# Thread cutting DIY tutorial



## TranquillityBase (May 16, 2006)

*This is for 20 tpi, thread form.*

The first photo shows the tip of the cutting tool at zero, or just touching the part to be threaded. A magnifying glass is indispensable for this initial 'touch off'. Even if you have exceptional eyesight, the magnifying glass will help you produce better threads and speed things up for you.

I set my zero point, once I have produced a very light scatch with the cutting tool. This my take a few attempts, just don't rush the initial set-up.

All the photos are loaded! WOO HOO!

As you can see, the photo on the right, is repeated until the 5th and final pass. This is the 'Cross-feed/Cross-slide' dial.

The center photo is the 'Compound/Top-slide' dial, set for 29.5 degrees (Or better said, what you may think is 29.5 degrees) You'll never know unless you use a 'Sine bar' for the set-up, and nobody does this, not even me.

The thread profile will tear at the crest (indictative of aluminum). A full thread profile insert would elimnate this, but those tools are normally reserved for high production CNC machines. Full profile inserts eliminate deburring, and also controls major diameter and thread pitch, all at the same time.

The threads shown in my photos may look crappy, but what you are seeing is, reflection from the torn thread crest. The flank of the thread profile is like a mirror, and will trick your eyes. After step 5 is completed, deburr with some 400 grit wet/dry paper, and the threads will be crisp and clean.

The amount of passes will vary according to the size of your machine. You may think spreading the cuts out will improve the finish, until you realize your eyes have been tricked by the torn thread crest.


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## TranquillityBase (May 16, 2006)

First pass.

Cross-slide at zero.

Top-slide .020" 

I don't disengage for each pass, takes too much time. Just roll the Cross-slide out and reverse the motor. This way you'll never re-ingage at the wrong point (it always happens on the final cut)






Bottom photos are;

Lube shot on the left. Before and after deburr, on the right. (top tube in right photo is not deburred, bottom tube in right photo is deburred, and the lube has been blown off) It's difficult to capture this with my camera, lots of reflected light.


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## TranquillityBase (May 16, 2006)

2nd pass.

Same old, same old.

Cross-slide at zero.

Top-slide .030"

Roll out, and reverse.


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## TranquillityBase (May 16, 2006)

3rd pass.

Yawn

Cross-slide at zero.

Top-slide .037"

Roll out, and reverse.

We're gettin there


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## TranquillityBase (May 16, 2006)

4th pass.

Real tired, Yawn.

Cross-slide at zero.

Top-slide .040" Leave it right there for the next pass.

Roll out, and reverse.


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## TranquillityBase (May 16, 2006)

5th and final pass, WOO HOO!

Cross-slide at .001" *Not zero.*

Top-slide still at .040"

You will see a different chip curl off, with this pass. Don't disengage until you check with your micrometer. 

Deburr, and your threads will look and be, nice, clean and crisp.

TB


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## PEU (May 16, 2006)

from the thread photos it seems a little lubricant would help, they look a little jumpy. BTW, nice tutorial !


Pablo


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## TranquillityBase (May 16, 2006)

PEU said:


> from the thread photos it seems a little lubricant would help, they look a little jumpy. BTW, nice tutorial !
> 
> 
> Pablo


I follow the 'Dry cut, jumpy thread profile' parameters out of the 'Machinerys Handbook' LOL :laughing: 



 I must have blown the lube off, before the taking the other photo.

The part is nearly dripping with lubricant Pablo, you just can't see it in the other photo.

TB


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## Soniq7 (May 16, 2006)

Very nice, just what I need to get into the threading capabilities of my machine. Thanks!


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## TranquillityBase (May 16, 2006)

Finally got all the photos to load.  

I hope this tutorial inspires you, to give it a try. Single point threading is not a difficult operation. All the critical numbers are in the 'Machinerys Handbook'. With practice, and when you find what works best for you, you'll find it's not any different from other turning operations.

My mentor looked at me like I had a screw loose, when I told him, I don't disengage for each subsequent pass. This is what I found works best for me, it may not work for you?

Enjoy, and please point out where I need to make corrections.

TB


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## wquiles (May 16, 2006)

Cool - thanks so much for going to the trouble of documenting how to do it 

:goodjob: 

Will


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## TranquillityBase (May 16, 2006)

wquiles said:


> Cool - thanks so much for going to the trouble of documenting how to do it
> 
> :goodjob:
> 
> Will


 You're very welcome!

