Four methods for cutting internal, external, left handed and right handed threads on the lathe
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- čas přidán 9. 06. 2024
- Follow my journey leaning how to cut threads on the lathe. We look at four different approaches to screw cutting from easy to more advanced methods. We look at cutting not only right handed threads but also left handed threads, internal and external threads, measuring threads and cutting metric threads on an imperial lead screw and imperial threads on a metric lead screw. We also have a sneak peak at engraving metal with a fibre laser.
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Timestamps
0:00 Introduction
0:23 How is a screw thread formed?
03:58 How to configure a lathe for thread cutting
04:58 Thread cutting - Method 1
07:04 The threading dial
10:20 Understanding thread dimensions
12:05 Thread cutting - Method 2
14:48 Measuring threads
16:24 Cutting left hand threads
20:55 Cutting internal threads
23:42 Left hand internal threads
24:52 Internal threading in blind holes
25:04 Engraving metal with a fibre laser
25:45 Thread cutting - Method 3
28:45 Cutting imperial threads with a metric lead screw
29:18 Thread cutting - Method 4
31:46 Conclusion
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Love your videos, man
Just a heads up, the compound should be set at 60.5° actually. Due to the direction of the scale, you should set the complementary angle of what you intended. In other words, you should subtract the angle you want from 90° (90° - 29.5 = 60.5°). The way you set it, the angle was equivalent to 30.5°.
Ahhhh, thank you so much, I didn’t realise that was the case. Your explanation makes perfect sense. Shame I can’t update the video. I’ll pin this comment instead. Much appreciated.
@@joneseymakes Appreciate your response. That's easy to overlook, specially since your scale stops at 60° lol
Nice to see someone really getting down to the nuts and bolts details of it 👍👍👍 Great video
Honestly for the mini lathe, I think adding an electronic lead screw is a great idea too.
Yes I like that idea
@@joneseymakesnot just for the mini lathe, for the big lathe too. I haven't put an ELS on my mini lathe yet, but I did put one on my 14x40 floor-standing lathe. I never throw a gear lever any more, and I have thread-to-shoulder and rapid return for the next pass. No reason to disengage/re-engage the half nut. It's a great upgrade!
@@MichaelKJohnsonMay I ask which lathe you did this to and whose ELS you used? I have a PM1640TL, and I’d like to add an ELS and VFD.
@@marclevitt8191 I went with the Clough42 ELS and made my own fork of the firmware. I put it on a G0709.
@@marclevitt8191 also if I were doing it again I'd look at what @stefanobertelli2650 has been building.
I almost always use method #4, leaving the lead screw engaged. I retract the tool, and reverse the spindle simultaneously. That is the way my Dad taught me 60 years ago. I only use the threading dial when I am cutting a long thread. Great video! Solid information, and instruction.
Thanks!
Yes, my preferred method as well. I have the advantage in that my old round head Triumph has a brake on it. Makes it a lot easier, if more time consuming.
@@billdoodson4232That is a nice lathe you have there, Colchester Triumph, I assume. The spindle brake is a nice feature.
@@billdoodson4232even better if you have a VFD with almost instant reverse, then you can use a clapper box style threading tool too.
@@chrisstephens6673My polishing machine (I made it myself) has an inverter, but if I stop it too quickly it trips out. It must be a pretty good inverter to cope with that.
I'm so glad you got the flats of the nut's to align by the end of the vid, I did wince a little half way through watching 😂
That alone has gained you a new subscriber! 😉
P.s. Top marks for the content too, was very helpful for a muppet who's just bought his first lathe ⭐
Haha thanks! Good to have you on board!
Great summary. The laser markings look beautiful. Looking forward to the video.
Even with method #4 you CAN disengage the half nuts, if you reengage them at the same value on your thread-dial when running in reverse.
Ok, that's good to know, thanks!!
I have watched many videos that explain single point thread cutting but I think yours is the most thorough and informative. Very well done, friend. Great pace, great visuals, and most of all you don't hide your mistake of cross threading!
