Clock Movement Hole-End Mainsprings

Hole End Clock Mainspring - For a mechanical spring driven clock movements that have a barrel cover over the spring. - Clockworks
MainspringsMeasuring the MainspringAssessment of damageReplacement serviceRemoving a barrelHermle barrel numbers

Please view these information tabs to help with the proper Clock Movement Hole-End Mainsprings size for your clock.

About Hole End Mainsprings

The type of springs that are wound in a brass barrel enclosure is known as a Hole End Mainspring. Measure the Hole End Mainspring by taking the spring out of the brass clock movement barrel. The mainspring has to come out of the brass barrel in order to measure it. There is no other way to do this task. This sounds easy but carefully read the following text on how to do this safely.

Warning

WARNING: Always wear safety glasses and gloves when working with hole end mainsprings. They can, and will be, extremely dangerous to work on. Removal can be violent so please be cautious and know that springs always store power when it is in a coil for so long. The spring can be broken, or off the hook from the center, and still have an extreme amount of power in the spring. It can whack, cut and may even shatter, into pieces. Severe damage to fingers and eyes is a real possibility so protective gear is mandatory.

Let us do it instead

Clockworks offers a mainspring replacement service so send us the entire barrel and avoid the hassle altogether. We will use special tools to safely remove the spring, measure it, and swap it out for the new one. Measuring Hole End Mainsprings includes the thickness, the length and also the width. Then a comparison of these measurements to the mainspring chart will show the appropriate spring to install. If sending in the barrel, please leave the mainspring in the barrel. Do not remove it. This is because we need to know which way the clock mainspring gets wound inside the barrel. If the spring is out of the barrel the direction will not be known. Of course this is important in order to replicate the same direction with the new one.

Measuring Hole End Mainsprings

Measuring is done to get the size of the new mainspring to match up to the old one. Measure the width first, then measure the thickness with a micrometer. Then the final measurement is the approximate length. Take all those numbers and compare them to the chart.

Width

Width of Hole End Mainsprings is done first. Measure this in inches or millimeters with a digital micrometer. Then see which spring matches the best in width to the old one.

Thickness

Once the width of the clock spring is written down and you are in the right location of the chart, continue with the next measurement. The thickness of the Hole End Mainspring is done next. This measurement can be in inches or millimeters with a digital micrometer. Take this measurement and compare it to the chart along with the width measurement. Then see which spring comes closest to the old spring.

Length

Measuring the length can be the hardest part of this. Close enough is sufficient for this. If the spring is way too short it only means the clock will not run for 8 days. So more frequent winding will need to be done. It is not easy to uncoil this spring to get the length. What we end up doing is putting one end in a vise and stretching it out with a tape measure. Of course when you let go it snaps back quickly and wildly.

Diameter

This is just the width of the inside of the clock barrel. As we said before, the barrel is what houses the Hole End Mainsprings. The barrel inside diameter is in the list because it can help determine the size of the spring that can fit into that space.

Measuring a Hole End Mainspring

If there is no match for the Hole end Mainspring

Sometimes there just is no match for a mainspring and another size has to be put in. It's a tough choice at times what to substitute with in this situation. As far as the width goes it's best to go with a skinnier one instead of wider. The spring that is too wide will make the barrel cap not go on, or stay on. The thickness is pretty important to hopefully get right. If it is too thick it will put up a fight getting in the barrel and may not want to go in. If it is too thin it may not run the clock. The length is the duration the clock will run such as 8 days or less if it's too short.

Clock Mainspring
Clock Mainspring
Measuring the Clock Mainspring
Measuring the Clock Mainspring
The content of this website is copyright by Clockworks and written by James Stoudenmire in year 2020

Clock Mainspring Damage

When a clock mainspring breaks the impact can cause damage to the movement. Damage would be within the parts of the gear train itself. It is possible that the pivots that go into the outer plates or the arbors have bent. Best to check the clock movement's condition before ordering a clock mainspring.

