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OK, I removed all the plastic parts at the back of the Samyang 135, and got to this, mostly metal, and couldn't remove further (even removed the 0.9mm hex with a spring). Everything appears to be bolted on tightly, but I don't know by what. Any idea how do I get to the iris from here?

I can see the iris, just couldn't get to it. (By the way, where exactly does that little ball that creates the aperture click stops go? By the time I have everything on my mat, the ball was just sitting there :-). Not that it matters since my plan is not to even use the aperture iris, and I have been using my leses wide open, with an externall aperture mask anyway.

Chen

      Ah, I see two hex (I think) grub screws. But my 0.9mm hex wrench is too small, and a 1.3mm wrench does not work either. I need to order some assorted small hex wrenches.

      Do you have the prcise size for those two screws, and are they wa=hat are kwwping me from reaching the iris?

      Chen

          w7ay I think you will need to use the lens spanner down by the glass. I think the ball will be part of the parts you took off.

          • w7ay replied to this.

              w7ay I have 0.9, 1.0, 1.5mm hex wrenches but I do not know what sizes they are as most of the parts on mine were tiny Philips screws.

                Kevin_A

                OK., these are the two grub screw that I found... do I need to remove them? Seems to have some Loctite or something smeared over them.

                I did find my set of small German metric wrenches... 2, 1.5, 1.3, 0.9, 0.7.. 1.3mm appears to be the right one. But with the Loctite, it means they don't want you to fool with them?

                I think the ball will be part of the parts you took off.

                Yeah, I found the ball, but which hole is it supposed to go into? :-)

                I think you will need to use the lens spanner down by the glass.

                Hmm, that won't allow me to remove the iris and replace with a milled part, though, does it? I need to be able to remove the iris completely.

                Interstingly, there is an aperture stop somewhere that is fully circular, when you open the lens up completely to f/2.

                Chen

                    w7ay I would check that they do not use some imperial sizes along with metric… heck they might even use some weird screws too. Try an imperial size allen key when in doubt.

                    • w7ay replied to this.

                        w7ay maybe you have to remove a lens group before you get to the iris assembly.

                        • w7ay replied to this.

                            Wow, how may turns with a lens spanner does it take to remove the glass anyway? I am at some 10 turns and the things is still in there.

                            The Neewer protractor type lens spanner is great, by the way.

                            Chen

                              Kevin_A Try an imperial size allen key when in doubt.

                              Heck, I don't have many imperial wrenches anymore. 1/16", 1/4", 3/8". I have just one plastic box (about 1/4 cubic ft) of imperial bolts for 5/16", 1/4" and 3/8", while the same size box is barely large enough to hold my different M6 bolts. Between button heads and socket heads, and different lengths, you really need to stock up with M4 and M6 nowadays.

                              Chen

                                Kevin_A maybe you have to remove a lens group before you get to the iris assembly.

                                I thought you had gotten to remove the iris completely? Do you remember what you had to remove?

                                The glass elements are still in there. Time for lunch. This thing can wait for a different day when I am in better mood. Go work on the Sigma 40 base plate first.

                                Chen

                                    w7ay I never got to my iris as mine has electronics and that adds another layer of complexity. Some of the Samyang/Rokinons have to have the outer barrels removed before you get to the isis, so the red ring and barrels may need to be removed first. So many variations. Look on YouTube under Rokinon disassembly as some require the outer barrel to get at an inner sleeve and some you just keep pulling out lens sets.

                                    • w7ay replied to this.

                                        Kevin_A I never got to my iris as mine has electronics and that adds another layer of complexity.

                                        Ouch, I thought you said you got to the iris.

                                        OK, this project is definitely in the backburner now; perhaps buried for good. I will try to put things back to as normal as I can, and see if I can still get a working lens, without the aperture click stops (still have no idea where that ball goes into).

                                        I don't like redneck engineering; working with no documentation. Life is too short for that.

                                        Started to work on the Sigma 40 already. I am just going to modify the base plate of the Rokinon, seen here with a 1:1 printout and the Sigma to measure where to move some of the holes, and to figure out if I have the right belts in my stockpile. Perhaps send the design out before the next workweek for the web machine shop to work on it.

                                        Speaking of belts, it really helps using 10mm belts instead of the 6mm astro hobbyists seem to like to use. Everything feels more solid. Well, that extra bearing to hold the EAF shaft definitely does not hurt either.

                                        That Blue Fireball CAA that you see in the photo above, really helps in this case, belt or no belt. That tripod ring does not allow the lens to be rotated.

                                        I am still trying to get used to the Nikon's left-handed bayonet! I keep tightening the bayonet when trying to remove the lens, and wonder why the bayonet does not even budge :-) :-).

                                        I am still on the look out for the Sigma 40 with an EF mount. I don't think a new one exists on this planet anymore.

                                        Chen

                                            w7ay check on YouTube as I think you might have to remove the focus barrel to remove the rear barrel.

                                              w7ay yes, the reverse bayonet still on Nikon lenses still confuses me everytime… still!

                                                Ah, the ball goes into the spring, that I orignally thought was a 0.9mm hex grub screw.

                                                Reversing the disassemby process now :-).

                                                Chen

                                                  Not the 135 but similar I would think.

                                                  • w7ay replied to this.

                                                    The click stops are created by this spring loaded ball pressing against a set of serrations on the aperture ring :-).

                                                    Pretty smart, but pity the people on the assembly line :-)

                                                    Chen