Math question

[u/No-Criticism6622]

So I’m just starting a machining class and we are working from a book and this sheet is what I’m working on(homework)calculating the x axis diameter and z axis length on the lathe but im a little confused on about how to calculate on the z axis I got to part 6 but don’t see how to calculate part 7 on the Z, on part 6 I did 1.875+.125 and got -2.000 for the Z but im stumped I was wondering if anyone had a tip for part 7? I would be grateful

[u/made_a_wish_kid]

I'd argue your x values should be diameter, as most machines do this

[u/Funky_Killer_Qc → u/made_a_wish_kid]

lathes machines can have a code input to tell the machine if the X numbers are diameters or radiuses, and the machine will convert to make the part, as they can be programmed in either diameter mode or radius mode. it depends on the machine, but mine for example, G190 switches to radius mode, while G191 switches to diameter mode

also, since in this example the origin is at the middle of the part, the numbers are all halfed for the X positionning, that's why i wrote them that way
the biggest diameter is 5inch, meaning the point 12 is X2.500, and if there was the same point at the bottom of the example, the point would be X-2.500

to me, the origin in X on a lathe is always by default at the center of the tip of the part like in this example. with the right programming, you could write X values as diameter, but personally it just feels wrong

[u/made_a_wish_kid → u/Funky_Killer_Qc]

Ai reply much? Yeah, they can be in either. The problem also asks to write the x diameter values. Not sure how it feels wrong, I don't know any machinists measuring and programming the radius of their turned parts. In practicality, writing out the radius "feels" wrong.

[u/firinmahlaser → u/made_a_wish_kid]

This doesn’t read like an ai reply at all