Thursday, 17 January 2013

Servicing a Bolex D8L

A little history

The legendary Swiss camera maker Bolex Paillard introduced their first 8mm "pocket camera" in 1942. The "L8" was a single lens, single speed camera with a rather small and dim viewfinder. During the 50's the C, B and D series models followed, adding dual or triple lens turrets, variable focal length viewfinders, multiple speeds, through the lens metering, adjustable shutter angles, and rewind facility. With remarkable ingenuity, the Bolex engineers somehow kept the size the same while continually adding features!

The triple turret D8LA of 1961 was the high point of this evolution, one of the finest standard 8mm cameras ever made. Although the following service procedure is done on a D8L (more or less a D8LA without the rewind facility), all of the pocket cameras used basically the same internal mechanisms, so portions of this procedure can also be used on them. This includes the B8, C8 and D8 variants and the zoom reflex models P1, P2 and P3.

Servicing a camera

Due to dust contamination and the drying out of lubricants, many of these cameras may be found to be running sluggishly, or not running at all. Often the winding key feels scratchy to turn, or the run switch is sticky. The viewfinder optics can become hazy and dust specked, the turret a bit hard to turn. Sometimes the single frame operation isn't working, or the through-the-lens meter switch doesn't quickly pop up when the camera is run, leaving the internal meter sensor still blocking the light to the film instead of retracting out of the way. But because these cameras were so well made, a little cleaning and relubrication can often bring them back to virtually new condition.

Some damage, of course, may not be reversible. If a camera judders intermittently while running, the spring has likely been deformed and cannot be restored to smooth operation. This can happen if the camera was stored for a very long time with the spring wound up. If the winding key keeps turning (clockwise) without winding the spring it's likely the spring has broken inside its casing (although to be honest I've never come across this in a pocket Bolex). Signs of corrosion are a bad omen for any mechanical device, and should always be avoided when choosing a camera to buy. But sometimes they can be cleaned back to working order.


It's important to use the right tools when working on any machine, let alone a precision instrument like a movie camera. In particular, make sure screwdrivers are the right fit for the screw they are turning. Using the wrong size driver can easily damage screw heads or slip and damage other surfaces. Most of the screws in a pocket Bolex are slotted, except for the screw holding the turret and (in later models) the screws holding the adjustment dials, which have a special head with 4 slots around the edge. If it's necessary to undo these, a pair of needle nose pliers is risky but can do the job - I prefer to make a driver by filing out the centre of the right size screwdriver so that it has 2 prongs which will fit a pair of the screw head slots.

These should be all the tools you need to service your camera:

Small, medium and large slotted screwdrivers
Needle-nose pliers or 2-prong driver
Pair of tweezers
Small brush for applying grease
Syringe for applying oil
Lint-free cotton buds
Isopropyl alcohol or napthal
Soft bristle cleaning brush

I also find it very useful to have a compartment tray to put the parts in as I disassemble a camera. It keeps all the screws, washers and other bits together and in the order you took them out, making it much easier to put it all back together.

If there is any corrosion, I use a rust inhibitor product like CRC 2-26 to clean up surfaces. If there are any hard to remove screws, a few drops on the screw head, left for 10 minutes, can free things up. I avoid WD-40 in cameras, as it has an oily base and can migrate to other areas, particularly optics.


I'm using oil and grease purchased from Bolex, specifically recommended for their cameras, but for amateur camera lubrication I don't think it's necessary to be quite so picky. A good quality clock oil (or even sewing machine oil) and a light general purpose grease will do.

Definitely avoid using silicon spray anywhere near a camera or lens.

Service Procedure

The first step is to run down the spring until the camera stops, and unscrew any lenses.

Open the door, flick the gate lever to open the pressure plate, and pull the plate up and out.

Undo the screw holding the movement cover.

Remove the movement cover, taking care to hold the top sprung roller in place. Note the direction it springs, and how the little coil spring at the pivot is hooked at each end. If the roller falls out you will need to refit it with the spring correctly latched.

Using tweezers or a dental pick unhook the spring from the end of the claw arm.

Undo the screw holding the claw arm. The eccentric beneath will turn as you twist the screwdriver, so you may need to hold it firmly with one hand. Be careful not to slip and damage the highly polished surface of the gate directly next to it.

