Thank you so very much for posting this. I’m new to machining, had my lathe less than a year and was having the worst trouble cutting my first metric thread. Your video really saved the day :)
I had considered this threading method (but the opposite way i.e. cutting inch thread on a metric lathe) soon after its launch many years ago, but regarded it too complicated and forgot about it. But recently it started to bother me again. I re-watched the video and understood it better. Oh yes I tried it and what a sweet safe way it is to turn a thread to a shoulder. I am very grateful to you and your source for this excellent method. There are really no more steps than threading normal way. You only re-engage on the reverse instead on the forward. It is just that easy and fearless.Thank you Tom.
On older machines with lots of backlash etc, ensure that you engage the 1/2 nut with the same amount of closure if it is variable. The other is to wind back enough off the thread for the start and I put a little of drag on the hand wheel to take up any backlash in the system, then I let go of the hand wheel before the cut starts. The main thing is not to change any gearing for when reversing etc. My other tip is to cut at a speed that you are comfortable with stopping by disengaging the 1/2 nut. This is very useful when cutting internal threads to a blind shoulder etc. I was shown this as an apprentice back in 1982. A great video .
Tom Lipton Yes, even an old dog like me can learn, after leaving a comment on metric threading with Keith F. tonight, I stumbled on your tutorial on just that, it is a work around that I have never seen before WOW-COOL. I have had to teach customers (angry customers) that had been sold a lathe that should do inch metric threading and I had to teach that stop and backup routine for years and I see this and it is so simple, can’t believe that I hadn’t thought of it! JON
Pretty pleased with myself, I was wondering what the heck you were going to do, then I figured it out just before you said it. Brilliant idea! Now I just need to find a set of metric change gears for my old lathe (almost impossible)
I've been cutting metric threads for years and have never thought of this trick. I will certainly give it a go on the next job. It should releive the blood pressure problem of having to wind out the tool and disengage the clutch and still have to worry about the inertia of the machine and the risk of having a prang.with the tool runing into the shoulder. Thanks heaps.
Damn. I'm a prototype machinist, and I didn't know about this. I was always under the impression that you had to keep it engaged the whole time. You just made my life easier.
Clever, really good idea for machines that don''t have a foot brake (probably not the proper term for it) And, for anyone doing metric threads- due to backlash, don't forget to pull your tool out before reversing! Quite a few winners I've seen forget to do that, not realizing how much slop some machines have
I have one of these moriseiki lathes. When I got it, it was set up for metric, with 36 drive gear. I had to replace with 72 drive gear. Am now learning how to operate this machine. I love the machine. Bought it out of a shop for $1000.00 dollars, and they thought it was european with european power. I built my own 3 phase unit and run it fine. My serial is 990.
I've used this for quite a while. I actually figured this out on my own because I thread a bunch of metric threads on my inch lead screw lathe in my ATV/Motorcycle shop. One problem I also had was that my metric side didn't cut 1.25mm or 2.50mm threads which are pretty common in the metric world. After seeing Keith Fenner calculate that a 20TPI is practically the same as 1.25mm! Now I can cut them all. Thanks for all of your great detailed videos. Andy Maul
This is a good "trick". Thanks. I have not done much threading, just a 3/4"-8 LH SQ thread on some chuck screws, and some 1/4"-20 threads where I turned the tool upside down and used reverse. I kept the half-nut engaged for the 8 TPI because it was too hard to hit the dial tick with a 16 TPI leadscrew and a little 64 tooth thread dial on my little HF 9x20.
Absolutely brilliant my friend! I wish I would have thought of that a long time ago, as it would have made many a job easier. This is great for threading to a shoulder, but for through threading like I did recently I'll just keep it engaged. Thanks for doing our homework for us, and showing us another way to getter done. Thanks bud! Adam
Hey Adam, I was so excited when I tried it. It was like finding a new Starrett tool on the sidewalk in perfect condition. It just put a smile on my face. Talk to you soon. Tom
Not necessarily. i don't see any reason to use the old fashioned way of setting the compound at 29 degrees and then letting one side of the tool burnish rather than cut. Might be OK with HSS tooling but most inserts don't do their best work with a very small depth of cut. That's what results when using the compound to advance. The left hand side of the tool would cut but the right hand side would burnish & heat. What do you gain by using the compound?
