inverted threading tool method

[benmychree]

You are correct, carbide does not like low speeds, it will break down; an exception to this is using very hard grades of carbide on quite hard steels, such as the old Kennametal K6, it will accurately cut steel up to nearly 60Rc, although ceramic type tools work even better and at much higher speeds; where I apprenticed, one of the regular jobs was to rough turn rotary shear blades to remove nicks, then finish grind them; these were about 24" diameter and 2" thick and in the high 50s Rc, then a guy doing it tried ceramic for finishing them; revved it up, and the chips went straight up in a ribbon, nearly straight back down from a height of about 20 ft! a pair of these blades were used to trim the edges of plate up to 1" thick, 40 ft long in the production of line pipe.
Also, carbide especially does not like threading without a run out relief; try to pull out like you do with HSS, and nearly guaranteed is a chipped tool.

 

[middle.road]

After the crash(es) I experienced, I switched to Joe Pie's method above.
Those were a couple of gut retching moments. Darn lucky that nothing collided hard.
I've been putting together the pieces to fab a handle for the 1440 as Steve Jordan shows.
I just plain don't have the reflexes (or talent) to go from Right to Left under power, and now I'm too skittish
after the half-nut mechanism mess-up.

 

[Al 1]

middle.road, I like the crank handle idea. Do you have a particular design for your crank. Will it insert into the spindle.
Thanks, Al.

 

[Dan_S]

The method Joe demonstrates works, but its not great on small lathes as it lifts the carriage. It also falls flat on it's face when you have to turn a metric thread on an imperial lathe or vise-versa.

IMO the absolute best method on a manual machine, is to use a vfd with a proximity stop. The proximity stop can also be beneficial wen turning to a shoulder etc.

 

[benmychree]

I think our (USA) method of threading with the compound set at an angle is far better than what is shown, which tends to induce chatter with coarser pitches and harder metals, the chip is forced into itself , which inhibits free cutting; also, one can see how easy it is to forget the dial reading when repeatedly feeding inwards with the cross feed; the prevalent USA method, the dial is always at zero, only the compound is fed in.
The German or European method with the compound at 90 degrees to the cross feed (parallel to the lathe axis) is (perhaps) second best; the cross feed still is not at zero the whole time the thread is cut, but the compound is fed in a bit at each pass in proportion to the amount of infeed, so the tool does not drag on the backside. I know of no drawback to the USA method, except possibly that one does not know easily what depth the tool is fed into the work; I know there are tables for compound depth, but these things do not work for anything but sharp vee threads, and most insert tools (especially), have flats at the point and most HSS thread tools for coarser threads will have flats at the point also for several reasons, one, for strength and less tendency for cracks to develop under stresses, and the fact that a flatted point holds up much better with respect to dulling and breakdown of the point.

 

[middle.road]

middle.road, I like the crank handle idea. Do you have a particular design for your crank. Will it insert into the spindle.
Thanks, Al.

The end of the spindle on the birmingham is threaded, but the cover well, covers it. and I don't want to run it with those gears in the open.
The spindle end is flush with the cover.
So my thought is to make up expanding arbor, based on the style Joe Pie shows in one of his videos, mount it to a round disc, Ø6" or larger then mount the crank to that.
For the disc I'm also kicking around the idea of using a Ø12" V-Pulley. I used a Ø10" on the table crank of my Index and had Ø3/8" fuel hose in the V-Groove and that provided 'grip' to turn the disc/wheel/pulley for a tad bit of finer control.

The method Joe demonstrates works, but its not great on small lathes as it lifts the carriage. It also falls flat on it's face when you have to turn a metric thread on an imperial lathe or vise-versa.

IMO the absolute best method on a manual machine, is to use a vfd with a proximity stop. The proximity stop can also be beneficial wen turning to a shoulder etc.

That would be sweet, however I wouldn't put it past the 'stink bugs' to get inside the stop switch. And I don't have a VFD on the 1440.
I was pressed for time and had to get out (24) pieces and the left to right, upside down, method seemed to me to be the quickest solution.
It's been working well for me and as the saying goes, 'Use what works.' or something like that.

 

[benmychree]

The method Joe demonstrates works, but its not great on small lathes as it lifts the carriage. It also falls flat on it's face when you have to turn a metric thread on an imperial lathe or vise-versa.

IMO the absolute best method on a manual machine, is to use a vfd with a proximity stop. The proximity stop can also be beneficial wen turning to a shoulder etc.

My absolute best is a toolroom lathe with lead screw reverse with trip dogs set for travel in both directions; all one has to do is retract the tool at one end and reset it against the cross feed stop and feed in the compound and move the reverse lever to take another cut. I had a 14" toolroom Monarch lathe with this feature, and it was wonderful! I have heard of lathes that also retract the tool automatically when the trip is actuated as above.

 

[Al 1]

The end of the spindle on the birmingham is threaded, but the cover well, covers it. and I don't want to run it with those gears in the open.
The spindle end is flush with the cover.
So my thought is to make up expanding arbor, based on the style Joe Pie shows in one of his videos, mount it to a round disc, Ø6" or larger then mount the crank to that.
For the disc I'm also kicking around the idea of using a Ø12" V-Pulley. I used a Ø10" on the table crank of my Index and had Ø3/8" fuel hose in the V-Groove and that provided 'grip' to turn the disc/wheel/pulley for a tad bit of finer control.


That would be sweet, however I wouldn't put it past the 'stink bugs' to get inside the stop switch. And I don't have a VFD on the 1440.
I was pressed for time and had to get out (24) pieces and the left to right, upside down, method seemed to me to be the quickest solution.
It's been working well for me and as the saying goes, 'Use what works.' or something like that.

My machine is a S/B heavy 10 with a open spindle. The expanding arbor is most likely the way for me to go. A larger disc would be easier to turn.
Thank you. Al

 

[Dan_S]

My absolute best is a toolroom lathe with lead screw reverse with trip dogs set for travel in both directions; all one has to do is retract the tool at one end and reset it against the cross feed stop and feed in the compound and move the reverse lever to take another cut. I had a 14" toolroom Monarch lathe with this feature, and it was wonderful! I have heard of lathes that also retract the tool automatically when the trip is actuated as above.

If your describing what i think you are, that still doesn't work for metric threads on an imperial lathe. Mainly because you can't disengage the half nuts, well technically you can but you have to catch the exact same half nut location when you reverse the travel and that's a pita.

 

[petertha]

The method Joe demonstrates works, but its not great on small lathes as it lifts the carriage.

I was wondering about that, but I see several folks make upside-down parting tools on small machines where they otherwise have problems. Do you think threading would be more load than parting within the reasonable size of threads?

It also falls flat on it's face when you have to turn a metric thread on an imperial lathe or vise-versa

Do you say that because you are starting in the relief groove with lead screw engaged & then powering moves tool into the threads within a very short distance, or???

IMO the absolute best method on a manual machine, is to use a vfd with a proximity stop. The proximity stop can also be beneficial wen turning to a shoulder etc.

That's what I was daydreaming about - an external 'threading' motor that basically just turned the drivetrain but you had a separate control. Kind of like putting a motor on the Steve Jordan crank handle. But located where? Maybe just as well change the lathe motor to VFD & figure out some sort of contact>ramp down>stop cycle. Unfortunately above my pay grade.