• The NAWCC Museum and Library & Research Center are currently open. Please check the Visiting Schedule for Days and Hours at the bottom of the Visit Page.

Identification of Half Moon Marks Around Pivot Holes

Vint

Registered User
Oct 14, 2020
103
3
18
70
Country
Region
Could someone please tell me what purpose these half moon looking marks serve on a clock movement plate?
What tool was used to stamp these markings? I’m attaching a photo showing these marks at S4, T3,T4. I have a feeling it may be part of the bushing process. Thanks.

994C123A-B300-44CA-A2EA-161375076F89.jpeg
 

Micam100

Registered User
NAWCC Member
Nov 11, 2019
80
10
8
70
Country
Region
INSTEAD OF the bushing process. Punched where they have marked with an X to close up the holes.
Michael
 

MartinM

Registered User
Jun 24, 2011
3,086
111
63
El Dorado, CA
Country
Region
In lieu of bushing, some simply punched the plate on the side of the hole that was wearing to upset the metal towards the worn hole. Everything from a simple dimple punch to a point to tools more purpose built to deface the plate as in your case.
 

Cespain

Registered User
Nov 14, 2019
86
8
8
Dublin, Ireland
Country
They could have been scribed by a depthing gauge in preparation for rebushing. The idea is that you use the depthing gauge to find the precise gap between the pivot holes on the plate where the hole is not worn, i.e. if the worn pivot hole is on the back plate then you use the front plate and vice versa, of course if the pivot hole is worn on both plates this procedure will not work. You set the gauge to the gap between the mate of the worn hole and another nearby hole then keeping the gauge fixed at this gap you move to the plate with the worn hole and place one of the runners in the same nearby non worn hole and use the other runner to scribe an arc across the worn pivot hole. You repeat this process with another nearby hole so that you end up with two arc criss-crossed across the worn pivot hole and this should be where the centre of the worn hole was. I know it sounds complicated but I saw it being demonstrated by an experienced clockmaker and it really does work. I'm not sure if it is better or faster than using a centering punch or just a visual determination of where the center should be.
 

wow

Registered User
NAWCC Member
Jun 24, 2008
4,668
410
83
75
Pineville, La. (central La.)
Country
Region
They could have been scribed by a depthing gauge in preparation for rebushing. The idea is that you use the depthing gauge to find the precise gap between the pivot holes on the plate where the hole is not worn, i.e. if the worn pivot hole is on the back plate then you use the front plate and vice versa, of course if the pivot hole is worn on both plates this procedure will not work. You set the gauge to the gap between the mate of the worn hole and another nearby hole then keeping the gauge fixed at this gap you move to the plate with the worn hole and place one of the runners in the same nearby non worn hole and use the other runner to scribe an arc across the worn pivot hole. You repeat this process with another nearby hole so that you end up with two arc criss-crossed across the worn pivot hole and this should be where the centre of the worn hole was. I know it sounds complicated but I saw it being demonstrated by an experienced clockmaker and it really does work. I'm not sure if it is better or faster than using a centering punch or just a visual determination of where the center should be.
 

wow

Registered User
NAWCC Member
Jun 24, 2008
4,668
410
83
75
Pineville, La. (central La.)
Country
Region
This procedure is very unprofessional. It is done to avoid disassembling the movement and doing it right. If an experienced clockmaker does this, he is doing shotty work. That movement in the photo should be disassembled, punch marks repaired, thoroughly cleaned, bushings installed, pivots polished, and everything else inspected and repaired if needed. IMHO.
 

Cespain

Registered User
Nov 14, 2019
86
8
8
Dublin, Ireland
Country
In fairness to the clockmaker involved he had the movement disassembled at the time, it was an old unused one and he was doing this just to show me one of the uses of a depthing gauge - I was on a training day with him. I can testify that he does excellent work and have used him to do repivoting and making arbors for me since then. I had just remembered that the marks left round the pivot holes were similar to those described by Vint and offered this as an explanation.
 

novicetimekeeper

Registered User
Jul 26, 2015
10,517
767
113
Dorset
Country
Region
Punching to close up pivot holes was an accepted practice once. Did those semi circular punches exist for anything else, I don't know? I've seen them done all round making a flower pattern.

I think it is something that has been done for centuries.
 

wow

Registered User
NAWCC Member
Jun 24, 2008
4,668
410
83
75
Pineville, La. (central La.)
Country
Region
Punching to close up pivot holes was an accepted practice once. Did those semi circular punches exist for anything else, I don't know? I've seen them done all round making a flower pattern.

