We figure out how to cut some metric threads on a Southbend lathe with a quick change gearbox using 2 commonly available gears and no other modifications. All the math is included in this video. This is going to be used for an upcoming er-40 collet chuck build.
Very good! This video really fills the knowledge gap on metric threading on the small South Bends. Thanks!
That was some fancy work, backing the tool and hitting the reverse. Congrats on the successful threading, and thanks for the demonstration.
Thank you for going through the math. I really like knowing what is going on rather than just dump in this gear and go. :)
A+ on all the math you did and making the metric thread !!!!
Excellent. Thanks for the timely info.
Awesome stuff, Greg! You can hear the satisfaction in your voice, and it's nice to hear ;-) Gotta love when a plan comes together.
Cannot wait to see the collet chuck video since I'm getting ready to tackle the same project.
Bravo. Figuring out what combinations of gears will give you a given pitch thread is not a simple problem. There are supposed to be programs out there on the net that will give you one or more solutions, but I have no threadcutting capability so I have never looked for them. Your explanation was crystal clear. And you will love those ER collets. I got some last year. I call them my crocodiles. They will compress about a millimeter, release on order, and never slip.
Thanks for this info. I own a SB 10k and it makes it quite clear. I will add those gears to my eBay watch list. Great Job.
Nicely Done.
I'm really excited for the collet Chuck project. I just bought my first lathe, and one of the things I really want is a collet chuck, it'd be very neat to make my own
Greg . . . That's slicker than snot on a doorknob! You must feel a great deal of satisfaction because your plans worked! Good luck with the actual build! Have a good one! Dave
I'm late to the party but finding this video answered many questions for me. Thank You
Hi Greg (again!). It is good to see you back doing 'stuff'on your very nice Southbend. Please pass our collective thanks onto your wife for letting you have the time to do it! You have cheered me up as well this morning, just watching your obvious pleasure at seeing the results of your thinking, dare I say, turning (!) out right. Yes, well, the old puns are the good puns. Cheers. Bob.
+Robert Hawtin :-) I get to have my shop time when she's at work.
Great work, I liked you showing your calculations. Have good Holiday! impressed with the speed that you can operate at. You're the man!!
+Steven G Rochelle Than ks!
cleaver Greg, nicely done!
Cool nice job on the threads. Looks like a real nice fit on the threads.
i have two 9'' southbend lathes one all apart.don t have room for two. i have cut a lot of threads and not bad.but watching what you did to cut metric threads i don t think i want to try. if you were be side me i might try it. but you are very good and smart. thank you very much. sal
Dude, GREAT episode! I had bought 127 and 100 tooth gears for my Logan, but they didn't fit inside the enclosure. Now I know I can still do my ER chuck!
Hi Bob, I take your point. What I really liked about the solution was that you don't have to faff about in the change gear enclosure to get quite a decent set of standard metric threads just by using the gearbox. What would be very interesting to new comers like myself (how did you guess!) is 'how close is close enough' for the tpi errors resulting from the myriad of spreadsheet solutions. Thanks for correcting me, I don't want to be misleading others. Sorry Greg, seems it was not that novel! Cheers, and A Very Happy Christmas to all. Bob Hawtin.
On a belt driven machine like this you can loosen the belt to stop the cut, then shut the motor down, tighten the belt, back out and then reverse the motor. This is what I have to do when threading without a threading dial on my south bend. My original 1938 motor will continue to run in the same direction if I switch the switch quickly and don't wait for the motor to come to a complete stop before reversing.
I once had to cut internal and external 5/8 BSP left hand threads for some propane gas fittings on a Harrison M250 with a 6 mm leadscrew. Not being able to disengage was a pain. That was about 25 years ago, haven’t had access to any machining facilities for many years now.
Hi... good information well put across and nicely explained on the calculations of gear cutting metric threads on the South Bend. Oh... I hope you put your wife's toothbrush back before she noticed it had gone! 😋 Great videos - keep them coming! John 🇬🇧
Gears setting in banjo does not cause any problems, but reverse cutting does it. Thank you so much for about the making of these videos! It is said that in male-dominated production sectors aka. machinist. Work places has so call "silence information about working techniques" which not transfer at the next employee's because of the all-knowing master retires. So video's can be Very informative giving how-to tips and tricks for beginners like me. Thanks! 😊
Used your recommended 54/80 gear setup on my 68 South Bend Heavy 10 to cut 2mm threads to build an Accuracy International barrel it was dead nuts, a real class 3 fit!
+Mike Calafatis Nice! glad it worked out for you.
nice work great video.