What to check

If working with a hole end clock mainspring it's best to check the teeth on the barrel for damage. A barrel is a container that covers the mainspring on some clocks. The barrel and the next wheel up gets the most impact and is where most of the damage would be. If there is damage to the movement that is, sometimes there is no damage at all. Then check the arbor on the next wheel up since it gets bent often when the mainspring breaks. Another option is to send it in for a movement restoration. Clockworks will clean, oil, re-bush, repair and test the unit doing a full movement restoration job.

Get a new movement instead

A movement that is 25-30 years old has lived its life. Subsequently, a new movement would be the best thing at this point because of the cost and time it would take to make it right.

If you would like to explore the new movement option rather than replacing the mainspring, please provide the movement numbers off of the back plate of the movement itself and email this information to us. There is another option also, send the clock mainspring barrel and we will swap it out with the correct new mainspring for a fee.

The content of this website is copyright by Clockworks and written by James Stoudenmire in year 2020

Hole-End Clock Mainspring replacement service

For a hole-end clock mainspring replacement, send clockworks the clock barrel and we will swap out the mainspring. Leave the Hole-End clock mainspring within that barrel. The price for this service is $80 and includes the cost of the Hole-End mainspring and shipping back.

What will be done

clockworks.com will remove the broken or worn spring from the container in a safe way. Then measuring the thickness and width and stretching it out to get the length. Next we will use the chart to get the right one from the list. We will then pull that spring from the inventory that is already here with us at Clockworks. The installation of the spring will be done with the special tool called a mainspring winder.

The content of this website is copyright by Clockworks and written by James Stoudenmire in year 2020

Removing a clock mainspring barrel

Often a clock mainspring barrel can be removed without disassembling the clock movements outer plates. The mainspring will also still be contained within the barrel.

Letting down the mainspring power

The mainspring let down tool allows the release of the mainspring with the fist rather than the fingers. Put the mainspring let down tool over the square post the key goes onto. With a flat screwdriver, move the click out of the way. The click has a tension spring that needs to be held back. This is what holds the mainspring so that it winds in only one direction. Slowly allow the mainspring to unwind in the fist. This method lets you control the speed of the unwind with your whole fist rather than the fingers. Unquestionably, doing this with a key will result in a painful experience on the fingers. Of course, if the mainspring is broken, there usually is no worry since there isn't much tension to begin with.

After the barrel is out

Once the power has been let down, the next step is to yank out the winding arbor shaft. The clock mainspring barrel should then fall out the side of the movement. After the barrel is removed, it can be seen the number that is on the barrel end cap. This will tell what hole end mainspring to order. You can locate the mainspring by using the hole end mainspring chart. Be sure to check the movement for any damage as a result of the mainspring breaking. In particular, inspect the teeth of the gears, as well as the arbor on the next wheel up. This could have consequently been bent.

The content of this website is copyright by Clockworks and written by James Stoudenmire in year 2020

Hermle mainspring barrel numbers

Hermle mainspring barrel numbers

Mainspring barrel number to size spring

Barrel NumberMainspring Dimensions MM
1017 x .45 x 1490
1117 x .42 x 1500
20 & 5617 x .38 x 1200
21 & 5017 x .40 x 1200
3112 x .34 x 1150
3212 x .42 x 1100
3312 x .32 x 1150
4017 x .38 x 1100
4121 x .40 x 1550
4217 x .40 x 1100
5217 x .42 x 1200
5421 x .42 x 1900
5521 x .45 x 1800
The content of this website is copyright by Clockworks and written by James Stoudenmire in year 2020

Clock Movement Hole-End Mainsprings

The width is measured first and matched up to the width below. Next is the thickness is measured with a micrometer. Lastly the approximate length. MB stands for Music Box, and H stands for Horolovar. Please select View Product to see the list of mainsprings we have to offer and the prices.

