Annoyed by the mount on my J-8

[WJJ3]

I like the images from my Jupiter 8 a lot. I like the stepless aperture and compact size. Overall I am really happy with the '60's era Soviet build and no nonsense of this incredible bargain lens. But the one thing that always annoys me a little when I am out shooting is the little rattly screw mount on this lens. Who's bright idea was that? Can I please have this wonderful little lens with a solid, one-piece mount like all the other lenses ever built? (rant over). Anyone else feeling like griping about the J-8 mount?😛

 

[Sid836]

J-8s rarely had any problems with their mount. It could be some fault on yours. Which J-8 do you have? There are a few (four at least I know) with different focusing styles.

 

[Ko.Fe.]

This J8 needs repair. Copies in working condition does not have problem of yours.

 

[WJJ3]

J-8s rarely had any problems with their mount. It could be some fault on yours. Which J-8 do you have? There are a few (four at least I know) with different focusing styles.

Mine is SN 62xxxxx. I believe its an early PT3065.
I'm pretty sure mine is the way they were intended to be. It works fine. I just think the jiggly screw mount ring is annoying 😱

 

[WJJ3]

This J8 needs repair. Copies in working condition does not have problem of yours.

Thanks for your input.
Is the screw mount ring on the mount of your J-8 tight?

 

[Ron (Netherlands)]

Thanks for your input.
Is the screw mount ring on the mount of your J-8 tight?

If it is jigly then one or probably more screws are loose - take the thing apart and put the screws back with a little locktight
(if you don't know how to take a J-8 apart, then read the notes made by Kim Coxon)

 

[ForestCap]

Check the three screws on the mount ring.

And, talk about bad lens mount:

 

[WJJ3]

If it is jigly then one or probably more screws are loose - take the thing apart and put the screws back with a little locktight
(if you don't know how to take a J-8 apart, then read the notes made by Kim Coxon)

Thanks, its the mount that is jiggly, not the keeper ring as Coxon calls it. I don't think I will be putting loctite on my lens.

Check the three screws on the mount ring.

And, talk about bad lens mount:

Haha, man, and I thought I had problems with my Jupiter 😕

 

[WJJ3]

Illustrations

Illustrations

I whipped up a couple illustrations to try to clarify what I am talking about.

In this photo you can see there is a lens mount with the M39 threads, a keeper ring that is attached with 3 screws, and the focus ring. The keeper ring is screwed onto the focus ring (screws are unscrewed and backed out here).

PT3065 Jupiter 8

In this photo you can see the lens mount, the keeper ring and the focus ring. Note that the flange on the mount is higher than the keeper ring. This flange is the surface that seats on the camera mount when you mount the lens on your camera. The surface of the keeper ring does not make contact with the camera mount. It is screwed to the focus ring and turns along with it when you focus the lens.

PT3065 Jupiter 8

As you can see from the illustrations, the mount is not held tight on the back of the lens. It floats between the keeper ring and the focus ring. This design makes the mount slightly jiggly

 

[Livesteamer]

Your J 8 is a victim of sloppy machine work. With this design of mount, several parts must be made to a very close tolerance. Your parts allow some slop if I understand it correctly. I have an Industar 26 with a similar problem. Easiest solution is to get another J 8 or a friend with a machine shop. Good Luck, Joe.

 

[WJJ3]

Your J 8 is a victim of sloppy machine work. With this design of mount, several parts must be made to a very close tolerance. Your parts allow some slop if I understand it correctly. I have an Industar 26 with a similar problem. Easiest solution is to get another J 8 or a friend with a machine shop. Good Luck, Joe.

Thanks, yes I agree tighter tolerances would probably make the floating mount more secure / less jiggly.
I wouldn't mind getting a handful of these and picking the best copy. I haven't the slightest inclination to ask my machinist friend to try to make mine better 😱

 

[David Hughes]

Hi,

Making to a finer tolerance isn't the only answer.

It's legit to measure and match parts; so the fat inner goes with the wide outer and so on. People often take lenses apart and swap bits and may not be aware of the need to measure carefully.

A good example is lenses where codes show the exact focal length as assembled and it's often not what's marked on the lens...

Regards, David