I remember that wire rope lube we called it gear shield, black and if you got it on your clothes it never came off. Good stuff.
When measuring threads without a thread guage it's much more accurate to measure across multiple threads, alternatively just rotate the chuck 10 times by hand while measuring the carriage travel with a indicator, it's the most accurate way of checking the it's easier than trying to directly measure the threads
well done.
very nice! Thanks
I am wondering if it would work better to drop the 29.5 degrees on the compound and feed with the cross slide. You might be able to just reverse then without the angle of the compound (leave it on 0) to drag on the back of the metric thread. Give it a try? Very interesting project. Things are happening quite fast on your metric feed with little time to get out of the thread relief groove! You certainly paid attention in your shop class. Doug
I think the .471 ( from original calculations ) is the lead screw relative speed created by that multiple gear ratios to give you the 1.5 mm travel per one revolution requested not the actual carriage travel distance for thread cutting. I think the formula would be: Carriage travel = Pitch x lead screw speed ( different gear ratios from original calculations ) for example 0.125 x 0.471 ( original calculations ) = .058875" inch and multiply this by 25.4 mm you will get the carriage travel in MM .058875 x 25.4 = 1.495425 approximately 1.5 MM which is the required carriage travel distance per revolution. Now this all good, but what tricked me that you used the formula and used a relative lead screw speed 1.89 not actual speed, and it worked, but finally I figured that you still kept the rest of the gears in to give you a factor of 1.319 x 0.471 = 0.357 which is the ratio of the existing gears 20/56. Very nice work, very smart. Check my work please, I'm not a Machinist but I love this stuff. Thanks D. Sanduby
Oh dear.....I don't have a feed gearbox on my lathe just a set of gears......so now I use the recommended gear train ratios according to the info plate and set the gears accordingly......but luckily the gearset does have the 127 gear to translate the ratio for Metric pitches on an Imperial leadscrew. Normally, without the gear sets chart on the brass name plate, I would have to use the standard screw cutting gear formula of TPI of leadscrew over the TPI of the job to be cut, or the pitch to be cut on the work piece over the pitch of the leadscrew.
Good video as usual! You can easily make the collet nut without the snap in groove and eccentric. all that's needed is the 30degree internal taper for it to compress the collet properly.Then you can use whatever thread pitch you want for both the nut and chuck. However, after making my own, I do prefer the manufactured nut, mostly on the vertical mill as it prevents the collet from dropping down. To cut the 1.5mm thread on my 9A, I simply substituted a 26 tooth gear for the 20 tooth stud gear which creates a 1.50091mm (16.9231 imperial) pitch thread at position B4. For that length of thread engagement you will not feel or see any difference (.06% error). The gear can be easily made with Delrin, PVC, Nylon etc simply by slotting the teeth with a form tool on the tool post and indexing the spindle.
+martik778 Yup that will work also. Just have no provision for gear cutting here. Have a bunch of change gears though :-)
Seet project..;) I will be making a er32 collet chuck.. What material are you using please for the chuck body
The actual Metric Threading part starts at 8min15. If you don't want to go to the expense of a thread guage you can use a metric M10x1.5 bolt/screw (coarse) as a handy substitute. Another useful shortcut is to press a small piece of paper onto the threads. The dirty lines so impresed can be measured with a ruler. If the threads are too clean to make distinct marks you can rub the paper against the threads with a soft pencil.
Great job . Old Tool Maker JT Hay Fort Worth Texas
Hi, how did you calculate the size of the stock to cut the thread on and how would a novice now how deep to plunge the tool to get the desired Thread Depth? Great video
I really admire all your efforts on the Math side as I'm exactly the same. Only, as I figure out these things, I put them all into an Excel book. I've done a full write up some time ago, of the problem you've set out to solve here so I understand all your efforts. All I need to do is to enter the Pitch required, the gears I have and it tells me what changes are needed to give the Pitch in Metric. I'd be happy to try and pass along what I have as I'm certain you'd find it just as useful. Also, working with so much math and trig, I've found just how surprisingly simple is working on Metric threading with an Imperial lead screw where you CAN disengage the half nuts anytime and move the carriage and turn the chuck and then very quickly return to threading precisely as at the start. This I needed to learn when internal Metric threading to a blank. It turned my hair grey but I'm happy to say I solved it. Great work with what you have shown us here and again my tip is once you solve math problems, keep them on an Excel file and in a book.
Would you happen to know what gears would be needed to hit a 1.25 pitch metric thread for the 9A? I have the 54 and 80 like Halligan said but his list doesn't show the 1.25 pitch which is also pretty common.
