Bushing mainspring barrel & cap

kologha

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Dec 11, 2011
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[FONT=Times New Roman, serif]I need to bush the Strike mainspring barrel on the Kienzle Box-clock I am overhauling and need some help. I will have to make the bushes for both barrel and cap as well as bore out the worn holes. I have never attempted bushing mainspring barrels before although I have made a few pivot bushes in the past. I need to know exactly how to accurately pick up the original centre, as I am not sure about using the 4 jaw chuck on my Myford lathe. I am wary of crushing or distorting the barrel in the process. Any tips?[/FONT]​
 

roughbarked

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Most barrels have some kind of raised section around the arbor holes. If yours has this then it may be assumed as a guide to centering?
You can either find or make a backboard that is same shape and size from say wood. Clamp or glue the barrel lid to this for added strength?
You should be able to make a similar insert for the barrel.
 

kologha

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What I have thought of doing is to chuck a piece of hardwood about an inch thick in the 4 jaw and then bore a hole the same size or a few thou smaller than the dia of the barrel. Then fit the cap and using the tailstock to keep it all square, force the barrel into the bored hole. That should align everything and using a dial bore indicator just make sure the face is true, I should be able to bore both barrel and cap. The small mount of brass taken on each cut should not disturb the setup.
 

David S

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Dec 18, 2011
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I think you are on the right track. I had to do something similar to bore the ID concentric with the OD and used your idea.

worn wheel prior to removing crossing in lathe.jpg

David
 

R&A

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Oct 21, 2008
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I did a tutorial on this operation. But for some reason it's not on my page imagine that. Go through my post it will help you out allot.
 

AJSBSA

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It is a rare week when I do not have to do this I use a three jaw with outside jaws and an adjustable backplate however a four jaw with outside jaws would work just as well, for the cap I clock the centre hole of a good cap or inside edge of the jaws. Never damaged the teeth on the barrel you do not need to grip the barrel that hard with good quality outside jaws.
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R&A

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Oct 21, 2008
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icon1.png Hermle Barrels and Caps

So I had another a guy challenge me on this so here we go. I was told that these barrels are garbage when the cap and barrel bushing wears out. I said why don't we just bush them and he told me it couldn't be done. And this is why I thought it would be a good post. Because they can be bushed and saved. I figure now. I would rather bush these if the teeth are not worn to bad and all would be good.

I first polished the arbors so I would have a smooth surface to work from. Then I bored the cap and the barrel to .375.
Made the bushing with a .050 (at .475 OD) lip and .005 proud of the thickness of both pieces. The diameter of the arbors were .293 for both ends. So this is why I made the bore .375 So I would have enough meat so the bushing walls would not collapse when pressed in. I made the bushing .394 ID so it would be a slip fit to the arbor. For a press fit,the OD for the bushing was cut to .2765.

Okay.Bushing made and pressed in. The .005 I made the bushing proud so I could stake the bushing secure to the cap and barrel. Broached the bushing out after staking it in. And to my surprise it work very well and here are some picks. I have come to the idea that now I can do this and make a profit off my labor at the same cost they would cost me new. This took me about an hour and ten minute to complete.

attachment.jpg attachment.jpg attachment.jpg attachment.jpg attachment.jpg attachment.jpg
Now I notched the cap so I could pull the cap off after the bushing installation. If you don't, the bushing will come out from hitting the arbor to get the cap off from the opposite end.
I installed it in the clock and it works great. Hope this helps somebody with limited funds. But the equipment to do this.
Found it​
 

AJSBSA

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Hi R&A I turn down the Hermle arbors to 7.00mm and do the barrels, caps, arbors and bushes in batches you can make the barrel bush quite thick so should be a better than new repair and makes it very cost effective at least in the UK where barrels are $40 a piece. I properly degrease and use Loctite 638 to secure the bushes.

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shutterbug

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Those who do not have access to a lathe but do have a bushing machine can make a tool that is helpful. Mine came with it, and it might require a bit of help from a machinist to make. It will clamp right on the bushing machine and allow bushing either the cap or the gear end of a barrel. Of course, for a shouldered bushing you'd have to have a way to make one :) 311116.jpg 311120.jpg
 

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