Wood Body Pinhole Camera - #5 Starting the Film Knobs

With the top, bottom and sides pretty much done I did a dry fit to make sure the method for winding and rewinding the film worked.  In doing so it occurred to me that adding a peg under the take-up spool would help keep it centered and aligned.  That way the spool is constrained between the pin and the recessed hole.  However, as the spool has a web across its bottom that has to be removed.  A little work with a sharp chisel, knife and round file took it out.  The top renderings show spool then to the right a view showing the webs and on the far right with the webs removed.  The bottom shows the bottom piece with the peg added on the right side.

The peg’s base is 3/8” in diameter to fit in a 3/8” hole that’s drilled 3/16” deep.  The upper part of the peg is cut down to 1/32” under 3/8” to fit in the spool’s end and just under 5/16” long.  It starts out as a ½” square piece and gets turned down.  In the photo below it's ready to have the last little bit removed and parted off.

Here is the finished peg partially inserted into the base.  Since it is a snug fit if I install it completely I probably won’t be able to get it out so will wait until the end to glue it in place.

The takeup/rewind knobs and their axles are next.  Each assembly has three parts; the axle, steel washer and knob.  The steel washer along with two rare earth magnets in the top firmly holds the assembly in place but allows for removal when changing the film.  Here is the drawing that shows how all those pieces go together.

The walnut knobs are first.  The already squared blank gets centers marked on both ends.  Here the driven end already has had the toothed drive set on the blank and struck with a wood mallet then reinstalled back in the lathe.  The blank is now ready to mounted between centers.

Once the blank is mounted taking it from square to round can begin.  I use the roughing gouge shown to do that being careful to get a consistent diameter the entire length.  The tolerance in diameter is plus or minus .008”.

After the cylinder is turned the blank is taken off the lathe, the drive center removed, a four-jaw chuck is installed and the blank reinstalled in it.  I use the live center in the tail stock to assist in making sure the long axis of the blank is in line with the lathe axis when tightening the chuck.  The next step is to face off the end of the blank to make sure the end is square with the center line of the blank.  That’s followed by chucking up a 1” Forstner bit to make the recess for the steel washer.  Here is what that looks like.

Next is to drill the 5/16” hole where the axle will get glued in place.  When that’s done the drill and drill chuck are removed from the tail stock.

A live center is installed in the tailstock, brought up snug against the outer edges of the axle hole and the outside face of the knob is turned down to its final diameter.

Last is to part off the knob.  Here in the top photo you can see where the roughed-out knob is ready to be cut off the blank.  The small cone shaped piece will stay with the knob and is there for a good reason which will be covered later.  The bottom photo shows both roughed-out knobs.

Turning the axle for the knobs is next.  It starts with a rectangular piece turned down to just 1/64” oversize as shown in the top photo.  The blank is flipped end for end and the same turning is done on the opposite end.  The bottom photo shows both ends turned.

The question naturally is why not finish turning the first axle to size before starting on the second?  If you look at the photo below you can see a different center installed in the live center.  The original one has an adjustable point and a larger outer ring holding the piece in place.  The photo below has only a fixed conical point.  With the original point and ring center I could not turn the axle small enough without hitting the live center.  I wanted to use it rather than the conical point to reduce the chance of splitting the blank while doing the rough turning.  With the blank turned very close to its final diameter I felt comfortable using the conical point to finish fitting the axle to the knob.

Here you can see the end result where the axle is friction fit to the hole in the knob. 

Now all that needs to be done is to lightly mark the insertion depth and the overall length as shown below then part it free.

Once cut free the full length of the axle is 5/16” in diameter which friction fits into the knob just fine.  However, part of the axle goes through the hole in the top of the camera and rotates when winding and rewinding the film.  This hole is also 5/16” so the axle needs to be a little smaller than that.  If I had 21/64” bit I could just drill a larger hole but I don’t so the next best thing is to mount the axle in a small chuck and sand enough off its diameter to rotate freely.

Cutting the slot in the axle where it will engage with the web in the film spool is next.  That’s done on the bandsaw.  A hole is drilled in a block the same size as the axle then a rip fence is set so the blade hits the axle dead center.  Last a crosscut fence has the block clamped to it and the cut can be made.

There is only one more step to complete that axle.  Since the web in the film spool is wider than the bandsaw blade kerf it needs to be widened a bit.  The left photo shows the axle and little file that will be used.  The right photo shows how the axle will set in the film spool albeit upside down from how it will be installed.

Next Up – Completing Film Knobs & Starting the Film Boxes