3D printed Minolta MD to EOS mount conversion

Started Oct 23, 2019 | Discussions thread
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E Dinkla Senior Member • Posts: 2,392
3D printed Minolta MD to EOS mount conversion
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There are different ways to convert a Minolta SR mount to Canon EOS mount. In this case I went for a conversion that is less destructive on the original mount. It has been done before but I have not seen a successful 3D printed version of this method.

When I saw a Minolta MD III 50mm 1.7 at 5 Euro a purchase could not be resisted. The actual bayonet cams of its mount (stamped steel part) can be removed, so I asked a friend (with a lathe) to alter a Chinese EOS reverse adapter that it no longer had the flange but just the bayonet part. A 3D printed part to fill in the gap between the two bayonets and secure it on top with the same screws as used on the stamped steel cam part fixed it. Added some glue between the 3D part and the Chinese EOS bayonet cylinder. Position marks for an EMF chip to glue etc added in the 3D design. With a Dremel I added the EOS lock hole in the MD original flange, it is on the edge so not ideal and a bit ugly. To overcome that I added a 3D printed ring that fits around the flange edge and creates more of the locking hole.

As the register distance of the Minolta SR mount is 43.5mm and the EOS mount has a register distance of 44mm there is still a difference, the lens will be 0.5mm too far from the sensor. However that is not much and can be compensated in the infinity calibration of the lens. Where to find that varies per Minolta SR lens. On the Minolta MD III 135mm 3.5 it is as easy as removing the rubber grip, take the black tape off, adjusting the infinity stop with the lens set at infinity ( I use a my hand made collimator) and adding tape + grip again. More often some screws have to be freed a bit and a similar calibration done.

Not all the Minolta SR mounts have the bayonet cams part stamped out of steel sheet. I thought it would be possible to 3D print both a female Minolta SR bayonet + a male Canon EOS bayonet with no flange added. A kind of sleeve that is turned on the SR mount. Similar 3D designs I downloaded were rudimentary, reversed 3D printed and by that not accurate, etc. As I intended to buy a Minolta MD III 35-70mm 3.5 Macro anyway I bought one together with a body + a Vivitar SMS Close Focusing 28mm 2.8 (Komine). Nat as nice as the 2.0 but quite good already at 4.0.

Paid 40 Euro in total which is a good deal. Both in excellent condition, helicoids turn well, glass superb.

Long story, now the images:

Finished MD to EOS bayonet sleeve. Small hole added for the screw that fixes  it on the SR bayonet lock slit/indention on one cam. That creates the Minolta SR to EOS register so aperture/focus marks are on top.

Ring to cover the half lock hole on the flange, also makes it easier to mount the lens as it will be more straight when inserted.

Bayonet sleeve on the Minolta zoom. Small screw fixes the sleeve in the MD bayonet although it is already very difficult to turn the sleeve off again.. Beauty ring also added with an epoxy glue to the edge of the MD flange.. The parts are printed with black PETG filament. It would be perfect when it is made with polyamide on a better 3D printer than I have. Probably outsourcing that is the way to go.

Vivitar mounted as it is more cute than the Minolta zoom

35mm setting

70mm setting

at the 1:4 macro setting

near the 1:4 macro setting

more  near the 70mm setting

35mm setting

70mm setting

Met vriendelijke groet, Ernst
No photographer's gear list is complete without the printer mentioned !

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