I love that gear setup!! I think your novel approach of massively changing the gear ratios, then driving the whole thing from the tailstock end of the lead screw is pure genius! ...And thank you for sharing your spreadsheet too. I tried a simpler version of that a while back but couldn't get it to work. Having it automatically solve for all of the ratios in your quick change gear box is an even better idea. A few comments: First, please understand that none of this is intended as personal criticism of you, or to disparage your skills or abilities. None of us are born knowing this stuff, and there are a LOT of overlapping things to learn. I didn't have anyone handy to teach me, so have picked up most of it from watching TH-cam videos - and from breaking lots of cutting tools tools and ruining work pieces when there was still one more thing I didn't know or understand as well as I thought I did. Anyway... Slop: That's a huge amount of slop to be coming from the gear train. Even with your additional gears, adjusting how closely they mesh should allow nearly all of it to be eliminated. I'd guess that a worn out half nut on the lead screw might be causing most of it. It's easy enough to check; just close the half nut, and try to push the cross slide assembly up and down the bed. There shouldn't be any noticeable movement, and even the dial indicator should only show a tiny bit of motion. (I don't remember what the specs say on my Logan.) If the half nut is worn out, lathe.com sells parts for old Logans. They're proud of their stuff though, and you might be able to find one on eBay or elsewhere for a lot less. (They also have parts diagrams that you can download.) Oh, and you might try usimg the dial indicator to see if the lead screw itself can move up and down the bed. It's at least possible that your mod to add a nut to the end of it may have had unintended consequences. (That happens to me all the time! 😖) Aluminum worm gear: You mentioned possibly using aluminum to make your worm gear. Aluminum is a good choice for a lot of stuff, but may not be ideal for that application. Aluminum alloys are pretty soft, and it's kind of a 'gummy' metal. It galls, wears, and binds up really badly when sliding against another metal surface. Lubrication will help some, but not all that much in the mid-to-long term. Brass or bronze are good choices, but both are expensive. Steel or cast iron will work too and are a lot cheaper. Cast iron is even self-lubricating to some degree, due to high levels of carbon graphite in the alloy. Depending on how much of a load you're going to put on it, you may be fine using something like the plastic one you 3D printed. Some plastics are better than others though, and I don't know what kinds your printer can use. You mentioned making a 40° angle tool so you can cut both sides of a metal worm gear in one pass. I admire your creativity in coming up with that. However, trying to cut both sides at once will put an enormous cutting load on the tool. On top of that, having the cutter tool interact with both sides at once is goimg to make it want to bounce around in the channel, chatter like crazy, and ruin the tool and the work piece. "Railroad" steel: Man, I feel your pain on that one! As you discovered when cutting the flange of that pin in your other video, working steel in a hardened state is almost impossible. I'm all for using salvaged materials, and I bought a few pieces of similarly tough "railroad steel" from the scrap yard a few years back. ...Every bit of it is still sitting around my shop too; some with a few scratches from trying to cut a chunk off with a bandsaw. Yes, it was really cheap for "good" steel. But until I get around to annealing some of it, they're just a bunch of really big paperweights. LOL, one of the pieces I got is a pin that looks a lot like that one. It's so hard that my very best file won't even scratch it! Factoring in the cost of special tooling & processes to work it, it winds up being some pretty expensive scrap metal! I'm looking forward to seeing more machining videos from you. Cheers!
Yeah, I just watched the slow-mo part again, at around the 6:35 - 6:45 time stamp. When the lead screw turns that much before the carriage starts moving, the half nut is worn out. (There's a small chance that the lead screw could be worn instead, but the half nut wears a lot faster and is designed to be replaced as a normal wear item. ...It's bronze, so is much softer than the hardened steel lead screw.)
