CNC Lathe Programming Question

[Sp1raleyes]

Hello there, I'm about 5 minutes ago new to the site.

I am currently a Lathe Set Up/Operator, and I am learning everything on my own. I have a question about a picture I have uploaded with this post, and I hope it's not to silly of a question.

-In the pic, this is the back end of a shaft I set up a lot, and need to do some reprogramming on. Here is my only question.

See how the Diameter is .500 +0/-.003? Well, my question is, once I program that diamter to be cut, I can't figure out how far to cut in Z. The 1 " dimension is where the radius of .130 will end, but where would the .130 radius begin?

I feel as if I should know this, but I am not afraid to be honest and say I don't. If anyone could please help me out with the answer to this, I would be very grateful. Thanks, and have a good day.

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[Jim Dawson]

The radius would start at 1.000 - 0.130 or 0.870.

[Sp1raleyes]

That is exactly what I thought, but when I was drawing the part in Fusion 360, and I attempted to do that, all of my lengths went out of tolerance and it just didn't work out for me. I must have done something wrong inside of Fusion. Thanks a lot for the clarification!

[Jim Dawson]

Just set the back of that operation on the -1.00 inch line. Fusion will just cut what is there including the fillet.

If you are drawing it, then do the fillet last. That way it will be in the correct place. If you are doing a profile sketch, then make that intersection a sharp corner, then add then add the fillet using the fillet tool.

[deadlykitten]

hy spiraleyes pls check attached

[Jim Dawson]

Deadlykitten is correct. But I get 0.916, but I think 0.92 is close enough.

[deadlykitten]

i just checked, really i didn't do it to show that it is not the same value as others have discovered

as for 92 or 916, i think that a metric persons should not care, but all those inch guys, really holding to their decimals, aren't they ?

if you have patience, than you can see that the radius is not tangent at both ends, and such cases may create problem for beginers; they can be easily fixed in okuma igf/conversational software ( once you understand the way needed to input data in it ), or by using the correct contrains inside a cad sketch ... correct constrains, that's the thing that one needs to apply

such details can be easily omited, even by an experienced person, because of rush, or, for example, if the drawing quality is poor / kindly

[Algirdas]

Mr. deadlykitten is right - Okuma IGF does this job very easy :-) . Take the .MIN file and use it on your lathe :-)