I used one once. From memory, it's attached so as to be free to slide along and cut the thread while being drawn along by its own threading action. A stop is arranged, so that at a predetermined point the die head can no longer be drawn along. This triggers a mechanism that makes the threading "jaws" spring out of action. Useful if making several identical threads, quickly and neatly.
The head is usually used in a turret lathe or in a standard lathe. The back end is clamped in the turret and the handle with the ball on it is pushed to close the threading dies. The head is advanced to the rod being threaded and it grabs the bar like a manual die and threads along the bar being pulled in by the thread cutting action and with some help from moving the turret slide. When the thread is getting long enough the slide is reversed or just stopped from advancing. the front part of the head is pulled out a little, releasing the jaws with a spring action. The threaded bar is now loose in the die and it can be pulled back cleanly.
I use these things in a cnc lathe for quick threading studs and rod on short run parts.
... and exactly what I was wanting to do with it~!
I just got a turret lathe, saw an opportunity to put one of the jobs I do on it, was thinking of different ways to accomplish the threading portion of it, and remembered that I had this thing.
Thanks for the replies, guys.
As an aside, I was also thinking about making an adapter that would hold a chasing die, with the adapter having a shank that I could insert into a Tapmatic, and then mount the Tapmatic in the lathe turret.
O.K. First off -- is yours that large? 1" shank, and 1" maximum thread size?
Anyway -- these are normally mounted in a turret on a lathe. Or in an automatic screw machine, which has turrets and lots of automatic things happening.
The workpiece is normally bar stock fed through the spindle, and other tools on the turret do things like reducing the diameter to that necessary for the threads, knurling the workpiece OD, or drill and tap the center of the workpiece before it is parted off from the bar and the bar is advanced for the next workpiece.
The turret has several "stations" (mine has six) which hold tools of a specific shank diameter. Mine uses 1" shanks.
The red or black ball knob on the short lever causes the four "chasers" (they look like a cross between a 4-jaw chuck's jaws and the inside of a die) to move in to the proper diameter. The skinny lever behind the head (not present on all models) will adjust the size for either a roughing cut or a finishing cut.
You operate a control on the turret which moves the turret towards the workpiece, and the chasers grip and start cutting threads, and pulling the turret along (with a little assist from your hand on the "spider" to advance the turret.
When the turret reaches a specific travel, it stops, but the chasers keep pulling the head of the Geometric die head on for another turn or so (depending on how fine or coarse a thread). When it moves just the right distance, the ball-handled lever is released and the body turns a bit, opening the chasers so they no longer engage the workpiece. This allows you to back the turret and die head off the workpiece while it is still spinning.
For coarse threads, you will probably prefer to use two passes, the roughing and then the finishing one. You have to move the lever with the ball handle each time to close the jaws before the next pass.
To cut a different thread, you pull up on the knurled knob while the chasers are open, and this will let the ball-knob lever move a little farther, and the chasers can be slid out, and replaced with another set for the different thread diameter and pitch.
It is *possible* to use one in a quick-change toolpost with a boring bar holder -- but it is a real pain, because you have to adjust the cross-slide to precisely on center, and you need a bed stop for the carriage which will allow the release trip to work.
That would have problems, because the Tapmatic needs to rotate for its reversing to work.
That's what they are good at. But there are quite a few sizes. They don't work too well for really small threads in a fairly large head, because the force needed to trip the larger head is sufficient to strip smaller threads.
What size die head do you have, and what size thread do you plan? a 3/4" die head would work fairly well down to perhaps 3/8" or
1/4" threads -- but if you want to do smaller threads, you will need a smaller die head. I've got 5/16" 1/2" and 3/4" which I use from time to time, with collections of chasers (mostly used eBay acquisitions).
And the smaller ones need to be mounted in adaptor sleeves to keep them on center with the smaller shank.