Minolta Rokkor-QF 40mm f1.8 Conversion Part Deux

I first converted this lens with filter ring and glue, as I wrote in this post with more pictures here.  It was a relatively easy conversion so I decided to redo it with the lathe, to hopefully make it look and work better.

Most of the conversion work was already done so this second conversion was pretty quick. I just needed to machine the spacer with the required thickness for infinity focus, drill and tap holes on the lens board and the newly machined spacer to attach them together, and then do the same for the E-Mount adapter, which was original a Rollei to E-Mount adapter with a missing lens release pin, and I decided to to use it as the mount.

The part at the right is the spacer I machined.  The left part goes inside the spacer.

I am quite happy with this particular conversion.  The lens fit together very well with no play and wiggles, except at the mount if you really twist it hard.  I did messed up the spacing of the mount and it's not perfectly centered, and this has the effect of off-setting the aperture index mark slightly.  Not a big deal but I could have done much better.  When I get more adapters, I will redo it, or, my next exercise, make my own E-Mount!  Another small problem is the focusing is not as smooth as I would like, probably because the focus guide hole is a bit tight.  Hopefully I can tweak it and make it feel a bit smoother.

Home made drill bit sleeve for the collet.

For this project, I used the milling attachment that came as part of my lathe.  It was used to mill the path for the focus guide to go through, and also used to hold the parts for drilling, as I don't have a drill press.  There is also a set of collets that came with my lathe but none fit the tiny drill bits, so I made a sleeve from the shaft of a Dremel bit.  A hole was drilled with the same drill bit that this sleeve will hold.  Once the hole was drilled, I cut a slit on one side of the shaft, thinking that should be good enough and it should give and clam on the drill bit when put on the collet.  But because it was made of hard steel, the sleeve didn't clam on the drill bit at all, so I had to cut more slits on the other side and is now working like a charm.

All done.  Looks pretty good, eh?  You can see the aperture index mark is off to one side.

This has been a good exercise for me.  This gives me more confidence that I could do more complex conversions later on.  Below are pictures I took after the new conversion, with the Sony A7.

Update on the Progress of the Lathe Project

I have been quite busy with other stuff lately so I haven't really spent as much time as I would have liked on learning to use the lathe.  But, so far, I have done a few small projects, mostly with positive results.  Now that I know what the lathe can do for me, it would be hard to live without one.  It is, of course, not without lots of frustration.  The learning curve is steep, especially since I had no prior experience with a lathe.  Below is a very condensed summary:

• The 1/4 horsepower motor is not powerful enough to do quick, smooth deep cuts.  It often stalls when making what I consider reasonable thickness of cuts.  Boring a larger hole or making a parting cut could take a long time and this simply drives me crazy.  I have to remind myself that the Taig Micro Lathe was designed to make small parts and I need to be patient.

• The lack of thread cutting capability as a default feature on this lathe is now a small annoyance.  I actually have a need to cut threads, and it's more often than I originally thought I would need.  Outfitting the Taig Micro Lathe II with thread cutting feature would mean an expensive upgrade (for me).

• The small size of the lathe is one of the best features.  It sits on a small desk with space to spare.  That, alas, is something of an Achilles heel.  This means working with anything larger 3 inches in diameter is difficult.  Also see point #1.

• It's hard to describe the feeling when a project is completed.  It's a feeling that should be experienced.  A sense of purpose, accomplishment, and the whole process was therapeutic. 

So far, I have used the lathe to help convert a few lenses to work on Sony E-Mount, from very simple turning of the lens barrel to actually making parts.  The pictures below shows few of the lenses I have done.  One thing I have learned, is that drilling and tapping small holes and making them aligned perfectly is no easy task without proper tools.

Three Amigos - Konica 45mm f1.8, Argus Cintagon II 48mm f2, and Minolta Rokkor-PF 45mm f2.  The Konica and Minolta lenses share the same 12-17mm focus helicoid for focus.  Both uses an M42 mount I savaged from old lenses to mount to the helicoid.  If I could cut threads, I would have no need to use old parts, because eventually, I will run out of them.  The Cintagon II modification is only partially successful.  It works, but not well.  You can see extra holes on the part that I made.  Those are mistakes :) I think I will get rid of its original focus mechanism and use a helicoid for focus instead, or converted to L39 or M mount.

In all, I really enjoy using the lathe to make lenses work better on my camera.  Hopefully my skills on using it will improve and the conversions will look and work better in the future.

Bokeh - Minolta Rokkor-PF 45mm f2 (from the AL rangefinder) & Sony A7.

First Lathe Lesson - Centering the Work Piece

I want to share my experience with anyone who is considering or starting to play with a metal lathe, and will post whatever I consider useful.

I wrote last time about the very bad run out of the 3-Jaw chuck.  Did some more research and found that there isn't too much can be done about the chuck itself, other than buying a high quality one with high precision.  But that is just one of the factors that affect the precise centering of the work piece.  A 4-Jaw chuck is still a little better, but it takes much longer to get everything true.  I have a dial gauge with a magnetic base on order and should be here soon.  In the mean time, I learned that using a ball bearing can make the work piece on a 3-Jaw chuck run much more true than without.

Got a broken bicycle bottom bracket that has a ball bearing still on, and it broke at the perfect place.  I really don't need to modify it, except to thread a screw on it, and then clamp it on a tool post, like this:

Work piece centering tool using a ball bearing from a broken bicycle bottom bracket.

To use it, mount the work piece just tight enough that it won't come off when the lathe is turned on.  Run the lathe in slow speed, and gradually a advance the ball bearing until the bearing start to turn.  The work piece should now run true enough to start turning.  I don't have the dial gauge yet to check the run out, but to my eye, it was light years better than when I was turning the Angenieux 70mm f1.5 projection lens.

All these changing of tool posts and change the belt position for different speed of the lathe is quite tedious.  All the more motivation to convert this lathe to use a variable speed DC motor, and buy a quick change tool post.

Water Quality Sampler Post - Zeiss Opton Tessar 75mm f3.5 & Sony A7