BTW, lots of new and used thread micrometers on ebay. The one in my photo is an old Lufkin, ebay purchase ($30) I was very well taken care of, and is my favorite thread mic, of the three I have.

TB


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## aosty (May 16, 2006)

TB - thank you very much for the step-by-step dummy photo tutorial! :goodjob:

I recently started messing with threading and it took a bit of trial-and-error  to figure out the proper steps... I finally made something resembling a thread the other day. I'm glad my steps, for the most part, do match yours... thanks for the tip on the cross-slide on the final pass.

Looking forward to your next photo tutorial.


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## cmacclel (May 16, 2006)

Everyone cuts threads differently.

This is the way I was tought by a 30+ year machinest.


-Touch off the part then zero BOTH the crosslide and compound slide.

-Back off the COMPOUND slide around a full turn.

-Turn in the CROSS slide in to the depth of the cut. For 20 TPI I believe it's 0.056

-Turn in the compound slide and touch off the part again.

Now turn your threads taking around 0.005 passes until the COMPOUND slide hits ZERO. 

Done.


Mac


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## PEU (May 16, 2006)

I have a pitch thread gage always near when I do threading, and btw, I also use single point technique 


Pablo


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## cmacclel (May 16, 2006)

BTW I almost forgot I Do NOT use the compound slide at all when cutting threads, Only the Cross slide.


Mac


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## Amonra (May 16, 2006)

that's a very nice tutorial. i do it the same way. so here is a question i was wondering if anyone could answer: how do you do inner threads ? do you all use a taps or there is a method of doing it with the lathe ?


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## cmacclel (May 16, 2006)

Amonra said:


> that's a very nice tutorial. i do it the same way. so here is a question i was wondering if anyone could answer: how do you do inner threads ? do you all use a taps or there is a method of doing it with the lathe ?





You use one of these (Picture on the top)

http://www.discount-tools.com/threadtoolindexmain1.htm


Mac


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## cy (May 16, 2006)

thanks for this tutorial!!!!


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## Amonra (May 16, 2006)

thanks o thought something like this would do it. so im guessing it's the same procedure as the outer thread right ?
so here's another question, my lathe's slowest speed is 140 or 170 rpm ( can't remember exactly ) and i never manage to stop it in time so i end up turning the chuck manually which as you might guess is hard work. so how do you guys stop in time ? apart from having that small groove at the end of the thread ( even with groove i still never manage to stop in time )


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## aosty (May 16, 2006)

Amonra said:


> t
> so here's another question, my lathe's slowest speed is 140 or 170 rpm ( can't remember exactly ) and i never manage to stop it in time so i end up turning the chuck manually which as you might guess is hard work. so how do you guys stop in time ? apart from having that small groove at the end of the thread ( even with groove i still never manage to stop in time )



My current project is making a hand operated crank for the spindle... just for this purpose.


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## TranquillityBase (May 16, 2006)

Amonra said:


> that's a very nice tutorial. i do it the same way. so here is a question i was wondering if anyone could answer: how do you do inner threads ? do you all use a taps or there is a method of doing it with the lathe ?


 I will try and add I.D. threading, in the next day or two. 

TB


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## Morelite (May 16, 2006)

Amonra said:


> thanks o thought something like this would do it. so im guessing it's the same procedure as the outer thread right ?
> so here's another question, my lathe's slowest speed is 140 or 170 rpm ( can't remember exactly ) and i never manage to stop it in time so i end up turning the chuck manually which as you might guess is hard work. so how do you guys stop in time ? apart from having that small groove at the end of the thread ( even with groove i still never manage to stop in time )


 
Are you threading with the tread dial? or are you doing the "reverse" method?
If your using the tread dial, then you should be able to release the half-nuts at just the right time even at 170RPM.


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## Morelite (May 16, 2006)

TranquillityBase said:


> I will try and add I.D. threading, in the next day or two.
> 
> TB


 
Start off with reverse feed threading first. Just a thought


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## cmacclel (May 16, 2006)

My lathe slowest speed is 160rpm's but I do have a thread dial which makes things easier 


Mac


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## Amonra (May 17, 2006)

i do not disengage and go forward and back many times until it's done
What is a thread dial ?
Good idea about the reverse, thanks.


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## TranquillityBase (May 17, 2006)

Amonra said:


> i do not disengage and go forward and back many times until it's done
> What is a thread dial ?
> Good idea about the reverse, thanks.


