methods of single point threading ?

[Bob Kelly III]

Then practice engaging and disengaging the half nuts well away from the work. Do it slowly and feel what is going on. The lead screw is usually Acme, which means the half nuts ride on the flats if you start the engagement too early, and then fall into place properly. So try it over and over maybe 50 times, trying a little bit before it drops in and then go later and later until you miss the proper tooth on the threading tool. Soon you will have the feel for it, and will know that moving the lever a little bit early is not a problem, it only postpones dropping into the correct tooth. Right on the number works perfectly, and engaging too late, even by a little, can make you miss entirely and cut a double thread. With a little practice and knowing nothing can go wrong by dry practicing, you will soon be doing it confidently every time.

I sort of stumbled upon this.... on my own and it really is a crucial step !
although I have not yet explored how far away from the mark I can go before I Miss that thread I do know it is not very far !
1/16" to an max of 1/8" on my thread dial..... and like you say if your a tad early , it lust falls into place anyway.... ( I keep my hand on the half nut lever at all times )..... slowing the lathe down to the slowest lathe speed was actually still a bit fast for me so I used the VFD and slowed that down by half again..... that really helped allot !
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a very good write up Bob.... ! thank you very much !
Bob..........

 

[Bob Kelly III]

Well I just came back in from the lathe....
I did a bit of practice on threading....
and I made a few mistakes.... the most notable was not using the tailstock on a 1/2" diam. bolt ( it was a long lag bolt that the end of the bolt where the threads were was cut off.)
so I just tried to thread it again.... discovered that the threads of the 1/2" nut were 13 TPI so I set the machine up for that
put the gear back in so I could thread towards the chuck oiled it and started threading.....
1. the 60 deg threading tool was dull.... it looked sharp enough but it obviously was not.
2. I forgot to use the compound till after about 5 passes but I decided to see what the threads would look like if I just used the cross slide...
3. with no tailstock the work caught and rolled up on the cutter bending the bolt.... even with only .005 of a depth of cut.
I had only about 3" to 4" hanging out of the chuck... I didn't expect it to flex that much... but it certainly did !
I noticed that the piece was flexing so much that I was only really forming threads back toward the chuck !
so I did indeed learn something
using the compound ( at least on my machine ) is necessary as the threads were abysmal....using the thread gauge on the threads placed the
gauge so it showed a gap on the left side of the threads..... just by not using the compound !
and it doesn't seam to matter how much is hanging out of the chuck you need the tail stock in there just to keep it from flexing so much !
and a very sharp tool is a MUST !
... after the bolt bent I straightened it back out to almost perfect and just cut all the threads off, put the tailstock in to play and planed it down to about 3/8"
I was going to try again but gave up as it was getting cold outside....
I had no trouble at all getting the half nuts engaged at the right time today as I ran the machine in back gears and turned the VFD to about 30%
so it just crawled !!!!!
it was so slow that it took me about an hour to do that ! LOL....
but it was just about right as I could catch the thread dial on it's next revolution with everything ready for the next pass LOL.....
I did speed it up a bit and still had no trouble with the half nut....
and I discovered that the thread dial is supposed to have a flange with the alignment mark on it..... I had made a mark at 90 degrees to the dial
and I think that was part of the problem in the past.... today I simply aligned the thread dial with the edge of the bolt that holds it on....
where the mark SHOULD be.... and I never missed it once !
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so some progress....
I need a better cutter !
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later all
Bob......

 

[Bob Kelly III]

I couldn't stand it ...so I went out there and tried another threading attempt....
this time using the compound, a sharpened cutting tool and allot of patience ! LOL....
the results were much better but about half way through cutting the 7/16" x 18 TPI thread I notice it wasn't cutting as much.... my tool was dull already
( yes I am still using the piece of old file in a special holder I made many years ago because I didn't have any HSS then and still don't )
anyway fearing that if I took the tool out and re sharpened it it would bugger up the fairly pretty threads that I have ... so I pressed onward
every once in awhile I could see the cutter take off some metal but not much at .005" depth increase on each pass....
the threads seamed slanted but I kept going and that seemed to straighten up making them more uniform I stopped when they looked about equal in length on each side......
tried the nut and it went on about 1 thread and stopped...obviously I didn't go anywhere near deep enough....but the threads did look like threads this time instead of a tore up mess ! i was very pleased.... so I tried to sharpen the cutting tool and get them deeper but in the process i wound up pushing the threading portion clear out of the tail stock so it rode on top of the cutting tool again... ( bent the rod )( I think I took too big a bite)
so that ended that experiment !
other than bending the rod I think I finally got some good looking threads.... they were not deep enough but they were getting close !
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OBVIOUSLY a threading tool is an absolute must for me ! but I think I finally got everything down pat....
I didn't make any screw ups ( except bending the rod )
so I grabbed the parting tool and checked to see how sharp it was and it was quite dull too. ( sense it is also an old file )
so.. I freshened up the grind on it and used the parting tool to cut off that piece of thread !
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I'm getting there ! slowly but surely ! LOL......
thanks to all the help I have had from you guys ! my hat's off to you for that ! thanks !
Bob......