Threading woes

Think you're right... I thought these levers did the same thing....
No, the one youre using is a mechanical geartrain inside the apron that is for removing material from the diameter of the part.

The higher lever is for the half nut and works directly with the change gears used for thread cutting. Start off by engaging it only on whole numbers....because....I forget what the rule is for even vs odd thread counts.:rolleyes:

Just looked at your pic again, it has the instructions for the levers on a sticker on the apron..

Is your threading dial engaged?
 
Based on the chart, the 80t and 127t gears are simply acting as idlers. The ratio of the a and b gears, along with the QC gear box gears determine the thread pitch. In the configuration shown, the input shaft to the gear box should be turning at the same RPM as the spindle.

I see two possible explanations for your result. First, the half nuts may be engaged at the wrong position on subsequent passes, giving the effect of a multi-start thread. Second, lathes that I have seen using your setup have an alternative method of using power feed; namely, there is a key slot in the lead screw which drive the power feed to produce a finer lead than would be obtained with the typical method using the half nuts. Assuming that you are cutting decent threads but the wrong pitch, it would suggest the latter.
Using the wrong feed lever really makes sense.
 
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