Video: Threading Made Easier with a Dog Clutch

There's a more complex version on the www.model-engineer.co.uk forums, search for "screwcutting simplified" - it includes a leadscrew reverse so eliminates cranking the leadscrew to return the carriage. Be Warned, it's an *incredibly* long thread, and covers a variety of conversions on different lathes, all based around the principles in the Hardinge HLV-H.
I'm working out how to do similar on my lathe, but struggling with the trip mechanism and getting the controls onto the lathe apron - I may need a *fourth* shaft in front of the bed... Bevel gears... Micrometer stops... Eek!

Dave H. (the other one)
 
Gadgetbuilder
I have had that article bookmarked for a long long time.

I was recently in the UK (Two weeks ago) and found a new book. Projects for Your Workshop Volume 1 by Graham Meek. The article is a updating of Martin Cleeve original. The design has been modified to fit more lathes.

DaveH
There is a write up here that shows it on the generic Chinese lathe. There are 3 pages with drawings here, check on the index page.

http://modelengineeringwebsite.com/Screw_cutting_clutch.html

Pierre
 
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morph,
The half nut engagement mechanism may need some TLC. On mine the male dovetail's thin end needed to be filed down to allow the flat part of the dovetail to mate properly - made all the difference in ability to adjust and smoothness of operation. I removed the pillow block on the right end of the leadscrew and the two bolts securing the apron to the carriage, then slid the apron along the leadscrew to get it off. Yours may differ if it has the leadscrew cover, I haven't worked on one of those.

Dave H.,
Gray Meek's version of the dog clutch is considerably more professional than mine. The thread describing it is convoluted and difficult to follow so I can't tell if it requires cutting gears or not for the 7x12 version. Per Cleeve, including the reverse drive is a mixed blessing - for fine threads it takes a relatively long time to get back to the start point. Backing up by hand is fairly quick and simplifies the dog clutch implementation. I considered automating it with a micro-switch on the retracting tool holder and another micro switch on a right hand stop plus a gear motor drive and sprag clutch on the leadscrew - all easily removable. When the dog clutch triggered, retracting the tool would cause the carriage to back up to the right hand stop automatically. Didn't seem worth the effort for the amount of threading I do. Cost of my dog clutch was nil, a local sewing machine dealer gave me a dead machine with the right angle gears and everything else was from my junk box.

MikeWi,
I added text to (I hope) more clearly explain the dog clutch's operation, see the first paragraph here: http://www.gadgetbuilder.com/Dog_Clutch.html#DogClutch
If this doesn't help, let me know more about what is unclear (here or via my site) and I'll try to help.

John
 
Following the links suggested above led to some fascinating browsing through several different threads and forums. I understand how it works now. My initial confusion was caused by my missing the two pins on the shifting fork on gadgetbuilder's version. I couldn't see how the clutch was being moved! LOL It will probably be a year before I have my mill, but this will be a project I'll want to work on.
 
this method is talked about in "screw cutting in the Lathe by Martin Cleeve. He has details about dog clutches and lift up tool posts, and also much valuable info on screw cutting. see www.ebook3000.com › Study › Hobbies & Leisure time for details, this site offers a download of the book free!
Phil.
 
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