Friday 22 February 2013

Bolex H16 RX5 disassembly

Bolex H16 RX5

The RX5 first released in 1967 is for many 16mm afficionados the high point of the Bolex range, the last of the reflex C-mount turret series before single bayonet mount models arrived on the scene, which were designed to hold the heavier zooms that were all the rage at the time. But the zooms never matched the optical quality or speed of the C-mount Kern Switar primes, particularly the Macro-Switars pictured above. And with its flat base, triple lens turret and sleek magazine port like a Greek helmet all in tuxedo black leatherette and chrome, no other camera ever looked so handsome.

The following post documents the dismantling and servicing of one of these beauties, primarily for the curiosity of those interested in the procedure. It's not intended to be a guide for people hoping to do it themselves, because it requires certain tools and years of accumulated knowledge that are beyond most non-professionals. If your Bolex needs a service, take it to a professional!

Having thoroughly tested the camera to ascertain what may be out of tolerance, the first step is to remove the viewfinder. The next step is to remove the front. This loses the shutter to pull-down synchronisation, which must be reset during reassembly. It also breaks the light seal.

On reflex cameras the shutter assembly remains in the front, as opposed to non-reflex models. This makes removing a reflex front a considerably easier prospect than removing a non-reflex one.

After removing all the knobs and levers on the control side that are necessary, the entire mechanism can now be removed. The light seal is now completely broken.

The mechanism removed. The speed governor, release mechanism and claw drive gear are visible at the front.

After disengaging the spring limit gearing and winding the spring all the way down, the upper and lower plates can be separated.

A close up of the upper plate.

Both plates with the motor removed.

Complete disassembly of the gears, spindles and drive belts.

After ultrasonic bath cleaning.

The mechanism reassembled after lubrication, and play tolerances checked.

The claw assembly after ultrasonic cleaning. Claws are checked for wear and replaced if necessary.

Setting the sprocket height with a gauge. Later the rotational position will be set for optimal loop forming.

The mechanism is now fitted back into the body.

If necessary, focal flange depth adjustment and reflex prism alignments are done to the front before fitting. Also any work required on the variable shutter mechanism or viewfinder prism. The gate is cleaned, and if it has been removed, reset with a jig. Shutter/pulldown sychronisation is set when the front is fitted.

Having lubricated and fitted the claw assembly, the forward and reverse claw torques are measured. If they are out of tolerance, new spring washers are fitted.

Using a gate jig, the claws are checked for alignment and adjusted if necessary. The sprockets are adjusted rotationally for smooth loop forming.

The light seal is reapplied.

Various speeds can be checked with Bolex stroboscopic discs fitted to the 8:1 driveshaft.

As they spin, an upper and lower tolerance band seem to spin in opposite directions if the speed is within tolerance. They work off the 50 Hz frequency of electrical lighting, much like old record player speed displays.

A more accurate technique is to use a strobe gun that can be set to three decimal places of a pulse rate per second, which I use for modern film cameras but is a bit of an overkill on spring-powered Bolexes. But it shows me that they are very stable for at least the first 15 or 20 seconds. This one slowed down considerably after about 15 seconds before service, now it maintains 24fps (within 0.3 fps) up until the last few seconds.

The take-up torque is checked.

Using a Bolex RX test lens designed to check infinity incorporating the prism in the light path, the camera focal flange depth is double-checked on a bench collimator.

After a final scratch test with fresh film, where film is run through the camera and checked for scratches using a loupe, the camera service is complete.


  1. beautiful guide! what material can be used for refilling the light seal?

    1. Hi dimakisp,
      I use a sealing compound available from Bolex, but I guess you could use any light-proof sealant that won't crumble over time or be too hard to remove if the camera needs to be re-opened later.

