Your second paragraph implies you are in possession of the lathe.
If the topslide dial has 100 divisions and it is imperial the divisions will be thou. Therefore one turn moves 100 thou which is 1/10 of an inch, therefore ten turns moves an inch so it is a 10tpi screw which is also the most likely.

If the handle moves along with the toolpost in a direction away from your hand as you turn it clockwise then it is a right hand thread like a common woodscrew.

If the toolpost moves away from you hand while the handle stays fixed in space then it is a left hand thread.

The cross slide is likely to be the same thread tpi but could easily be the opposite hand and the dial might have 200 divisions or the divisions might not be thou. If you play with the topslide a bit and get the feel for its movement relative to the dial you should be able to work the details of the cross slide out for yourself.

Backlash can be reduced but not in a trivial manner so it will be better to gain a little experience of metalwork first.

Backlash is dealt with by accounting for it when the tool position is changed. Say it needs moving out by some amount. Note reading, move out that distance plus backlash plus some more and then wind in to the correct reading.

The plus some more needs to be several times the amount of backlash. Often a near full turn is convenient – and a good idea for accurate work.

So called jam nuts used to adjust it out are a bit of a joke long term.

John

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You might find this manual useful. Grizzly also do a very comprehensive one here.

Russell.

Edited By Russell Eberhardt on 19/02/2016 10:58:47