Home made glass crystal sizer

[Hamish]

I guess most of you would have been frustrated not having an exact size crystal for pocket watch repair. I got an idea from a tool I saw on eBay and made a simple sizer. I have found it works really well.

Using a slip fit cement chuck I had on hand I bought a 10mm bearing from eBay ($1.49) and in the first picture you can see that I made a small cap to fit over the bearing from 12mm aluminium rod, I used some lock tight to secure it with an interference fit and them turned down a cement chuck to fit the inside of the bearing. 

I then glued some rubber (probably an old bike inner tube would do, its best if it slightly compresses and then you can see how tight it is) to the bearing end and did the same to the other chuck end and its good to go.

Simple slide up the tail stock and carefully place your crystal so that it is held. You will need to adjust several times to centre it, then in the last picture I use a small diamond file like this to take a shaving off. I was amazed how much control you actually have and the slightly rough finish from the file aids glueing or you could sand for a smooth interference fit with the pocket watch.

Not my idea really, I got it for nothing from Ebay!

 

[Geo]

That's an excellent idea Hamish!  I've sized a couple using an extra fine diamond lap, but holding the crystal in my hand not a lathe.  It looks like I'll be using my lathe the next time.

[SSTEEL]

What a great idea, can't wait until I start putting my mini lathe to work, need to restore it first, and of course invest in some tools for it.

[Watchtime]

simple and fantastic...