Making a watch case (part 3), turning the ring on a lathe

Making a watch case (part 3), turning the ring on a lathe

The ring is placed into a three jaw self-centering chuck. The three jaws automatically move together towards the centre of the chuck so the piece is automatically centred. If I've hammered the ring to a good circle then the ring should be pretty near centre too.

I hold the piece on the outside of the ring to start with and cut the inside to a perfect circle, within the limitations of the lathe and chuck, which for this Sherline lathe are more than adequate!

Inside of the ring is cut

I also cut the front face of the ring, not shown in this photo, it's either on the other side or I put it back in the lathe and did it later. Once the inside is cut I use the inside to clamp the ring:

clamping by using the inside of the ring,

the copper shims lift the ring off the clamps. The shims are removed with some pliers before the ring is turned, leaving the ring with 0.7mm clearance off from the back of the clamps. This allows me to cut the outside edge of the ring all the way back to the chuck without cutting away at the clamps themselves. However, when cutting the front of the ring its good to be aware that there is nothing pushing back except friction, so light cuts and a sharp graver are essential.

But hold on a minute! Lets do a sense check:

Sense check the size of the ring,

my cloisonne frog is going to be used for the dial, and it falls right through the ring. The ring is meant to be the centre body that provides a holding shelf for the dial! Oh dear!

Right OK, we're learning as we go, mistakes are good yeah? Just so long as I learn from them! Putting things right often stretches the skill set!

I need to reduce the size of the ring so I cut a piece out of the ring, so I cut around the solder joint

Shorten the ring by taking a piece out.

and now I re-solder the ring

re-solder the ring.

This time I don't try to make the ring too circular before the soldering as I know it's easier to do it afterwards. I hammered it quite a lot this time as I was just curious how the metal shined with consistent hammer blows

metal made circular and very shiny,

I think it looks beautiful like this, I wonder if I can use this somehow? Anyway for this project it needs to be more perfectly round, so it goes on the lathe again:

Cutting the inside.

As before, I cut the inside first. Due to the thickness of the ring there is no problem with cutting the chuck clamps as they step down in height underneath the ring and are lower at the inside of the ring. So I don't need to raise the ring on shims when cutting the inside.

I cut the inside and the front surface before changing the clamping position and cutting the outside and the, now, other front surface.

The finished ring

This is the finished ring. Freshly cut brass is so similar in colour to gold, as you can see comparing with my wedding ring!

 

 

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