@@jerkfaceskater I'll answer fairly quickly but will be happy to keep working through the problem until you have what you want. Very simply, you need your drive train gears to have the ratio of 1(Drivers) : 2 (Driven) (or vice versa)? where you will be using an Imperial 8 TPI Lead screw. In Imperial, these ratios will cut a Thread of 20.32 TPI but this is in fact 1.25mm. IE: 20.32x1.25= 25.4mm = 1 inch. I'll give an imaginary set of gears with using the Transposition gears of 127/100. Stud gear 11. Comp #1 gear 24. Comp #2 gear 84. Screw Gear 77. Disregard the Transposition Gears in the calcs. DRIVERS = Stud(11) x Comp #2(84) = 924. DRIVEN = Comp #1(24) x Screw(77) = 1848. Therefore the RATIO = 1:2. In the quick change gearbox the selectors are at C1 with 'Change Gears' of 60 and 47. Position C1 gives a drive train ratio of 1:2 and gears 60 and 47 act as the 'Transposition Gears' having the same ratio as 127:100. (almost). This ratio is important in the train and as long as its included in gears, it should then be FORGOTTEN. What it does is to change the Lead screw TPI from 8 in Imperial to 3.175 mm. I've probably totally confused you. Best is to study videos of Metric threading with Imperial lathes. That's all I did. Don't disconnect the half nuts but learn the art of zeroing your carriage with your spindle with a dial gauge so that if you accidentally disconnect those nuts, you can in fact find the very beginning spot and be in correct synch to keep threading.
So where he uses the 24 grear i would change to an 84 instead and swap the 80 for the 77.
@@jerkfaceskater Divide each 'Driver' gear by each 'Driven' gear. Multiply as you go. Then multiply by 3.175 which is the Metric pitch of a 8TPI Lead Screw. The first 'Driver' is the Spindle or Stud gear. The last 'Driven' is the Screw gear. Below is just an example of me looking to achieve a carriage advance of 1.25mm on a single 360 deg spindle turn using an Imperial Lead Screw. (11/18) x (63/77) x (100/127) = .3937 x 3.175 = 1.25 Solving what the final ratio needs to be, can be trial and error using any gear combination and you confirm what pitch you'll get by dial gauge measuring how far the carriage will advance (in mm), on one single turn of the spindle. Same procedure even with a 'QuickChange Box' and with 'Change Gears'.
Would you happen to have an 80 and 54 tooth gear i can buy off you or do you have any other ways to make metric threads on this lathe? I was thinking of getting 3d printed gears but i cant find anyone to do them.
Liked your AIRCOMPRESOR
Jan 2022. My suggestion to anyone interested in Metric Threading is to go and buy a handful of metric nuts of all pitches and then just practice cutting those pitches on plastic electrical or garden conduit tubing . Its cheap. It threads easily and you'll see with whatever gears you select, what pitch they are producing. It also allows for endless practice which is important to get comfortable with this different technique before doing a 'real' job.
Having to pull out the cutter has to do with the back lash of the lead screw.... The magic 127 magic conversion to get metric threads from an imperial lathe. The Canon is a great choice, this is the one I use also, happy with the results, just added a wide angle adaptor to make wider shots in the shop (About $20 from Chinese friends).... ;)
+pierre beaudry Yeah I picked it up for the ability to add lenses also. It'd help out when you need those shots of the whole machine.
very nice ...
What size South Bend is yours? Will this combination work on my South Bend 16?
Ok sorry just rewatched yours in imperial, mine has as norm the 20 gear at the top and a 45 on the gearbox this then makes position 1 D 3mm pitch (or 1 to 1 rotation of chuck to lead screw) I'm now messing around with other gear ratios as I have the other issue I want to make a 8TPI thread to screw onto the head stock :)
Will this work for a 13 south bend?
just in case you have not decided on a clearance hole size yet, some suppliers are selling er40 collets to hold up to 30 mm
Hi Greg, that is genius! I have not seen that gearing transposition before and I think you may very well have come up with a novel solution. It would also presumably work in reverse for those of us this side of the pond with metric lathes (bit of a rare breed in the UK) - we can cut imperial screw threads. Cheers. Bob.
+Robert Hawtin It is not novel, just old school math. Greg did a fine job of describing the process. Some people have taken the list of all the gears they have and made a spread sheet of all the possible combinations. Thousands of choices...
1.5 mm pitch it really close to 17 tpi (the pitch is within 0.3 thou), would that be close enough for them to fit? If not, how close would they need to be?
