Hi
@6Sally5
Hopefully, the following and attached maybe of some use to you.
Sometime ago a developed an automated Excel Workbook (spread sheets) to generate all of the possible TPI and feed rates that I could obtain with my PM1440GT and the external gears that I had. In the process I decided to make it more general so almost any lathe could be set up as separate work sheets in the workbook and the user can decide which external gears should be considered.
The Vevor YS1875a that you have discussed does not seem to have a built in gear box so it was pretty easy to set up a sheet for your lathe. It seems clear now that your lathe has the 16TPI lead screw so I used it. I then ran the workbook macro that generates a list of all of the possible TPI values your lathe could make. I included the 65T gear along with the list that can standard gear set. That makes 9 possible gears but 2 of them (60, 40) are redundant so there are really only 7 unique values.
Since, it appears that all of your gear axles have the same diameter I assumed that any of the gears could fit on any of the axles and that you have 4 duplicates of each gear. I know this is unreasonable, but it allows the program to run and cover all cases of any gear on any axle. In this process this also means that you could use any pair of gears at the transpose position. Obviously, the gears must physically fit and only the user can determine this for sure. So, clearly, there are some cases which are not physical and there will be duplicates, but hopefully a table of all of the possible combinations would be useful. I then sorted the table by increasing TPI values so you can just scan down to find the gears needed for a given TPI. The metric value is also provided. You can also see if there is an approximation that is close enough to be useful.
Attached is a pdf table of the results for your lathe. With 4 possible gear positions and 7 possible gears there are 7^4=2401 possible combinations, or gear combinations in the pdf table. Let me know your feelings about this.
Later I will try to attach a copy of the Excel Workbook with your lathe as one of the sheets (tabs) which you can modify if you ever need it. There are macros included so I have to zip the file to get HM to accept it and this aways gives me problems. You can then run the spread sheet manually or in an automatic mode. So it is useful to see what values you might be able to get if you make a new gear. There is a "Readme" tab that tells you how the sheets are laid out and what the macros do etc. Meanwhile you can find the workbook without your sheet at
NB06: Currently Available, LatheModel TPI sheets:
There are some extra features built into the macros of the workbook. For example, the macro that runs through all of the possible gear combinations generates a table called AllTPI which I attached. Other macros: hides or unhides columns of your choice, underlines every so many lines to make things more visible, sorts on any or multiple columns to order things, searches for a value or an approximation to a value of your choice, provides an automated search to create a table of standard TPI or metric thread to within the accuracy of your choice, etc.
Good night.
