richard wrote: || I went and had a look at a lathe today, with the view to replacing || both || my lathes with one. looked nice'n'heavy.. || I didn't check the leadscrew but the crossslide was marked in metric, || and no thrteading dial fitted. it had listing for mod, metric, || imperial || all from the box. 19tpi but no 26, i just no if i get it i am going || to get asked to do loads of cycle bits.. || || || || || anyway the question, what's the technique for threading leaving the || half nuts engaged? || || -- || richard
You will have to withdraw the tool in some way...... if you mean screw cutting without dis-engaging the leadscrew nut then......
when you reach the end of the thred you are cutting (works best iff cutting into an undercut but with care it can be done without) stop the machine, move the topslide one whole turn out..... away from the job (one whole turn so you remember where you are) then reverse the spindle so the tool goes to the start of the thread, and then move the crosslide back to its original possition plus the depth of cut you want to take.
I use this method all the time at work, cutting metric threads on imperial lathes and it works every time