I was told today by an engineer who is making replica knurled wheels for the front standard rise/fall mechanism on my 1/4 plate Lancaster Instantograph 1890 patent that the thread size is
No 8 Unified fine with 36 threads per inch.
Might come in useful for someone in the future? The wheels in question are 1/2 inch diameter and there are 4 on the standard.
Just as important is a contact with the knowledge, tools, time and inclination to make replica brass items! Ask him whether flange making is something he could do.
From a historical engineering point of view this is very interesting.
A thread that old predates the final agreement on Unified Threads by more than fifty years. I would have checked almost every other possibility before considering Unified. Great detective work by your engineer.
Originally Posted by Sean Mac
From a historical engineering point of view this is very interesting.
A thread that old predates the final agreement on Unified Threads by more than fifty years. I would have checked almost every other possibility before considering Unified. Great detective work by your engineer.
Apologies - now corrected to 4BA. Personally I know nothing about it so I'm going with what I'm being told.
Can you post a picture please?
Indeed I can.
I manage with the adaptable universal iris clamp for smaller lenses, but bigger petzval weigh about 2 kilos and I am loath to take a risk.
Here is a typical example of a flang.
It is well over engineered and there only needs to be about 2 or so thread lines to be absolutely secure. These are on offer but it is rare that there is a match of the thread type and size!
The B.A. (British Association) thread would make perfect sense.
That type of flange thread was commonly cut by "thread chasing" rather than generated with a gear train.
Tricky enough to replicate.
The issue here might be finding a suitable piece of metal at that size if a new flange was required (rather than say re-tapping an existing one). And then the problem of finding a tap the correct diameter and thread pitch to match the particular lens....
My wheels are only 1/2 inch diameter so it's at least easy to find the metal.
The person I'm dealing with is using another engineer from his workplace to get the work done (in his lunch break!). Their main business is pump maintenance and coatings. If it was a home workshop setting that might make it more feasible.
Here's a picture of what was made for me - the diamond knurling is common nowadays apparently and hardly anyone is able to do straight lines as per original.
Nice job though?
Looks like a fine piece of work
Please show the finished restoration, bringing something that old back into use is great to see.
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