Thanks for the feedback and thanks for watching!
Lots of good information here. I would add that when cutting left hand external threads or internal right hand threads, it's necessary to move the compound to the opposite 29.5 degree angle so the forward edge of the insert is making the cut rather than the trailing edge.
That’s a great observation. Thanks for pointing that out.
Hi Jonesey. Thank you for a very interesting overview of single point thread cutting. Very enjoyable.
Looking forward to you showing more about your new laser engraver. 👍😀
Thanks for watching!
Excellent video. A couple of questions... What is the purpose of the second smaller tooth on the screw cutting tool? and... How did you get the nut faces to line up with the middle "nut" at the end of the video? Ciao, Marco.
Thanks! The purpose of that smaller tooth is to properly form the crest of the adjacent thread. This only ever comes into play when cutting at the full depth of the tool though. Those inserts are meant for a specific pitch. The tool I use in the video is for a 3mm pitch, but as I'm using it to cut smaller pitches I never get to full depth. Ideally you'd have different cutters for each thread pitch, but this can get expensive, so I use a larger cutter at partial depthfor most stuff. I got the nut faces to line up by taking small cuts off the face of the nuts until they lined up
@@joneseymakesit only becomes a relevant feature if the insert is designated as a 'full form' thread cutting insert.
Edit to add: there are general purpose inserts with either 60 or 55 degree inclusive angles that are not pitch specific.
Great video. I’ll be coming back for reference time to time
Thanks!
Excellent vidéo, thank you!
Thanks!
Mate, that LASER next level shit! I want one
Full video coming soon!
Threading is such big subject with many alternative methods and a few sacred cows thrown in.
The main sacred cow is the setting of the top slide at funny angles, much favoured by old timers and Americans. I have conducted experiments to prove/disprove the need, and using both methods on some 12mm 303 as my test and using a full form insert you could not tell the difference even under a microscope. Granted there may be a case for using the top slide method on really flimsy lathes or when cutting particularly coarse threads but the benefits of having the top slide parallel to the lathe axis out weigh any threading ones. It reminds me of a time I was demonstrating Threading at one of the ME exhibitions using the radial feed method, and some oldies said you can't do that, their apprentice master had shown them the only way to do it, using flank feed. Then a younger chap piped up saying that he had learned the flank feed method but when he got his first job and was asked to do some Threading, his foreman said something to the effect of what are you doing wasting your time moving the top slide, just go in! And he had done ever since. Sorry if this is a little long winded but I have made a study of Threading over the years, looking for the best method and I can say there isn't just one. It depends on equipment / tooling available and skill levels and comfort zones. In other words do it any way you get the results you want, not following anybody's dogma.
There is a special tool that works extremely with your 4th method using a clapper box style tool, the idea is not new as it dates back to victorian times but seems to have been forgotten of late, there are a few videos on them, just by coincidence there is one on my channel 😉
There is perhaps a 5th method of note that is excellent for beginners who worry about crashing, that is turning the spindle with a crank handle. Because the lathe is not powered you can start and stop at will, great for building confidence. Myford even sold a handle for just this purpose, but much cheaper to make your own following the principle design from Geo H Thomas' book.
Thanks for the comments Chris. I will certainly do some more experimenting with going straight in. I've just watched your video on the thread cutting clapper box, very interesting indeed! I'd like to make one of those myself, thanks for sharing.
@@joneseymakes if you want to see another version look up "blogwitch" he has two videos "threading".
The one in my video is inspired by the ancient patent, blogwitch's is a more modern style and was I think a collaboration with someone on one of the forums. Their use is more relevant these days with the need for cutting metric threads on an imperial lathe or vice versa and an instant reverse using a VFD helps greatly, as does a crank handle .
I find a cranking handle the fastest method on my Boxford A. Only if I'm doing 5-6 threads though.
