Which actual lathe is it? Seems more than a mini-lathe.
You should never change the chuck jaws, they (should) be made to match the body. Just putting a round bar in a chuck whatever the conditions of the jaws does not by any means result in it being in line with the spindle. If you put a dial indicator on the end of a bar and tap the bar it will move even when it has been moderately tightened.
If turned between centres, and tailstock on centre then non parallelism is normally attributed to twist of the bed, which is corrected by 'levelling' which is nothing to do with being horizontal.
However it can also be due to the alignment of the spindle wrt the bed if the bed has been levelled and the work truely aligned with the spindle, when turning without the tailstock.

Changing the chuck jaws would not correct it in any case.

Either bed is twisted or the headstock is not aligned with it.

A taper could stem from a huge variety of causes.

Your question immediately raise a number of others in the search for a solution, so a lot more information is required..

Even you checking methods need to be examined closely. (Are the measurements consistent and repeatable. If not the figures are not worth much.

1.How accurate is the bar that you use to check alignment?

2. As already said, the bed could be twisted. If it is, the cut bis likely to be tapered.

3. How is the chuck fitted to the spindle? Screw on or Flange fitting?

4. Are the mating faces between chuck and spindle clean, and free from burrs?

ANY dirt or damage will throw out alignment.

5. is the chuck a close fit on the register / flange / face of the flange?

If the fit is not tight, misalignment will be present, and possibly inconsistent.

6. Has work held in the chuck been checked for run out close to the jaws and at a distance, say 100 mm away? Bear in mind that a perfectly round bar held in the jaws of a 3 jaw chuck will exhibit r eccentricity. A 3 jaw chuck holding work absolutely true is VERY rare.

7. Has the alignment been checked between a centre in the Headstock and one in the tailstock?

8. IF the alignment fo Headstock and Tailstock centres appears to be satisfactory, has it been checked with a properly centred Alignment bar?

You sound as if you need face to face / hands on assistance.

Where are you located?

What brand and model is your lathe?

Answering all these questions will give a better chance of finding a solution to the problem.

Howard

Lots of suggestions but no clarification from the OP as to what the actual problem is. Cedric mentioned both run-out and taper. As someone suggested it would perhaps be helpful if he could explain exactly what measurement was made, and if this is an eccentricity problem or axis alignment problem. He mentions a "new metal lathe", if it is actually new it might be better to reject it as not fit for purpose.

I'm with Grindston Cowboy if the taper is worse the thinner the work being cut then deflection of the workpiece sounds likely. Would help to know over what length the 0.07mm taper is and what sort of diameter is showing this taper.

Need pics of how you have your lathe set up and how you are testing for parallel etc. Too many variable factors to tell what is going on otherwise.

This is a fallacy. It is not that it MUST be set to face slightly concave, but is must (according to Schlesinger limits, Myford inspection sheets, convention etc etc) to cut between dead flat ie 0-0 across the face, to a small amount concave, usually about half to one thou maximum.

The reason is that a concave surface will sit stably on another flat surface if two pieces are to be bolted together etc. but a convex surface will rock and the pieces will end up out of alignment when bolted together etc.

Adjustment has to be made by scraping the ways on the carriage that the cross slide rides on to bring them back into square with the lathe's axis, providing bed and carriage ways are all up to snuff. On a Myford it can be an issue of the vertical guiding surface of the carriage to bed interface is worn, allowing the whole carriage to kick around at an angle and requiring repair, or wide guide conversion etc. Inverted V beds don't have that same problem.

This is how I test "facing alignment"  video

Edited By Huub on 28/12/2022 10:19:32

It really is best to start a new post when asking questions. Your question was not "on the subject" as the OP was asking about taper on a new lathe.

It saves a lot of messing about trying to seperate 2 questions and the myriad of answers that ensue

Also when people search for a particular answer to a question it will not be hiding in a post with a totally different title.

Anywho I hope you get the answer to your problem.

regards

According to some foto's I have found, this small lathe can't be bolted to the table. That won't mean the lathe bed can't be twisted (due to inaccurate grinding or metal relaxation).

You found a facing misalignment of 0.03 mm/100 mm. Causing a taper towards the chuck that can explain the turned taper.

The facing misalignment the sum of the headstock misalignment and the carriage misalignment. The next step will be measuring the "headstock alignment" using the method in the first video.

Edited By Huub on 28/12/2022 15:52:20

Edited By Huub on 28/12/2022 15:57:54

Surely that would only work if you know the tailstock offset is correct (i.e. zero).
One you have set up the lathe to turn parallel unsupported by the tailstock, then it might be a quick guide to re-setting the tailstock after an intentional. between centres, taper turning session.

Bill

I looked at a manual for the the 2506 lathe as I can't find the manual for the 2406 lathe. No mention of screws for alignment of the headstock. But most lathes do have them. Although it is on a dovetail, does not mean that it can't move a small amount left or right. You have to take apart a fair amount of the covers etc just to get to the head stock hold down bolts. 4 of them, 2 through the middle of the Vee, and 2 through the middle of the back flat area.

I am of the opinion that the head needs to be readjusted slightly. It may be that just loosening the hold down bolts and re tightening again may just realign it all. Or it may need a small amount of pressure to the side that needs correcting, then tightened in that position.

Most sales people will have no idea about how to set up or how to adjust the head stock alignment. Most machines are fairly good from factory, but every so often one is not. I don't think that scraping of parts or adding shims will be required in your case. It is not that far out that sort of procedure is required. If things are really wrong, take it back and ask for another machine.

Cheers Neil

Edited By Neil Lickfold on 28/12/2022 22:39:45