Single point threading speed for aluminum

[o0norton0o]

No gearbox! it's a gear change lathe,.. meaning you take the cover off the back of the headstock and assemble a given gear set to change the ratio of main shaft/chuck revolutions to lead screw revolutions. Would I like a lathe with a gearbox?... A: Yes, but I don't have the room for a bigger lathe really atm.

The real twilight zone part is that I have a labeled diagram with all the assembled gears I used to cut the first batch correctly last summer, and those same gears don't produce the correct thread pitch now..... I must have made changes after I made the diagram and didn't note the changes, so the labeled diagram is wrong and the pitch is wrong because I plugged in the wrong lead screw pitch in the formula... which makes sense. God only knows how my parts came out correctly last time, but I must have figured it out then,... so I will figure it out again....

I have somewhere to go tonight and tomorrow is a religious holiday (college basketball) so I will get back to it within a few days and post the result.

 

[WobblyHand]

No worries. My mini-lathe is like that. My 10x22 has a gear box, but it really is for helping out with feeds and adjusting ratios of 2:1, 1:1 and 1:2. Otherwise I had to change gears, just like my mini-lathe.

On my 10x22, I designed and made an electronic lead screw for it, so I don't have to change any gears for either imperial or metric threads. But if I thread metric using my imperial lead screw, I have to leave the half nuts engaged to get good metric threads.

Hoping the following is encouraging. You should be able to get to this point (and beyond) once you sort out your threading issues. Did this barrel nut in steel on my 10x22. 1/2"-20 external threads, think it was M8 internal threads. Did the internal threads using a Micro100 left handed threading tool going away from the chuck. The M8 threads on to an airgun barrel to tension it.

On the lathe, just finished the external threads. No picture of doing the internal threads, sorry. Second picture is on the mill, just before drilling the shroud vents.

3rd picture: Finished barrel nut. 4th picture: Air pistol barrel, barrel nut, spanner wrench and moderator I made for the airgun. Only trouble I had was not making the internal thread gutter deep enough. Had trouble screwing the barrel all the way in. Had to put it back in the lathe and just slightly deepen the groove. Kind of tough, since it is blind work. Thank goodness it came out ok, doing that small internal thread single pointing was not that easy for me.

 

[o0norton0o]

Just to be certain, here's an image of my 2mm thread gauge held up against my lead screw to compare the threads. 2mm Right?????

 

[WobblyHand]

Sure looks like 2.0mm.

 

[Just for fun]

Frank,

Here is a program that may help you determine the correct gear ratio needed for your project.

Ride The Gear Train free software by Evan Lewis

 

[o0norton0o]

Thanks Tim. I watched the Creighton vs Seton Hall overtime barn burner, then went out to the shop to play with the gear changes for many hours. The ride the gear train format takes some getting used to using, but looks better suited to my calculation than the calculator that I was using because this one lets me chose my stud gear size. I wondered how the other calculator knew what my stud gear size was since the formula had no input for that.... Maybe that was half my problem.

I am making progress, and burning up lots of scrap fooling around with different cutting speeds, depth of cut, and lubricants. I have found a combination to cut 20 tpi on my metric lathe, so that part is resolved.

Thanks for all the help!

 

[Just for fun]

Good deal on getting the 20 tpi figured out. I did a little project last night cutting 5mm away from the chuck. It was a small project but time consuming as I had to make other (smaller) tools to get it done.

The one thing I learned is to take really small cuts. The other thing and I'm not sure exactly how important it is, but it seems important. When leaving the half nut engaged when you back up to the starting point, I go a little further and then take up the backlash getting to the exact point where I want to start.