Tamron adaptamatic pentax PK mount

marcusBMG · Joined: 07 Dec 2012 Posts: 1319 Location: Conwy N Wales

Made from a miranda adaptamatic mount and a PK - 52mm reversing ring.

nicola0890 · Joined: 30 May 2014 Posts: 5

marcusBMG · Joined: 07 Dec 2012 Posts: 1319 Location: Conwy N Wales

(i take it you mean the mount) No sorry, I just threw this in by way of example. I acquired a miranda mount with a lens and decided to make use of it in this manner - more convenient than juggling with m42 adapters
Most people just attach a standard M42-PK adapter to an M42 mount.

marcusBMG · Joined: 07 Dec 2012 Posts: 1319 Location: Conwy N Wales

Luis has alternative way:

marcusBMG · Joined: 07 Dec 2012 Posts: 1319 Location: Conwy N Wales

Following on from the suggestion by Luis I quoted above:
1. it is clear to me from inspecting a newly acquired 300mm adaptamatic that the adaptamatic mount locking ring thread is not 58mm x 0.75mm but (probably) 58mm x 0.5mm. Step up rings or filter rings will go on sufficiently to stay put but only just, and they tend to be sticky to remove.
2. the 58mm-52/49mm step up rings have a female 58mm thread, but a male 52/49mm thread. A female thread is required to connect to a reversing adapter. One possibility is to cut down the ring off a 52mm/49mm filter to screw on.

I'll try this and see where infinity focus is...

marcusBMG · Joined: 07 Dec 2012 Posts: 1319 Location: Conwy N Wales

So a solution is a PK -58mm reversing ring and a ring cut down from a filter with the glass removed. The cut down filter ring is essentially a male to female converter so that the reversing ring will screw on to the lens. There are different designs of filter rings, the type required is one that has a screw retaining ring for the glass. I used a lens spanner to remove that, but simply breaking and removing the glass (care) to free it up is an option.
This combo will screw on sufficiently to stay put but only a quarter turn or so. Not very secure! You could try really cranking it on, it looks like the lens mount is steel so it's the alloy reversing ring threads that will yield.

Pic 1. I used a coarse grit to take off the male thread, finishing with a diamond stone. I used a second filter as a handle and to keep the shape of the ring being ground, and also because the ring gets hot. Then I had to cut a couple of nicks to use my lens spanner to separate them!
Pic 2. The finished ring, the reversing ring and another filter ring, that one was "ready to go" with M58 female thread both sides once the glass (actually plastic) had been removed, but didn't allow infinity focus being thicker, with a rim in the middle.
Pic 3: ring on the reversing adapter.
Pic 4: feels quite firm actually. To make it secure the way to go would be a plate from the tripod ring to the bush on the camera body. After this pic I took off a bit more of the ring on the diamond stone to try to get the lens to align at 'O clock instead of quarter to (=of to you yanks).
So this does work, just about hits infinity focus and it's pretty easy to do. Just bear in mind it's not that secure.
If anyone knows a source of M58 x 0.5mm threaded rings let me know. I did inquire at my local engineering works for a similar thing. After a bit of tsk tsk tsk fine threads are difficult they quoted a hundred quid +! So that's out.