inverted threading tool method

[petertha]

I watched the Joe.P YouTube video Threading on a manual lathe BEST TECHNIQUE EVER !!!!
The gist of the demo is: He inverts a left hand threading tool holder, reverses the chuck rotation (thus reversing the lead screw direction) in order to traverse from left to right (headstock to tailstock direction). So now he begins in the relief groove, threads out safely past the end & repeats. This, as opposed to the 'conventional' direction of forward chuck rotation, traversing right to left with right hand tool & the pucker factor of disengaging thread or otherwise stopping the threading operation within the relief groove & not beyond.

I don't do a ton of threading. Right now I have el-cheapo brazed carbide tipped threading tool of the offshore variety, external only. I've been a Right-To-Left, stop short & hand turn the last bit, conservative kinda guy but it still requires staying alert threading towards a shoulder. Now I have to do metric threads which means my lead screw must stay engaged throughout. Plus I have to do some internal threading & don't have tooling so I'm evaluating options. A popular style seems to be triangular flat inserts with 3 Vee shaped nibs. They come in all sizes, internal, external, different IC. Yes, more $ and yet another set of inserts to consider. From what I can tell a 'pro' line like Carmex appears to be the same standard being cloned by the likes of Shars for about half price & cheaper again on Ali. The partial form inserts can be found at the usual discount places I've had decent luck with regular cutting inserts.

Back to the Joe.P topic. Can the triangular style inserts function in the same (inverted left to right) mode? It seems to me the only way it could work with a shoulder is an inverted left hand tool holder, but then the forces are pulling on the insert away from the pocket. Can these be operated like this? Hopefully pics illustrate what I mean.

 

[petertha]

Joe.P left hand inverted tool holder

 

[petertha]

Triangular insert sketches showing right hand tool, upright & inverted

 

[petertha]

Triangle inverted left hand tool

 

[petertha]

Joe.P video link

 

[magicniner]

I always thread away from the shoulder/bore bottom/etc. where possible, it allows me to run carbide inserts at the cutting speeds recommended by the manufacturer and I find I chip the tip far less often that way. In conjunction with a DRO this makes full threads to the bottom of a blind hole or right up to a shoulder a breeze, even when I need to keep the lead-screw engaged for metric pitches.
It depends what I'm doing as to whether I use the tool inverted on the front or right way up on the back side of the work, for threading blind holes having the tool cutting at the back sometimes allows a better view of the work,
Regards,
Nick

 

[Doubleeboy]

I have used Joe P method for a long time. HSS or insert, I like the Mesa bar and tool for insert. Threading away from headstock is great until the threads get below 10TPI in my experience. Sulphur cutting oil, a good amount of speed and threading away from HS makes for beauty threads in good steel.

 

[middle.road]

Mesa Tool has some interesting threading tools.
Inserts look to be ~$10/ea. but if you're going to be threading an smallish inner diameter they might fit the bill.
http://www.mesatool.com/products/threading-tools/

 

[benmychree]

Call me old fashioned, but I do all my threading with HSS tools (even though I do have some insert tools), whether for external or internal threads; for external, I use the Aloris form relieved tools that are sharpened on top only and last for MANY years; for internal threads I use the Bokum threading tools, also form relieved and sharpened on top also and also enjoy long life, and I also use their boring tools; being not entirely old fashioned, I make free use of carbide insert boring tools, using mostly TP triangular inserts. For backside threading, I mostly use a left hand forged HSS threading tool. Backside threading is a wonderful technique, especially for blind holes, but if you have a lathe with threaded on chucks, they must be threaded on good and tight, or risk having them thread off while cutting, likely ruining the job.
I recently had a job of threading that was a bit challenging, a double lead Acme thread with one inch lead, 1 1/2" diameter, with the external thread up to a shoulder with only a 1/2" relief at the end; I had to shut the motor off (direct connected, no clutch) before the end of the thread and let it coast at a diminishing speed so that I had time to disengage the half nut; the internal thread was in cast iron and was no trouble, just lots of cuts. When the two parts were engaged vertically, they would thread together by gravity. This was for a project to restore a steam donkey to operation, where the clutch actuating parts for one hoist drum were missing, so we copied the parts from the other drum, made patterns, had castings made of iron (about 100 lbs) and machined it all up; DONE!

 

[petertha]

Steve Jordan shows how he manually feeds (the same flat triangle) threading insert external/internal tooling using an Armstrong VFD. The material is brass, not steel & only 0.005" DOC/pass. Still rather fascinating. I've looked at those retracting type & flip up type tool holders, but there is something simple & appealing about this demo. What I would really like is an 'rpm knob' on my lathe motor that I could just dial it down & creep the last 0.1" travel to the shoulder & eliminate all this fuss. I've also heard carbide doesn't like slow speed. But I wonder is that more about production cutting efficiency & perfect finish, or is the harder material it actually more prone to chipping the edge over HSS? The video makes them look pretty resilient. I'm not in production, I have lots of time. I just don't want to crash my lathe.