The thread dial is just a point of reference, so you can re-engage the lead screw at the proper time, for consecutive cuts. 

My lathe was built for the US market, so if I do any metric threading, I must leave the half-nut closed, and reverse the motor for each cut. I learned on metric thread sizes, so for the most part, I always reverse the motor. It's much faster for me to do it this way anyway. 

The part in the photos, has about a 90 second cycle time, this includes time to double check with the micrometer. In actuallity, it's probably 2 ~ 2.5 minutes per part, with chucking and moving parts from the bench to the lathe. It goes fast, once you develop a good rythm.

TB


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## cy (May 17, 2006)

I've been doing loads of ID threading with a tap, using lathe to insure perfect centering. 

having a hand crank handle sure would make things easier.


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## Amonra (May 17, 2006)

Thanks a lot for your help guys.

i guess having taps and dies would be the best for good quality threads but they are too expensive to have all the sizes, so i guess the lathe option is best at least for the large diameter threads.


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## Anglepoise (May 17, 2006)

Just like to add a small warning. Many of us use the top slide to advance into the work. Nothing wrong with that. And most people quote 29.5 degrees as the angle to set over the top slide. However it is important to get the angle right. Note that the angle is NOT with the job but with a line square across the job. A quick check is to remember that the top slide must always be parallel to the flank of the tool bit. 

 In the picture above, the slide is set to 30 degrees ( brown arrow) but is actually 60 degrees to the work. Wrong. In the above case, the slide should be set to the markings with the red arrow to feed in parallel to the tool flank. I would venture to say that this has caught out most of us at some time.


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## Amonra (May 17, 2006)

possibly another stupid question here but why do you set the tool post at an angle ?


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## cmacclel (May 17, 2006)

Amonra said:


> possibly another stupid question here but why do you set the tool post at an angle ?



From what I have learned the use of the compound slide set to 30 degrees lets you take deeper cuts while putting less of a load on the tool. You have to be careful using the compound slide as some machines need to be set at 30 degrees and some at 60 degrees. It all depends on what surface the lathe designer referenced from.

When I originally started cutting thread I used the compound slide set at 30 degress when on *MY* particular machine it need to be set at 60 degrees. Basically your compound slide angle should match the 30 degree angle of the thread cutting tool. (60 degree cutter / 2 = 30 degrees)

I myself do not use the compound slide at all and take 0.006 passes with no issue. 


Mac


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## TranquillityBase (May 17, 2006)

Amonra said:


> possibly another stupid question here but why do you set the tool post at an angle ?


29.5 degrees is standard, even if the scale is etched differenly from machine to machine. 29.5 is 29.5. Call it 59 degrees if you like. It's not really that critical, anywhere in the range of 30 degrees. This is why I made the statement about a sine bar, early in my tutorial. 

As you advance the top-slide for each cut, you're moving the left edge/left flank of the cutting tool into you work piece, it should only be cutting off the left flank for all but the last cut. This prevents the right edge from excess rubbing on the part, The more the right edge rubs, the quicker the heat builds up, and the faster the cutter dulls and chips.

Look at my photos, the right edge of the cutter is just along for the ride. It's easy to see, if you look at the photo. The cutter will stay sharp for a very, very long time, if the right edge is given space. Your cutter is traveling to the left, towards the headstock, left edge is making the cut, like it or not.

The final cut is .001" advance of the Cross-slide, and you will see a different chip curl off from the very tiny amount the right edge is cutting.

TB


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## Anglepoise (May 17, 2006)

Amonra said:


> possibly another stupid question here but why do you set the tool post at an angle ?



Most of the work we do is on aluminium and many times it is thin wall tubing.
Also light machines do not improve the situation. 
Using the top slide to in feed basically works like turning. A singe chip is formed and it rolls off smoothly leaving a nice finish. The threading tool is working like a standard knife tool. 

On a small , light machine, this is the way to go.


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## TranquillityBase (May 17, 2006)

Awesome quick change tool post. What brand is that?

My lathe is etched the same way, it's kinda confusing.

Excellent photo, now were getting somewhere.

Here are some photos of my internal, and external threading set-up. Not to forget the confusing scale photo. 59 = 29.5  

*I hope all of this is helping, and not confusing anybody that's not sure on how to get started?*


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## kromeke (May 17, 2006)

Tool post is a swiss style 40 position "multi quick" or "multi fix" depending on where you get them from. It allows you to easily move your toolholder in 9 degree increments. Enco sells them. They are expensive here in the US.

