Tight 645 Lens Mount

Kmier · 01-15-2019, 03:28 PM

I first posted the following in the ‘Repairs’ section, but had no replies, so forgive me if I’m not posting in the appropriate forum sub directory:

Now that I’ve added a 2nd lens (75mm + 45mm f2.8) to my 645, I’ve noticed that removing and mounting lenses requires more force than it should. I definitely feel the flanges dragging / grinding excessively as the lens is rotated.

I suspect the tension spring (or whatever the proper name is) has become deformed, but I haven’t seen any form of parts schematics online (free, at least). Further, it looks like removal of the body shell is required to get inside to replace it.

Does anyone know of a procedure for fixing this issue? I have done google and YouTube searches to no avail. Thanks in advance.

**ProfessorBuzz** · 01-16-2019, 06:57 AM

Have you cleaned the inside edges of the bayonet mount on camera and lenses?
Use a dry QTip or similar cotton swab, perhaps a smaller diameter one from an electronics component supply.

Which 645 model?

Kmier · 01-16-2019, 07:52 PM

Originally posted by ProfessorBuzz

Have you cleaned the inside edges of the bayonet mount on camera and lenses?
Use a dry QTip or similar cotton swab, perhaps a smaller diameter one from an electronics component supply.

Which 645 model?

I have the first gen 645, circa 1984, I suppose? The mount was only a little dirty, but my cleaning may have helped a bit. Thanks for the reply.

01-15-2019, 03:28 PM	#1
Kmier Forum Member Join Date: Aug 2018 Posts: 53	Tight 645 Lens Mount I first posted the following in the ‘Repairs’ section, but had no replies, so forgive me if I’m not posting in the appropriate forum sub directory: Now that I’ve added a 2nd lens (75mm + 45mm f2.8) to my 645, I’ve noticed that removing and mounting lenses requires more force than it should. I definitely feel the flanges dragging / grinding excessively as the lens is rotated. I suspect the tension spring (or whatever the proper name is) has become deformed, but I haven’t seen any form of parts schematics online (free, at least). Further, it looks like removal of the body shell is required to get inside to replace it. Does anyone know of a procedure for fixing this issue? I have done google and YouTube searches to no avail. Thanks in advance.

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01-16-2019, 06:57 AM	#2
ProfessorBuzz Loyal Site Supporter Join Date: Feb 2018 Posts: 1,903	Have you cleaned the inside edges of the bayonet mount on camera and lenses? Use a dry QTip or similar cotton swab, perhaps a smaller diameter one from an electronics component supply. Which 645 model?

01-16-2019, 07:52 PM	#3
Kmier Forum Member Join Date: Aug 2018 Posts: 53 Original Poster	Originally posted by ProfessorBuzz Have you cleaned the inside edges of the bayonet mount on camera and lenses? Use a dry QTip or similar cotton swab, perhaps a smaller diameter one from an electronics component supply. Which 645 model? I have the first gen 645, circa 1984, I suppose? The mount was only a little dirty, but my cleaning may have helped a bit. Thanks for the reply.