@@markrainford1219 I admit I only use a crank on my Myford, which I bought purely for cutting imp threads. Metric threads I cut on my Colchester with a VFD. I don't cut many Imp threads but it is useful to give beginners some training without the risk of a crash.
Excellent explanation for newbies.
Like how you included your flub for honesty.
Thanks!
That was a really good video. Cheers
Cheers, much appreciated!
One of the very most enjoyable videos on machining I've seen, Thank You.
Fun bit of threading that is possible: Threading a piece of shafting like you have done (bigger is better) with both left hand and right hand threads, and then fitting both a Lhand and Rhand nut to it. Yes you can even combine this into one nut, but it gets messy in the nut and hard to clean up.
Thanks very much, glad you enjoyed it!
Very good
Thanks!
It was probably worth mentioning a few things.
Cutting tips for screw cutting are very often R/H OR L/H thread use only as they don't have the proper clearance. Some have adequate for both but it is worth keeping in mind.
When cutting L/H external with your 2nd method the compound slide needs to be rotated around so it feeds in the direction of cut like it does when you set up the R/H example. this keeps the cut on the leading edge.
There are other methods of cutting threads using a calculated move on both the cross slide and the compound but you need to calculate the movement to keep in sync with the thread angle.
Thanks, that's great advice on the cutting inserts. Didn't occur to me to move the compound for the left hand threads, but looking back at the footage your spot on.
20:45 Isn't that the minor diameter your measuring? Ah. 22:40. Well at least I was paying attention!! 😂👍
Haha! Yes indeed, good spot!
For method 3 instead of turning the tool over, use the internal threading bar.
To keep the cut on the leading edge. Leave the compound at zero and advance the tool half the depth of cut per pass. This simulates advancing at 30 degrees.
Great tip, thanks. I’ll try that for sure.
If your toolpost placement allows for it putting the tool behind the workpiece or putting the tool upside down and running in reverse should be able to cut a left hand thread without an extra gear, and it also allows you to move away from the workpiece instead of into it with the passes, which also removes the risk of overshooting and crashing into the workpiece. Running the tool upside down probably reduces rigidity of the setup too much though. Running the tool from behind should probably be the default way to do it for beginners since it removes the biggest risks with threadcutting.
Interesting, thanks.
When threading away from the chuck with the tool upside down, do you change the 39degree compound angle or leave the same as threading into the chuck? thanks for the great videeo's, very clear instructions.
Hi Brad. I actually made a mistake on that angle, it should be 60.5 degrees on my lathe. I’ve pinned a comment that explains it. I leave the compound the same as for the other direction personally.
Just curious. How long did it take you to get comfortable with all four methods? Great tutorial;thanks for your time and skills!
Not too long really. Just practiced for a few hours. Still got lots to learn!
you can disengage at end of threads just reverse lathe and close halfnut exactly where it was on the same rotation easy peazy
Ok, thanks. I’ll give that a try.
Just aside. You can disengage the lead screw. Then reverse the machine and re engage it at the correct position. Works fine. Cheers
Ok I'll try that, thanks.
Hello Jonesey. I really enjoy your channel and your high quality videos. I can tell that a lot of effort goes into them.
While I was watching around 9:30 it appears from the video at least that the half nut lever may have been engaged slightly before/after the mark and that may have caused what seems like a huge/too deep final cut. It looks like the tool is only cutting on one side and there is a tiny ridge left over. I am a relatively new lathe owner and still a beginner at thread cutting. I have done something similar numerous times myself before realizing the issue, but I think this is it. I thought I might share and see everyone's thoughts and possibly correct any of my own misunderstandings.
The half nut will only engage in specific places, usually right on the nunbered lines and half way between them. Being off by a small margin shouldn't matter. To better understand this, run your lathe and slowly engage the half nut lever and feel where it drops in.
Of course there is always an exception with hundreds of different types of lathes but as a general rule this should hold true.
