Need Help! Lathe Cutting A Taper!!!

blaser.306

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I need some input and or suggestions. I have a 10x22 king lathe, ( I know , sorry for your luck) all kidding aside. It seems that all of a sudden I am cutting a taper .002" over about an inch, two inches out from the headstock. I am using an ER 40 collet chuck that I built. The work is slender so I am expecting some deflection, but even with spring passes the taper continues. I have made a test bar and re adjusted my tailstock to less that .001 run out turning between centers. I checked for chips under the mounting register and face of the chuck, re adjusted the headstock bearing tightness and can see no appreciable movement there I have done the compound hold down mod for added rigidity, any suggestions where I should be looking. The only thing that I haven't looked into is leveling the lathe bed, and do not know if it can even be done as the lathe is in my basement and not anchored to the concrete ( yet ). As I had mentioned this is a new problem to this machine and I have been running it for 3 years with very little in the way of issues. Any help is greatly appreciated and thanks in advance.
 
Are you using the compound or the carriage?
Check your cross slide gibs

Cheers Phil
 
The cuts being made are using the carriage and power feed. Backlash has been taken up and gibs are adjusted, in both the cross and compound slide.
 
My taper is toward the headstock ( smaller end ) large outer dimention. One thing I do know , after doing the compound mod ( 4 bolt plate ) the backlash adjustment screw is near impossible to keep adjusted. I am thinking of countersinking a button head cap screw over the edge of the adjusting screw for it to lock it in place.
 
A smaller headstock diameter & larger tailstock diameters can typically be caused by cutting tool deflecting the unsupported end of work, so its not cutting as much so the net diameter is larger. As it gets to the chuck thats the rigid side so it cant deflect that portion as much. The skinnier the material and/or less tensile strength, the more pronounced taper effect. I'm not sure if that's what you are saying but yeah, that's when tailstock support is for sure required. Or a travelling steady.
 
The material is o-1 1/2" diameter with 2" protruding from the collet too small for a live or dead center and definitely to short for a follow rest! will have to try and slow down the cut and use HSS see if that helps, like I had mentioned this just seems to have arisen as of late.
 
I'm surprised you cant sneak a tool point in next to a centre. Alternatively can you extend your work piece out further, (say another 1"), and then use a centre but start your cut away from the centre. It will mean burrowing into the work and wasting the extra 1" at the TS end. Perhaps its time for one of these to be added to your collection
183318952_rhm-26571-type-670-carbide-tipped-half-point-dead-center.jpg

Cheers Phil
 
First thing I would do is to try the same cut but with a larger diameter piece of material. That would let you know if its deflecting or a lathe issue.
 
My taper is toward the headstock ( smaller end ) large outer dimention. One thing I do know , after doing the compound mod ( 4 bolt plate ) the backlash adjustment screw is near impossible to keep adjusted. I am thinking of countersinking a button head cap screw over the edge of the adjusting screw for it to lock it in place.
You might try a dab of LocTite on the backlash adjustment setscrew.
 
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