Undo the 2 screws holding the footage counter cover and remove it.

Undo the 5 screws holding the film chamber plate. On some models the front corner screws are also securing plastic film guides.

Remove the plate by lifting the front first. A shaft hidden beneath connects the front of the plate to the footage counter at the back of the body, but it should slide out of the back connection as you lift the plate.

You can now inspect the mechanism inside, and even wind up the spring and run the camera to see how it works. Change camera speeds to see how the brass governor on the right works. Make sure to run the spring all the way down again before dismantling anything further.

At this point it's possible to lubricate some of the important parts, and avoid further dismantling. Nine times out of ten this will get a camera running well again, but you won't be able to clean and lubricate the winding mechanism, access the front shutter bearing or fix problems like a sticky run switch, faulty meter sensor mechanism or unreliable single frame operation. Further dismantling will also allow a little better access to the following areas for lubrication, so skip the next three steps if you wish to continue on with a full service.

Otherwise, place a drop of oil under the claw eccentric. (Do not undo the screw holding this eccentric on to it's shaft or you will lose shutter/pulldown synchronisation.)

Place another drop or two of oil behind the brown helical gear that drives the governor. Ideally try to get to the other side of the plate, where the bearing is fitted. This is the only 'ball' bearing in the mechanism, and usually the spot that most needs lubricating. Try not to get oil on the gear teeth.

Place another drop of oil on each end of the governor shaft.

On the back of the film chamber plate you removed earlier, directly beneath the take-up spindle, is the take-up clutch. This allows the spindle to slip while the little spur gear underneath keeps being driven by the gear on top of the spring casing. The take-up spindle needs to slip because as more film gets wound onto the spool, the diameter increases, and so it needs to turn at a slower rate, while the driving speed from the spring remains constant.

While holding the spindle on the other side, undo the screw in the middle of the spur gear. Dis-assemble the clutch, noting how the gear and friction disc are located on the shaft with D cut-outs.

Clean off the old grease from the friction discs, and clean the spindle shaft and its bearing.

Apply some grease to the friction disc surfaces, and put a drop of oil in the spindle shaft bearing. When re-assembling, make sure the D-cutouts line up with the shaft. When it's together, hold the spur gear and turn the spindle to make sure it is slipping smoothly.
The other gear on the back of the chamber plate drives the footage counter via a worm gear. Unless it's very stiff, I generally don't find it necessary to touch it, or the spring lever assembly that keeps the worm gear engaged.

If the turret feels stiff or scratchy to rotate, now is a good time to service it. By removing the centre screw, the turret can be eased out. The only thing to watch for is a spring-loaded ball recessed in the turret's edge that locks the turret into its three positions. Once the turret is removed, clean and grease the centre shaft, the spring and ball, and the inside edge of the wall around the turret.

At this point you can either reassemble the camera, or keep going for a more complete service. If you wish to continue, the next step is to remove the front.

To access the screws at the top of the front it's necessary to remove the lightmeter/viewfinder cover by removing 3 small screws around the edges. When the cover is off, be very careful of the fragile meter needle. Now remove the 2 screws at the top of the front.

There are 2 more screws holding the front, under the turret.

If you haven't removed the turret for cleaning, you will need to rotate the turret slightly to access the second one.

Fit the meter cover back on to protect the needle, and remove the front by first sliding it towards the door side. It may need a little jiggling to break the painted light seal around the gate. Take it slow, and watch how the front mechanism mates to certain parts in the body. One end of the governor will detach as you lift the front off. Watch also for the small felt strip that blocks a potential light leak from the viewfinder.

Carefully remove any loose parts, such as the governor and the rewind gear (if the camera has one). Now we can begin to remove the spring motor. First undo the 3 screws on the winder cover plate.

Now undo the large screw in the centre, which is securing the spring motor inside. Once it's loosened, you may want to hold the motor in place as you undo the screw completely. The mechanism around the screw allows the winder key to spin free in an anti-clockwise direction but grip when turned clockwise. I usually don't find it necessary to clean and relubricate it. Once the centre screw is removed, this mechanism can be lifted out as a unit.

It's often a good idea to fit things back in the orientation they were in before. Before removing the motor, make a mark from the square key to the plate around it, so you can fit it back in the same position.

