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| p.5 #2 · lens repair, modification and disassembly guide thread |
Thanks again for posting this, The 45's aperture mechanism differs slightly from the 28, but otherwise looks the same.
Well I have 2 lenses apart, now to combine the two.
sebboh, you said elsewhere that you had a drawing for the spacer, was that for the NEX or M mount? As I'm planning an M mount for mine, is this the type of adapter you are planning? And if it isn't, which one?
Thanks in advance.
yup, that looks just like the adapter i was planning on using for the mount. i haven't gotten my drawings back from the machinist on the g28 design yet, but i was planning on doing a g45 myself this week. since i actually trimmed down the filter ring on the g45 for my previous conversion of it i'm planning on incorporating the rokkor's filter ring into the design.
for the front piece that will attach to the g45 optics and the rokkor helicoid i'm making an aluminum ring with an inner diameter of 40.21mm (to snuggly fit the contax g 45mm optics) and an outer diameter of 49mm. the thickness of the ring is 3.77mm in the center with a step down to 2mm thickness at a diameter of 44mm (the rokkor filter ring will lay in this inset). the fabricated ring will have 4 evenly spaced holes tapped for 0-80 screws at a diameter of 43mm to fasten the optics to it (i'm using 0-80 screws rather than the original screws because i didn't want to pay for a tap for whatever crazy metric size those screws are). finally there will be 4 evenly spaced countersunk holes at a diameter of 45.8mm to attach the aluminum ring to the helicoid with the original screws.
for the new mount i'm making an aluminum ring with an inner diameter of 39mm and an outer diameter of 58.9mm. the ring will be 7mm thick. on the helicoid side i'm cutting a 2mm deep inset at a diameter of 56.9mm (going all the way into the center) this inset will be the part that is screwed flush to the helicoid while the thicker outer part of the ring will keep the rokkor aperture ring from coming out. 4 evenly spaced deeply countersunk holes will be placed at a diameter of 48.4mm to attach the ring to the helicoid. i'm planning to make a 1mm inset with a diameter of 51mm on the other side for the m-mount adapter to fit into and then choose the best location for screw holes tapped at 0-80 to attach the m-mount. it looks like this will mean i need to mill out a little slot for the mount locking pin on my aluminum ring, so if you want to make this quicker you might want to forget the inset and just make this aluminum ring 1mm thinner.
note: i don't have precise measurements on for infinity focus here, so i'm leaving myself some slack to adjust the lens for infinity afterwords.