Unidentified lathe bit...

[John Rumm]

I decided to go through the box of bits that I got with the ancient lathe I was given. It seems like I have a lifetimes supply of cutters, various face plates, a few widgets for fixing to stock and engaging with same when turning stock between centres, plus the usual three and four jaw chucks.

Now most of them I can make a stab at identifying, however there are a couple of things there that I don't recognise. Here is one such:

probably about 2.5" by 1", and about 1/2" thick.

Any idea what one is supposed to do with it?

[Donwill]

It looks like a parting off tool mounted on a platform which possibly fitted on the rear of the carriage. Don

[dennis]

From the angle ground on the one end it could have been done to cut a thread. On the other hand it could just be a cutter holder with a random cutter in it. Are there any mounting points on the lathe to fit it to?

Chuck it away? Use it as an excuse to find the FM?

[Donwill]

For carriage read cross-slide, looking closer at the pic, it may be for parting off wood. Don

[nightjar]

It looks like a home-made toolholder. The diagonal bit ought, then, to be made from tool steel. A quick touch on a grinding wheel should tell you that.

Bignell

[Norman Billingham]

"nightjar .me.uk>"

Not easy to tell from the photos, but if the tool bit is more or less square section then it may be a home made version of the diamond tool holder or tangential tool holder. This is a device where the end of the tool bit is simply ground flat at an angle across the section, so that it looks like a diamond shape. The rake and clearance angles are created by tilting the tool bit rather than grinding them.

You can see a commercial version at

there?s a description of a home-made one at

[nightjar]

Not so much home made, as the normal way of making tool bits before insert tools.

Even when I started using insert tools, I still used to make up a number of shaped plunge turning tools, which were often a lot quicker way of making complex shapes. I also have a couple of turning tools made from a length of silver steel inserted into a file handle. They were used with a T tool rest, to turn metal by hand, in much the same way as wood turners turn wood.

If you look closely at the photos, there appears to be some top rake ground in.

Colin Bignell

[pcb1962]

between centres

'dogs'