The reason for 29.5 degrees (or whatever your lathe uses) is that the right flank will make a "skim cut" to leave a nice finish. If it was exactly 30 degrees, it will just cut on the left flank. Your bit should be properly ground as a 60 degree bit, so it will cut 60 degree threads no matter how it is advanced into the work. Advancing it at the proper angle will keep the nose (the point) of the bit from getting too hot and dulling. The left edge should do most of the cutting (assuming you are approaching it from the right).

Are you using an carbide insert? Often HSS will give a better finish, at least that is my experience. But I started out grinding my own bits, so I'm accustomed to it. I like to have a little more positive rake on the left flank, to give me a better finish for aluminum.


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## TranquillityBase (May 17, 2006)

kromeke said:


> Tool post is a swiss style 40 position "multi quick" or "multi fix" depending on where you get them from. It allows you to easily move your toolholder in 9 degree increments. Enco sells them. They are expensive here in the US.
> 
> The reason for 29.5 degrees (or whatever your lathe uses) is that the right flank will make a "skim cut" to leave a nice finish. If it was exactly 30 degrees, it will just cut on the left flank. Your bit should be properly ground as a 60 degree bit, so it will cut 60 degree threads no matter how it is advanced into the work. Advancing it at the proper angle will keep the nose (the point) of the bit from getting too hot and dulling. The left edge should do most of the cutting (assuming you are approaching it from the right).
> 
> Are you using an carbide insert? Often HSS will give a better finish, at least that is my experience. But I started out grinding my own bits, so I'm accustomed to it. I like to have a little more positive rake on the left flank, to give me a better finish for aluminum.


 Excellent explanation kromeke.

I've also been told HSS will produce a better finish on aluminum. I wimped out, and bought insert style holders, instead of grinding my own. 

I've found my carbide inserts will produce excellent surface finish, if I thread at 170 rpm or higher.


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## cmacclel (May 17, 2006)

The only tooling I purchase anymore is Micro100 carbide tooling. This is all my machine shop at work orders, and now I know why. I've tried all different brand tooling and have found the Micro100 to give the best finish and they stay sharp 


Mac


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## Amonra (May 17, 2006)

Well thanks guys all of this helps a lot. as you may have noticed i'm a beginner on the lathe and im taking the learn as you go approach but this info helps a lot. 
i had given up on cutting threads with the lathe as the first threads i did looked like s#%t so reverted to taps and dies. 
but now i will give it a try with the lathe again.

Thanks

P.S. can anyone point the direction to a nice insert tooling set at a good/cheap price that will ship overseas since the cheapest set i have found locally costs about $400 and $26 a piece for extra inserts.


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## cmacclel (May 17, 2006)

Inside threading tool $25

http://www.wttool.com/c/10320820p

External Threading tool 

http://www.wttool.com/c/10110193p

I could not find the micro 100's but if you call them they do stock them.


Mac


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## Icarus (May 17, 2006)

Hi Scott, great idea to post this Thread Cutting Tutorial for Dummies!  :twothumbs
Now I just need to find some time to try it myself!  

:wave:


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## TranquillityBase (May 17, 2006)

Freddy!!! Where have you been? No PM's, No email........:mecry:


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## alexccmeister (Aug 3, 2008)

Hi all,

This is my first post. I know this is an old thread but I just want to say thank you to TranquilityBase for this amazing tutorial on thread cutting. I just did my first thread cutting using his technique on a C3 (7x14) lathe without a thread dial. It wasn't perfect but I now have a feel on how to cut thread. I did it on a brass stock as it is easy to cut. The challenge will be cutting SS or rolled ballscrew. 

Alex


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## Icarus (Dec 15, 2013)

Another bump for this great thread! I think it should have been made a sticky.


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## precisionworks (Dec 16, 2013)

Icarus said:


> ... it should have been made a sticky.


+1 Lots of good info.

IMO the best single article on threading is from Modern Machine Shop, 01-15-2003 & it says this about compound angle: 



> A 29½-degree infeed angle will normally produce the best results, but in practice any infeed angle between 25 and 29½ degrees is probably acceptable.




http://www.mmsonline.com/articles/threading-on-a-lathe


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## Icarus (Dec 16, 2013)

:thanks: for the additional info. :thumbsup:


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