Sunday, November 29, 2015

Handle for a plane

Here's a short lathe project...  My dad likes restoring old woodworking tools.  Here's a plane that's missing a front handle.

Here's a handle I turned from a piece of oak.

which has a bored recess on the back to fit the socket on the plane:

Here is the handle installed!

Timer is finished!

I made a number of finishing touches to the gravity escapement timer.  It now runs reliably!
First, I turned a thicker barrel on the lathe

Using a square file, I cut a keyway to engage with the metal teeth on the existing barrel.

Here's the finished barrel, ready for installation...

...and here it is installed.

Many of the wheels weren't running smoothly.  To find where to file, I used a pencil to mark the pinion teeth...

... which transfered to the driving wheel.  This could be filed down as needed.

Quite accidentally, I made the pinion teeth an integer multiple of their driving wheel teeth.  This made debugging easier!  Because I found certain pairs of teeth consistently binding.  I marked them like so

which allowed me to track down the problems! 
 I made a 4 oz pendulum bob from two halves that friction fit to the pendulum. 

The excess screws are for weight!

It's worth noting setting that a gravity escapement in beat is quite a bit more delicate than I expected.  Here's a picture of the timer in action...

And a link to a video!

Friday, November 27, 2015

Timer improvements

Current specs:
  1. Pendulum bob is around 2 oz
  2. The barrel should be 1/2"-3/4" diameter and about 1" long
  3. The hand should be about 2.5" long
Working off the timer improvements list...
  1. I replaced the pendulum hanger with plastic.  Much more rigid, and keeps the pendulum where it should be.
  2. The gravity arm hangers were remade.

They're two-part pins that press together.  This took a bit of doing since I misjudged just about every diameter and had to remake them...  But in the end, they seem to be an improvement.

Saturday, November 21, 2015

Balance staff (preliminary)

I have several broken watches in which the problem appears to be (at least) that one of the balance staff pivots is broken. I'd like to build my experience to the point where I can fix this problem, which involves making a new balance staff. Fortunately, I have a balance wheel with this issue that doesn't go with any watch that I have. So, I attempted the repair on this part first, knowing that failure wouldn't be much of an issue.

I started with a 1/4" steel rod, which I turned to fit the 3/16" collet I have for my lathe. Unfortunately, my lathe seems to take 4C collets, which aren't very common. The smallest collet I have is 3/16", so that's what I have to use.
After two tries, I was able to turn a passable start at a balance staff. That is, the balance wheel fit the rivet nicely, and the pivot came out intact.

The picture above shows the view of the new (left) and original (right) parts. I wasn't careful with the lengths, and I haven't yet cut the second pivot. At this point, I needed to reverse and regrip the staff in the lathe. If I had a suitable small collet, this would be easy. But I don't, and therefore needed to hack something.

I came up with the idea of gripping a pin vise (which happened to have a handle 3/16" in diameter) in the collet, and the part in the jaws of the pin vice. The vice seems to run true, but it took a bit of doing to keep the end of the vice straight. In the end, there was a bit of runout, which I'm not pleased about.

Again through the microscope, the new part is on the bottom.

Staking the balance wheel.

Post staking... It's securely attached!

Roller table reattached. This is a taper fit; I probably made it too loose, and was able to push it on by hand (in the staking tool).

Finally, a picture of the finished assembly, to show size.

In the end, it went together pretty well. The major remaining issue is how to regrip the part in the lathe without runout. Of course, there is the possibility of running between centers, but I don't have centers made, so this would involve obtaining such as setup...

Sunday, November 1, 2015

Reaming a piston cylinder

In order to have a perfectly fitting piston and cylinder pair, it's necessary to have an accurately drilled cylinder.  When I tried drilling before, I was unable to get the accuracy needed for smooth motion.  The inside of the cylinder changed diameter and had internal ridges that the piston would get caught on.

The usual solution to the problem is to drill an undersized hole (bearing in mind that a typical drill bit will drill slightly larger than its stated size) and then ream it to the correct size.  This requires a reamer, which can be made as needed.  This is the first such reamer I made -- loosely inspired by this page -- it's passable, but not perfect.

To start, I turned the reamer body from a 1/4" steel rod to precisely the size I wanted to have the cylinder bore.  In this case, I turned it to a diameter of 0.19" -- just 2.5 thousandths larger than 3/16". 

One roughly turned, I polished it with several grades of carbide sandpaper, finishing with 1200 grit and parted it off.

Then, I ground about half of the diameter away on the griding wheel and beveled the leading edge. 

This came out much more messy than I intended, but after cleaning up on an oilstone, the edge was sharp.  I heat treated the reamer tip and left it dead hard. I never got the rest of the reamer hot enough to harden it.

Here's the cylinder after drilling with an 11/64" bit.

Here is the reamer in action, cutting about 1/16" at a time before needing the chips (rather a fine powder) to be cleared.

After reaming, I turned a piston to fit. 

I cleaned both the piston and cylinder in isopropyl alcohol to remove chips.  The piston slides smoothly and is a quite close fit. 

A little clock oil improves the action, and you can feel a small amount of compression as the piston moves in.  If the piston is pushed in quickly and then withdrawn, the end of the piston is slightly warm.  Not hot enough to be used as a fire piston (it should be longer, so more compression occurs), but still enough to indicate that the fit is close.