My Simple Approach To Threading

[rake60]

I'm making some brass studs for a project and decided to try and show
my approach to single point threading. It is a 1/4"-20 thread in brass so
I cut straight in as I usually do. The original full video was 5 minutes.
I did abbreviate some but nothing was added or removed in editing.
Being an even number pitch I could use any number on the thread dial.
To keep it simple for myself, I used #1. The thread depth was never checked
prior to finish. I go half the Double Depth plus .003" and it usually fits.
It may be an oversimplified, dirty approach to threading.
Most times that's all it takes to get an accurate thread.

This is what I ended with.

And, how I got to that point.
[ame]http://www.youtube.com/watch?v=UjUfWq9j6fA[/ame]

If you still haven't tried single point threading give it a go!
It ain't rocket science...

Rick

 

[gilessim]

Rick, that is a fantastically done little vid, I've always been a bit frightened of threading on the lathe ,you make it look simple!, what speed is the lathe going at by the way?

Giles

 

[rake60]

Remember it IS brass.
The speed is 300 RPM which works out to about 20 SFM
For steel I would run about half that speed.

I rarely mic threads at home. If it fits it's good.
I was a little curious of just how close I do come the the
proper size. The constant for a 20 pitch thread over triangles
is .3242" add that to the nominal .250 and its .5742"

Huh, .571 I missed it by .0032"
Oh well, the nut doesn't seem to mind.

Rick

 

[lathe nut]

Rick, that was a great video, that threading at a fast speed, can tell that is not your first time, I did what you said in some post of the past and got in front of my HF 14X40 got if done after a few messed up what ever it was, I love to thread, I find it is the most satisfying thing that I can do on the lathe, I need to get something to measure the threads, I think you were close enough, that was great, does Enco have that tool that you have in the threads and what is it called, guess just show how dumb I can be or I won't learn, thanks again, Lathe Nut

 

[rake60]

Enco used to carry Thread Triangles but I don't see them there now.
MSC still shows them. http://metalworking.mscdirect.com/CGI/NNSRIT?PMPXNO=4759937

Another option is Thread Wires. Enco does list them.
http://www.use-enco.com/CGI/INSRIT?PMAKA=619-3127&PMPXNO=16720849&PARTPG=INLMK3

I find the triangle easier to use myself.
It's a personal preference thing.

Rick

 

[steamer]

Nice Job Rick!



Dave

 

[rake60]

Thread mics are an even easier method of measuring a thread.
I've never owned them because of the cost. A little searching
around turned up an import set that is just a little more than a
set of good Triangles.

Shars 0-1" Thread Micrometer

If I had those I probably would mic threads at home more often.
Another addition to my hobby shop wish list.

Rick

 

[kvom]

I have been trying to do the same thing to finish my first engine, but using 1/8" brass rod 5-40 threads. Unfortunately the rod seems to deflect slightly giving a distorted thread form. So I'm just cutting the threads to ~ 2/3 full depth and then chasing them with a die to full depth. I might try angling the tool bit just enough so that the flex results in a good thread form. I might also try center drilling the end of the rod with a #0 center drill and using the live center to keep the rod straight. It might be too thin for that though.

Given the diameter of the rod, I don't cut a relief groove. Since the 10EE spindle control is right at the headstock and since the spindle will stop very quickly (almost immediately at low RPM), I run it at about 50 RPM and just stop it at the end of the thread, rather than trying to coordinate the halfnut/crossfeed.

 

[rake60]

Elmer's Grasshopper engine has a connecting rod that is 1/8" threaded
5-40 back 3/8" on one end. I single point threaded it.
I left the stock long, pushed it back in the chuck and center drilled it as
deep as the material would allow. Then pulled it out, engaged the live
center and cut a relief back far enough to allow the tool to clear the center.
That was a starting point for the thread. The center helped to keep the material
from flexing. After the thread was finished I cut the material from the groove forward
off with a pair of side cutters and dressed up the end of the threads with a
small fine file. No center drill mark.

Rick

 

[kvom]

Thanks Rick. That's basically what I'm planning to try later on today. I will report back if it works for me.

 

[rake60]

The thread depth of a 40 pitch is about .017/side.
Cutting a groove to clear that makes for a pretty thin spot.
If you make the starting groove a radius instead of a square
sided groove it will be a little stronger. Every little bit helps.
It doesn't have to be anything special, you're going to cut it off
anyway. Just round it out to eliminate square corners.

 

[rake60]

I just received a comment on this thread from a buddy of mine.
He is a machinist but not a member here. He does follow the
posts and asked me why anyone would try to single point thread
a 5-40 in 1/8" brass.
"A die would give you a perfect thread and you could turn it with
your finger tips. Easy as screwing in a light bulb."

I asked him if he could screw in a light bulb.
Then I told him that I had been playing with single point threading
the 5-40 today and my lathe was all set up for it.
He did get it in time but my ears are still recovering from the evening.
There are still a few word he used that I need to look to find an English definition.
In the end he said he understood WHY...

Rick

 

[kvom]

Tried it with the center drill/live center, and it worked just fine. ;D Took it in 3 passes so as not to break it off at the starting groove.

The die does work too, but getting it started straight is a PITA.

 

[rake60]

Congratulations kvom!

Single point threading the little stuff is a real character builder!

Rick

 

[Kermit]

Perhaps a little off topic,but full of charts and even a change gear ratio list

http://books.google.com/books?id=lr...+making"&lr=&as_brr=1&as_pt=ALLTYPES#PPP11,M1


I found it a VERY good read even as old as it is, most of it still applies today,
Kermit