Hafco AL336 not cutting straight

Good luck with the new machine.

As for the other one, obviously when the headstock is pointing towards the front or the back it will turn with a taper along the length, it will also result in a concave or convex face. What happens when you get the parallel bit right and you still have a convex or concave face. It would appear that you have corrected the parallel part by the wrong method.

You first need to confirm that the centerline of the headstock is parallel to the bed in the horizontal plane, that is, it is neither pointing up nor down. If it's pointing up or down that will cause it to turn tapered even when lined up correctly. So you need to correct the horizontal alignment first, by shimming under the headstock, so that the center line of the H/S is the same height above the bed along its length, or at least at both ends.

Once that is done then you can continue as before to correct the parallel turning in the normal way. This should result in the lathe turning parallel and square across teh face. If it does not then one would have to assume that the cross slide is not square to the bed. I don't know how you can correct that.
 
I corrected the parallel part using Rollies dads method in both planes. I did shim under the front of the HS to get it level with the bed. This immediately had the lathe turning parallel within 0.02mm over 130mm with the larger collar at the TS end. The lathe cut a convex of 0.03mm on a 100mm diameter bar.

The issues are

1. I can not level the bed. I had the lathe bolted to the concrete floor on jacking bolts so I could easily level it. It needed the front TS end raised but this also moved the HS end out of level. With the HS end level (0.02mm/1m level) at the TS end the bubble was hard to the rear of the level.

2. Both chucks have the jaws splay so it is impossible to re-chuck something concentric.

3. The spindle nose has 0.01mm runout and possibly the cross slide is not at 90° to the bed.

I have indexed the chucks so the runout in the face is 0.01mm. New jaws may fix the splay issue but for the cost of new chucks I decided to buy the Colchester it still has its original Burnerd 4 jaw and a Burnerd 3 jaw so the cost of these would be nearly what I paid for the machine.

For hobby work I would have lived with it. It probably cuts as good as most cheap Chinese lathes but I am machining engine parts for a V12 Jaguar (pistons ATM) so I need the lathe to cut more accurately than it does.
 
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