First thread

[bronson]

So i am pretty happy with myself i cut my first thread on my lathe ;D. When i was done the nut threaded on nice and was tight but i do have a question. OK first i will tell you the set up. We are working with 9" southbend lathe quick change tool holder high speed steel tool bit very sharp all screws tight for compound and crossfeed angles set. I was holding work between centres, live centre on tail stock side 3/8 16 thread 6 inches long cutting fluid speed about 130rpms advancing compound .003 to .005 last three cuts and i ended up with a chatter look on the threads i don't know if you can see it in the picture what would cause this? Thanks. Just added i think the steel was cold rolled but not a 100%.

Thanks Bronson

 

[student_Machinist]

Not bad. The chatter is from lack of rigidity which would be hard to remedy for such a long thread. You could try a follow rest but Ive never tried that when threading. Another thing to make sure of is to feed with the cross slide while angled to 30deg so the tool is only cutting on the left side of the tool. This reduces the load on the tool and should help with chatter.

Heres the first thread i ever cut on a lathe

The white thing is a guitar pick and yes the threads have a lot of gunk in them :

 

[willburrrr2003]

Nice looking threads there, good job my friend

Regards,

Will

 

[Blogwitch]

All I can suggest is to use a finer cut for finishing off, maybe 1/10th of what you used, or even exactly the same setting as the last cut, with nothing added, run up and down the thread a few times.

It is amazing how much a 'no cut' setting will take off a thread. In fact sometimes you will find that it will clean it up too much and the thread will be slack.

Take your time, don't rush, and creep up on it as you are getting very close to the ideal depth. The job isn't going to get up and run away, so spend those extra few minutes striving for the best you can do.

After a while, you will start to achieve good results every time, then you will know you have mastered the technique.

Well done BTW. The first is always the worst one to do.


John

 

[lensman57]

So i am pretty happy with myself i cut my first thread on my lathe ;D. When i was done the nut threaded on nice and was tight but i do have a question. OK first i will tell you the set up. We are working with 9" southbend lathe quick change tool holder high speed steel tool bit very sharp all screws tight for compound and crossfeed angles set. I was holding work between centres, live centre on tail stock side 3/8 16 thread 6 inches long cutting fluid speed about 130rpms advancing compound .003 to .005 last three cuts and i ended up with a chatter look on the threads i don't know if you can see it in the picture what would cause this? Thanks. Just added i think the steel was cold rolled but not a 100%.

Thanks Bronson

Hi,
The piece is too long for such a small diameter stock, you should use very fine cuts on a piece like this and perhaps a follow rest . A die chaser might be able to clean things up for you.

A.G

 

[Ken I]

Nicely done Bronson - your first thread is definitely a milestone.

Did you use the half angle approach suggested by Student ? - if you cut on both sides of the threading tool you more than double the load on the tool, the colliding chip streams add to this and increace the propensity to chatter or tear giving a poor finish.

As Bogs suggested - I normally take a couple of "no infeed" passes just before finished size to get a feel for how much more is going to come off (not reccomended when dealing with work hardening steels).

That said I normally plunge cut but switch to half angle at the slightest sign of trouble - in the case of your thread which is relatively long I would probably have gone half angle from the get go.

Congratulations on your first thread.

Ken

 

[steamer]

Nicely done Bronson - your first thread is definitely a milestone.

Did you use the half angle approach suggested by Student ? - if you cut on both sides of the threading tool you more than double the load on the tool, the colliding chip streams add to this and increace the propensity to chatter or tear giving a poor finish.

As Bogs suggested - I normally take a couple of "no infeed" passes just before finished size to get a feel for how much more is going to come off (not reccomended when dealing with work hardening steels).

That said I normally plunge cut but switch to half angle at the slightest sign of trouble - in the case of your thread which is relatively long I would probably have gone half angle from the get go.

Congratulations on your first thread.

Ken

Ditto!

 

[b.lindsey]

Nicely done Bronson, and if the nut fits well you should be good to go.... Not sure if you did it or not, but setting the compound to 29-30 degrees as others have already noted should help with the chatter.

Bill

 

[n4zou]

Nicely done Bronson, and if the nut fits well you should be good to go.... Not sure if you did it or not, but setting the compound to 29-30 degrees as others have already noted should help with the chatter.

Bill

In trade school we were told to set the compound at 29 1/2 degrees when threading standard 60 degree threads and 14 degrees when cutting ACME threads.

 

[kvom]

Problem with turning between centers is that you can't easily test the thread with a nut.

My preference nowadays is to partially single point and finish with a die. Threads are straight and accurate.

 

[MachineTom]

I agree with previous posters that 6" on a 3/8" without a follow rest is to long. It may be the photo, or not it appears to me the groove is too wide, the angle of the compound is from the centerline of the crossfeed, meaning inline with the crossfeed is 0° then 29° to the right is the angle to set the compound. So depending on the witness line you used you may have to set the compound at 61°, one of my old SB lathes had the numbers that way. I don't recall if it was the 9 or the 16.

 

[bronson]

Well thanks for all the replies. I did set the compound at 29.5 degrees but i also agree it was a long thread for the size but i needed it for i boring bar holder i made and made the tool a little to tall but didn't want to have to cut it down so just made a longer thread. I will take lighter cuts next time and I'm sure the length will be much shorter next time. Thanks again to everyone for the tips i was pretty pleased with myself. I have had a lathe for 5 years and just now are starting to make time for it on a regular basis. Thanks



Bronson.

 

[Lew Hartswick]

When I need a long (more than a few inches) threaded rod I use "all-thread".
...lew...

 

[rake60]

Very nice for a first thread Bronson! Thm:

Single point threading is like eating spaghetti.
There are many ways of doing it but the best way it the
way that works for you on your machine.

Rick