# First Thread cut on the Lathe



## Robo_Pi (Feb 11, 2019)

I'm actually making a collet drawbar.  But for the last three days I've been setting up to cut the threads on it.   The reason it took so long is because this is the first thread I ever cut on this lathe and I had to learn how to do it.   By the way, a shout out to "This Old Tony" and a thank you for the videos he made on grinding a thread cutting tool and on how to cut threads on a lathe.  I used his procedure and it worked out really well. 

First order of the day was to figure out which gears to use.  This is the first time I ever changed the gears in my lathe.  No quick change tool box.   And trust me, this lathe is NOT user-friendly when it comes to changing gears.   What a pain.  Very poor design.   Everything is really hard to get at and when you take the bolts out that hold the gears on the nut behind the bolt falls out.  Then you need to try to hold that nut in place when putting on the new gears and there's no room to get your fingers in there.  A very bad design to be sure.   I'll need to redesign this lathe and make some kind of clip or cage to hold the nut in place when you remove the gears.   

In any case, I finally got the proper gears on the lathe. 

The next step was to make the cutting tool.   I chose a 1/2 square tool bit.  I had one an old one on hand that had never been ground on one end.  So I built a sled for my tool post grinder to hole the tool bit at 30 degrees.   It's not much of a sled but it did work.   It took me about two days to grind that 1/2" square bit down to a 60 degree point.   I probably would have benefited by having a coarser grinding wheel.




Finally with the tool made and the proper gears installed I cut the thread.   First thread I ever cut on a lathe.  As I mentioned previously I used Tony's method.  Or at least the method he explained in his video.  I set the compound to about 29 degrees.  Set the table to zero when just touching the work.  And then used the compound to increase the depth of cut on every pass.   The rod wasn't quite straight either.  So I had to take that into account.  I had to touch-off at the most concentric point in the middle of area I was threading and use that as my scratch pass.  From there I just keep cycling through the process cutting a few thou each pass.  This rod was some tough stuff too.  So I actually ran through each cutting depth twice and it took off as much material the second pass as it did the first time through.   So apparently this was a necessary double-pass on each cut.   But I was patient and it worked out well.  As you can see in the photo I had a nut on the end of the shaft that I could use to test the thread as I progressed.




Here's a close up of the thread and the cutting tool.  It turned out pretty nice considering it was my first thread ever.   And when I was finished the nut went down the entire length without a problem.  That was good because I was afraid it might bind up along the way because of the bend in the rod.    But apparently that wasn't a problem.   I think this rod was originally an axle on a small cart of some kind.




In any case, that's what I did in my shop today, and for the last three days.   I changed the feed gears back to the original gears after I was done, and again, what a pain.  I'm definitely going to need to make changing gears easier.    I'm planning on making quite a few threaded projects.  So I'll be cutting threads of all difference sizes as time goes on.   

The thread I cut here was 3/8 - 16 

As I've said, this is a drawbar I'm making for MT3 collets for this lathe. 

I know this isn't a very exciting project, but it was for me.  

My first thread turned out to be a total success.  That's not too shabby.   And it was even cut on an old bent rod of unknown steel alloy.   Definitely some tough stuff whatever it is.


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## Martin W (Feb 11, 2019)

Good Job on the threads James. Always good when a plan comes together
Cheers
Martin


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## Cadillac (Feb 11, 2019)

Good job. From your picture I would get a fish or thread gauge to align your tool perpendicular to the piece. Your tool looks turned alittle to the chuck. Should be perpendicular.


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## markba633csi (Feb 11, 2019)

First thread is always fun.  Practice tool grinding by hand, pretty soon you won't even need a fixture
Having a gauge helps too
M


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## ttabbal (Feb 11, 2019)

Nice job! We all start somewhere, and threading is a milestone. It requires you to do a number of things right to get a good thread. 

If your lathe is safe to run in reverse, you can also try the reverse and upside down method. I first saw it on Joe Pieczynski's YouTube channel. It's great if you need to be close to the chuck, as you thread away from it. I run all my threads this way now.


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## Robo_Pi (Feb 11, 2019)

Cadillac said:


> Good job. From your picture I would get a fish or thread gauge to align your tool perpendicular to the piece. Your tool looks turned alittle to the chuck. Should be perpendicular.



You're right, the tool is slightly off center.   As it turned out when I had everything set up I couldn't get the tool up against the chuck, so I ended up lining it up by eye.  And it was indeed off a bit.   Hey that's a pun.   A bit off.  (hee hee)

So yes, the thread is not perfectly symmetrical.   But apparently it's close enough that it actually works.