  2. Great subject! Are there separate strobe discs for each speed?

    1. There are several speeds on each disc, and on the reverse side.

  3. Great blog, congratulation. Maybe I can ask a suggestion about how to remove a stuck Rex-O-Fader. I proceeded following the installing instructions (in reverse) by unscrewing the locking screw and the rewind handle, but the Rex-O-Fader doesn't come out, since is kept in place by the small cog or sprocket where the rewind handle is screwed in. From what I can understand by watching at pictures on the web (Rex-O-Fader instructions don't help) the cog should stay screwed on the rewind handle (which seems it is a special handle and not the normal one).
    In my case instead, the cog stays screwed on the rewind spindle, where it seems is stuck.
    After removing the Rex-O-Fader cover (by removing the four small screws) I unsuccessfully tried to unscrew the cog (turning clockwise, of course), also with the aid of pliers, but of course I didn't dare to apply too much force, fearing to damage the cog itself or the motor spring.
    Can you suggest me some trick to easily do it, or do I need to go to a service (which is not easy to find any more here, in Italy)?
    Thanks much if you can help me, and keep on this great blog
    Livio - Milano - Italy

    1. Sorry for the late reply, Livio.
      It sounds like you've done everything you can. If you can't remove the cog with pliers, maybe a specialist can help.

    2. Many thanks Dom!. At the moment the rex-o-fader is still in place, and the camera is doing a nice work anyway. But I haven't felt the need for an automatic fade yet!

  4. Hello, please, how can I se tup the shutter back? Thank you.

    1. It's too broad a question to answer I'm afraid. If you mean the timing, it depends on the model. But a way to check is when the single frame is set to T, the shutter should stop just above the gate aperture (looking through the front). When running, the shutter should cover the gate just before the claw advances the film.

  5. Nice blog you've got! I'm shooting with a Bolex myself, though a non-reflex one. Having some trouble with the lower spindle/take up spindle that runs to slow and at an irregular speed. It has become impossible to shoot properly, since the spool won't take the filmstock. You have any tips how to fix this?

    1. Generally that means the spindle needs to be removed, cleaned and relubricated. Which means dismantling the camera down to separating the plates to access the back of the spindle.

  6. Very professional, and meticulous work. I repair old watches. I can spot perfectionists. You are one!

  7. Hello Dom,

    Firstly sorry for bothering. I am a technician in Hong Kong who works on mechanic (still) film cameras. Recently I purchased a as-it Bolex Rex5 for my own interest, and I would like to seek for your advice.

    My Rex5 shutter release is not working no matter you set it to M or P, but the spring can be fully loaded.

    At one point i try to shake the crank slight and it release suddenly with the shutter set to Stop, at this moment if you set to P, the camera stops (in M and Stop position it goes). after that I try to wind the crank again, and then the camera stuck again at spring loaded situation.

    Since I am not familiar with movie cameras, I'd love to hear your advice if this situation can be fixed, so that I can spend some time on it and walk on a easier path with your kind suggestion.

    I am looking forward for your reply.

    Best Regards,

  8. Hi Ron,
    Well it seems to be a problem with the release stop. You need to disassemble down to separating the plates and assess what's damaged or incorrectly assembled, and maybe replace a part. If you've never worked on a Bolex it might be a steep learning curve! Don't forget to completely wind the spring down, and when you have the mechanism out of the housing, undo the circlip holding the little gear next to the spring motor, uncouple that gear, and run the spring down even further before separating the plates. Good luck!

  9. Hi Dom. are you still working on Bolex H16s. Wondred where you are and what the outlay for a service on a reflex would be. have messaged you also in google hangout. You can email me at

    1. Hi Dom. Just did some more research and discovered where you are. Damd. its just to far to send a camera. Oh well never mind. unless you know someone with the same bent for windups here in the UK. Hints very much welcome. Take care. DaveSalt.

  10. Hi Dom! Are you still working whit Bolex Cameras, I need to check one. Where are you? Thanks. Charlie.

  11. Gday Dom, I'm heading to Melb in next week or so with my Pentaflex kit, I was keen on stopping in and saying hello. Drop me a line if you get this?

  12. Hello, would it be possible for you to share the strobe disk through an image? I will love to try it out, even if not the perfect method. Thanks in advance!

  13. Hello,

    I'm also searching for the strobe disk.


  14. To those looking for an image of the stroboscope: I created one from scratch, which you can find here:

    It has bands for 12, 16, and 24fps with 60hz light, and is meant to be used with the 8:1 drive shaft. If you print it at 2 inches diameter and cut a small notch in the outermost band, you can tape it onto a rewind crank. I hope this helps you all.

  15. Do you know how to remove the rewind knob? There are holes present on the edge of each end of the knob where the pin runs thru the center shaft (where you attach a rewind crank or a drive motor) but the pin does not appear threaded.

    1. The pin is press fitted. A special Bolex tool is used to hold the shaft and push the pin out so you don’t damage the bearing underneath by trying to punch it out.