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Discussion in 'Horological Tools' started by Dave Coatsworth, Nov 30, 2019.
Does anyone know what this is? The box is about 3.5 inches square.
I think this may be a wheel stretcher.
graham - i’ve been hoping someone would answer... but what the heck is a ‘wheel stretcher’?!?
Graham is correct.
The tool is designed to be held in a vice. The wheel, which is usually a replacement for a damaged one, and found to be correct apart from having too small a diameter, is set up in the sprung centres in the frame at top left, with its teeth between the punch at bottom left and the circular anvil. The punch is then gently tapped as the wheel is slowly rotated, stretching the rim of the wheel. The amount of stretching possible is clearly quite limited, but this was a viable repair to avoid having a new wheel cut.
After this treatment it would probably need to be topped in a topping tool, to correct any irregularity in the teeth.
It's just that. It's used to stretch a wheel, ie, increase it's diameter. Don't ask me why. Maybe you need a wheel just a tad bigger in diameter than what you have.
The wheel to be "stretched" is held by the arbor between the two centers in the smaller U shaped frame. The tool itself is held in a vise by the small stepped end that is visible in the upper right corner. The two frames are set apart just enough such that the edge of the wheel is resting on the small anvil in the larger frame. Then the wheel is "stretched" by hammering the punch such that the wheel edge is squished. You hold the punch lightly between your thumb and index finger and use your middle finger to slowly rotate the wheel in between punching. This rotating the wheel while punching is somewhat like you would do when staking a staff to a balance wheel.
You would of course have to top the teeth after this "stretching" to get the correct tooth profile.
I hope I haven't confused anyone. I don't think I can make it any simpler.
Seems Graham just beat me to the answer by a few minutes.
Thank you very much, guys!
Never used one, but from what I'm told it can also be used to stretch a wheel in a single spot at the rim to repair a damage tooth. You would then use a topping tool on order to bring it back to pitch diameter and shape the tooth back to it's original profile.
I was thinking wheel stretcher too, but was having trouble to find something on it, when searching on the internet.
Not much can be found on the net, old books do provide answers, e.g. in the writings of Claudius Saunier, one can read about the way the jobbers made wheels by hand.
Essentially, wheel stretching tool was used to correct improper depthing caused by eccentricity of the wheel. In the old days wheels were in most cases made by hand filing, sometimes ending up with slight eccentricity. Thus to correct the eccentricity of the wheel, they were first corrected by stretching followed by rounding them in the rounding up tool, at the same time correcting the shape of the teeth.
Search older watchmaker books, not the internet and you will have success...
Myself, I found welt of info in the periodicals of the like of "Deutsche Uhrmacher-Zeitung", for those that are interested, most of the issues can be found online.
thx for the info... learn something new every day.
Guten Tag Dushan,
Aber, Ich spreche nicht sehr gut Deutsche.
Unless you can point me at some translations.