This is a super technique which should have been standard fare in all textbooks published in the last 50 years. For us who live in a metric standard country and purchase regularly from the States (Imperial dimension tools and supplies) this procedure is worth its weight in gold. I really enjoyed your demonstration (very well done) and continue to enjoy the RU-vid machining community's generosity. Great stuff!
you can do the same idea but still manually move the carriage back if you are using a carriage stop. i do this on inside threading for when i cant have a relief cut. like on the inside of a pressure vessel. ( relief cut can make wall thickness to small) you unlock the halfnut then shut off the machine, then roll back the carriage to the start position then start the machine in revers without the halfnut engaged until it lines up with number you started with on the threading gauge. set cutter to depth reengage halfnut then start machine.
Thanks for sharing that technique Tom. Just recently I was faced with the same scenario of metric threading up to a shoulder. To cut back on the stress factor I set up a micro switch mounted on a magnet on the lathe bed that would shut down the lathe motor just in time to allow the tool to coast up to the shoulder. Worked great but this would have saved me some screwing around.
Hey Chris, I feel the same way. Somebody mentioned you can hand turn the spindle with the half nut engaged if the thread is in easy material and fine enough. Cheers, Tom
If the motor is 3 phase and the gearbox is industrial strength you can get very good repeatability from a micro switch by using "plug reversing", which is basically the same idea as the ancient dodge of stopping a steam engine by throwing it straight into reverse. Plug reversing used to be in common use on turret lathes, at least in the UK, and the motors were often fitted with a "zero speed sensing" switch, which would turn the power off at the moment rotation ceased, effectively using the motor as a very powerful brake. However for threading this switch is not necessary, as you actually want to reverse the spindle rotation to get back for the next pass. The concept works particularly well with a swingup toolholder, a modern idea based on an ancient one (the clapper box used on shapers and planers) which makes it unnecessary to withdraw the tool for the return to the next pass. It makes it possible to thread at CNC spindle speeds, at least if you have a VFD (where decel and accel can be set to make reversing a bit less instant, hence easier on the gearbox). It can even eliminate the need for a thread relief groove, at least when using HSS (except in very hard materials) If this idea had been commonly known a hundred years ago, the need for such things as threading dials, single tooth dog clutches, rapid retract toolposts and crosslides, ball-stop crossfeed, snaptap threading devices etc etc, would have been much more limited -- mainly I would guess being needed for internal single point threadcutting, where a swingup toolholder is impracticable, or for hobby lathes with single phase motors or lightly built gearboxes.
Great video, I have a metric lathe and was struggling to cut an imperial thread until I discovered that the threading dial wouldn't work so used the keeping the half nuts closed method. I'm thinking that this method will also work for cutting imperial threads on a metric lathe, will try it. Many thanks.
Hi Tom, Good trick to not end up with a broken shoulder when working on a lathe with no pedal brake. I'll try for sure... Today is another good day where I've learned something new. Thanks, Pierre
Thanks for the video. I just picked up a set of Metric gears for my SB 10L and was thinking about how to go about using them. I figured it out about 2 seconds before you showed it. Thanks again!
Cool technique. I have become VERY dependent on the footbrake and jog button when doing such a thread. It's nice to take some of the pressure off by being able to release the half-nut. I shall use this in future. Thanks to the original poster and yourself for the excellent demo. Colin
Very good technique for people to see. Like most of my generation I was trained to never uncouple unless absolutely necessary and there are times when it is much easier to be able to momentarily uncouple as sometimes we were cutting inch threads on a metric lathe, ha ha - same problem. I will add that when one cuts one of the rare fractional pitches (11-1/2 TPI comes to mind here) that your demonstrated technique will prevent the "doubling" that can occur. Good job.
