Threading attachment

[brino]

Hey Richard,

The threading dial normally mounts to the right end of the carriage and has a spur gear that engages with the lead screw.
On the same shaft as that gear, but on the top of the shaft is a dial with numbers, often the numbers 1 to 4 with little ticks at the halves as well.
The purpose is to give you a visual indication of the synchronization between the spindle and the carriage.

For certain thread pitches and lead-screw pitches, there are rules about when to engage the half-nuts (any line for some pitches, any even line for other pitches, except for February that has only 28, yadda, yadda, yadda....) I just use the same number for any given thread....so I don't need to remember the rules.....but I hafta wait for my lucky number to come around.....

However, for cutting metric thread on a lathe with an imperial lead-screw (or vice-versa) you cannot dis-engage the half nuts for the duration of the threads.

Since the gear must engage with the lead-screw, you should NOT need to change it based on the thread you're cutting.
The various numbers and rules should account for all threads that the lathe cuts (with the supplied gears).

Sometimes you can find original threading dials on ebay, or you might be able to find a 3D-printed alternative....but you'd need to find one for that exact lathe and lead-screw....

-brino

 

[Richard Beitzel]

Thank you for the information

Sent from my moto g(7) power using Tapatalk

 

[francist]

It’s a TOS Trencin SN40 lathe, I believe. Manuals can be had, and I think there’s an on-line one at scribd. I think some lathes had different threading dial gears so you could actually thread metric or imperial using the dial, I think. Or maybe that was if you had the choice of metric or imperial lead screw as well, can’t remember.

-f

 

[francist]

Did the disks look something like this?

This a a screen shot from the TOS SN 40 manual, and I think we’re looking at a section drawing of the threading dial and change discs. I’m not quite sure how this worked, suffice to say the machine is extremely capable. Eastern Bloc made, TOS-Sigma hailing from Czechoslovakia and with considerable history. There’s another manual on line that gives more description of how to execute various processes, that might be the most helpful one. Both at scribd.com

-frank