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Hukshawn
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YesAre you setting the cross feed to zero on the dial each pass and feeding in with the compound?
YesAre you setting the cross feed to zero on the dial each pass and feeding in with the compound?
Make sure your tool is not loose in the holder, or the holder to the tool post, or the compound loose. Wrestle them to make sure. Use the same spot on the threading dial for each pass. It does not matter if it is even with a line or number, just the same place each time until you get this sorted out. Make sure the threading dial gear that engages the lead screw is not slipping on its shaft, and that it engages the lead screw well, and without the fit changing as it revolves (bent shaft, bad bushing, damaged gear, etc.) Some lathes have shear pins on the lead screw or other means of failing soft in case of a crash. Make sure your lead screw is not slipping between it and the change gears. Slide the carriage left and right with the half nuts engaged to see how much wear they have. Also inspect them visually as best you can, after cleaning them up, and check for swarf filling the threads. Might there be a key missing or broken in one of the change gears, the lead screw, the spindle, or anywhere that might cause a slip?
Every good test is worth a hundred expert opinions, and perhaps a million hobby-machinist opinions...
its set at 61 deg on the graduations. which makes the tool 29 deg to the work piece. i guess some compounds are labeled differently?In your photos, it looks to me like your compound is set at 60 deg instead of 29 deg. That may not be the cause of your threading problem, but it will give you a poor quality thread.
Ted
i suppose that would help with preventing crashing the lathe on a shoulder cut?What about making a manual handle to fit in the at the rear of the headstock spindle and cut the threads by manually turning the handle.
I cut the 39x4mm threads for my back plate this way, slow but steady.
The compound angle looks correct in the pic above. It is certainly not 30 degrees off of where it is supposed to be.its set at 61 deg on the graduations. which makes the tool 29 deg to the work piece. i guess some compounds are labeled differently?