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Threading by hand
andyf:
Hi Wong,
The tommy bar hangs down below the top of the bed, so it will only move a few degrees either way before being stopped by either the front or the rear bedway. That's the whole idea - the tommy bar keeps the dieholder stationary while the spindle handcrank is used to turn the workpiece and cut the thread. One of these days I will fit a boss to the tommy bar so that it fills up the space between the bedways and doesn't knock from side to side so much as I crank forward and back (see below), but the parts of the bedway it bumps up against are not critical.
The dieholder has to be pushed on to the work during the first one or two turns to get the thread started, but after that the die pulls itself to the left as it cuts the thread.
By the way, as with tapping by hand, take one turn forward, then half a turn back, another turn forward and so on. This helps to form a clean thread by clearing the chips from the die (or the tap) as the work proceeds. A little lubrication can help, too. Specialist cutting fluids are on the market for tap and die work, but for steel I find that any lubricant works well enough for me. Sometimes I find myself tapping a hole by hand on the kitchen table, and use cooking oil because it's nearby. WD40 and paraffin (kerosene) are good on aluminium alloys. I don't use any lube when threading cast iron or brass. Others may have better ideas about lubrication.
Andy
wongster:
That's a good idea! I'll only need to turn the spindle without having to stop the holder from moving.
Thanks for your help Andy.
Regards,
Wong
No1_sonuk:
I made a hand crank for my lathe, but found it didn't hold all that well when threading hard materials with taps and dies.
What I do now is to hold the chuck with my left hand, and turn the holder with my right. Then move the chuck back to bring the die holder handle round, then hold the chuck while turning the holder, and so on.
I find that gives better control, and means getting a decent arc.
Another thing, Wong, it looks like you don't have a slot between the ways on your lathe. So you can't use it to hold the handle.
All this assumes threading with no power, of course.
When I use taps and dies, the only time I use power is at very low speed in reverse to "unscrew" the tool off the material when I'm done.
wongster:
Sonuk,
When I turned the holder more than the chuck, the chuck was stuck to the spindle that I had a hard time getting it off.
I just returned to office after running out to the hardware store. Both a set of taps & die made in India. Most important for me at this stage is to have a set of die with the same OD. Best of all, it's smaller which mean lesser material to remove... Lazy me... :)
Ok, back to work now.
wongster:
Ok. Managed to part off the 40mm aluminum. This is my 1st real parting off of a large diameter. I'll complete this die holder for the bigger die to get an overall feel. At least a completed project despite the look...
To make thing simple so that i can go back to make the brass torches, I'll just drill and tap 3/8"-24 at the back of the holder and use the adaptor (one end MT #0 and 3/8"-24 on the other) to mount it on the tailstock. Too bad my Knurling tool can only handle up to 1" in diameter. I'll drill a few holes for tommy bar instead.
Regards,
Wong.
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