Re: Geometric Self Opening Die Heads

On 13/07/2024 19:31, Bob La Londe wrote:

Geometric Self Opening Die Heads
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I've made simple die heads.  Some driven by a tommy bar, others by a pin in the mandrel that can be set up come out of the groove and free spin when it reaches the stopping distance.  recently I started researching my $350 Lin Huan TL-25 lathe score in the long term plan to getting it running again.
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Its a copy of a Hardinge turret lathe. Jet, Enco, and probably some others sold it under their own label with some form of "25" in the model name.  I've been watching videos during my connection time with the brain sucker box while drinking coffee in the mornings.  There are lots of cool tool holders available for the turret, and I have some ideas for the head stock top mounted parting blade holder to add "one more" function to it for some repetitive jobs.  There are parts I would probably offer for sale more aggressively if I had this machine running and a few setup configurations ready to go.
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A lot of the "expensive" special tool holders for it are pretty easy to make, and I may make them as needed or in some cases make batches.
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I found only one really good video on setup for one of these machines. Lots of guys did a short video that was basically "look at my machine," and a number of machinery dealers did a short video showing the machine runs and most of the function work, but there was only one I found so far that seemed to show the setup and setting up a job.  Its about 3o minutes long, and its a little slow for my taste, but the first 15 minutes shows his setup for a job, some of the limitations, and finally cutting one piece in the job setup.
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Here is where he introduces the part.
https://youtu.be/WXoG9uEMIpA?si=li89-lU1laugGfOE&t=295
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The video showed one tool that might very well be a challenge for me to make.  I also looked them up and new ones are fairly expensive.  A self opening die head.  One some types of jobs this could really be an efficiency tool.  I am sure I can my shop made simple die heads on the turret lathe much the same way I use them on the engine lathe, but I have to stop, reverse, reengage the tool, thread the die off the part, and then stop the lathe to switch it back to forward.  The self opening die head pops open when it reaches its "limit" which would allow me to simple back off the turret and use the next tool.  At most change the speed (which is supposed to be shift on the fly).  A speed change is something I would have to do anyway if the next tool demands it.
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If you don't want to watch the whole video here is where he runs through one part.
https://youtu.be/WXoG9uEMIpA?si=eZCT38b5dpSwocNM&t=1141
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I am sure if I look around I can find a used version of this tool for less than a brand new one, but I need to ask. Have you used a tool like this.  The self opening die head, not a turret lathe.  I am sure lots of you have used a turret lathe.  How easy was it to setup for each job? How affordable where the thread jaws?  Did you find it worked reliably? Do you have nay other feedback for using one or reasons not to?
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I've looked at them in the past but haven't had a job where I could justify getting one as mainly doing low volume stuff so just used split dies although I did make a double ended die holder with a die for roughing and the other end set for a finish cut for one job threading stainless tube. On this side of the pond they're called Coventry die heads and the heads and chasers are quite common on ebay. If you have a surface grinder my understanding is the chasers can be resharpened a few times if they become worn.