - -

Loop End Mainspring
Clear
LESPRING: $14.89$49.89

Loop End Mainsprings Measurements to item #

WIDTH inch | mm THICKNESS inch | mm LENGTH inch Item #
1/8" 3.2 .010" | 0.25 19" CML 245
9/64" 3.6 .009" | 0.23 25" CML 246
5/32" 4 .009" | 0.23 26" CML 247
3/16" 4.8 .012" 0.3 31" CML 252
3/16" 4.8 .016" 0.41 54" CML 253
13/64" 5 .0105" 0.26 25 1/2" CML 254
7/32 5.6 .011" 0.28 24" CML 255
7/32 5.6 .017" 0.43 30" CML 256
1/4" 6.4 .010" 0.25 26" CML 257
1/4" 6.4 .012" 0.31 41" CML 259
1/4" 6.4 .013" | 0.33 24" CML 260
1/4" 6.4 .016" | 0.41 54" CML 261
9/32" 7 .009" | 0.23 30" CML 262
9/32" 7 .012" | 0.3 27" CML 263
9/32" 7 .012" | 0.3 30" CML 264
9/32" 7 .017" 0.43 48" CML 265
19/64" 7.5 .015" 0.38 39" CML 266
5/16" 8 .009" 0.23 20" CML 267
5/16" 8 .009" 0.23 36" CML 268
5/16 8 .010" 0.25 30" CML 269
5/16 8 .013" 0.33 24" CML 270
5/16" 8 .013" 0.33 30" CML 272
5/16" .013" 0.33 30" CML 272
5/16" 8 .015" 0.38 42" CML 273
5/16" 8 .016" | 0.41 54" CML 274
5/16" 8 .016" | 0.41 72" CML 275
5/16" 8 .017" | 0.43 42" CML 276
5/16" 8 .020" | 0.51 46" CML 277
3/8" 9.5 .011" 0.28 51" CML 279
3/8" 9.5 .013" 0.33 34" CML 280
3/8" 9.5 .014" 0.36 48" CML 281
3/8" 9.5 .014" 0.36 60" CML 282
3/8 9.5 .015" 0.38 53" CML 283
3/8 9.5 .016" 0.41 60" CML 284
3/8" 9.5 .017" 0.43 96" CML 285
3/8" 9.5 .019" 0.48 48" CML 286
7/16" 11 .014" 0.36 72" CML 287
7/16" 11 .018" | 0.46 48" CML 288
7/16" 11 .018" | 0.46 60" CML 289
1/2" 12.7 .015" | 0.38 84" CML 290
1/2" 12.7 .016" | 0.41 66" CML 291
1/2" 12.7 .018" | 0.46 60" CML 292
1/2" 12.7 .018" 0.46 96" CML 293
6/16" 14.3 .015" 0.38 78" CML 294
9/16" 14.3 .018" 0.46 96" CML 295
5/8" 16 .013" 0.33 69" CML 296
5/8 16 .018" 0.46 96" CML 297
11/16 17.5 .015" 0.38 108" CML 298
11/16" 17.5 .018" 0.46 96" CML 299
3/4" 19 .012" 0.31 72" CML 300
3/4" 19 .014" 0.36 108" CML 301
3/4" 19 .016" | 0.41 78" CML 302
3/4" 19 .017" | 0.43 120" CML 303
3/4" 19 .018" | 0.56 96" CML 304
13/16" 20.6 .018" | 0.46 96" CML 305
7/8" 22.2 .018" 0.46 96" CML 306
1" 25.4 .018" 0.46 96" CML 307