Nikon F Mount Mechanism

Fully working Nikon F Mount Camera mechanism.  If you've seen my lens mount, this an adaptation/refinement of that and what happens when you get carried away and build the rest of it.

You can cock the mirror, opening the lens aperture, preview the DoF, fire the shutter (closing the aperture) and [by inserting a variable resister] measure the aperture selected on lenses with aperture rings.

There's lots of parts, I've put them in folders to help make it clear, but I suggest using the 3mf where I've arranged them all in the ideal printing orientation.  I used 0.16mm layer height in PolyTerra PLA.

Be very carefully removing some parts, particularly the pulleys as they are pretty delicate.

This is a work in progress, the aperture “sense” side I'm pretty happy with and is very similar to what Nikon actually used in the FM2 (though positioned differently).  The other side is more experimental, I've made a few different mechanisms but this is (so far) the best.  Making the controls not move is challenging.

If it's all constructed correctly, the distance from the lens mount to the rear of the frame will be 46.5mm; the back focus distance for F-Mount lenses.

Feel free to remix with a different mechanism/frame - just credit me; this was a lot of work.

Updates

The v2 folder includes refined versions of various components; a crank to cock the mirror, larger Aperature preview guide and better knob.  Making the controls less cramped

Instructions

I'll use the names of the individual parts, so you can see what I'm talking about.

You will need

• 2 M1.4x4 flat head bolts
• 1 M1.4x8 flat head bolt
• M2 flat head bolts; various lengths 4mm, 6mm, 8mm, 10mm (3.2mm head diameter, 1.3mm head height)
• 2 M3x4 flat head bolts
• 3 18mm long “pen” springs
• 2 badge reel's (the little retractable reels your work pass clips onto your belt with)
• Small screwdrivers
• Small metric drills; M5 and smaller, M5 & M2 are probably the only ones you really need
• [optionally] a standard variable resister “pot”

Front Frame (lens mount)

Take the Mount.Baseplate, insert the Aperture.Control.Arm into the left side (lump facing away from the lens).  Screw a M1.4x4 bolt into the back of the Aperature.Sense.Ring, then place that onto the Mount.Baseplate.  Place the Lens.Mount in the middle of it, align and screw 4 M2x10 into it to secure.  Everything is threaded so make sure you squeeze the parts together so there's no gap.  Make sure the Aperature.Sense.Ring bolt is in the recess at the top of the Mount.Baseplate.

The Aperature.Sense.Ring should move back and forth smoothly.  The Aperture.Control.Arm should rock up and down a little too loose.

Left Frame

Take the Frame.Left and put the Lens.Mount.Release into square slot.  We've going to use a small piece of 1.75mm filament as an “slide rail” for it to slide on - ideally you'd use a steel M2 rod but I don't have one handy.  You might want to clean out the holes with a drill as they printed horizontally.  One pen spring goes behind the Lens.Mount.Release, the filament through the middle (protruding out the front) and a M2 bolt fixes it in place.  This is where we'd attach a handle.

Be careful over tightening it as the Lens.Mount.Release might break; I have strengthened it from my original design.  When working it should move back and forth, pulling the filament and the filament working as a slide rail in the housing.  This will be what clicks in place and stops the lens rotating back.

Now take apart one of the badge reels.  Inside you should find a long spiral steel spring; hopefully they are somewhat standard.  This goes in the Aperature.Sense.Pully.  Take the string from the reel as well, trap the end as you wind the spring inside the pulley.

If you want to actually measure the aperture take apart a variable resistor and place the PCB with the track in the hole at the bottom.  The Aperature.Sense.Pully has small blobs on top; these will need cutting down but will fit into the holes on the wiper.  Note I've not actually figured out a good way to get all this together, taught yet - so try without the wiper to start and let me know when you figure it out.

The Aperature.Sense.Pully fits into the circular hole, the string should pass through the hole toward the front.  Wind the spring and slot it into the peg in the middle.  You will probably want it quite taught so bolt the Aperature.Sense.Cover over the top with some M2x4 bolts to stop it springing out.  If it's frustrating and keeps going everywhere … you're doing it right.

If all works you should be able to pull the string and it reel back.

Attach the left frame to the front frame by screwing the lens mount bolts all the way - threading the string through the hole in the Mount.Baseplate as you do.  The bolts aren't really long enough but we don't have the space - in a final design you'd glue all the frame parts together with the baseplate to make it a rigid 3d block.

Pull the string and carefully thread and tie it around the Aperature.Sense.Ring's bolt.  It should pull it toward the mount release mechanism and run smoothly.

Right Frame

Take the Frame.Right, and slot the Shutter.Release into the slot at the bottom - it should just fit.  Make sure this is running smoothly all the way to the front of the slot.  You might want to rebore the hole at the front with an M5 drill as it printed horizontal.  You also might want to just sand the Shutter.Release barrel and the slot.  It should run smooth, when it does, push another pen spring in behind it.  It should spring back satisfyingly as you press it.

Put the Mirror.Release.Arm on its post and rotate it in behind the Shutter release.  Connect the two with a M2x4 bolt; make sure you don't tighten them too much and check the whole mechanism works smoothly and flicks back into place.

Now attach the right frame to the front frame with the lens mount bolts.  As you do, fit the Mirror.Frame between the two sides.  The “kink” in the Mirror.Frame should be on the top.  Make sure the shutter still works smoothly and that the Mirror.Frame moves up/down smoothly.

The Aperature.Control.Block fits into the slot next to the front, the end with the M3 thread should be toward the top.  Put a M1.4x8 bolt through the side and screw it into the Aperature.Control.Arm in the front frame.  It can be tricky to align it - don't screw it too tight, the whole piece should move smoothly up and down; a little loose is fine.

Take apart the other badge reel to get the other spring.  Wind this into the Aperature.Control.Pully and place it onto the post with the screw thread part facing up.  You should be able to wind and attach the spring to the post; this doesn't need much winding and it should all move smoothly - moving the Mirror.Frame as it does.

Take the final pen spring, carefully bend the last two loops of each end out flat with some pliers and use the M3 bolts to attach one end to the threaded hole on the Aperature.Control.Pully, and the other to the Aperature.Control.Block.  Now when the Aperature.Control.Pully is cocked it should pull the Aperature.Control.Block up, opening the lens aperture.

Put a M1.4x4 bolt into the hole on the back side of the Mirror.Charge.Hat and the Aperature.Preview.Guide.  These will be attached with elastic bands to bolts in the top of the right frame.  This is the least refined part of this design - my apologies.

Fix the Frame.Right.Cover between the Aperature.Preview.Knob and the Aperature.Preview.Guide.  Make sure they move smoothly and and the M1.4 bolt is facing “in” and toward the top.  This will push on the top of the Aperature.Control.Block to allow you to preview DoF.

Attach the elastic bands, put the Frame.Right.Cover in place and use M2x4 bolts to hold it there.  Pop the Knurled.Knob onto the post of the Mirror.Charge.Hat and everything should work.  When the shutter fires the Knurled.Knob and Aperature.Preview.Knob [DoF preview] controls should not move.  Winding the Knurled.Knob counter clockwise will cock the mirror.

Frame.Base

This is experimental so either you'll need to glue it in place between the two sides.  A future version will probably bolt on so it's easier to experiment with different designs of mechanism