Checking My Nuts

[DaveH]

I have to prove it  
A long time ago when I did this ........... The thread you wish to cut is 10tpi or 5 threads per 0.5" or 2.5 threads per 0.25" (best to read half inch, quarter of an inch)
Remember 2.5 threads per quarter of an inch.  

Lead screw 8tpi and a 16 gear pinion ......... so 4 turns of the lead screw will move the carriage one half of an inch (0.5") as well the chaser dial will move 2 divisions.
If the half nuts are engaged all is fine because there are 5 threads in the half inch - the tool has moved exactly 5 threads.
Now is the lead screw only turns 2 revolutions the carriage will move one quarter of an inch (0.25") or one division. So the tool moves 0.25" that will align the tool 2.5 threads further from where the tool started if the half nuts are engaged here it will be half a pitch out.
So the half nuts have to be engaged every 2 divisions.
The half nut have to be engaged on a complete thread not on a half thread as 2.5 threads. 
Hows that for proof  

I am assuming an 8tpi lead screw and chase dial with a 16 tooth pinion.
 
DaveH