# Colchester master cutting multiple threads



## graduate_owner (9 Apr 2017)

Hi all,
I have a Colchester Master Mk2 and have been trying to cut some threads but have had problems with multiple starts. After engaging the half nut at the same point each time on the indicator, I still get multiple starts. When I bought the lathe the half nut wasn't engaging so the apron etc had to be stripped and cleaned, although the half nut wasn't damaged, nor the lead screw. 

Does anyone have any ideas on why I am getting these multiple starts?

K


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## CHJ (9 Apr 2017)

Are you mixing Imperial and metric standards, imperial leadscrew and metric thread via change wheels by any chance, Problems are usually down to the ratio differences between change wheels and leadscrew thread pitch.

Being lazy and trying to get my head round what matches and doesn't I more often than not leave the nut engaged. 

Think for ease you would best leave the leadscrew engaged and run the lathe backwards then inch it forward to take up backlash before engaging threading tool.


If you are having problems engaging on imperial threads that on the face of it should be easy it might just be that you are not traversing along your leadscrew in complete multiples of an inch so not engaging correctly.


Have a read through this thread as it gives some good explanations, certainly better than I can get my head around.


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## mcostello (10 Apr 2017)

Is there a shear pin that has sheared and just catching?


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