[wings]

I purchased some lenses for the Pentax, including a Spotmatic F series camera, on a government auction and purchased an M42 to K-mount adapter. I am puzzled why some of the lenses will not screw onto the adapter? It is just not making sense to me. Included in this lot was some k-mount lenses which work just fine with my K-1.

[timw4mail]

There's another mount, the 'T' mount, which has the same diameter, but different thread size than M42.

[stevebrot]

As noted above, it is possible that those lenses are "T-mount" and have become separated from the required second part that allows mount to multiple brands of cameras.

That being said, please provide details about the M42 adapter being used (photo is helpful) as well as what lenses are problematic. Above all, don't force the threads on either lens or adapter.


Steve

[wings]

There's another mount, the 'T' mount, which has the same diameter, but different thread size than M42.

Wow, thanks.That just might be the problem. I assume that there is an adapter for that?

[timw4mail]

Wow, thanks.That just might be the problem. I assume that there is an adapter for that?

Yeah, for virtually any type of camera mount.

[wings]

As noted above, it is possible that those lenses are "T-mount" and have become separated from the required second part that allows mount to multiple brands of cameras.

That being said, please provide details about the M42 adapter being used (photo is helpful) as well as what lenses are problematic. Above all, don't force the threads on either lens or adapter.


Steve

That was it. I found an adapter T-PS on one of the lenses. I would not have thought about looking for that as it appeared to be part of the lens, but after reading your posts was able to find it upon closer inspection.

Some of these lenses are quite nice, but most of them have a s/n engraved on them. I do not need some of these and will probably sell them, but it may make selling some of these difficult.

[timw4mail]

That was it. I found an adapter T-PS on one of the lenses. I would not have thought about looking for that as it appeared to be part of the lens, but after reading your posts was able to find it upon closer inspection.

Some of these lenses are quite nice, but most of them have a s/n engraved on them. I do not need some of these and will probably sell them, but it may make selling some of these difficult.

You mean like a hand-engraved serial?

[Not a Number]

If the equipment was for government or institutional use they may have had serial or control numbers engraved or tags affixed.

[wings]

Yes, probably from one of those vibrating hand held engravers, see photos of some of the lenses attached. I also included photos of the M42 adapter which I purchased here and the T-PS adapter that was on one of the telephoto lens.

[wings]

More photos

[stevebrot]

Be careful with that adapter. It is of the type that is likely to become stuck in the mount and once stuck may be extremely difficult to extract (sad voice of experience here). The standard suggestion is to use them with the retention spring removed. If you have already done so, that is a good thing.


Steve

[wings]

Be careful with that adapter. It is of the type that is likely to become stuck in the mount and once stuck may be extremely difficult to extract (sad voice of experience here). The standard suggestion is to use them with the retention spring removed. If you have already done so, that is a good thing.


Steve

Thanks Steve, I was not aware of that. However, I did discover that I had to screw the adapter in (tighten) slightly before I was able to release the leaf lock. I didn't have problems after that, but perhaps I will remove it anyway.

LeRay

[stevebrot]

Thanks Steve, I was not aware of that. However, I did discover that I had to screw the adapter in (tighten) slightly before I was able to release the leaf lock. I didn't have problems after that, but perhaps I will remove it anyway.

LeRay

Google "stuck M42 adapter" for lots of sad stories. When it happened to me, it took multiple attempts over a three hour period to free my Bower-brand adapter from the camera. I was on the verge of resorting to the Dremel tool.

With the spring lock, gone the lens is free to rotate out of the mount. This may be a problem if the focus ring is stiff. I hate to say it, but a common solution is to notch or drill the face of the lens to accept the K-mount retention pin.


Steve

[wings]

Google "stuck M42 adapter" for lots of sad stories. When it happened to me, it took multiple attempts over a three hour period to free my Bower-brand adapter from the camera. I was on the verge of resorting to the Dremel tool.

With the spring lock, gone the lens is free to rotate out of the mount. This may be a problem if the focus ring is stiff. I hate to say it, but a common solution is to notch or drill the face of the lens to accept the K-mount retention pin.


Steve

I have an idea about this. I may cut the adapter on one side which would allow one to squeeze it if necessary to remove it, yet it would allow the use of the spring lock while attaching and removing a lens.

LeRay

[wings]

This modification works. See video

Youtu.be

Youtu.be

LeRay