sub threading lh?

[hacdlux]

tsugami ss32 on the sub side matl 316 ss full anneal

ok so im single pointing a 4-40 3b that goes into a cross hole

this cross hole is a gd&t mine field including a 2 micron roundness callout

it was suggestes by the customer that i single point the thread from bottom out, so i mounted my tool pointing x- and went z- to z+ rh tool

is this going to make a lh thread or are my eyes playing tricks on me

M01
(TOOL - 32 OFFSET - 32)
(ID THREAD - MIN. .08 DIA. )
G28 U0.
G0 T3232
G97 S200 M104 G0 X-.08 Z.25
X.-.08
Z-.150
G76 P010029 Q0. R0.
G76 X-.112 Z.100. P1360 Q520 R0. F.025
G0 Z.25
T00
G28 U0. M05
M01


im thinking of changing to standard threading and the using the threading bar to bore and back chamfer the threads

cycle time is no object ive got 6 minutes left before the main finishes its ops
i am however out of tool positions without having to use the back of my main slide

[SirDenisNayland]

the bar facing x- does not matter, the cutting edge is still the same and the spindle must rotate in the same direction in order for cutting to occur irregardless of whether the tool is upside down or not.

With a right hand internal threading bar you will perform a right hand thread going from z0 to z+ (thread end) and a left hand thread going from z+ to z0

test it for yourself, take a screw with a right hand thread and hold it against an insert. Rotate it in the cutting direction and watch which way it moves in "z"
By feeding z in the opposite direction with this same direction of rotation we'll form a thread in the opposite direction.

I have a situation where I have a fairly long thread and I do not have enough guide bushing land. I flip my sp threading tool backwards and reset the core, giving me +.375~ more room to work with. I have to reverse the spindle, but since I also thread it backwards, going from z+ to z- I still create my right hand thread.

I went through this mind game before trying to create an OD thread on the sub spindle where all you have available for use are ID threading bars. Took me a while to wrap the relation around my head. One thing that makes it easy is ER = IL and IR = EL. So for my external right hand thread I use an internal left hand threading bar. This goes for inserts too. Cant find an IL? an ER will work. I know though that some manufacturers set their geometries differently for external vs internal threads.. but that is another story, and a nit picky one if you ask me. They work fine in my experience.

Confusing at first, but its really simple once you get your head around it.

[hacdlux]

yep its a lefty then,

to make the rh thread i would need a lh tool

but the cool thing is i wont have to reset the tools just flip the z moves

im just going to use the bar to debur the threads

[SirDenisNayland]

Yep, its a trick I use all the time :bigthumb:

The reason you don't really think about threading in reverse is because not often is it necessary or even possible. I could have made my rh od thread with a rh id bar but there was a shoulder, meaning I would have zero lead.. no good.