big thread - small lathe

[@bkoholliston]

I have read about this technique several times but it is great to see it worked out in practice!

[@rupunzel6299]

Nice illustration of reducing cutting loads on small lathe by making small segments cutting passes towards the finished thread form. What is also clearly illustrated in this example is how thread cutting involves both cutting edges of the thread form cutting tool by the pattern of metal being deposited in the edges of the thread form cutting tool. On modern A60 series "lay down" threading inserts, edges of the insert have a positive rake moulded into the insert designed to accommodate the fact both edges are cutting the thread form. It is why the Anglo-American method of threading in-feed using the compound makes no significant difference in single point thread cutting relative to the rest of the world's direct in-feed for single point thread in-feed threading.

[@advil000]

If you had a small lathe with CNC capability, it should be possible to make this a conversational routine! This would be a game changer if it was a normal option for cnc threading on small machines you could get away with some monster threads and not have the real danger of human error involved with this process.

[@HaraldFinster]

Good thought. Yes, I agree (although I am not a CNC machinist).

[@dariodamico3033]

Good trick. Watching the video I thought it would be nice to have a second tool on the opposite diameter already offseted axially so it would be possible to cut on the returning stroke as well.

[@HaraldFinster]

Thank you. Yes that would certainly speed up the process. But I suppose that the setup would be difficult due to the backlash in the lead screw.

[@BronzeAgePuritan]

I will try this on my hobbymat just for the fun of it. It seems that this could also be used to create multi-start threads.

[@HaraldFinster]

Yes, you can certainly use this technique for multi-start threads. I am not sure if the precision of the combined cross- compound-slide adjustment is sufficient if you just trust the dials. Alternatively (or in addition) you could use a dial indicator to measure the longitudinal displacement of the tool. Certainly worth a try (and a video :-) )

[@MegaRiffraff]

👍🏻