It’s the same. Consider this. Example. Drive is 10 toothIdler is 5 tooth Driven is 20 tooth If drive turns 1 turn, it ‘outputs’ 10 teeth into idler. The idler turns 2 times and ‘outputs’ 10 teeth. The driven intakes 10 teeth and turns 1/2 turn in the same direction as drive. Take the idler out and direct mesh, drive one turn, driven 1/2 turn but in opposite direction. So no matter the arrangement, the idler only ‘output’ the number of teeth the drive ‘inputs’ into it. Hth,Dave
You don't need different gears to cut a left hand thread. If you push the thread (cutting toward the head stock) you get a right hand thread, if you pull the thread ( cutting away from head stock) you get a left hand thread.
good topic.. and its the same on my g4000 , i dont even bother , i just buy the chinese dies on amazon , especially for small size left hand threads.
Quote from: JPSAXNC on February 04, 2023, 04:39:15 PMYou don't need different gears to cut a left hand thread. If you push the thread (cutting toward the head stock) you get a right hand thread, if you pull the thread ( cutting away from head stock) you get a left hand thread.At least on a Grizzly G0602 type lathe without an idler, this is not true. As a matter of fact you will cut a right hand thread if you put the lathe in reverse and cut outward. I did that to cut the threads on a cast iron back plate for a set tru ER40 chuck. I used a left handed tool, turned the lathe in reverse, and I made a perfect 8 TPI right hand thread, that exactly matched my spindle thread. To cut a LH thread, you need an idler gear to change the rotation of the lead screw relative to the spindle. If you reverse rotate a RH screw, it doesn't turn into a LH screw. If you call Grizzly and ask them if the stock G0602 will cut a left hand thread, they will tell you it is incapable of cutting left hand threads. You need an idler gear.That being said, instead of installing an idler, I designed an electronic lead screw of my own. It can cut any thread I like, metric or imperial at the touch of a touch panel display. No changing gears at all. Wrote all the code myself. This thing works great. The first picture is of the electronics being assembled. It has a 3.2" touch panel display. It also integrates DRO's if you have them. Second picture is it fully installed on the lathe and cutting a 5/8-11 thread, just because I could. (If you zoom in on the picture, you can see 11 TPI on the display.) If I wanted to, I could program it to cut a unique thread, oh, like 3*pi TPI, or 1.89mm, if needed. By touching the Right Hand button, I can toggle it to Left Hand, or toggle it back to Right Hand. Pretty convenient. (But not on the fly! Only when the spindle is stopped, do I allow changing thread or feed pitch, or handedness.) Even managed a 4 TPI thread as a test, and 100 TPI while I was testing this, along with the equivalents in metric. Feeds are selectable by touching the display as well.I made that cast iron back plate threading outwards and in reverse, as I described in the first paragraph. I machined the back plate it before making the ELS. Started out with a raw chunk of cast iron. The back plate locks up to the spindle beautifully. No run out that I can measure, since I machined it on the spindle. The ER40 Chuck has 0.0002" TIR mounted on the back plate. I could probably do better, but chasing the last few tenths is hard.