If it's just one high spot, lower it with a scraper. You don't need the whole years of practice, tubs of engineers blue, fancy tool made from unicorn horn and 2000spots per inch deal, just a few strokes with whatever you have. I found all three of my tools benefitted from a few minutes of this, once use made such spots obvious.

Is it the top of the ways or the underside? Without the hold down plates is there any evidence of a high spot? You really don't want grinding paste anywhere near the bed and if there is a problem scaping may be a better solution,

Yes, but what about using rear-mounted tools?

The shims under the Myford carriage are there for adjustment to a fit.

I always lock down the carriage when parting off, so it is not very likely to be lifting during that operation?

There is never a good reason to lap in machine ways. It's the exact opposite of what a moving way requires to be properly lubricated. You might (probably will) see an apparent improvement in function in the very short term but once done, wear will be highly accellerated.

It's a pretty good way to ruin a machine in short order.

Russell

I think it’s fair to say that the accumulated wisdom of the posts so far is:

Lapping is not the appropriate technique … But there is no harm in identifying specific ‘high spots’ and reducing them with a scraper.

Proceed gently and you should see some improvement … then quit whilst you’re winning !

MichaelG.

FWIW my particular mini lathe carriage was loose @ headstock end & too tight to move @ tailstock end out the box.

Measuring with a mike induced me to run a 4" file(.minus handle) along the lower ways on the bed towards the tailstock end.( what the saddle plates run on)

It took a while,it's still not perfect, but carriage will traverse it's full movement without any looseness or overly tight spots……

I'd leave the top of the bed well alone, unless i was a lot.lot more knowledgeable.