Hi Robert, Yes you have the inverse problem. I am upset that I learned this trick after so many years of doing it the hard way. Thanks for the comment. Cheers, Tom
I'm new to actually doing any machining. I've been studying for a couple years but just got a lathe this spring. I've only done a few threading operations whatsoever. As I've read about going metric threading on my old Logan 10" it always seemed to me like this method you show should be perfectly doable. But everything I read said that you MUST leave the half nut engaged to do metric threading on an inch leadscrew. Thank you for confirming my "naïve" suspicion. :)
Hi Jon, This is why this technique is so important. It really shows that the must leave half nuts engaged is not needed with a little care. Thanks for the comment. Cheers, Tom
Thanks Tom, excellent demo! Had just got done reading Conrad article and I noticed this video had come up in my search window and BAM, now to the video😀. Awesome job! Now threading metric to a ridge won't be so tense😎
Damn, why have I never thought of that. And there is nothing stopping you from doing the same at both ends of the thread. I wish I'd watched that a month ago, I had a part to thread with very little room at each end of the thread. It was very stressful
This is GREAT I have always left the 1/2 nut engaged on metric threads in the past but this makes perfect sense!!! Another note on most lathes you can grab a faster spindle speed on the reverse if you are cutting a long thread, as the feed drivetrain is driven directly off the spindle and doesn't care what gear the spindle is in. We have a couple of lathes with clutches that run faster in reverse for this exact purpose. PS you can turn the spindle by hand for real finiky right up to a shoulder super fine rifle scope type threads
Very cool Tom, Always great to learn something new after all the years we put in to our profession. After I learn something, I always comment back, "Now I'm smarter today than I was yesterday" Thanks for sharing! I'll be coming to the open house, looking forward to meeting you and yours. Ray.
This will come in very handy if I ever end up with a lathe capable of cutting metric threads, or even one capable of reverse without flipping wires for that matter! lol Thanks for the great educational demonstration.
Thanks for the great advice Tom. Got some adaptors to turn tomorrow so going to give it a go. I have always been in the habit of keeping the half nuts locked at all times when cutting a metric thread.
That's one for the collection for sure! Thanks for putting it in living color...RU-vid is great. My eye caught something during the video that I wondered if you would give us a better look at? That is the rack for your quick change tool holders. Thanks! Dru
Awesome tips here! I’ve been wondering how cut metric threads on my small American lathe. As a fairly new hobby machinists, I’ve learned a ton from you and absolutely love the channel!!! 👍
Very Nice and Cool. That was nice and clever, but exhausting too. You are on the top of the world after completing a successful project not without a feeling a high. Thanks for the Video.
Conrad Hoffman is a pretty good guy, I have had a couple of conversations with him over at PM, didnt know he had this up though, thanks for pointing it out and the great demo. Stan
LOL.....well I'll be, now that is a really clever method of stopping the saddle travel when you get to the end of the thread and have to run up to a shoulder etc. I don't have a threading dial on my old 1930 Colchester Bantam lathe but now I think I can use one even for Metric which I do mostly now......been using the manual spindle wind back method for years. This is the never too old to learn new tricks scenario we are all in to if we want to get clever.
Thank you very much!!! That is really what I have searched for, no calculation, just the most simple and useful method for my chinese lathe without a brake :D
As you demonstrate, on fine threads in relatively soft material, you can advance the tool with the cross slide. But there's zero reason to have the compound set @ ~30* if not using the compound to advance the tool. A coarser thread in some 4140, not so much. As far as the temporarily disengaging the half nut. I've become aware of this. Great tip.
Not watched you for a while Tom but this is a top tip was struggling with doing the same this on a lathe I recently changed and and handles a half nut lever was on opposite sides,thanks again for all the videos you post Dan
Good Trick. Another addition would be to set the Cross slide dial handle at 9:00 position zero the dial or mark it, (so down on the handle is always out, away from part) on every cut. Feed into part at 29.5 degrees with the compound slide. Then you wouldn't have to remember how deep you were on the last cut. I always marked my cuts on the compound dial with a marker. You wouldn't even use the DRO. (much faster) Actually that's the "classical" way to do it. On very large, course threads, it is the only really efficient way to do it. With the classical way one is actually turning the thread not gouging it out, which is what going straight in, actually is. I do like your thinking Tom, I've learned to think the same. When I found a better way, that's my new way! Doesn't matter who showed me. I once had my day saved by a janitor in 1980, who solved a chatter problem on a long small dia shaft I was doing with a trick he knew, and I didn't know. I never asked how he knew, but I tried it, and it worked.
