Lathe Not Cutting Straight

[Rick Leslie]

Bed twist is probably the most overlooked cause of tapered cuts. I'm neither cheating or uncaring, but I do factor in the precision required on the part being made. If dialing in the tailstock works, then I go with that. I usually do the 'point line up' thingy first to see how bad the tailstock is out. If you can see the misalignment, then it's pretty far out of whack.

Also, don't overlook vertical tailstock misalignment. My poor old Heavy 10 ha so much bed wear at the chuck that the closer I get the tailstock to the chuck, the more taper I have. But I know it so I adjust for it.

I have chucked a ground and polished bar in the 5C collet and gotten .002" TIR in about 8 inches with the chuck alone, then hung the same bar between centers and tripled the runout.

 

[Rick Leslie]

And thanks for the video Reeltor. Never thought about a plumb bob. Sometimes it's the simplest things...