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Help identifying a brass lens flange
- Thread starter Nas
- Start date
- Joined
- Jan 19, 2023
- Messages
- 123
Hi Nas
I find a pair or vernier calipers & and some thread gauges help considerably with questions like this.
Both can be got very cheaply, IIRC by 4" plastic calipers were around a pound, work adequately & are easier to store than the typical 12" models. Filters/threads of known pitch can be used to judge metric thread pitch if you don't have a proper gauge, but they don't work quite so well on female threads. FWIW the standard for metrics threads is for the quoted size to be the nominal dimension across the tops of male threads (actually the treads are fractionally smaller) Female threads generally measure smaller by about twice the pitch across the tops of the threads.
Many medium sized filters have 0.75mm pitch, while for everyday machine screws/bolts m3 are typically 0.5mm, m4 are 0.7mm, M5 are 0.8mm, m6 are 1mm & m8 are 1.25mm (some applications require finer non standard threads but these are the standard pitches)
The biggest difficulty comes when your not sure if it's imperial or metric, my most recent lens could be either M44x1 or 1 3/4" at 24tpi, the two are close enough to make ID uncertain.
My gut feel is that logo is more likely to be imperial (back from when Britian had an empire), and MIGHT even denote the Royal Photographic Society, which gave rise to a range of standard lens threads in the late 19th century. Most of these are 24tpi & go up by 1/4" increments.
I find a pair or vernier calipers & and some thread gauges help considerably with questions like this.
Both can be got very cheaply, IIRC by 4" plastic calipers were around a pound, work adequately & are easier to store than the typical 12" models. Filters/threads of known pitch can be used to judge metric thread pitch if you don't have a proper gauge, but they don't work quite so well on female threads. FWIW the standard for metrics threads is for the quoted size to be the nominal dimension across the tops of male threads (actually the treads are fractionally smaller) Female threads generally measure smaller by about twice the pitch across the tops of the threads.
Many medium sized filters have 0.75mm pitch, while for everyday machine screws/bolts m3 are typically 0.5mm, m4 are 0.7mm, M5 are 0.8mm, m6 are 1mm & m8 are 1.25mm (some applications require finer non standard threads but these are the standard pitches)
The biggest difficulty comes when your not sure if it's imperial or metric, my most recent lens could be either M44x1 or 1 3/4" at 24tpi, the two are close enough to make ID uncertain.
My gut feel is that logo is more likely to be imperial (back from when Britian had an empire), and MIGHT even denote the Royal Photographic Society, which gave rise to a range of standard lens threads in the late 19th century. Most of these are 24tpi & go up by 1/4" increments.
Last edited:
- Joined
- Aug 22, 2021
- Messages
- 526
Hey Mike, you're correct. I believe this lens flange turned out to be from the Royal Photographic Society, at least I found it mentioned in one of their catalogues. It came from a lens marked: Adams & Co. Augmentagraph Lens. I've started another thread asking for more info on that unusual lens which apparently covers up to 20x16.
Cheers,
Nas
Cheers,
Nas