Rebushing

Nicko

Registered User
May 11, 2007
196
1
18
Australia
Country
Region
The bushes in this plate need to be replaced, however there are a couple of things that I am unsure about.
Is the previous bushing a stepped bush, or a bush with some fancy embossing.
Where then should the new bush be trimmed at and the oil sink bored. If thats done at the level of the old bush then the new bush will be quite short. If at the level of the front plate then it might look a bit funny.

Any thoughts?

Can anyone suggest a source for stepped winding arbor bushes?
inside .125
width .250
overall length .125
step diam .3125
 

Attachments

Mike Phelan

Registered User
Dec 17, 2003
10,140
79
48
West Yorkshire, England
Country
Region
Neither holes on the pics look as if they have been bushed at all - do they need it? Both look perfectly round and unworn to me. :%
 

Joseph Bautsch

NAWCC Member
Dec 9, 2006
1,113
126
63
81
Atlanta, GA
Country
Region
Your picture shows a winding arbor bushing with a shoulder. The shoulder is there to give it more depth resulting in a longer life. If the bushing were the same depth as the plate it would wear out in no time because of the force exerted by the spring. The oil sink goes in the face of the shoulder. It does not have to be very deep. These bushings can be purchased from most of the clock material supply houses.

That being said, I agree with Mike. The bushing does not look worn enough to warrant its replacement.
 
C

clockdaddy

Nicko said:
is the previous bushing a stepped bush, or a bush with some fancy embossing.
Where then should the new bush be trimmed at and the oil sink bored. If thats done at the level of the old bush then the new bush will be quite short.
Nicko,
When bushings are installed, the face of the bushing on the inside of the plates must be absolutely flush with the surrounding area, The inside edge of the bushing should be chamfered only enough to remove any burrs.

If the bushing extends slightly beyond the surface of the outside of the plate, that's ok, BUT don't go overboard and let it stick out two millimeters! Allowing the bushing to extend 1/2 millimeter is no problem, beyond that and there could be problems down the road.

The oil sink is only on the outside of the plates and should only be about 1/2 the diameter of the bushing wall. Any more than that is worthless.

Whether you use bronze or brass bushings, KWM or any other brand, really doesn't mount to a hill of beans. Try out the various types and choose which is most comfortable. The various supply houses will help you if you explain that you're fairly new and need their suggestions based on "common" orders.

Good luck...oh, and don't forget, we're here to help if we can.

 

Nicko

Registered User
May 11, 2007
196
1
18
Australia
Country
Region
I've done it again. Confused everybody by talking about two items in one thread. Sorry.

The bush that the initial question was about is a pivot bush, it is recessed into the plate, although it is hard to tell looking head on. Here is another photo called "pivot bush" taken from an angle which shows this clearly.
Does it need rebushing? Thats a good question. Its feels pretty wobbly, but have a look at the picture of the wheel in the plate and tell me what you think.

I did ask where I could get a stepped winding arbour bush from, here is a picture of that bush.

Thanks again
Nicko
 

Attachments

shutterbug

Moderator
Staff member
NAWCC Member
Oct 19, 2005
46,988
2,003
113
North Carolina
Country
Region
Your bushing is a bit larger than it needs to be, but as stated - if it's round, it's not worn. Many clocks have "sloppy" fits and are designed that way. Look closely at the hole. If it's perfectly round, leave it.
 

David Robertson

Registered User
Jan 6, 2003
1,525
8
38
Country
Region
shutterbug said:
Your bushing is a bit larger than it needs to be, but as stated - if it's round, it's not worn. Many clocks have "sloppy" fits and are designed that way. Look closely at the hole. If it's perfectly round, leave it.
Wonderful advice from shutterbug.. worth repeating... and repeating... and repeating...
 

bchaps

Registered User
Dec 16, 2001
1,130
14
38
Mountain Top, PA
www.clockguru.com
Country
Region
Nicko...now I'll present the other "school of thought". I use Laurie Penman's book - "The Clock Repairer's Handbook" as my resource. I initially had the same questions as you...When do I bush?. What Shutterbug and David mentioned is generally OK, but what if the pivot has been polished ...the question still exists when is the hole too large? On Page 46 Laurie states acceptable pivot clearance is between 5 and 10 percent of the pivot thickness. So, that means if you have a 1.0 mm pivot and the pivot hole measures 1.10mm you are at the upper threshold of acceptable clearance. I normally bush train wheels as wear approaches 10% and I bush the Escape wheel tightly and then open it to free spin.

At least 50% of my in-home failures have been due to too much freedom between the EW and Verge. Since I detest callbacks, my standard practice now is to bush these two points to minimal clearance. The problem has not recurred since I've adopted that policy. Because these clocks will not normally see a service person again until it stops running, I am proactive and try to bring it back closer to what it was when it left the factory.