HEMSP: $10.00$40.00
View Product

Hole End Mainsprings Measurements to item #
WIDTH inch | mmTHICKNESS inch | mmLENGTH inchDIAMETER mmItem #
3/32" | 2.3.007" | 0.1818"14CMH 100
5/32" 4.008" | 0.224"17CMH 101
5/32" 4.011" | 0.2826 1/2"22CMH 103
3/16" 4.8.009" | 0.2324"17CMH 104
7/32" 5.6.008" | 0.226"20CMH 105
7/32" 5.6.0095" 0.2424"18CMH 106
1/4" 6.4.011" 0.2815 3/4"MBCMH 109
1/4" 6.4.011" 0.2839"26CMH 110
9/32 7.007" 0.1844"19CMH 111
9/32 7.010" 0.2518"MBCMH 112
9/32" 7.010" 0.2539 1/2"25CMH 113
5/16" 8.008" 0.227"18CMH 114
5/16" 8.010" | 0.2528"19CMH 116
5/16" 8.010" | 0.2532"23CMH 117
5/16" 8.010" | 0.2539 1/2"25CMH 118
5/16" 8.011" | 0.2845 1/4"28CMH 119
5/16" 8.015" 0.3840"34CMH 120
5/16" 8.016" 0.4154"38CMH 121
11/32" 8.7.013" 0.3366"38CMH 122
23/64" 9.011" 0.2845 1/4"28CMH 124
23/64 9.0125" 0.3218 1/2"MBCMH 125
3/8 9.5.011" 0.2848"26CMH 126
3/8" 9.5.014" 0.3648"32CMH 127
3/8" 9.5.017" 0.4354"38CMH 128
25/64" 10.011" 0.2845 1/4"28CMH 130
25/64" 10.012" | 0.3273"40CMH 131
7/16" 11.010" | 0.2532 1/4"22CMH 132
7/12" 11.011" | 0.2849"28CMH 135
7/16" 11.0155" | 0.455 1/2"38CMH 136
15/32" 12.010" | 0.2539 1/2"25CMH 137
15/32" 12.012" 0.353"32CMH 139
15/32" 12.014" 0.3672"41CMH 140
15/32" 12.013" 0.3327"25CMH 141
1/2" 12.7.013" 3360"36CMH 142
1/2 12.7.015" 0.3836"25CMH 143
1/2 12.7.016" 0.4165"32CMH 144
1/2" 12.7.018" 0.4660"38CMH 145
33/64" 13.010" 0.2539 1/2"25CMH 146
33/64" 13.010" 0.2845 1/2"28CMH 147
33/64".012" | 0.353"32CMH 148
33/64" 13.014" | 0.3638"30HCMH 150
33/64" 13.022" | 0.5528"32HCMH 151
17/32" 13.5.010" | 0.2672"34CMH 149
35/64" 14.011" | 0.2845 1/4"28CMH 152
35/64" 14.011" 0.2849"30CMH 153
35/64" 14.012" 0.361"35CMH 155
35/64" 14.0155" 0.437 1/2"36CMH 156
9/16" 14.3.012" 0.339"28CMH 157
35/64 14.013" 0.3327"25CMH 158
35/64 14.014" 0.3632"30CMH 159
9/16" 14.3.015" 0.3842"28CMH 160
19/32" 15.011" 0.2845 1/4"28CMH 161
19/32" 15.011" | 0.2849"30CMH 162
19/32" 15.012" | 0.353"32CMH 163
5/8" 16.010" | 0.2539 1/2"25CMH 164
5/8" 16.011" | 0.2845 1/4"28CMH 165
5/8" 16.011" | 0.2849"30CMH 166
5/8" 16.013" 0.3378"34CMH 167
5/8" 16.013" 0.33105"47CMH 168
5/8" 16.014" 0.3670"39CMH 169
5/8" 16.016" 0.4159"35CMH 170
5/8 16.0175" 0.4543 1/2"37CMH 171
5/8 16.018" 0.4641"36CMH 172
