in my last uh video thread cutting on the lathe part 4 I touched up on the subject of uh the thread cut or the threading dial and what it what it is and what it's used for well since my uh my hardinge didn't doesn't have a Threading dial I I borrowed this one from my dad's Atlas and attempted to explain how it worked but uh I don't know about you but Theory kind of bores me and I think it does you you guys too cuz I'm sure I I noticed some some eyes fogging over and some thousand yard stairs even over the Internet so I thought I'd uh revisit this subject and put the threading dial back on my dad's lathe where it belongs and give you a little practical demonstration of of how it works I know it's it's easy to look up on a chart and say and figure out which of these marks you have to engage on for whatever thread thread you're cutting but I find it easy to remember how remember things like that if I know the why behind it so let me let me attempt to demonstrate the why behind the threading dial and what you know the mystery of what Mark you can engage on and what marks you can't all right if you notice that when we move the carriage this threading dial rotates okay what it's doing is it's it's telling us where our Carriage is relative to the to the lead screw and the reason it's doing that is is so we can know exactly where to engage our our half nuts so that the threading tool will always go back in the same position on the thread we're cutting we don't have to worry about cutting a thread halfway between or some some ridiculous thing like that and ruining our thread so let me let me give a little demo on on on how this works if if we line up with a number one okay line the number one mark up with the with the indicator mark on the dial we'll put a little Mark on this piece of masking type I have stuck on my dad's La here all right now if we if we rotate if we move the carriage down so the dial rotates half of half of uh halfway around to the two put another Mark okay this was one and this is two if we measure those two marks you can see they're one inch apart all right so the distance between numbered marks is 1 in some dials have uh two number marks like this one some dials have four matter of fact a lot of them have four um right in this case since we only have two if we go all the way around put another Mark you can see the the total distance we travel is 2 in for one revolution of the dial uh if it had four numbered marks that this would be 4 in okay one revolution of the dial would be 4 in the important thing is to see that uh numbered marks on the dial the distance between numbered marks is one inch and why is that important well if we're cutting an even number of threads or an odd number of threads any pitch whether it's a 20 or a 13 or a 12 as long as it's a a whole numbered um as long as the threads have a whole number on them you not fractional threads we can engage our half nut or our dial any on any one inch increment or any numbered dial or any unnumbered dial if we want to do it that way I I prefer to stick with the with the number dials it's easy to keep track of now on uh even number of threads we have a little bit of an option okay even number of threads are divisible by two the 12 pitch for instance divide by two we get six so we can do the same thing on our dial here we can we can engage halfway between the numbered lines on one of these un unnumbered ones here and it'll still work it'll work fine okay so that gives us a lot more opportunities to engage our dial we don't have to wait around for the the right number to come up an even number of threads you can engage on any numbered division or any num unnumbered Division if we're cutting an odd number of threads we can't do that because odd numbers are not divisible by two uh 13 threads per inch can't divide it by two and get a whole number you can get you can divide it by two but you'll get six and a half all right so that means if we engage on a division between the numbered lines we're going to put a thread right on top of the thread we we cut the first time and totally ruin it okay then there's always the uh the odd or the fractional number of threads some pipe threads for instance like 1 in a 1inch pipe thread is 11 and a half threads per inch well we can't we can't engage on a 1 in increment for a for an 11 and 1/2 pitch thread because you can't engage on a half if we if we do we'll put a thread right on top of our old one 11 and 1/2 it's not a whole number so we have to go we can only GA engage on 11 and 1 12 thread every 2 in okay two * 11 a half is 23 okay so that's that's a pain pain in about to to machine a a half pitch thread because you can only engage your thread dial every full Revolution so it's a lot of waiting around all right so I have a setup here to to demonstrate the the right and wrong way to use a thread dial um I have the the 1in 12 thread that we cut in the last video mounted in the Chuck and I'm I'm getting ready to to make a nut to fit this thread so I have a an internal threading tool made up on a boring bar and I've got this thing pointed or I got it lined up with the thread just so you can see what happens when you engage on the wrong line on the thread dial all right I also got my little paper trick to backlit paper trick so you can see what's going on a little easier so let's turn this thing on and see what happens all right you can see the thread dial going around and now we're cutting an even number of threads that means I can engage the half nut on any numbered or any unnumbered mark on the dial let's try the two here all right going to let this thing go over the get over the thread and then I'm going to shut the spindle off and let it coose to a stop leaving the Half nut engaged okay now if we back our tool out until it goes in starts cutting in or going into the thread you can see it's perfectly aligned with the thread all right all right let's try it again that was that was on the two let's try engaging it on a numbered division remember I said an even you can do it on any numbered or unnumbered division whoops I missed that one let's try it the next time around miss that one too hard doing my hammer in one hand and a left hand on the half cut all right so let's shut the spindle off let it close to a stop okay now you can see that the thread the cutting tool goes right into the thread perfectly lined okay just like before all right now here's what happens if you do it wrong let's go back out here start it up okay let's say uh we engage uh we miss our Mark by a little bit like about here okay Half Nuts engaged little bits heading for the thread let's see what happens shut the spindle off leave the half nut engaged now look at how the the tool lines up with the thread okay we're in big trouble okay what we've got is we' cut a thread right on top of the original thread we cut that would ruin your day okay so don't do that all right hope you hopefully you picked up a few pointers with this and hopefully you understand the concept behind the thread dial that's all I have for the moment