Help Metric LH thread

[lilyies]

Gday everyone
I am cutting a LH metric lead screw and want to confirm what angle to set my compond slide.
Do I set it to the left or right also for the internal thread on the nut is the compound slide
set to the left or right. thanks Tony

[Mayhem]

You angle your crossslide toward the direction of cut.  So if you are turning from left to right (i.e. moving the carriage toward your tailstock):



The angle depends upon the thread - is it an ACME thread?  If so, the angel is 14.5°

[chucketn]

Mayhem, what is the source for the pic you posted? I ask, because I saved it to my threading reference notes. Do you have the corresponding picture for right hand threading? Would be nice to have for reference , also.

Chuck

[Sunset Machine]

That setup will hit the chuck in a lot of cases. You can also go at it from the backside with the compound, otherwise as pictured. It'll get the handle out of the line of fire.

[Mayhem]

(09-13-2015, 06:02 AM)chucketn Wrote: Mayhem, what is the source for the pic you posted? I ask, because I saved it to my threading reference notes. Do you have the corresponding picture for right hand threading? Would be nice to have for reference , also.

Chuck

I simply did a Google image search.

[EdK]

You'll need to measure the angle. If it's an acme thread then it would be 29°, compound set to 14.5°. If it's a trapezoidal thread then it would be 30°, compound set to 15°.

Ed

[ieezitin]

Tony.

The only difference in cutting a LH thread is the direction of travel which is clearly shown in Myhems sketch.

The tool bit has been ground on both sides so it will be the opposite side that takes the cut apposed to RH thread cutting.

The compound will still be set the same for what ever angle of thread you're cutting.

Hope this helps.

Anthony.

[Highpower]

(09-13-2015, 02:24 AM)lilyies Wrote: Gday everyone
I am cutting a LH metric lead screw and want to confirm what angle to set my compond slide.
Do I set it to the left or right also for the internal thread on the nut is the compound slide
set to the left or right. thanks Tony

I set my compound in the same way used for an external RH thread. (Swung to the right.) The difference for an internal LH thread is that you would feed OUT on the compound instead of IN, to make your cuts on the leading edge of your threading tool. Carriage moving left to right of course...