# Metric gears for 1920 (that's the year) lathe



## AGCB97 (Feb 25, 2021)

I actually started this over 4 years ago but other stuff got in the way. I've wished I could make metric threads several times in the last few months so figured before another time came and went I would get this done for the next time.

My lathe has a unique quick change gear set up. There is a combination of 3 case gears (1-2, 2-1, 1-4, 4-1 and even) and there is a disk gear which is really 8 gears on a rotating disk. both are seen here.




So what I did was make a special case gear to change the ratio of the feed rod to very closely match the 4 most common metric threads.



















All I need to do is put a band around the edge to keep wandering fingers out.

Thanks
Aaron


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## benmychree (Feb 25, 2021)

Very clever solution for a difficult situation.


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## brino (Feb 25, 2021)

Brilliant Aaron!

Thanks for sharing this.

-brino


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## AGCB97 (Feb 28, 2021)

As I tried to cut a few threads I found as others have that picking up the thread on the second and following passes is a problem. I read  Martin Cleeve's book "Screwcutting in the Lathe" and after nearly 10 pages of his discussion on this he basically said "leave the half nuts engaged and move the carriage with the spindle in reverse". So I tried that but the main problem is my lathe coasts to a stop very slowly (while the tool is headed for something not good)! Using back gear to slow things down just adds greatly to the time spent. Also, in order to run it in reverse, one has to pull a long lever rod on the motor and then hit the power switch at just the right time. I've never seen one like this and although it does work, it is not convenient! The drum switch does nothing in reverse.




On this or another site, someone had mentioned that a 3 phase motor and VFD with all of its features would make it much better. So I ran out to the motor stash to see if there was a 3-phase motor of suitable size and configuration. Much to my delight I found a brand new 1 ½ HP TEFC    3-phase motor.  As close as I can see it even has the correct shaft size but if not, a 3” pulley is no problem.




The single phase 220 volt motor that is on it now is hardwired in a box right behind the lathe so power for the VFD will be easy. I'll put a 2 pole toggle switch to control power to the VFD with a night light bulb for a 'power on' indicator all within easy reach right in front of the operator.

I was hoping to get another VFD just like the one I put on the Powermatic drill press a few years ago so went directly to Amazon where it was found but at half again the price of the last one I bought. Initially disappointed about the money I searched on EBAY, where most were at same price and not too many sellers. Then stumbled onto a seller that had one on sale with 14 hours remaining till sale end and at less than I paid 3 years ago. Pushed the button and it's on the way. I looked at that same site this morning and it had gone up by $20. It's a XSY-AT1, 2 HP unit with all controls like start/stop, FWD/REV, and speed control knob built into the panel so no additional wiring to do.

I'm thinking that the lathe can be run at a reasonable speed as I'm used to threading with and then as it nears the end of the cut, slow it down and then let the braking stop it in comfort.  Then back out the tool and reverse, again at a good clip but with comfort just before the stop.

Can't wait to hook it up and have another try.

Thanks
Aaron


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## Winegrower (Feb 28, 2021)

Really clever, because back in 1920 there wasn't any metric.    Was there?


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## mattthemuppet2 (Feb 28, 2021)

that's a really interesting QCGB - I'm guessing you rotate the disk to bring one of the 8 gears into mesh? I like the 47/37 interconversion gear set up, very neat solution. Neat to have a spare 3ph motor in the "stash" too 

For metric threading you *can* open the halfnuts, as long as you can stop the spindle before a whole revolution of the threading dial. You can then back the tool out, reverse the spindle (by hand if necessary) until the point you disengaged the half nuts comes back around, then close the half nuts and continue reversing the carriage back to the start of the cut. A little more faffing around, but it makes it easier to thread to a shoulder.


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## AGCB97 (Mar 7, 2021)

Yesterday I got the 3-phase motor installation done with VFD control.




Also put the safety guard on the gear set.




Also looked into the endplay issue with the lead screw. Whatever type of thrust control devise was on the right end, is no longer, but found that installing a thrust roller bearing will be easy, so one is on the way for next week.

Very good day yesterday!

Aaron


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## jwmelvin (Mar 7, 2021)

The cover looks great. Nice progress; having a thrust bearing will be good.


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## AGCB97 (Oct 22, 2021)

Yesterday I cut a 25 x 1.0 mm thread on a shaft for the 'tool & cutter grinder' project. Everything worked great. I'm so happy!  
Aaron


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