5/8" 16.018" 0.4672"40CMH 173
5/8" 16.018" 0.4696"53CMH 174
43/64" 17.010" | 0.2572"34CMH 176
43/64" 17.010" | 0.2539 1/2"25CMH 177
43/64" 17.011" | 0.2845 1/4"28CMH 178
43/64" 17.011" | 0.2849"30CMH 179
43/64" 17.018" | 0.4654"40CMH 180
11/16" 17.5.012" 0.372"30CMH 181
11/16" 17.5.014" 0.3654"34CMH 182
45/64" 18.018" | 0.4644"38CMH 183
11/16" 17.5.018" 0.4696"53CMH 184
45/64" 18.011" 0.2845 1/4"28CMH 185
45/64 18.011" 0.2849"30CMH 186
45/64 18.012" 0.353"32CMH 187
45/64" 18.012" 0.361"35CMH 188
45/64" 18.016" 0.4156"39CMH 189
45/64" 18.016" 0.4161 1/2"42CMH 190
45/64" 18.0175" | 0.4470"45CMH 191
45/64" 18.019" | 0.4847"35CMH 192
45/64" 18.021" | 0.5348"40CMH 193
3/4" 19.009" | 0.2372"33CMH 194
3/4" 19.010" 0.2539 1/2"25CMH 195
3/4" 19.011" 0.2845 1/4"28CMH 196
3/4" 19.011" 0.2849"30CMH 197
3/4" 19.011" 0.2850"30CMH 198
3/4 19.012" 0.353"32CMH 199
3/4 19.012" 0.361"35CMH 200
3/4" 19.012" 0.375"35CMH 201
3/4".012" 0.390"35CMH 202
3/4" 19.014" | 0.3690"35CMH 204
3/4" 19.015" | 0.3872"36CMH 205
3/4" 19.0155" | 0.453 1/2"37CMH 206
3/4" 19.016" 0.4153"38CMH 208
3/4" 19.016" 0.4156"39CMH 209
3/4" 19.016" 0.4160"38CMH 210
3/4" 19.017" 0.4344"35CMH 211
3/4 19.017" 0.4345"36CMH 212
3/4 19.0175" 0.4470"45CMH 213
3/4" 19.018" 0.4696"53CMH 214
3/4" 19.019" 0.4868 1/2"45CMH 215
25/32" 20.011" | 0.2849"30CMH 217
25/32" 20.012" | 0.353"32CMH 218
25/32" 20.012" | 0.361"35CMH 219
25/32" 20.0155" | 0.453"38CMH 220
25/32" 20.016" | 0.4153"38CMH 221
25/32" 20.0175" 0.4470"45CMH 222
25/32" 20.018" 0.4676 1/2"48CMH 223
53/64" 21.011" 0.2845 1/4"28CMH 224
53/64" 21.011" 0.2849"30CMH 225
53/64 21.012" 0.353"32CMH 226
53/64 21.012" 0.361"35CMH 227
53/64" 21.0125" 0.3267"38CMH 228
53/64" 21.015" 0.38100"50CMH 229
7/8" 22.2.011" 0.2849"30CMH 230
7/8" 22.2.012" | 0.353"32CMH 231
7/8" 22.2.012" | 0.361"35CMH 232
7/8" 22.2.0125" | 0.3267"38CMH 233
7/8" 22.2.013" | 0.3372"33CMH 234
7/8" 22.2.0155" | 0.450"37CMH 235
7/8" 22.2.0175" 0.4470"45CMH 236
7/8" 22.2.018" 0.4684"49CMH 237
7/8" 22.2.018" 0.4696"53CMH 228
7/8" 22.2.0195" 0.556"42CMH 239
61/64 24.0175" 0.4470"45CMH 240
61/64 24.018" 0.4676 1/2"48CMH 241
61/64" 24.018" 0.4680 1/2"50CMH 242
63/64" 25.018" 0.4678 1/2"49CMH 243
1" 25.4.018" 0.4696"53CMH 244