Saturday, February 27, 2016

A drive pulley for the turns

Since I had sooooo much trouble driving the turns I made, I had to think of other options.  I realized that it might work to take the idea of a super-glue arbor for the lathe, and anchor the pulley to part with super glue.

Anyhow, I turned a very small pulley from 1/4" brass rod.

Here it is attached to the part with a tiny drop of super glue, viewed under the microscope and mounted in the turns.

It's still quite difficult to operate, but seems much less troublesome.

I added an electric motor drive that seems to make it easier to use.  I guess it's now a lathe...

Making a gouge

Edwin wanted to carve some details into his pinewood derby car.  So we made a gouge for him so that he could carve by hand.

We started by turning a wooden handle on the lathe

Then we moved on to metal; we took a 1/4" steel rod and turned it down to the width he needed for his detail work.  Then, we drilled out the center

once the center was drilled, we cut a bevel for the edge.  The bevel angle was taken to match a wood chisel.

After cutting the bevel angle, I polished it with 600 grid sandpaper.

Once polished nicely, I cut the tip into a semicircle with a file.  This was kind of rough, because I knew I would get it flat with a sharpening stone.  Then we parted it off

I reversed the part in the lathe chuck and beveled so that it would self-center into the handle.
Then I ground the cutting edge flat on the sharpening stone...
... and Edwin pressed it into the handle using the lathe tailstock quill.

Sunday, February 21, 2016

Door hinge turns

For doing delicate, precise work, between-centers turning on a lathe is preferable.  Generally, in the past this was done using a set called "the turns", a manual lathe of sorts.  I saw a pivot polisher setup by Charles Davis made from a door hinge, so this is my rendition of that idea.

Start by knocking the pin out from the hinge, and cut out the middle loop:

Then, I clamped the hinge on my lathe face plate and drilled holes for the locking screws:

While still secure in the lathe, I swapped out the tailstock drill chuck for a tap and threaded the hole:

The threads were checked with the thumbscrew:

Repeating on both slides and deburring results in a mostly complete turns frame.

Now for some centers... I made two from the hinge rods, since these seemed sturdy.  I started by center drilling the ends

and the tapering them.

I also filed flats on the side of each center, to ensure a stable grip for the thumbscrew.  Here two female centers are mounted in the frame:

The frame is intended to be used under magnification, and needs to be lifted to the microscope stage.  In order to mount the hinge to the top block, rather large screws are needed to not slip through the holes.  But I did not have any screws short enough to remain flush with the bottom of the block.  So I simply cut off the screw threads and made them into pegs that are hammered into the block.

Here is the completed setup under the microscope, ready for use.

Now for the bad news...  The Charles Davis setup is supposed to be powered by a squeegie blade, and is intended for clocks.  I'm intending for this to be used on watch arbors, and also didn't have a squeegie handy.  So I tried several other options, none of which worked...  For future reference, I tried:
  • kite cord on a bow
  • thread on a bow
  • 30 gauge kynar wire on a bow
  • 15 lb monofilament line on a bow
  • various things with rubber bands.
In each case, I tried to drive a small balance staff directly, like the Charles Davis setup.  Most of the literature suggests using a carrier of some sort for watch arbors, which I don't have. 

Saturday, February 20, 2016

Stabilizing gear tooth length

My wooden clock has been acting tempermentally lately... It seemed to run for somewhere between 5-10 minutes before stopping.  I tried relubricating it in place, but to no avail.  That is bit less than one rotation of the third wheel.  Upon disassembly, I found that the fourth wheel pinion roots where pretty heavily plugged with dried-up slipit, which could be the cause.  If the tips of the third wheel foul slightly on the roots of the fourth pinion and there's a lot of sticky residue there, it might be a problem.  I also checked to see if the teeth of the third wheel varied much in length by clamping an engineer's square so that most teeth passed by with no clearance.

 It turned out that a few teeth were just a hair longer, and these would have been presented to the pinion about every five minutes.  So I filed these teeth so that they, like the others, just pass the square.  Then I cleaned and relubricated everything... At last check, the was still running after 10 minutes...