Thread dial question!

[Larry$]

Thread Dial Indicator

That is an impressive solution.
Finally I find that something Imperial has an advantage.
With an 8TPI lead screw and my gear box I can run most Imperial threads by engaging the half nuts at any of the 8 marks. There are some pitches that have to use only one mark.

 

[Suzuki4evr]

He's referring to the gears on his thread dial. A METRIC thread dial has various gears that allow for spindle/leadscrew syncing so that they can be cut by releasing the half-nut, just like Imperial threads. His chart shows gears of 11, 13, 14 and 15 teeth which are changed depending on the pitch that you want to cut. He says that he only received the 15 tooth gear, which limits him to the pitches that he can cut using the half-nut release method (see chart in post #1).

A METRIC leadscrew can cut both metric and Imperial threads, just as an Imperial leadscrew can cut both Imperial and metric threads IF you have the correct gearing in the HEAD of the lathe. Regardless of the leadscrew, a metric thread requires a special thread dial (which he has) to be able to use the half-nut method of cutting the threads.

This is true. With my metric lathe with a 12mm pitch leadscrew,you can cut metric and imperial threads,BUT you can only do the metric spectrum using the thread dial indicator with the appropriate gear on the TDI on the leadscrew for the appropriate threads,but for the imperial threads,you need to have the halfnut engaged until the thread is done. I have tried with different tooth gears for the TDI, to do the imperial threads disengaging the halfnut and re-engaging again,but it will not work. Unless someone can prove this wrong?