TH-cam is so weird. It notified me of you comment on my other video but not of this one. I only saw it by chance. _"I didn't have anyone handy to teach me, so have picked up most of it from watching TH-cam videos"_ Same here, and hobby-machinist.com _"That's a huge amount of slop to be coming from the gear train... I'd guess that a worn out half nut on the lead screw might be causing most of it."_ Yes this lathe is "clapped out" as they say. It was probably several people's starter lathe before it was mine and I've just about outgrown it. Yeah the half nut is worn, the cross slide nut has 50 thou of slop, there's several thou dip in the ways by the headstock, etc. etc. I think after my big CNC lathe is running, this will serve another fulfilling life as a cutter grinder. It has been fun to learn how to squeeze ever more use out of something that any rational person would consider useless. _"Aluminum worm gear: ... you may be fine using something like the plastic one you 3D printed."_ That's the plan, aluminum worm driving a 3D printed gear. The plastic in the video is PETG and that will probably work but if not I just got a new printer that can do polycarbonate, nylon, abs, lots of options. _"However, trying to cut both sides at once will put an enormous cutting load on the tool. On top of that, having the cutter tool interact with both sides at once is goimg to make it want to bounce around in the channel, chatter like crazy, and ruin the tool and the work piece."_ Yeah you're probably right. So, new plan; 40 degree too is just shy of the width of the valley and it only is used to cut one side at a time. _"Railroad steel ... until I get around to annealing some of it, they're just a bunch of really big paperweights. "_ It can be annealed, and afterwards it machines beautifully. I kinda skipped talking about that in the video because the idea in the back of my head was about thread *_grinding_* in the home shop which is the direction I see this going. Ball screws, lead screws, titanium space shuttle bolts, whatever. It's usually not a great idea to cut threads and then harden; dimensions can change. Harden and then thread grind, is the way the big boys do it as far as I know.
Douglas, the 'cross slide assembly' is referred to as the Saddle, you mentioned when talking about half nut wear....your comments are great....laughing about the railroad steel, I remember drying to smooth out a one inch thick slice of a steam engine tire using a belt sander... I went through a lot of belts I tell ya...
Charles, you may consider using Nylatron for your worm gear, they use it for the sheaves on very large cranes and other pulley blocks..... note, this is not Nylon, but Nylatron...... I worked for a company that made rigging for theaters and we made blocks with either cast iron or Nylatron....depending on the customers wishes.... they were 10 inch diameter and up to 12 inches or more wide.... they had grooves for 6,8,10 or more 1/4 inch aircraft cable some only had one groove for the far end of the system.... they were called counterweight rigging......very common in theatrical theaters....for raising scenery, curtains , you name it....
@@charlesstaton8104 my dog who loved Frisbees ,but they only last 30 minutes before they were chewed to pieces, could never destroy the Nylatron one I made for him.....never even dented the the thing, Merry Christmas....Paul
Very nice! I’m building a thread mill attachment and you’ve given me inspiration!
Nice work man thanks for sharing
I love that gear setup!! I think your novel approach of massively changing the gear ratios, then driving the whole thing from the tailstock end of the lead screw is pure genius!
...And thank you for sharing your spreadsheet too. I tried a simpler version of that a while back but couldn't get it to work. Having it automatically solve for all of the ratios in your quick change gear box is an even better idea.
A few comments:
First, please understand that none of this is intended as personal criticism of you, or to disparage your skills or abilities. None of us are born knowing this stuff, and there are a LOT of overlapping things to learn. I didn't have anyone handy to teach me, so have picked up most of it from watching TH-cam videos - and from breaking lots of cutting tools tools and ruining work pieces when there was still one more thing I didn't know or understand as well as I thought I did.
Anyway...
Slop:
That's a huge amount of slop to be coming from the gear train. Even with your additional gears, adjusting how closely they mesh should allow nearly all of it to be eliminated. I'd guess that a worn out half nut on the lead screw might be causing most of it.
It's easy enough to check; just close the half nut, and try to push the cross slide assembly up and down the bed. There shouldn't be any noticeable movement, and even the dial indicator should only show a tiny bit of motion. (I don't remember what the specs say on my Logan.)
If the half nut is worn out, lathe.com sells parts for old Logans. They're proud of their stuff though, and you might be able to find one on eBay or elsewhere for a lot less. (They also have parts diagrams that you can download.)
Oh, and you might try usimg the dial indicator to see if the lead screw itself can move up and down the bed. It's at least possible that your mod to add a nut to the end of it may have had unintended consequences. (That happens to me all the time! 😖)
Aluminum worm gear:
You mentioned possibly using aluminum to make your worm gear. Aluminum is a good choice for a lot of stuff, but may not be ideal for that application. Aluminum alloys are pretty soft, and it's kind of a 'gummy' metal. It galls, wears, and binds up really badly when sliding against another metal surface. Lubrication will help some, but not all that much in the mid-to-long term. Brass or bronze are good choices, but both are expensive. Steel or cast iron will work too and are a lot cheaper. Cast iron is even self-lubricating to some degree, due to high levels of carbon graphite in the alloy.
Depending on how much of a load you're going to put on it, you may be fine using something like the plastic one you 3D printed. Some plastics are better than others though, and I don't know what kinds your printer can use.
