Joe, you are awesome. Old machinist here, and still learning from masters like you.

Thank  you Joe. Very well explained .

thank you

Great demo! Creo helped show the cut geometry very well!

Its a triangle, it will by the the nature of the shape cut on both sides.  You cannot get away from it.

Does the angle matter when going left to right , or right to left (away or towards the headstock), LH or RH threading?? I want to make a buffer drive shaft with RH on the right side, and LH on the left side.

Hi Joe. Great video. I'm still not convinced of the effectiveness of this method, because the chatter isn't solely a function of the contact area but also the contact volume. Since the contact volume using the compound at 30° is identical when using only the cross slide (for the same feed size), the chatter should be very similar, if not identical. What can you tell me about this?

I just cut my first thread yesterday on my new "toy" lathe --- RC210-E -- 8x16 brushless 1100watt rig with an Electronic Lead Screw.  I forgot about the angle on the compound part (SO much to learn) and i cut it straight up feeding directly in on the crosslide.   5/8ths #11 nonetheless -- is for a Drawbar for an MT4 collet set and the collets are 5/8th's #11.    It worked ok, i did gum it up a couple of times (1018 cold rolled) getting over-zealous with deep cuts, but overal i got my drawbar functional!!!!   Thanks for this -- next threads i cut am gonna try some compound angle feed and ease up on the machine.  I suppose i could have just changed the belt and put it in low gear to prevent binding and have better torque at 170rpm -- but maybe its just faster and easier to dial in the 30 degrees and cut that way instead.    Love ALL your educational vids i've learned alot so far!! Thank you Joe.

Hello Joe, first of al lthank you for sharing your knowledge, your videos are amazing, I´m studying lathe operation right now, and I use your backwards threading method all the time (it´s a little more tedious threading milimetric, but it always pays off, my question is if there´s any issue (advantage or disadvantage) to use that method and the 29 degree compound, it seems contraintuitive to advance in one direction and cutting in the other, but hey if something stoopid works, It aint that stoopid... thanks again and greetings from argentina!

You should generate each pass on the computer from a 29 compound setting, then blow the view of the right side up to see if there are any visual flats and/or ridges left. If there are, and the increments of stock removal are the same each pass, then I would expect to see a measured angle across the high point of the ridges at 29 degrees. If there are no chatter issues, the resolution would be to plunge the final couple of passes with the cross feed. (Lighter cuts of course). For typical nut and bolt applications, (which will be 99% of the time for most of us), we’re really overthinking this 😂.

Would you have to adjust the leading angle on the tool to adjust for a 25 degree cross slide? I picture a sawtooth thread if you didn't.

Very nice analysis.  I have always used 30 degrees and never had issues.  The only time(s) I have had issues is when  the tool is a POS.  Quality tools, quality product.

Thanks.. That's why the top of my threads are pointed left as I'm looking at it standing in front of my lathe

Yes less tool stress is cutting only on 1 side. Makes for a cleaner thread
Observing the depth usually the last 2 cuts go straight in.

The angle of the compound depends greatly on the material being machined.  Free machining materials single point well at 29 or even 29.5 degrees.  Most materials single point well at a true 30 degrees, but it requires that the compound be set with extreme accuracy and that your tool be a perfect 60 degrees and be set perfectly.  

Tool steels, many stainless steels or any fairly tough material won’t form a chip with out an adequate chip load, (minimum required depth of cut varies by material and alloy, so the statement is fairly general).  I have had good success on manual lathes at 25 degrees when single pointing stainless steels and tool steels.  For materials like Titanium have the compound set at zero degrees and do not take a spring pass.  I can’t address each material or alloy here, but as a general rule, when single pointing free machining materials, the closer to 30 degrees the better.  For materials that require a substantial force to form a chip, 25 degrees or less often works best, otherwise the tool will be dwelling on that flank until multiple passes finally provide enough pressure to form a chip, (provided that the tool has survived to that point).

Many CNC turning centers have a variety of patterns that can be used depending on the material and application.  The old default G76 code used a true 30 degree advance, so there was no worry about dwelling against the rear flank.  I would use that pattern when single pointing on a CNC, but not an engine or toolroom lathe.  That G76 code was easy on the tool and worked very well for many materials.  There is no one size fits all in metalworking.

I would also point out that many lathes have zero on the compound being parallel to the longitudinal axis, so the 30 degrees discussed would require the compound to be set to 60.

Can you make a video of the controls on your south bend lathe? I just started a job and I’m not familiar with it. Couldn’t even get the skirt to auto feed.

Great presentation Joe as always! Thank you!

If you use fullprofile threading insert, and feed your compundslide 30⁰ then your thread bottom radius goes too large

You are absolutely right .setting the compound at 30 degrees minimizes the load on the tool and the lathe with better finish.