M42 Auto Chinon f=55/1.4 - Need Help Assembling

[s-roll89]

Hi.

In my stupid haste to un-jam the aperture on this lens, I didn't take any pictures and cannot get this thing back together, especially pertaining to the front two elements.

In the photo below, I have the two lens elements labeled "A" and "B", with the aperture barrel labeled "C".

Are either of the lens elements supposed to fit into the aperture barrel, and is A or B the front element? Which side (convex or concave) is supposed to face the front of the lens for each?

Element B is the one with the black paint on the outside.

Thanks

 

[shutterfinger]

B as pictured into the lens housing above the aperture, A on the outer edge of B convex side out.
The element in B should clear the aperture blades, verify before attaching the retaining ring.

 

[s-roll89]

B as pictured into the lens housing above the aperture, A on the outer edge of B convex side out.
The element in B should clear the aperture blades, verify before attaching the retaining ring.

Thanks Shutterfinger. Is the retaining ring for element B Piece "D" in the first & second photo below?

D was held in place with three screws and also holds the aperture blades in place. As you can see in the 3rd picture, the flat edge of D fits around the concave side of element B perfectly, but it does not hold the element in place from the outside.

 

[shutterfinger]

I was basing the suggestion on basic lens assembly/design. I am not familiar with this lens or its assembly. I cannot tell anything from your pictures. I suggest finding another copy of the lens and using it as a template. Aperture assemblies usually fit into the barrel independently of the elements.
Have you misplaced some other parts for this lens?

Edit:
After downloading your photos, adjusting levels to expose fine detail, looking at examples for sale on ebay it appears that B in your first photo sits on the aperture ring, element A sits in the B tube, convex side up, then the front trim ring threads in and holds both in place. There may be a slight ridge in either the aperture ring or a recess in the tube for B that indexes the tube over the aperture.

Is anything other than the front trim ring threaded either internally or externally?

 

[s-roll89]

I was basing the suggestion on basic lens assembly/design. I am not familiar with this lens or its assembly. I cannot tell anything from your pictures. I suggest finding another copy of the lens and using it as a template. Aperture assemblies usually fit into the barrel independently of the elements.
Have you misplaced some other parts for this lens?

Edit:
After downloading your photos, adjusting levels to expose fine detail, looking at examples for sale on ebay it appears that B in your first photo sits on the aperture ring, element A sits in the B tube, convex side up, then the front trim ring threads in and holds both in place. There may be a slight ridge in either the aperture ring or a recess in the tube for B that indexes the tube over the aperture.

Is anything other than the front trim ring threaded either internally or externally?

Thanks Shutterfinger - I finally reassembled this beast with your advice!