You can now take the motor out, and see the limit gearing on the underside. These gears allow the motor to be wound a certain number of turns before the long gear teeth hit a shallow dip, thus protecting the spring from overwinding. In the other direction they allow the spring to unwind and stop before the spring loses power.

Undo the screw holding the spring main drive gear and remove the gear.

Undo the 3 screws holding in the winding plate.

Now you can take out the rotating winding plate and give it a good clean. Note how the outer spring and spring washer are located. The spring acts as another uni-directional clutch, allowing the winding plate to rotate clockwise, but not anti-clockwise.

The various parts dis-assembed and cleaned. Scrub the spring with a toothbrush to get it thoroughly clean.

Make sure to clean the cavity in the body also.

Apply grease to all the sliding surfaces, on the winding plate and its spring as well as the body. When re-assembling, remember to locate the little protruding hook of the spring in the slot.

Clean the drive gear spindle.

Give the governor pad a clean.

You can clean the front surface of the variable lens element inside the viewfinder if you move it all the way forward. But if the back surface of that element or the inside surface of the eyepiece optic needs cleaning, you will need to unscrew the eyepiece to get inside. Unscrewing the eyepiece can sometimes be tricky because there's nothing to grip it with, but you can use something like a cut down rubber eraser to make a gripping tool. Sometimes a drop of acetone (nail polish remover) helps to free it from the surrounding leatherette.

If nothing is working you may have to use pliers, but be careful or they will leave a mark. Once it's out, you can try to clean the optic in the eyepiece with tissue folded to a sharp point and moistened with alcohol or lens cleaner. But it's a very small optic!

Set the viewfinder focal length to around the middle, say 25mm. Now you can remove the viewfinder cover, lifting first from the back. The small felt strip near the gate will come off, if it didn't before when the front was removed.

You can clean the variable element inside with more tissues folded into a point moistened with alcohol or lens cleaner. Don't keep using the same tissue or you will start to smear the glass. A lens blower can help remove dust specks. The mechanism to move the optic generally shouldn't need attention. Replace the cover when you're finished to keep dust out.

Clean the drive gear with a toothbrush and some alcohol or napthal. Apart from the few helical gears (with teeth that slope at an angle) which can be lightly greased, all the gear teeth are meant to run dry. So no grease on this one.

Clean the gear teeth on the spring motor.

Place a drop of oil on the drive gear shaft, and refit the gear. Then refit the spring motor (lining up the squre key with your mark), and the winder assembly.

The next stage can be a little tricky, so only attempt it if you need to access the run or single frame mechanism, or the meter sensor isn't retracting properly. Or if you're just curious..
First undo the 2 screws that are holding the  2 pressure plate holder springs.

Then the 2 screws recessed in the gate (be very careful not to slip and damage the polished film rails).

Lastly this screw, near the bottom of the gate.

Then carefully lift the assembly off, noting the 2 spacer rings and gate shim beneath.

You can now have a close look at how the variable shutter mechanism works, by sliding the brass helical gear with the groove in its centre back and forth. Have a look back at the body to see how the variable shutter dial moves a pin that sits in the groove of that gear. It's a very ingenious design.

Take off the (now loose) plate with the right angle arm that holds one end of the claw axle. It's now easy to access the bearings that need oiling. First the bearing beneath the claw eccentric.

Then the ball bearing behind the brown helical gear. That gear, by the way, is designed to slip at a certain tension, held on its shaft by the friction of a spring washer. This protects the governor from jolting starts and stops. I've never found it necessary to service that clutch. If you do happen to undo the circlip holding the gear, be aware that tiny balls will fall out everywhere!

Before reassembly, place a drop of oil on the claw axle pivot..

..and the shutter axle.

If you take off the gate shim, spacers and thin cover plate, you will see the rather complex mechanisms of the release, selector switch and retractable light meter sensor. Take a while to study it if you intend to clean and lubricate it. Many of the levers are sprung-loaded and can easily pop out of position. But cleaning and lightly greasing them will ensure the camera runs well for another few decades.

When fitting the gate and movement assembly back, one end of the gate is positioned by a pin, but a small amount of repositioning is possible. Try to make sure everything is spinning freely (with the run button pressed) and the shutter isn't scraping. Before refitting the front, remember to clean the viewfinder cover glass.

