[Albino_BlacMan]

I recently got an M 135/3.5 along with a bunch of other stuff. It seems alright except for the fact that it has a SIN number (or some kind of number) has been engraved on the lens mount. I know it's a cheap lens and I could probably just buy a new one but I want to replace the mount on this one (to a mount with nothing engraved in it).

I'm wondering if I can use any Pentax-M mount or if I needed a mount specifically from a 135/3.5.

The other problem with the lens is that hood seems a little bit loose. Is there anyway to tighten it up a bit?

Thanks,
Chris

[wombat2go]

You might be in luck.
The Takumar (Bayonet) 1:2.5 135mm was a common lens but not so good because it flares badly in strong light differential.
So you might be able to get a low cost one and swap mounts. The 5 main screws are easy but a small jis screwdriver would be necessary for the 3 tiny radial screws
I measured the aluminum K mount ( the outer shiny metal part) for that lens with calipers and it appears to be identical to the SMC Pentax M 1:3.5 135mm.

I measured a few other -M lenses and it is possible that that outer aluminum ring might be common for many, but I did not disassemble to measure the whole ring

[tom1803]

The metal part of the mounting flange is the same amongst most K and M series lenses (one exception I know of is the K50/1.2). The black plastic baffle that is attached to the flange IS lens specific.

The five screws that hold the flange in place are JIS #0 size and proper screwdriver should be used to avoid stripping the head. Ordinary Phillips Head driver may work if the screws are loose, but if they are held in place with Loctite or similar, you'll risk damaging the screws.

The three screws that hold the plastic baffle to the lens mount are JIS #00.

The built-in lens hood becomes loose when the strip of felt material that lines the inside surface wears out and loses friction. I can't recall the exact procedure for removing the hood for the M135/3.5, but you'll obviously need to partially disassemble the lens.

[Albino_BlacMan]

Wow tom1803!

Apparently you know your stuff. This was pretty much the exact answer I was looking for!

And thanks for your work wombat2go. Looks like I have a project to work on!

[Just1MoreDave]

...The built-in lens hood becomes loose when the strip of felt material that lines the inside surface wears out and loses friction. I can't recall the exact procedure for removing the hood for the M135/3.5, but you'll obviously need to partially disassemble the lens.

Peel back the rubber grip on the focus ring and there are three holes underneath. Turn the focus ring until the holes line up with screws. I think these are #00 JIS. I can't remember exactly what the screws are holding on but something comes off at that point. My M135/3.5 is hiding somewhere at the moment; Ill conduct a search for it if you need more help.