As the other guy says, the half nut will only engage in certain places. It’s really obvious if you get it wrong as you’ll end up with a crossed thread. The problem at 9.30 is that I mistakenly wound on too deep a cut and removed way too much material. Best thing to do is just get out there and practice, which is what I intend to do!
Regarding the cutting tool, I don't think the 60 degree one is suitable for both metric and imperial. Common imperial such as Whitworth and BSP need a 55 degree tool and BA a 47.5 degree.
60 degree is OK for Metric ISO threads. Cheers Nobby
Cheers Nobby, I was talking more about the Unified standard which is common in North America and is 60 degree. I should have called this out specifically so thanks for commenting!
When you bored that nut out, and you said 22mm, I was wait a minutte and was ready to go back in the video to see the diameter of the bolt. But I think it is strong of you to show that error.
Thanks, we all make mistakes!
Thanks for the video! I think you glossed over an important part, the thread relief. How do you know how deep to make the thread relief? I know it has to be as deep as the deepest threads, but if you're checking the threads as you cut them, you're either going to be too shallow or too deep?
Thanks for pointing that out Christopher, yes, I should have said more on that. As a rule of thumb I normally cut the thread relief slightly deeper that the pitch of the thread I'm shooting for, i.e. in the first example I cut an M10 x 1.5mm, therefore I cut the thread relief a bit more than 1.5mm deep (I think I went 1.7mm). I hope that makes sense.
P.S. You can always go back in and cut the thread relief a little deeper to clean it up after the thread is cut if needed
@@joneseymakes Not if you leave the lead screw locked in.. Threading is one thing I need to work on more.. can I do it, ~yes, but it's not elegant.
If you set your compound to 59deg from parallel, you're cutting a malformed thread! You are then feeding in at a half angle of 31deg, whereas had you set the angle to 61deg from parallel the shape of the tool would dictate the thread form, allowing the trailing edge to clean up the right side flank.
Generally the last few passes are taken straight in, which gives the correct thread form no matter the top slide angle.
@@chrisstephens6673 Agreed, but as this is aimed at beginners, it should have been explicitly stated.
Yes, thanks for pointing this out. I didn’t realise my mistake. Another commenter has pointed this out and offered a good explanation too so I’ve pinned that comment for others to see.
Normally i make the nut first. It is easier to "fix" the external cut.
Good point
Why does everyone in the videos use the compound to feed in when threading I always just use the cross slide for every type of thread I cut. So does every Journeyman I have ever worked with at multiple shops.
Thanks Travis for the feedback. That works for you even in harder materials? I’ll have to do some more experiments.
@joneseymakes yes sir. 4140 HTSR, 17-4 SS, 316 SS, Inconel, Hastelloy and so on. I'm just asking out of curiosity. All the videos I see people threading on this platform use the compound. I have just never seen it in my 23 years of machining.
@@travis8623 Interesting, i will have to do some more experimenting
"Found a chunk of 3.1/2" round brass bar"! I bloody well wish I had a scrap bin like yours, where you can find a couple of hundred quids worth of brass tucked away in the bottom.😊
Haha! Indeed. I picked that up at an auction for a lot less than it's worth!
@@joneseymakesAh yes, the problems with auctions these days is they are all on line. Having said that I got about £2K's worth of milling cutters last week in an online auction for £100. The real kick was finding another £1,500 worth of carbide inserts in the bottom of one of the boxes of cutters. I now need to buy the tools to fit the inserts. 😁
Has anyone ever said you almost sound like the actor Rupert Grint?
Haha! No, but now you mention it...
Y waste so much brass for this? Aluminum would be alot cheaper
One of my lathes has a tapped hole next to the spindle, kind of hiding behind the banjo, where you can thread in a shaft for an extra idler gear. When it's installed, the banjo just sits in a slightly different position
Interesting. What lathe is that?
It's the harbor freight 8x14 lathe model #44859. I don't believe they still sell it and it was never very popular so it's a bit hard to find information on@@joneseymakes