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- Sep 22, 2010
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TO THREAD WITHOUT A THREAD DIAL by Jim B.
Start by setting up as you normally would, you can use back gear but that's a matter of how fast you are and how course the thread is.
Your part should have a thread relief.
Set the compound at 29 degrees (Standard 60 degree Vee thread, US or Metric)
Zero the compound, taking out the play in the in direction. (make sure you have enough travel in the "in" direction.)
Bring your tool in a just touch the work, zero the cross slide.
Back the cross feed out 1 full turn.
Back the carriage about ¼" past the start of the work.
Return the cross slide to zero. Advance 0.005 on the compound.
(NO THREAD DIAL)
Engage the half-nuts. NEVER DISSENGAGE THEM AGAIN UNTIL THE THREAD IS FINISHED!!!!!!!!!
When the tool enters the relief, shut the motor off. In back gear the spindle will stop within ¼ turn.
Back out the cross feed one full turn.
REVERSE THE MOTOR and back the carriage under power to a point ¼" past the start of the threads.
Shut the motor off.
Return the cross slide to zero. Move the compound in another 0.005. (0.010 total at this point)
Start the motor in forward.
When the tool enters the relief shut the motor off
Back the cross slide out one full turn.
Reverse the motor and back the carriage out ¼" past the start of the threads.
Every third pass is a spring pass.
Depending on the thread pitch after 0.010 to 0.015 reduce the depth of cut to 0.0025.
After about 0.040 to 0.060 reduce the depth of cut to 0.001.
When you are within 0.003 of the calculated depth start testing for fit on a "standard" nut!
When the nut starts to feel like it might be there, tight but does not screw in all the way. Start taking 0.001 at a time on your cross feed.
You can calculate the double depth in the following way.
(32/TPI)*0.040 = DD Or just remember that the Double Depth of a 32 TPI thread is 0.040 “
Your in feed is(of course) ½ the double depth.
This works well for short threads. For long threads its slow.
Unless you have a special metric thread dial with multiple gears it is the only way you can cut metric threads with an Imperial lead screw.
Start by setting up as you normally would, you can use back gear but that's a matter of how fast you are and how course the thread is.
Your part should have a thread relief.
Set the compound at 29 degrees (Standard 60 degree Vee thread, US or Metric)
Zero the compound, taking out the play in the in direction. (make sure you have enough travel in the "in" direction.)
Bring your tool in a just touch the work, zero the cross slide.
Back the cross feed out 1 full turn.
Back the carriage about ¼" past the start of the work.
Return the cross slide to zero. Advance 0.005 on the compound.
(NO THREAD DIAL)
Engage the half-nuts. NEVER DISSENGAGE THEM AGAIN UNTIL THE THREAD IS FINISHED!!!!!!!!!
When the tool enters the relief, shut the motor off. In back gear the spindle will stop within ¼ turn.
Back out the cross feed one full turn.
REVERSE THE MOTOR and back the carriage under power to a point ¼" past the start of the threads.
Shut the motor off.
Return the cross slide to zero. Move the compound in another 0.005. (0.010 total at this point)
Start the motor in forward.
When the tool enters the relief shut the motor off
Back the cross slide out one full turn.
Reverse the motor and back the carriage out ¼" past the start of the threads.
Every third pass is a spring pass.
Depending on the thread pitch after 0.010 to 0.015 reduce the depth of cut to 0.0025.
After about 0.040 to 0.060 reduce the depth of cut to 0.001.
When you are within 0.003 of the calculated depth start testing for fit on a "standard" nut!
When the nut starts to feel like it might be there, tight but does not screw in all the way. Start taking 0.001 at a time on your cross feed.
You can calculate the double depth in the following way.
(32/TPI)*0.040 = DD Or just remember that the Double Depth of a 32 TPI thread is 0.040 “
Your in feed is(of course) ½ the double depth.
This works well for short threads. For long threads its slow.
Unless you have a special metric thread dial with multiple gears it is the only way you can cut metric threads with an Imperial lead screw.
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