First threads!

higgite said:
I respectfully disagree. If the compound angle is set to more than 30 degrees from perpendicular to the spindle axis, it will definitely affect the shape and finish of the thread.
Click to expand...

Okay, I'll concede your point and say that only the portion of the cut of the last pass will have a 60º included angle. But I would also say that for any angle on the compound greater than 30º (for a 60º thread) that you aren't cutting a thread.
 
BrentH said:
@DavidR8 Have a read of this: https://rick.sparber.org/spt.pdf

It will explain how the set up at 29.5 degrees is critical to keeping your threading tool cutting on the right path and developing the root of the thread.

if you have a good threading alignment gauge it will also have depths of cut for the different pitches on the gauge:

View attachment 319819
Click to expand...
Ok I think I know how I messed up. Last night, Tom (@higgite) asked me if my coumpound was "23 degrees from parallel with the spindle axis or 23 degrees from perpendicular to the spindle axis?"

I mistakenly said from perpendicular to the spindle axis.
This is how its set.
IMG_5913.jpg
(An artist I am not!)

I now realize that I needed to be 59 degrees using this point of reference or 29.5 degrees measuring from a line perpendicular to the work.
I see the the intent is for the compound to be inline with the right side of the eventual thread. Thanks for the reference to Rick Sparber @BrentH, that made it click into place. Doh!
 
If that is how you had your setup, then you didn't move the compound, just the cross slide. If you just move the cross slide, it really doesn't matter what your compound angle is set at.

Your drawing can't possibly cut that thread above if you moved the compound. But it can only moving the cross slide.
 
SLK001 said:
If that is how you had your setup, then you didn't move the compound, just the cross slide. If you just move the cross slide, it really doesn't matter what your compound angle is set at.

Your drawing can't possibly cut that thread above if you moved the compound. But it can only moving the cross slide.
Click to expand...
I used the cross slide to back in and out of the work and advanced the compound to increase the DoC.
 
A South Bend compound is marked in degrees perpendicular to the work axis. Zero degrees is exactly perpendicular to the work axis and 90º is exactly parallel to the work axis. If you had the compound set to 23º, then it was 23º off perpendicular to the work, which will cut a thread. However, your drawing above shows an angle greater than 30º, which will NOT cut a thread.
 
DavidR8 said:
now realize that I needed to be 59 degrees using this point of reference or 29.5 degrees measuring from a line perpendicular to the work.
Click to expand...
The classic mistake. Aside from all the number and degree referencing this is one time when a good visual recognition is invaluable. “Does this Vee look right to me?”
Don’t worry, you’ll get it :encourage:

-f
 
SLK001 said:
A South Bend compound is marked in degrees perpendicular to the work axis. Zero degrees is exactly perpendicular to the work axis and 90º is exactly parallel to the work axis. If you had the compound set to 23º, then it was 23º off perpendicular to the work, which will cut a thread. However, your drawing above shows an angle greater than 30º, which will NOT cut a thread.
Click to expand...
I don't know what to say other than that is exactly how it was and is still set.
Pics for clarity.
Overall view of the setup.
IMG_5914.jpg

Protractor laid against compound and against chuck.
IMG_5918.jpg

Resulting angle.
IMG_5919-1.jpg
 

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