Next time I'll try to do better.



markba633csi said:


> First thread is always fun.  Practice tool grinding by hand, pretty soon you won't even need a fixture
> Having a gauge helps too
> M



Most of the grinding actually was done by hand.  I just used the sled more like a gauge to get me back on track at various points during the grinding.  The final touches were done by hand.



ttabbal said:


> Nice job! We all start somewhere, and threading is a milestone. It requires you to do a number of things right to get a good thread.
> 
> If your lathe is safe to run in reverse, you can also try the reverse and upside down method. I first saw it on Joe Pieczynski's YouTube channel. It's great if you need to be close to the chuck, as you thread away from it. I run all my threads this way now.



On my lathe I have to run in reverse to get the tool back to the beginning.  There is no thread dial indicator so I can't release and reengage the half-nut.   Once I start everything has to stay locked in.  So reversing the lathe is the only way to get back to the starting position.

And yes, I saw Joe's video and I wanted to thread away from the chuck.   But my tool holder doesn't have a height adjustment.  So there's really no way to turn the tool upside down and keep the cutting point on center-line.   So I had to cut toward the chuck. 

It was crazy too because I actually did this at a fairly high speed.  I know broke the rule that when starting threading you should start with the lowest speed until you get a feel for it.   But I also knew that with this particular material I'll get a better finish at a higher cutting speed.   So I went through a few dry runs just moving the table back and forth to get a feel for how fast the table was traveling and how far it would coast when I turn the lathe off.   It actually coasted pretty far.  Almost an inch and a half at the speed I was cutting.  But I was far enough from the chuck to allow for that.   So I did quite a few dry runs to build confidence before starting the cut.   

Once I felt confident that I had everything under control and wouldn't run into the chuck I set up and made the first scratch pass.  Then got out the thread gauge and measured the scratch.  It was right on the money!  So I had a little celebration, and then proceeded to cut the thread.   I didn't count how many passes it actually took to thread this.   It was quite a few passes to be sure.  And because this material was so tough, (and possible because my tool wasn't the sharpest bit in the world) I took two passes with every advance of the tool.   And the second pass almost always seemed to remove as much material as the first pass did.   I even tried a third pass early on, but the third pass was barely cutting, so two passes seemed to work good.   So I made two passes for ever advance the whole way through.   Took my time and didn't try to rush things. 

I did run the tool into the chuck at one point!  

Totally my fault.  It wasn't even at the end of a pass.  It was after I had made the cut, stopped the lathe and turned it back on to go back again.  I turned the switch the wrong way!   Ouch!  I shut it back off immediately, but it coasted into the chuck anyway.  One chuck jaw hit the too bit and put a nick it the tool bit.   Fortunately no serious damage resulted (I hope).    It also hit the tool bit on the body of the bit and not on the cutting edge. 

After that I was much more careful about turning it back on again.  

The switch on my lathe turns in exactly the opposite direction you want to feed.   So what I had done was turn the switch in the direction I wanted the table to go and of course that produces precisely the wrong result. 

My machine is a combo Lathe/Mill.   I turn the switch to the right to run the lathe in forward.   I turn the switch to the left to run the mill tools forward (or clockwise).    So after my chuck crash.   I started thinking "Lathe" when I want to go forward, and "Mill" when I wanted to go back. 

So for the rest of the cut I was thinking lathe, mill, lathe, mill, lathe, mill, lathe, mill, lathe, mill,...   Instead of forward/reverse.  And that kept me out of trouble. 

Someday I'll get a real lathe that has a quick change gearbox and a thread cutting dial so I can stop the cut by releasing the half-nut and just hand-wheel back to the start. 

By they way, if I do any threads that go up to a shoulder I'd have to use the upside down trick and cut in reverse.   So I'll need to get an adjustable tool post so I can cut threads away from the chuck.   When turning off the lathe is the only way to stop you can't stop without coasting for a while. 

So I guess I did pretty good considering the inadequate lathe I have to work with.


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## MSD0 (Feb 11, 2019)

ttabbal said:


> Nice job! We all start somewhere, and threading is a milestone. It requires you to do a number of things right to get a good thread.
> 
> If your lathe is safe to run in reverse, you can also try the reverse and upside down method. I first saw it on Joe Pieczynski's YouTube channel. It's great if you need to be close to the chuck, as you thread away from it. I run all my threads this way now.


I turned my first threads (M6x1.0) a few months back and that was the method I used. Was a lot easier and less stressful since I had to keep the half nuts engaged (metric threads).


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