You can also clean the governor flange. This surface rubs constantly against the adjustable pad in the body, limiting the speed. I lightly lubricate it with graphite powder, but this isn't essential.

The last step before putting the front back on is to put a drop of oil on the pivots at both ends of the governor.

You can lightly grease the helical gear, but try to avoid getting grease on the pivot (or oil on the gear teeth).

Now fit the governor back in the body, and carefully slide the front into place, latching the other end of the governor into it's bearing. Watch that the variable shutter pin lines up with the groove in the gear. Some matte black paint applied at the inner join will 'professionally' finish the job, though it's probably OK without it. The small felt strip should be glued or painted back in the spot it was fitted.

Once the front is back on, you can wind the spring up and see how she runs. If something's not right, you may have to dismantle again and re-adjust the position of the movement assembly. But hopefully it purrs like a kitten! Now you can fit the chamber cover plate back in. Fit the footage counter shaft to the plate, and then line the other end of the shaft up with its hole in the body.

You might need to jiggle the plate a bit to get the gear teeth underneath to mesh with the gear on the spring motor. Don't do up the screws until the plate is sitting flat!

Clean and grease the claw eccentric shaft before fitting the claw. Replace the claw spring, the claw cover (making sure the top roller is correctly sprung), and the footage counter cover.

Your Bolex is now serviced!


  1. Amazing job on this and very helpful. As long as 8mm can be had I think these cameras could run forever.

  2. Thanks for this very helpful guide! Excellent clear photos too.
    Unfortunately, I ran into a little snag while removing the front of my B-8 variable shutter: a couple parts fell out before I had a chance to take note of where they were. I'm befuddled as to what this conical headed piece is:
    I wonder if there's an exploded drawing of the 8mm assembly available to download somewhere?

    1. Hi Caitlin, it looks like the pin that locates the gate, see picture 52 of the plate under the gate/shutter with all the spring loaded levers. The pin is top left. (Click on a picture to enlarge and show the pic number.)
      I'm glad the guide was helpful to you.

  3. Thanks for the tutorial on servicing the Bolex 8mm.

  4. Thank you for the accurate tutorial. It was very helpful to restart my Bolex C8S.

  5. I just found this guide after a few days of research into how to repair my P1. Now my P1 is ready to shoot again. This was very helpful, thanks.

  6. What a wonderful and complete tutorial! This helped me enormously, thank you very much!

  7. Hi, following your tutorial I got a Bolex P3 8mm from completely dry and not running to running very smoothly at all speeds, but only for a few minutes. After a while the spindle will stop moving, and taking everything apart again I notice that the screw in the middle of spur gear has gotten loose. Hard to tell wether everything is in place in terms of the D cut outs, but I'm quite positive gears and disc are aligned. Could it be the soft disc is worn out?

  8. Thanks for this. Cleaned/lubed two Bolex B8. Couldn't have done it without this detail. The only thing I'd like to see is a detail of how to re-tension the claw cover spring if/when it falls away from it's hole in the plastic

  9. Thank you very much for this beautiful website! I enjoyed your detailed insight in the camera and I used your instructions to repair my Bolex d8l which is working perfectly again.

  10. Hello! Does anyone know what the screw sizes themselves are? I am in need of replacing the screw for the little, notched crescent that holds the camera door closed (this is located on the inside of the camera door, just on the other side of the knob to latch and unlatch the camera on the outside). The screw in the middle has come out and I need to find a replacement for it. Does anyone know what the screw size could be?

  11. Many thanks for this fine tutorial. Question - did I miss the type of lube, oil, cleaner, and lens cleaner to use?

  12. Well I think I broke the motor. Human error of course, this tutorial is amazing, and I had a blast with this little project. I unfortunately put the black felt in loose and it jammed the shutter. When I dissembled to find this, the motor limiting gears became misaligned. Long story short, I think I over cranked the motor during trial and error, or my limiting gears are off. The motor doesn't sound right when it winds.

    Anyone know where I can find a new motor?

  13. Many Thanks to this Video! It helps a lot.

    For everybody who uses a Bolex or will service it by himself - here are some more usefull informations: