Filthy Flange - possibilities.

[pgk]

I received parts of an 1850s lens today (for spares). The flange does fit some of my other lenses as I'd hoped it would. However it was quite literally black. It was covered with a hard layer of something which was sufficiently well stuck to it that at first I thought that it might be some sort of weird crinkle finish paint. I started cleaning it and discovered that it would come off with elbow grease and hot soapy water although slowly. Eventually it struck me that the coating was black from silver and what I was removing was a ~150 year old encrustation of silver salts from when the lens was used on a wet plate camera! This now explains the finish on this and other lenses, as, when its cleaned, the brass is left with a dull brown colour and missing most of its lacquer, except in the grooves where the encrustation had sealed it in.

[LabRat]

Probably not silver... On old brass, there can a variety of oxide layers that interact into strange forms...

I cleaned old brass that went dark black, and the layers that came off had strange shades... Including a layer with many old fingerprints from long dead users...

Steve K

[goamules]

Indeed, brass will eventually have a black patina that looks almost like anodized or lacquered finish. look at an old brass cartridge that has laid outside for a few decades. If it's dry, they turn very black. At sea, a brass bell can turn black in a few weeks, on a ship.

[pgk]

Its cleaning up well - halfway!

206361

[John Kasaian]

Make Nachos! Save the juice from the Jalapeno rings and put that flange in the jar. I should be gleaming by the time the nachos are gone;)

[Jim Noel]

count your blessings that you won the biddiig.

[pgk]

And FWIW, I have 4 lens housings which are from the same base lens, and three flanges (+ 3 complete lens sections). Despite this two of the flanges fit three of them but the other is just too tight and fits only one. An illustration I suppose of 1850/60s lenses being hand made and tolerances sometimes going slightly astray. The latest housing (missiong the lens itself) proved cheaper with the flange than having a new flange made. Well worth buying!

[Ron (Netherlands)]

Guess most of us have a pile of not fitting mounting rings and some lenses which lack matching mounting rings since the ones we have collected don't fit precisely or not at all.
Perhaps a good idea to start a thread where each of us can present all his/her spare mounting rings which precise (as possible) description - so we can have an exchange.
Seems way better than each time buying a pile on *bay hoping to catch a good one but in the end doesn't fit :-)

[pgk]

Sounds like a great idea - but might need moderator's approval. I've measured the spare flanges that I have and I think that the first thing required would be a 'how to measure and how to describe flange sizes and threads' post. Moderators?

[Ron (Netherlands)]

Sounds like a great idea - but might need moderator's approval. I've measured the spare flanges that I have and I think that the first thing required would be a 'how to measure and how to describe flange sizes and threads' post. Moderators?

Yes agree fully with respect to moderators approval. And yes we should try to agree on measurement (I have mine measured with calipers in mm and inch)

Can we post this question more directly to moderators?

[pgk]

I'll post some of mine in the sell/trade section soon. One thing I've realised is that older lenses and flanges can have well worn threads as the brass was quite soft. This means that measurements are tricky because the internal thread diameter will include some worn away brass. Not a lot but enough to potentially cause problems.

[Ron (Netherlands)]

Sure, I could do the same. The tricky part is measuring the thread - any idea how to do that precisely?

[pgk]

Its worth reading this: http://skgrimes.com/library/faq/how-to-measure-threads but older threads can be worn so a bit of adjustment or tolerance has to be applied.

I have a couple of screw pitch thread gauges (search eBay with this and you will find some and they are not expensive - the threads on flanges I have look as though they are of Whitworth form - 55 degree thread angle). You also need a fairly powerful magnifying glass to view the gauge and thread. When I first tried I found it difficult, but going back several times seems to help and eventually you settle on the thread (tip = threads per inch) which you repeatedly decide is right. I'll post my spares and wants in the for sale or trade section but it would be useful to have a 'sticky' thread there about flanges. They are a real bugbear and expensive to get made new.

[Ron (Netherlands)]

Its worth reading this: http://skgrimes.com/library/faq/how-to-measure-threads but older threads can be worn so a bit of adjustment or tolerance has to be applied.

I have a couple of screw pitch thread gauges (search eBay with this and you will find some and they are not expensive - the threads on flanges I have look as though they are of Whitworth form - 55 degree thread angle). You also need a fairly powerful magnifying glass to view the gauge and thread. When I first tried I found it difficult, but going back several times seems to help and eventually you settle on the thread (tip = threads per inch) which you repeatedly decide is right. I'll post my spares and wants in the for sale or trade section but it would be useful to have a 'sticky' thread there about flanges. They are a real bugbear and expensive to get made new.

Thanks for the advise on the thread gauges; will buy some imperial/metric/us....

Indeed lateron the British stepped over to whitworth, but used different threads before. I have some info found on the later standardisation I will post.
Perhaps its best to start here a separate post on 'Mounting Ring Measures', and it might be made sticky by the moderators.
We could post there general info, and info on measures of mounting rings that already match the lenses members have in their collection.

Something comparable with respect to double bookform plate holders Ian Grant and I made a posting for: https://www.photrio.com/forum/threads/wooden-book-form-plate-holders.171222/