Ok, so what was the chatter trick you learned? I learned how to drill perfect circles (holes) in sheet metal by placing a very small folded rag right over the drill bit and then drilling down on that through the metal.
That particular time I mentioned, it was to put the tool a bit above center. Another time in 1983, I was facing a large diameter flange (about 30" X 1.050 thick diameter) flange welded to a 3" bearing diameter shaft. This produced an annoying, high pitched squeal. An Allis Chalmers veteran of 35 years, (this was not at Allis Chalmers at the time), walked up and thru a mighty mag base which stuck to the back side of the flange and the squealing stopped. This was a new idea to me and I used it many times thereafter. (Harmonics) So if you encounter squealing or chatter, "sometimes" placing a magnet on the side of the boring bar or other tool, or on the part itself, will stop the harmonics. I later was given job (at a different shop) to turn 40" to 50" long, (1/4") wall ,5-6" diameter steel tubes. The old guys there laughed and told me that I had been stuck with the "shit" job, because in the past they had to stand and follow the carriage holding a lead hammer against the part during the whole turning process to prevent chatter(harmonics). So I removed the upright shaft from two indicator bases and I placed the magnetic bases inside the tube at each end on opposite sides (when the old guys weren't looking) and started turning. For effect, I sat on the bench while I turned the chatter free tubes with my legs flapping in the breeze looking bored, and smoking a cigarette (times have changed) all the while I could see these two older guys off to the side looking on, with a "WTF" look on their faces. The "shit job" ,turned into the best job in the shop, as I had very many of these tubes to turn. The tubes had a large tolerance on the O.D. but they could have no chatter marks. The moral of the story? Although I had learned the principle of the fix from a very experienced old guy myself, these "old guys" made the mistake of thinking a younger guy knew less than they did on every matter, simply because he was younger. The proper, and only right way, to view machining, is to always consider it a learning experience all the way up till your last day. When one thinks he "knows it all", he or she, is ineffective thereafter. There's nothing wrong with being proud of your effort to learn and your accomplishments, but it's necessary to have this primary restraint. There is an old saying in the Biz. "There are machinists with 20 years experience and then there are machinists with 1 years experience, 20 times". I actually met a pair of the latter, and proved that saying to be true, in Arkansas circa 2003. Although I was chief toolmaker, I couldn't have taught those two guys to run out of a burning building. Dumb and Dumber were steadfastly bound to stay that way, on their own volition. (Ain't no yankee gunna tell me nothin!), at least they were right on one thing. I hope this may help you Tom. After 40+ years I retired in January. I'm done learning about machining. Although I still show up with one of my three machinist sons at a shop, for special projects. I read books, play guitar, and other things now.................... Keep pounding,,(I just, had to say that...)
Fantastic answer.... I'll certainly keep it in mind. I have used bicycle tube wrapped around shafts welded to plate when the harmonics began. Sometimes with success and sometimes not. Also lead soldering sticks attached to boring bars but never the magnets and first chance I get, I'll give them a go. Here is a question you may be able to answer. I've been setting up a quick program (excel) to determine the depth of thread depths using a bit of trig and with using the compound to do all the 'work' as it were. Bit hard to explain my question other than this. When turning a piece of stock to take a (Eg), 12 mm thread * 1.75 where the recommended Major Dia (Max) is 11.97mm.... Can you see a reason why I should turn that stock to a dia of 12.35mm to then cut the thread to a depth of 50 Thou (1.26mm)? In other words and in all thread cutting operations, does the stock begin as a size a fraction larger in Dia than the Major Dia Max? Then as the correct thread depth is achieved, this Dia reduces down to what it should be? Refer to "Maryland Metrics Thread Data Charts" on the net. I like solving all manner of math problems using a hand held PC or the excel and then simply punching in whatever needs I have at the time and the answers get calculated. I've done that to date with all and any contour cut ever known to man in fitting piping together to give no gaps whatsoever when fitting pipe as structural pieces and or intersections. Just have a think on that question about Dia's and I'd be interested to get your thoughts. 12.35mm or 11.97mm?