I think it is something that has been done for centuries.
Good to know the clockmaker does it right. My dad worked on clocks in the 60’s and 70’s. He was taught that way and did it until he was able to get a hand bushing tool. Once he learned how to bush with the tool, he quit punching. I get punched movements often. Most of the time I am able to hide the punch marks with the new bushing.
 

Thomas Sanguigni

Registered User
NAWCC Member
Aug 22, 2018
171
38
28
secondhandclockshop.com
Country
Region
I recently worked on a Gebr. Kuner cuckoo clock. It had so many punches, drill holes and chisel marks that it bent the plates inward and locked the movement. The work was performed by a hacksmith in 2009. The clock had not been running very well. I get scared when I see these marks.
 
  • Like
Reactions: Old Rivers

howtorepairpendulumclocks

Registered User
Dec 18, 2020
210
48
28
53
Country
Yes. These are as above, punches or in this case, chiselled marks to re-configure depthing. Personally, I just shrug my shoulders in terms of doing anything about them i.e. actively hiding them. What is done is done and actively hiding them is just another form of change. Passively hiding them through the process of bushing is a different thing. I was once giving a lecture and a member of the audience went berserk when asking me "what was I going to do about the punch marks around a clock pivot?" of a slide I was showing. I said,,, "nothing". They say "I would drill and plug them and refinish the plate". It was at that point that the penny dropped for me....

Sorry, bit of a tangent but when I see those marks, I always remember that story. :=)
 

Vint

Registered User
Oct 14, 2020
103
3
18
70
Country
Region
Thank you all for the information as it helps me understand what these markings are.
 

bikerclockguy

Registered User
Jul 22, 2017
561
38
28
Country
This procedure is very unprofessional. It is done to avoid disassembling the movement and doing it right. If an experienced clockmaker does this, he is doing shotty work. That movement in the photo should be disassembled, punch marks repaired, thoroughly cleaned, bushings installed, pivots polished, and everything else inspected and repaired if needed. IMHO.
I have encountered punch marks on several of the clocks I’ve worked on; some looked amateurish, while others were well-placed and seemed to accomplish the intended purpose. I had always assumed that bushing pivot holes was a fairly recent(1960s or later)repair method, and that these earlier clock repair people just used the methods that were available and accepted at the time. After reading all of the criticisms here, I have to ask...how long have pivot bushings been in the mainstream of clock repair? I used “mainstream“ to avoid replies saying the earliest known use was when Grog the caveman whittled a hickory bushing for his rock clock in 900BC...
 

shutterbug

Moderator
Staff member
NAWCC Member
Oct 19, 2005
45,047
1,516
113
North Carolina
Country
Region
I think bushings have been around as long as the watchmakers lathe - prior to WWI. But not everyone had a lathe then either, and there was probably the same controversy then as there is now. The punching method cannot preserve the proper center location of the hole unless it is skillfully done. If you see the "flower' pattern all around the hole, you can bet the center is no longer positioned where it was when new.
 

howtorepairpendulumclocks

Registered User
Dec 18, 2020
210
48
28
53
Country
Bushings have been in the mainstream of clock repair for hundreds of years. There was a lot of interest in this in the eighteenth century in relation to "what material is best for bushings/bearings" etc. I imagine brass bushings in iron frames and brass bushings in wooden frames go way back.. There point here (...I think) is the context. The context in which the clocks are perceived and the context in which we interact and intervene with these objects changes all the time. Yes, an objective, evidence-based, peer reviewed study of historic bushing methods would be useful and interesting. The point of bushing or punching-up, if the aim is to maintain or return the object to working order, is to put the mobiles at optimal centre-distance. Not to put them back in their original position per-se. We cannot put them back :=), only bring about more change. Throughout the nineteenth and twentieth centuries the hand-made clocks industry in Europe (with a few notable exceptions) declined to the point of virtual extinction. The motivation, background, socio-economic environment of the people on this forum and the people who repair clocks today is immeasurably different from those that went before. Personally I see no point in damning the work of the past. It is what it is and is fascinating. The attitude and equipment we adopt today seem to be from the post WWII era. Very few people today seem to move pivots by punching-up. This was apparently a reasonably wide-spread method and therefore has validity in some historic context. No amount of drilling-out and plugging or bushing or re-finishing plates oblierates this work, it just layers change on top of change.
 

MartinM

Registered User
Jun 24, 2011
3,086
111
63
El Dorado, CA
Country
Region
We already have technology sufficient to recreate a plate, complete with stamps using a few different technologies. When entering a predefined program in a CNC or 3D print device becomes the accepted norm, bushing plates will seem like the work of witch doctors. Be kind to those who came before and had limited resources available to save a clock.