Set over tailstock centre

[tonyfoale]

Like most I am reluctant to disturb my tailstock from its dead centre setting. Rather than make a new device I decided that my small boring head would do the same job, all I needed was to make a new No 2 Mt shank to replace the No 3 which is usually fitted. Next was a decent hard centre to fit

My own reluctance to making tapers using an offset centre owes more to the offence that the imperfect centre geometry causes in my geometrically inclined brain. I have always thought that spherical or hemispherical ends on the centres was better for tapers. Coincidentally, only a few days ago I was considering this but could not find any for sale. I started thinking about how to make these, bearing in mind that they would need to be hard with a good surface finish.

Then I remembered that I had some small elephant's foot valve actuators. These have a male threaded shank with a ball on the end and a wobbly bit which contacts the valve. Removal of the wobbly bit leaves the threaded shank and hardened ground ball. Then it is just a matter of modifying a couple of non-hardened MT arbors or centres to take the threaded shank.

The pic. shows two types. On the left is what I was talking about, on the right is an alternative version which has a flattened ball. That ball could be replaced with a full circle ball. The version on the left would be my choice though, the ball is a better size, i.e. smaller.

Click for full size.