Tom I don't quite understand the question. But it was always standard practice to turn the diameter .005 under the nominal, beforehand when threading. I'll bet there is a chart showing thread depth on the internet. As there is on some thread tool setting gauges. The anti harmonic solutions don't always work but when they do!...wooohooo!... :-) I've used the inner tube solution also. Double lead threads can be done by fixture or by a rotation of a gear on the manual lathe. Pain in the .... The acme thread screw sleeves(up down) on old milling machines require double lead. One more thing about harmonics. Back in the 70's I was boring out Rexnord "lock Post" hydraulic cylinders for rock crushing machines.( funny, years later I machined many of the large eccentric bushings for the very same rock crushing machines, at another job shop), anyhow,The bore was about 8" diameter and 30" deep if I recall correctly. The owner of the company came buy and he asked me if I knew the purpose of the many lengthwise and dissimilarly milled out sections on the large boring bar I was using. I said no. He said it was to reduce harmonics. Apparently harmonics are more prevalent in symmetrical situations. So break up the symmetry, whether by shape or magnetism. I didn't know the magnet trick at the time. P.S. I've got a funny story about turning cable drums and another one about using a steady rest with brass pads if you'd like to hear such nostalgic dribble...
Yep, hard to explain in text. www.boltscience.com/pages/screw3.htm The Crest line is just lower than the apex. So do we begin the threading process using the apex dia is what I'm wondering? And yes I fully understand convention saying .005 under nominal but could it be .005 over? Anyone's input here?
Good tip! It also seems that after you pullout and shut down the lathe, you could manually move the carriage until the thread dial lines up, engage the half-nut, then go in reverse. Should be the same. I'll have to check it out. It may be easier for those with a fine lead screw.
Hi Tom , Thanks for your nice vid , in our shop we dont use chasing dial at all , just all time engaging and reversing at the and of the pass with out stopping the machine. (metric) i hope you understand what i'm saying .
Tom, that is a fantastic trick! Honestly I have never cut a metric thread with a lathe, however since I have seen you talk about it in some of your videos I feel ready to try one. In the shop at school I only have one lathe (a Nardini) capable of metric threads. My primary lathe at home is a 20"x36" American Tool Works circa 1903 and I am fairly certain none of these were ever built to do metric threads.
That is so stupid simple it's pathetic. Why did it take so many years for someone to think of this, and explain it so much earlier? Wonderful video, as always.
I too am having much difficulty cutting a metric thread on a standardized lathe. Standard threads L and R no problem. And this is a great trick for keeping that position on the lead screw. I understand why you would need to do this when cutting a metric thread just fine. But what I don't understand is how to set up the change gears that are made for standard size threads to cut for example a 1.5mm thread? How do you get the right gear ratio? maybe you can explain that to us Tom. Thank you for making your videos and putting them out there.
Nice demo Tom. Always learning! So much to consider for a seemingly simple little plug:) Keep in mind that there is a 3mm radius on the top flange of the transformer, so you can stop the thread 1mm short of the shoulder if you like.. You are getting me very excited now!
Hey Nick, Fenner had the million dollar steady rest series. Now I have the 500Kb (kilo buck) brass plug. Everybody is going to really want to see where this goes. Cheers, Tom
Wish I had seen this video a couple of months ago.I had to cut an internal 38 X 1.25 mm thread in a blind hole for an adapter I was making for a hydraulic puller.Great stuff. Mucky Mel
Hey John, Thanks for stopping by. I was excited when I learned this little gem. I can't say I thought of it myself. Thanks for the comment. Cheers, Tom
Neat trick. Works well if you have a spindle brake. Those of us with simple lathes may have to count rotations while the spindle spins to a stop. I do have a VFD on my Craftsman. I'll try it on mine. With the VFD it does do some braking on the stop but I bet I'll still get near a full rotation of the dial on mine.;)
rcdieselrc My VFD trips out on over current if I set the braking time much shorter. I have upped the current limit but it still must coast to half speed or so before applying the brake. I could optimize it more but also don't want to worry about the chuck unscrewing ;)
Hi Scott, No need to even use the brake. Once the half nut is disengaged there is no rush. It takes a long time for a full rev of the threading dial. Cheers, Tom
Just mount the Carbide tool upside down, start your threading near the mounting in the chuck at whatever length you want to start at, and just run that bad boy in reverse when you are threading. Works every time. When you mount the carbide tool upside down, you don't have to worry about the carbide tool breaking either, because if it ever bites into the material, it will just come up off of it's mounting, instead of forcing against the mounting and breaking.