You mentioned making a 40° angle tool so you can cut both sides of a metal worm gear in one pass.
I admire your creativity in coming up with that. However, trying to cut both sides at once will put an enormous cutting load on the tool. On top of that, having the cutter tool interact with both sides at once is goimg to make it want to bounce around in the channel, chatter like crazy, and ruin the tool and the work piece.
"Railroad" steel:
Man, I feel your pain on that one! As you discovered when cutting the flange of that pin in your other video, working steel in a hardened state is almost impossible. I'm all for using salvaged materials, and I bought a few pieces of similarly tough "railroad steel" from the scrap yard a few years back. ...Every bit of it is still sitting around my shop too; some with a few scratches from trying to cut a chunk off with a bandsaw. Yes, it was really cheap for "good" steel. But until I get around to annealing some of it, they're just a bunch of really big paperweights.
LOL, one of the pieces I got is a pin that looks a lot like that one. It's so hard that my very best file won't even scratch it! Factoring in the cost of special tooling & processes to work it, it winds up being some pretty expensive scrap metal!
I'm looking forward to seeing more machining videos from you. Cheers!
Yeah, I just watched the slow-mo part again, at around the 6:35 - 6:45 time stamp. When the lead screw turns that much before the carriage starts moving, the half nut is worn out. (There's a small chance that the lead screw could be worn instead, but the half nut wears a lot faster and is designed to be replaced as a normal wear item. ...It's bronze, so is much softer than the hardened steel lead screw.)
TH-cam is so weird. It notified me of you comment on my other video but not of this one. I only saw it by chance.
_"I didn't have anyone handy to teach me, so have picked up most of it from watching TH-cam videos"_
Same here, and hobby-machinist.com
_"That's a huge amount of slop to be coming from the gear train... I'd guess that a worn out half nut on the lead screw might be causing most of it."_
Yes this lathe is "clapped out" as they say. It was probably several people's starter lathe before it was mine and I've just about outgrown it. Yeah the half nut is worn, the cross slide nut has 50 thou of slop, there's several thou dip in the ways by the headstock, etc. etc. I think after my big CNC lathe is running, this will serve another fulfilling life as a cutter grinder. It has been fun to learn how to squeeze ever more use out of something that any rational person would consider useless.
_"Aluminum worm gear: ... you may be fine using something like the plastic one you 3D printed."_
That's the plan, aluminum worm driving a 3D printed gear. The plastic in the video is PETG and that will probably work but if not I just got a new printer that can do polycarbonate, nylon, abs, lots of options.
_"However, trying to cut both sides at once will put an enormous cutting load on the tool. On top of that, having the cutter tool interact with both sides at once is goimg to make it want to bounce around in the channel, chatter like crazy, and ruin the tool and the work piece."_
Yeah you're probably right. So, new plan; 40 degree too is just shy of the width of the valley and it only is used to cut one side at a time.
_"Railroad steel ... until I get around to annealing some of it, they're just a bunch of really big paperweights. "_
It can be annealed, and afterwards it machines beautifully. I kinda skipped talking about that in the video because the idea in the back of my head was about thread *_grinding_* in the home shop which is the direction I see this going. Ball screws, lead screws, titanium space shuttle bolts, whatever. It's usually not a great idea to cut threads and then harden; dimensions can change. Harden and then thread grind, is the way the big boys do it as far as I know.
great comments Douglas
Douglas, the 'cross slide assembly' is referred to as the Saddle, you mentioned when talking about half nut wear....your comments are great....laughing about the railroad steel, I remember drying to smooth out a one inch thick slice of a steam engine tire using a belt sander...
I went through a lot of belts I tell ya...
absolutely brilliant.
Charles, you may consider using Nylatron for your worm gear,
they use it for the sheaves on very large cranes and
other pulley blocks.....
note, this is not Nylon, but Nylatron......
I worked for a company that made rigging for theaters
and we made blocks with either cast iron or Nylatron....depending
on the customers wishes....
they were 10 inch diameter and up to 12 inches or more wide....
they had grooves for 6,8,10 or more 1/4 inch aircraft cable
some only had one groove for the far end of the system....
they were called counterweight rigging......very common in
theatrical theaters....for raising scenery, curtains , you name it....
Thanks! I'll check it out
@@charlesstaton8104 my dog who loved Frisbees ,but they only last 30 minutes before they were chewed to pieces, could never destroy the Nylatron one I made for him.....never even dented the the thing, Merry Christmas....Paul