You need to use an intermediate cog wheel with 120 teeth on one wheel and 127 on the same wheel on the same wheel. There are 25.4 mm in an inch. 120/127 convers the imperial lead screw to metric.
I have a 13" south bend and it has a 6 TPI leadscrew. Is there a gear or gearset I can use to get metric pitch out of this lathe ?
Excellent. You made it easy to understand. What marks were you using on your threading dial?
LOL. This makes me think you didn't understand though. He wasn't using the threading dial, but he was keeping the half nut engaged and returned the carriage by reversing the motor. That's why he needed to retract the tool. To prevent cutting the thread on the backside, because of backlash in the gearing. The threading dial can't be used in this setup, because the ratios between the rotations of the leadscrew and those of the spindel are not an integer, but have a very small deviation. Small enough to not matter over short distances, but apparently big enough to matter for picking up the thread at a different position than where you left off when you disengaged.
Dear Mr. Halligan, one thing I did not understand in the video: how to calculate the gears of the banjo if there is a Norton box in the lathe. In the specific case of the 32X1.5 thread whose gear ratio should be 1:4, Do I understand that the motor gear would be (for example) with 20 teeth and the motor gear on the spindle shaft with 80 teeth? But isn't this configuration made for lathes that don't have a Norton (CN) box? How then to direct the cn levers in this situation?
Hey Greg, totally off subject but I'm getting ready to get my hands on a south bend 9 lathe and wanted to do the gear box conversion like you did on one of your videos.. Just wondering if you ever had an issue with using 2 screws to hold the gear box on instead of the 3 it normally takes. Thanks in advance. -Adam
Haven't had an issue with the mounting at all. Only issue I had was that the very end of the replacement lead screw was bent causing it to wobble. I had to turn it true and sleeve it to keep it from wobbling on the extension I made.
Awesome, thanks for the info. Also, If you get a chance Oxotools has a video where he shows how to metric thread on an impearl lathe and still be able to release the half nut. Thought it was a cool little trick. Thanks again! -Adam
can i do this with my model c or do i have to have a quick change box?
Other than eBay, do you know of sources for the 80 and 54 gears?
+Jack Dinan Unfortunately that is most likely your best bet. You can contact Ted with an e-mail latheman2@aol.com and see if he has them. He is a reputable reseller of Southbend parts and I have dealt with him in the past.
Hello. It is good video. i understood about gears 58 and 80, but i did not understand about the gear box position. Did you use 32 and "C"? on the video 46 and "D" or the position of the does not matter? thank you
In the case of a 9" South bend you need the gear train set up shown and the gearbox tumblers set to cut a 32 TPI thread to be able to cut a 1.5 mm thread
Question about the idler gear - is it 80? or i can use any one? I just accidentally bought a 9A south bend lathe as a replacement for my Chinese lathe. thank you
Please sir I have a german lathe an the threat seletion giving problem i need help plz
Hi mate. I always wondered if that can be done, I would have tried but it's not so hard on my lathe, it being metric. I would like to know if you can still use the halve nut in a certain position. Well done mate.
+Marcel Timmers You could, but it's very specific. SB made a metric thread dial with multiple gears. You'd use a certain gear depending on the pitch range. I've only seen it in books and never out in the wild.
Could be worth finding out mate. You might get more and more metric repairs with all the import there is.
Mostly good info especially on the gearing. However the cutting did not have to be so hard. Unless your lathe is one of those that cannot be run in reverse, turn your form tool upside down and cut going away from the chuck. Gives lots of tome to pull back before changing direction.
And how did you derive the 54 and 80 combo from all the possible choices?
+Allan Noah A quick internet search started me on the right path. A lot of people just made a 26 tooth stud gear. Not an option for me. Found that these 2 gears can work. Also had a friend make a spreadsheet to try different combos and see if you can get any closer to be dead on metric threads.
what model lathe is this, I have a southbend 9" with quick change gearbox will this arrangement work on it?
+mcdangdang This is the same lathe.
+Halligan142 thank you, not real good at the lathe yet but working on it.
I just bought a SB 10k to learn on since retirement and came across your video. Great job...very innovative. I would like to do the same to cut metric threads. Are your 54 and 80 tooth gears "change gears" or specific end gears? I guess my question is will change gear work without modification? Thanks again. Brent
They are change gears from a 9" model B/C. Should work with no modifications. Mine are from my lathe. It was a model B when I bought it and I converted it to an A by adding the gear box.
