- Joined
- Aug 14, 2011
- Messages
- 101
For the past several months I have been working on a project with the objective of designing and implementing a threading clutch on my Grizzly lathe. I have now finished the installation and testing of the final version and thought it might be of some interest to others.
The concept is that you place a transmission between the spindle drive gear and the next gear in the train. The transmission functions as an idler so it does not change any gear ratios. The transmission in turn controls the gear train leading up to the gear box and can turn the lead screw in either the forward (towards the headstock) or reverse direction. The gear can shift between forward, neutral, and reverse and this shift can be generated by the position of the carriage. The carriage has a stop arm that engages an adjustable stop that is on a trip rod that is linked to the gear box.
To see it in action here is a link to a short video showing the threading of a 1/2 x 20 thread.
https://vimeo.com/84476330
Here are a couple of photos of the finished threads and of the gear box.
I have a grade 8 nut to test the thread clearance.
Here is a picture of the transmission with the shift handle protruding out the front.
After extensive testing I am convinced that threading on the lathe at speeds in the 300-500 RPM range results in a much cleaner thread. This is the easiest threading that I have ever done. I got into this because I was chipping and breaking carbide inserts when threading slower speeds. Using inserts required a landing groove else they would weld to the material and then chip. This solves that problem.
Regards,
Jim
The concept is that you place a transmission between the spindle drive gear and the next gear in the train. The transmission functions as an idler so it does not change any gear ratios. The transmission in turn controls the gear train leading up to the gear box and can turn the lead screw in either the forward (towards the headstock) or reverse direction. The gear can shift between forward, neutral, and reverse and this shift can be generated by the position of the carriage. The carriage has a stop arm that engages an adjustable stop that is on a trip rod that is linked to the gear box.
To see it in action here is a link to a short video showing the threading of a 1/2 x 20 thread.
https://vimeo.com/84476330
Here are a couple of photos of the finished threads and of the gear box.
I have a grade 8 nut to test the thread clearance.
Here is a picture of the transmission with the shift handle protruding out the front.
After extensive testing I am convinced that threading on the lathe at speeds in the 300-500 RPM range results in a much cleaner thread. This is the easiest threading that I have ever done. I got into this because I was chipping and breaking carbide inserts when threading slower speeds. Using inserts required a landing groove else they would weld to the material and then chip. This solves that problem.
Regards,
Jim
