[boriscleto]

So its the bit on the far right I want to replace with a K version?
I cant help but think that with this lens meaning to sit on a tripod, just putting a simply M42>K adapter would have the strength.

Six of one, half dozen of the other. A generic M42 adapter costs about the same as a T>PK adapter.

[vonBaloney]

Everything you took off the lens is all part of one adapter. (Turned out there was actually no reason to unscrew those screws, so just put that ring back into the adapter and screw it back together.) Yes, you can use an m42->K instead along with the current T->m42 and it will be fine. And probably more useful to you down the road that a T-mount K adapter. When I originally answered I was saying you can't replace the t-threads cause they are part of the lens. Then I realized it actually had the m42 adapter on it and added that line as an edit. So I think we've got it straight now...

[post_eos]

Yeah, so you could have just unscrewed it I guess (sometimes they are locked down though). So that ring goes back in the adapter -- not sure why they make them like that...

So that you can turn them once you have the adapter on and make the aperture scale end up in the correct place. The T mount thread doesn't always start at the same point on every lens. You loosen the screws, turn the lens to the correct position and then lock the screws back down.

[vonBaloney]

So that you can turn them once you have the adapter on and make the aperture scale end up in the correct place. The T mount thread doesn't always start at the same point on every lens. You loosen the screws, turn the lens to the correct position and then lock the screws back down.

Right! I probably knew that, but it has been awhile since I've used one of those and I'm not sure I've ever needed to adjust one. I have one t-mount adapter (like the one on ebay I linked to) which is just a solid piece and alignment has always been fine, although I only have a couple t-thread lenses...