Thread: strange Hercus dual graduated compound dials

During the ongoing process of sorting out what genuine parts are still around I came accross a small amount of these very interesting dials, I assume from the period when we where changing over to the metric system.
They are basically an imperial graduated dial, with an additional outer ring marked in metric. I was aware they produced a 2.54mm dial to go on the imperial machines but had never seen this one before. Although pretty useless on a metric machine, I imagine they could be handy in some circumstances were you need to compare the 2 while machining.

My metric CY 16 x 40 lathe has a 6mm lead screw and metric/imperial dials on both the compound and cross slide. It has seperate datum marks for each, which are seperated by a short distance. This was a bit annoying to me because the imperial datum mark is on a strip that extends over the top of the metric scale. It would not be so bad, but it was set so it blocked the numbers coming up when winding the dial in. I have since turned the compound (not pictured) datum plate over so the blocked figures were coming from the backing out direction. It is more convenient this way. I had to reshape the plate a bit.

I will do the cross slide sometime. It is a 6mm dial on 3mm screw and imperial dial is 0.236" per turn. Measures diameter, not radius.

3 Ball Handle Finished Fitted.jpg

Dean

Dean,
I think the dials in the photo actually show 'reduction in diameter', not 'diameter'.

My comment comes because my lathe is cursed with the same stupidity.

When are lathe builders going to swap the scale direction to show actual true diameter ?

I have tried this approach on my previous imperial lathe by gluing on a metric scale reading diameter directly, it worked a treat as long as you stayed away from the zero offset.

John

Dean,
I think the dials in the photo actually show 'reduction in diameter', not 'diameter'.

Yeah. It was just meant as a generic description.

When are lathe builders going to swap the scale direction to show actual true diameter ?

Probably have to use DRO to acheive that. My first lathe had no cross slide wheel when I got it. (long story) I made one 375mm in circumference. It was an imperial Nuttall. I used a 375mm length of metric stainless steel tape measure as a scale. 3mm was equal to 0.001".

Dean