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Learning Threads

#1
So, not much of a building project as much as it is just a learning project.

As many of you know, I am green, super green. I just got my lathe and have been playing around with it and learning it. So I figured I would share my experience playing with threading.

Attempt#1
Had a bar that I needed to thread, 4" long 1/2-20UNF
Because it was long I needed to use tailstock support.
Discovered that my live centre is too big and I couldnt get the cutter close enough. So I needed to have some "Dead" material and start the threading further away from the live center. I was still super close to it and though "meh, I should be good and started to thread". What I didnt take into consideration was when I advanced into the work part of my tool holder still hit the live center and then it botched up the start of my threads.
(Sorry, no picture)

Attempt#2
Just for practice I used a shorter bar without tail stock (So I didnt have interference issues while learning this.)
Started to make repeated cuts and thought.... "Well poo, that doesnt look right"......
IMG_1570.jpg
Figured out what I did.
Imagine your compound set 90deg to your cross-slide.
This is where my scale is for setting angles on my compound. So I set it to just shy of 30deg. Stupid me, that is 30deg on the wrong axis, meaning I was advancing into my work at 60deg. So i had to go back and fix my angle. (Which was a pain on my compound because the scale is only on the one side and maxes out at 45deg. Silly.

Attempt #3
Looking good,
IMG_1571.jpg
Got some good thread forming and then BANG, snapped the rod I was working on.
I was advancing 10thou per..... I guess that is way too much :) So the work climbed up the cutter and snapped.

Attempt #4
SUCCESS
IMG_1580.jpg
I was trying to make 1/2-28tpi on this one.
Slowly advanced by 2.5thou per and finished with this.
While I was advancing and I new I was getting close I was trying a muzzle device to see if it would fit. I could tell I was getting closer and then the next pass it fit, but fit kind of loosely until the threads hit the shoulder. So I think I still need to step down my advancements to 1thou when getting close. Also, I think I need to buy a wire thread gauge set now too.

IMG_1578.jpg

Next I got to figure out better ways to clean up the threads.
This one was done with just some scotchbrite.
I had a buddy recommend emery cloth. I am assuming by folding it and using the edge to chase the threads.

Ill open it up to the floor to see how everyone else cleans up their threads.
 

John Conroy

Super User
Premium Member
#2
When you get close to your finished size try taking a couple of "spring" cuts. Don't advance the cutter any further and run it through a couple of times. The part you are threading will naturally be pushed away from the tool and spring passes will reduce the effects of that. If you need to take more off after spring passes stop cutting advance the tool .0005" at a time to get a nice fitting thread.
 
#3
When you get close to your finished size try taking a couple of "spring" cuts. Don't advance the cutter any further and run it through a couple of times. The part you are threading will naturally be pushed away from the tool and spring passes will reduce the effects of that. If you need to take more off after spring passes stop cutting advance the tool .0005" at a time to get a nice fitting thread.
Thanks for the tips!
 

John Conroy

Super User
Premium Member
#4
Although his videos can be long and maybe contain too much personal stuff, you should check out Kieth Fenners channel. I have learned a ton of valuable stuff from him.
About the 30 minute mark of this vid he is threading a large shaft and the final pass is a spring cut. Check it out and see how much material it removes in the spring pass.

 
#5
I will try to watch that video tomorrow night. (Late night board meeting today)
But, I have tried to watch some of his other videos before but zone out because of all the irrelevant content.