Could be that the spindle is fine but the test bar is not seating properly in the headstock taper.

Andrew

The first thing you need to do is wait until 30 minutes or more after sunset when it is good and dark. Stand outside your workshop door and lick you finger and hold it up to determine which way the wind is blowing. Then throw that bloody test bar as hard and far in that direction as you can. Those things cause more problems than they solve, particularly in the sweaty hands of beginners.

And you need to separate headstock alignment from spindle runout. Two different things. Alignment is setting the lathe headstock and spindle in line with the lathe bed's central axis. Runout is the reading you get with a dial indicator when rotating something. If it is running eccentrically, you have runout.

A Myford headstock never needs realigning with the bed, under normal circumstances. It is done at the factory by trained fitters who set it up metal to metal, scraped to align it. No shims used.. If you return your headstock to its original position with the jacking bolts so the headstock metal is pressed up against the bed metal, it's aligned.

Now, if you want to set your lathe up to turn parallel (without a tailstock centre), do what we all do when all else fails: read the instructions. The Myford ML7 Users Manual gives a thorough run through on how to shim or adjust the lathe bed to bench mounting points to twist the bed slightly to make it turn parallel. You don't need to use a fancy level, and especially not a fancy test bar. It is done by taking test cuts over a piece of 1" diameter x 4" long steel bar and measuring the diameter at each end. You then shim or adjust the lathe bed feet at the tailstock end to make it turn parallel. Simple as anything. The ML7 User Manual is widely available for free download on the internet. It has all you need to know about aligning your headstock spindle to the bed.

On your million-year-old lathe, the internal Morse taper in the headstock spindle is almost certainly scarred up, butchered, abused or othewise out of whack enough to make it run out of true. And the spindle can even have developed a slight bend over the countless eons since is left Beeston. Mounting a fancy test bar in there tells you nothing, as you have found out.

Re your bed measurements, you are on the right track there, if you lathe is a pre-1972 narrow guide model that uses both vertical sides of the front way to guide the carriage. One thou of wear is very good. Three thou is Myford's recommended limit before regrinding. The thickness of that front way measured vertically is allowed a couple of thou more as it is less critical.

BUT, if your ML7 is post-1972 or has been converted to wide-guide configuration, it uses the front of the front way and the rear of the rear way, so you need a 4" micrometer to measure that overall distance to get a true reading of wear.

I thought I had a pic of that manual page on alignment to post but don't seem to be able to find it. But you can fiund the manual all over the net.EG the Myford lathes group on groups.io in the Files section.

Well said Hopper, good and to the point

Brian

Unless you want to use MT collects in the spindle the runout of the taper doesn't matter. As long as it grips you can skim and indeed should skim the taper in situ every time you use it. I wouldn't go attacking it with abrasives, not localised enough

Have you checked that the test bar is not bent>?

Set it between centres and run the DTi along it (This assumes that the gibs on the saddle are set to give minimum clearance. No point in doing any checks if they are not )

If the bar is bent, the DTI reading will may well increase and then decrease as it approaches, crests and then passes the bend.

Might be worth carrying out this check with the bar rotated by 90 degrees relative to the first check.

Having established that the bar is acceptably straight , < 0.0005", CAREFULLY clean up the tapers, internal and external. To be sure, use marking blue, (Not layout blue ), to confirm optimum contact between bar and spindle bore.

When this satisfactory, the straight alignment bar can be used to adjust the Headstock so that the spindle bore is parallel to the axis of the bed ways.

Once this has been done, the the b lathe can be used to remove twist from the bed, as per the Myford manual.

Once all seems to be in order, the Alignment bar can be fitted between centres and used to align the tailstock..

This post reads like a cautionary tale..

Hopefully, anyone reading this thread and tempted to take apart their lathe,may like to consider if they have the knowledge, skill, and equipment to take on such an exercise..

It is far too easy to strip a reasonably accurate machine and make it into a very costly doorstop!.

Stripping and reassembling a lathe or any machine tool is not a task for the overconfident and under skilled!

There are many skilled and time served Engineers who would think very seriously before taking on such a task!

Howard

Jon, I don't know if you've read this thread on the subject of test bars, but it's worth perusing, as is the link Ketan provided to a previous thread as well
https://www.model-engineer.co.uk/forums/postings.asp?th=183626

Bill