Laurie concedes there is a wide variety of opinion on this subject, but I know failures occurred for me when I allowed considerable tolerance. You will find that 10% is not much tolerance , especially when it's an .8 mm pivot. If I see daylight around the pivot, it's ready!



Bill
 

Nicko

Registered User
May 11, 2007
196
1
18
Australia
Country
Region
Thanks for the replies.

There are no oval shaped bushes like you see in "how to rebush a clock" tutorials. A couple are slightly oval. On the other hand the sideways play on the shafts is between .006" and .013" on a .067" shaft. That equates to between 10 and 20%. There is little play on the front escape wheel bush.
I think I could safely put this one down as a rattler. I don't have any doubt that it will run OK when the other problems have been repaired.

Again, thanks for your help.

Cheers
GN
 

Jeff C

NAWCC Business
May 26, 2005
2,123
2
38
Seven Fields, Pennsylvania
Country
Region
I don't mean to sidestep anything here but is the a tool made that you can put in a bushing hole to determine ID? There is the micrometer for the pivot but how do you determine the ID for the bushing other than the new ones in a box labeled for their dimensions. :?|
 

Kevin W.

NAWCC Member
Apr 11, 2002
23,193
570
113
63
Nepean, Ontario, Canada
Country
Region
Bushing size, you need the thickness of the plate and diameter that you will size the hole to, to put in the new bushing.Also you need to know the size of hole in the bushing, by measuring the pivot which goes into it, this whole likely you will broach to size as well.
 

Nicko

Registered User
May 11, 2007
196
1
18
Australia
Country
Region
Jeff

I've never seen an inside gauge that small, although they would exist. Possibly the simplest method would be to use a burnishing broach and measure the place on the broach where it fits the bush.
If you are asking how did I measure the play, I simply pressed the pivot to one side of the bush with the tail of some digital calipers, zeroed the calipers and moved the pivot to the other side of the bush, read the result.

I have found, much to my surprise, that the absolute measurement is not the critical thing, it the fit that counts.

Cheers
GN


 

David Robertson

Registered User
Jan 6, 2003
1,525
8
38
Country
Region
Jeff said:
I don't mean to sidestep anything here but is the a tool made that you can put in a bushing hole to determine ID? There is the micrometer for the pivot but how do you determine the ID for the bushing other than the new ones in a box labeled for their dimensions. :?|
Jeff,

One fairly easy way to measure hole size is to insert a smoothing broach into the hole and then measure the smooth broach at the entry to the hole with caliper or micrometer. (not 100% accurate but close enough for most things we do)
 

Tom Kloss

NAWCC Member
Dec 5, 2003
1,882
6
38
N.E. Pennsylvania
Country
Region
Jeff said:
.... There is the micrometer for the pivot but how do you determine the ID for the bushing other than the new ones in a box labeled for their dimensions. :?|
Jeff

[colour=blue]Insert a round smoothing broach into the bushing hole and, using a caliper, measure the diameter of the broach at the point it begins to bind. [colour=black]
Tom :cool:

[colour=blue]“Sometimes you really don’t know if your being rewarded or punished”
 

Attachments

Tom Kloss

NAWCC Member
Dec 5, 2003
1,882
6
38
N.E. Pennsylvania
Country
Region
I agree with Bill and adhere to the 10 percent maximum wear rule of thumb. I find it has served me well. Of course, all measurements being taken after the necessary pivot work is complete. Cleaning, burnishing etc.

Tom :cool:

Just remember, the enemy of "good" is "better"
 

Kevin W.

NAWCC Member
Apr 11, 2002
23,193
570
113
63
Nepean, Ontario, Canada
Country
Region
Pin gauge set is nice, but not cheap.
I was not sure if the question was measuring the id of the old bushing in the clock or the new one that is going into it?:cool:
 

Nicko

Registered User
May 11, 2007
196
1
18
Australia
Country
Region
veritas said:
Pin gauge set is nice, but not cheap.
I was not sure if the question was measuring the id of the old bushing in the clock or the new one that is going into it?:cool:
I wasn't sure either.

What are the increments in a good pin gauge set down around that size? I thought of using the shank of some number drills, but that may not be accurate enough.

Cheers
GN
 

Jeff C

NAWCC Business
May 26, 2005
2,123
2
38
Seven Fields, Pennsylvania
Country
Region
Sorry guys I was asking about the ID of bushings already installed in a clock. David and Klosse provided a very good answer to my question. Thank you very much:thumb:
 

Forum statistics

Threads
167,222
Messages
1,457,277
Members
87,380
Latest member
Ruralchick
Encyclopedia Pages
1,057
Total wiki contributions
2,914
Last edit
E. Howard & Co. by Clint Geller