Flange Troubles

[Two23]

I bought a nice Darlot 14 in. Petzval and it came with an ill fitting flange. I would screw on a couple of laps but no more. Obviously not correct, so I took the brass barrel and bad flange to a local machine shop. After a month they came up with a new aluminum flange for me today. The guy screwed it on in front of me and I paid $200. (ouch) Got it home and noticed the flange was put on backwards--that is, the light trap extension was put on first and facing the front of the lens. I took it off, turned it around, and screwed it on the correct way. Except, it only went for a couple of laps and stopped! I didn't try to force it. Took it back off, completely covered the threads of both flange and barrel with white grease, and tried again. Same deal. For $200 I'm not happy. The flange easily screws on "backwards" but not the correct way. Is this fixable? I tried my other large Petzval, a big 12 in. Voigtlander with original brass flange, and it easily screws on from either direction. So do the flanges of several other of my small 8 in. Petzvals. What's the deal with this new flange?


Kent in SD

[Keith Pitman]

Take it back and show the machinist the problem.

[LabRat]

Original has right diameter, but wrong pitch...

Old lens makers often had their own unique pitch for their lenses...

Steve K

[Two23]

Original has right diameter, but wrong pitch...

Old lens makers often had their own unique pitch for their lenses...

Steve K

Why does it screw on all the way one direction but not the other?


Kent in SD

[LabRat]

Flange thread might have a taper...

Steve K

[Tin Can]

And machinist may not have known which way was what

[John Layton]

Ha! I remember watching the video of an astronaut by the name of...Musgrave? Cory Musgrave? At any rate...there he was, floating in space - fixing some problem, in situ, on the Hubble Telescope...and as he places his wrench on a bolt, he hesitates a bit, as he asks himself (audible on the video) "hmmm - righty-tighty...lefty-loosey?"

[Chauncey Walden]

Put it on the back side of the board??

[Conrad . Marvin]

Could be that the “machinist” didn’t know which way the flange went and only went as far with the thread as he thought was necessary to screw it onto the lens, therefore he needs to finish the thread so that it will start from the other side (not easy to find the thread and continue with it, but possible) or make another part correctly from scratch. If he was in question about which way to put the flange on, he should have asked. If you didn’t make it clear which way...

[Ron (Netherlands)]

Did you or the machinist measure the thread? If you know the thread why not ask here if someone has a matching flange?

some other threads with comparable flange questions/problems:

https://www.largeformatphotography.i...ounting+flange

https://www.largeformatphotography.i...-possibilities