Thanks, you a a great resource for someone getting started!
nice , like to learn
Since my lathe doesn't have reverse, I'm still looking for a way that will let me do this and disengage the half nut. The alternative is to buy a new motor, and wire up a reversing switch, or rig something to turn the chuck backward with a drill or by hand to move the carriage back between passes. (Myford ML-7 lathe)
Just buy a cheap Chinese 3 phase motor & a VFD controller. I just did this upgrade to my drill press & it’s so easy & so much more controllable. You’ll probably find you can reverse that motor though, you can with most AC motors by reversing the connections to the start winding.
hi mate I have made an excel sheet for my Hercus in Australia which is basically a copy of the southbend. I have the 3mm pitch metric lead screw, I can send a copy do you know a way to exchange email without telling the rest of the world :)
You left out one option for that collet nut. Since you're making your own collet Chuck and you can make it any Dimension you want simply turn the metric threads off since they're pretty fine and turn whatever you want back on to the collet nut. Adjust the size of the Chuck that you're making to accommodate that new thread and throw it away. Easy peasy
Making a nut is really difficult. It’s not even the thread. That ring inside is actually a retaining ring. It’s hardened. The nut NEEDS to be hardened. The face taper needs to be extremely accurate. It’s what determines the accuracy of the collet seating. The inside of the nut needs to be plated with something, otherwise the friction when tightening won’t allow you to tighten it enough, and the collets WILL slip. I may have missed something. What alloy are you using for this?
why not use the 127 teeth gear since it will have to anyway mess with the banjo for gear change.
I'm missing something here. Home made ER40 collet chuck, but no metric pitch gage?
Never needed one and never really planned on working with metric threads so it was on the low list of priorities
Hi ! I do threading this way ... without dis-engaging the halfnut AND PULLING back the cutter BEFORE turning into reverse - it works fine ! I do it this way because I don't have a threading dial - and I have to do some fine-thinking to make one OR maybe just engage - I havent found out yet. But my lathe IS a metric lathe with a metric lead screw - I beleave I would have similar problems if I had to cut IMPERIAL threads - but I'll works around this as long as posible !
+Keld Sørensen The thread dial is nothing more than a worm and gear, with the leadscrew playing the part of the worm. So if you can't find one, you could probably make it, but it would involve cutting a gear the same module as the leadscrew and a housing, which of course you would cast from your supply of beer cans :)
Juan Rivero Ha, ha, yeah, I have no need for buying material for casting a housing ... but I need to do some fine-thinking to UNDERSTAND how all this relate to each other ... and I beleave this video has something I can use to get this understanding ... but I need to do this fine-thinking and relate it to what I have noticed earlier in this understanding process.
Model of your lathe?
South bend 9a
Need a CUP of tea after that , 3 teaspoon ?
I'm confused with a certain part of this video! right around 10:01 into the video you say that in the gear train you used to achieve a 1.5mm pitch thread and after the 56 to 44 Tooth gear that inside the gear box you have a 4-tooth gear that goes to a 5-tooth gear. I hope that these figures are reduced to the lowest common denominator or something, like from a 20-tooth gear to a 25-tooth gear. because I have never seen a 4-tooth gear I don't think it's possible. I think the smallest number of teeth possible is 9. But don't get me wrong I still found the video very informative and maybe I missed something? hopefully you can clarify that for me. Here is a 4-tooth gear ( + )
Sorry those are great ratios in the gearbox.
i guess i'm gonna have to watch this whole video because i was under the impression the transposing gears were 47 and 37 tooth I skipped ahead in this video to watch you assemble them you must ....ess i'm gonna have to watch to watch you assemble them you must be doing something totally different here I guess I would have to watch the whole thing
As much as I like my 14-1/2 South Bend I bought a lathe that cuts metric by just moving levers.
I would too if I was doing a ton of it but honestly 90% of things I’m making will have imperial threads and out of the remaining only a small fraction of those metric threads will not be able to be made or will be too expensive to make with a tap and die.
@@Halligan142 100% Greg, I do about 50/50 metric vs inch so I'm reluctantly giving up my South Bend, it has served me well for over 30 years and with a DRO and quick change tool post is still great save the threading dilemma.
Well done on the explanation but if you are serious about threading you might want to make yourself one of the tools in these two links. Copy/paste the following into the youtube search box. Gewindedrehen ohne Rückzugshalter ( www. rb-werkzeuge.de ) Teil1 or threading 2.AVI Either type have advantages over a "normal" tooling, one of which is that you never have to bother with threading dials again. You needn't worry about chucks unscrewing because there is zero load when running in reverse. Just because Tom or Adam don't know of them doesn't mean they should be ignored, they have been around since Victorian times, the tools that is not Tom or Adam. :>)