Did you use the tailstock for support?

Has the tailstock beed adjusted front/back to make sure it is lined up correctly? having that rope tied round it may not have helped

Edited By JasonB on 09/11/2017 07:45:33

John gives good advice.

Regarding level, the lathe could be at 45 degrees as long as the bed is 'level' from one end to the other!

If the bed were true and flat and level, the lathe should turn without taper – but conversely, if the lathe cuts without a taper, the bed should be true (even if not quite level in the absolute sense) This means that shimming of the tailstock end, to remove any taper cutting should level the bed.

Obviously, levelling the lathe initially is a good ploy, but things like the floor or bench/stand top can also introduce extra levelling requirements. I expect that shimming the tailstock end (if the the root cause of the problem is pinned down to a slight twist of the bed) would be more than adequate for our small lathes.

I would try your test again with a piece of 25mm diameter steel protruding 150mm out of the chuck. Just to make sure the problem is not deflection of the long thin piece of bendy aluminium before you start attacking your new machine tool

I would also check the tightness of the headstock bearings because if they are loose it can cause taper turning. With a newish lathe they might need adjusting after initial bedding in.

And check for burrs on the ways and slack in the carriage and cross slide ways.

Then slacken off all the foot mounting bolts where the lathe bolts to the bench. Try sliding a thin feeler gauge under each foot. If there is any gap at any foot, a piece of shim needs to be slid in there to take up the gap. Otherwise, you are pulling the bed out of shape when you cinch down the mounting bolts.

After all that, if still turning a taper, you may need to first "level" the bed using a precision level to make sure there is no twist along it.

Then, if it still turns a taper, you can go two ways. Either twist the bed by adding shims under one or other of the tailstock end mounting feet until the lathe turns true. This method is an ok bodge for small taper errors. Probably not for 0.2mm though. The more properer way would be to set the alignment of the headstock to the leveled bed so that it turns parallel.

Edited By Hopper on 09/11/2017 08:28:58

+1

Russell

Assuming Chris used the tailstock to support his rod, Jason may be on to something. I found the balance point on my WM280 to be much closer to the headstock. To position the strap at the balance point I had to remove the chuck guard (one bolt and it slides off a spindle). That rope in Chris' picture would pull the tailstock, possibly enough to shift it's alignment.

If Chris didn't use the tailstock to support the end of the rod, then deflection might well be causing the taper. Rods bend, even under their own weight! It's instructive to experiment with various diameters and lengths in the chuck. With a DTI on the far end of the work, pushing the rod's end with a finger will cause the DTI to register a deflection. You may be surprised at how much spring there is in a hefty lump of steel!

Dave

I don't know what the experts think but the picture shown seems to imply that having the lathe a little closer to the ground might do a world of good.

Michael W

Tim,

Not unless Malta (or Wales) has moved!

Well spotted! I'm one of several who missed the blindly obvious…