No longer the owner of a ML7, ( Superceded by a larger Far Eastern machine – which has been satisfactory for the 16 years that I have owned it from new )
With regard to space around the machine, my advice would be at least a foot at each end to allow for material passed through the Head or Tailstock.
The more changewheels that you have the better, even if you do have a gearbox (That will increase your purchase price! ) Do try to find a 127T, in case you ever want to cut Metric threads on an Imperial machine, or vice versa.
It will be large, and probably expensive, but if you want the facility, you need to pay for it.
Enter stage left all the 63T exponents! And all the other exotic gear combination supporters.
Do get books which guide you on how to set up a gear train.
"Myford Series 7 Manual" by Ian Bradley; "The Amateur's lathe" by L H Sparey., and the more recent "Gearing of lathes for Screwcutting" by Brian Wood, all contain tables of geartrains to cut various threads.
"Screwcutting in the Lathe" by Martin Cleeve , (No.3 in the Workshop Practice series ) deals with the theory of setting up a train for a particular thread pitch in detail, and the calculations.
Almost all of these will touch on the form of the screwcutting tool, and how to go about the job.
Changewheels can also be used to provide a feed rate / revolution of the mandrel. Both for turning, and if if your machine has power cross feed, for facing.
But do ensurev that any changewheel that you buy is correct for a Myford. The gears are 20 DP but the pressure angle is 14.5 degrees. Other machines may use 20 DP gears, but with the more usual 20 degrees pressure angle, and are not really suitable.for a Myford.
Hope that this is some help rather than confusing.
Howard Look below hers, more follows!
"The Amateur's Workshop", by Ian Bradley; and "Model Engineer's Handbook" by Tubal Cain are useful books to have, but do not contain tables of change wheel set ups..
Edited By Howard Lewis on 19/07/2019 18:13:13
Edited By Howard Lewis on 19/07/2019 18:14:26