Thanks for that Ketan, helpful and well informed as always.
I'm very much hobby and have no formal engineering training, other than telecoms.
When I shelled out £20 delivered from India, I presumed I would be receiving something, at best at the limit of tolerance, or maybe a reject out of the back door.
Prior to its arrival, all I had ever used was a length of silver steel, or the inner chromed rod from a car shock absorber or suspension strut. I'm not making or reconditioning machine tools, or doing any fancy setups in industry; I just use it for setting something up prior to a final tweak with a DTI.
In view of your comments, and for my own curiosity, I've just been out for a quick play, but it should be noted that the nearest I have to a temperature controlled environment is whether I open or close the garage door(s), nor is any of my kit formally calibrated.
Using a M&W Micro 2000, and a couple of comparator micrometers, they seem to confirm the diameter along the length to be within a tenth, and ovality as close as I can measure anyway, to be spot on (I guess it could be lobed in some way though); For those not familiar with either instrument, they take the measurement based on a constant spring pressure, rather than relying on me to operate a screw thread and know the feel of the mic. which would be down to my experience over the years (i.e. lacking).
Setup between centres on the lathe, and gently turned by hand on the stationary centres, with a tenths DTI, seems to show concentricity along it's length, and the DTI barely moved when set up in the middle of the test bar, so I guess it's not banana shaped, Similarly on the morse tapered section.
Installing it in the headstock taper, and again turning by hand, though obviously the spindle not just the bar, showed no measurable runout at the headstock, but about half a thou at the far end (obviously unsupported by the tailstock).
I guess this is as much a measure of the lathe as the test bar (I tried it in the horizontal as well as the vertical plane to try to allow for any sag.
The lathe is a Warco 720; Myford clone from the '70s, but runs in taper rollers, rather than a bronze bush.
Just for information, and an explanation of one reason, apart from safety, we were told at school not to lean on machine tools. With the setup stationary; test bar in the spindle morse taper and a tenths DTI touching the side of it at the distant end, tailstock not in use but locked at the far end of the bed, just resting my arm reasonably heavily on top of the tailstock showed a movement of about 2-3 tenths on the clock. The lathe is bolted down securely to the factory stand.
I just make and mend things, so not really chasing tenths, other than as an exercise and out of interest.
Whilst I do understand that said test bar may not meet NAMAS calibration standards, it will do what I need on a budget, though I fully understand Ketan's reluctance to sell something which would reflect badly on his business it it was out of spec.
It really does give confidence that something from his company should do the job as advertised, and it's likely me at fault, rather than the product if not.
I'd welcome comments from someone who is trained in this stuff
Bill.
Edited By peak4 on 09/10/2022 12:57:59