There are 2 other ways to "remove the excitement". You still have to be fast on the half-nut! One is to thread either with the tool upside down, or with the tool behind the work. You RH thread with lathe in reverse, permitting the START to be at the shoulder and the END out in the open. The other way is to equip the lathe with a VFD controller. You can slow the speed and creep right up to a shoulder. In fact, you can thread without any relief cut at all!
Hi Tom, now that's my kind of shop tip, awesome, man, if I did a video showing that, I'd get tattooed. Just a continuous stream of comments of how I'd be doing it all wrong. And it seemed you did it as a straight on thread as well, I get accused of that all the time, though I'm actually only cutting the leading edge. As you say, this is great practical information to be shared and used, I like to use the term "bumblebee engineering" Great video as always! Uh oh, I just realized, I guess I'm going to have to look for my threading dial now if I'm going to use this, fair enough. Thanks Tom, I'm trying to get caught up on all the videos I've been missing. Mike
Hey Michael, I don't know what they put in the water around your place but it sure makes for troll magnets to stick to you. I generally do compound feed but in this case for a shallow thread in easy material it doesn't matter. If the tool fits the groove its right. Incidentally down a bore with a small thread relief against a shoulder radial feed is your only option. Its done all the time. Your threading dial is under the pile of chips on the carriage to your right. Thanks for the comment. Best, Tom
Very eloquent Tom, maybe another good reason to follow your advice and de-chip the shop, repel the troll magnets LOL Thanks for the practical information reinforcement!
interesting video Tom .....but what i find most interesting is the very early lathes had very interesting features like dept stop etc..that more modern lathes including my cholchester does not...yea the Hendey lathes and maybe some others really were setup to do these kinds of jobs...
Hey Lawrence, The Monarch lathes have a really slick threading setup on them as well. Not quite as extensive and elaborate as a Hardinge but darn useful. cheers, Tom
Obvious when you think about it, but it takes an intuitive genius to put it all together. I wonder if it works the other way, Metric lead-screw cutting an Imperial thread? It should.
Hi Tom, stand by for shouts of "heresy" from your fellow colonists for using the cross slide and not the top slide for in feed, for some do not believe you should even think about doing it. In truth all it is is a little knowledge is just not enough and a closed mind is no mind at all, but they believe they are right, bless 'em. ATB chris
Ho Chris, Good to hear from you my friend. Yes it is the dreaded straight infeed. That stub of thread will never meet its female mate in our lifetime. I'm hoping to trick them with the slight of hand and thread dial closeups. Cheers, Tom
Hello Oxtoolco, This was a very well balanced video, filmed in real time which is the very best way to show it. However you seem to have got it all wrong from what I saw of the film, you have the compound slide correctly set at half the thread angle, but you are incrementing with the cross slide handle, this does away which the whole reason for setting over the compound slide, which is to be cutting only on the front edge of the tool. I have used this method for the past 40 years, although not at these revs, well done for surviving!
Hi French, Thanks for the comment. I pretty much leave my compound set at that angle all the time to keep it out of my way. So I didn't actually set it to do this video. I do use the compound for larger threads in tougher materials. For little threads and a nice rigid machine you can go either way and be fine. So got it all wrong might be a little over the top. The tool is perfectly capable to cut on both edge at the same time. If you do what most guys do and infeed a thou or so with the cross slide as your last pass to polish both sides of the thread wall you are basically doing the same thing. So you saw it worked fine right? Maybe do some experiments with your machine and tooling and see how it works for you. Cheers, Tom
Hi Hedron, We call those Doubleboost lights after the famous British explorer that braved the wild zombie hordes that dwell at Ikea eating Swedish meatballs. Cheers, Tom
