Jimmy
I've looked at the manual, and of course it doesn't say what the spindle threading is. But that something that you should easily be able to measure, and since lathe spindles are fairly standard, you just need to figure out which of the standard threadings your machine has.
I presume that your lathe is new. Vintage lathes can be all over the map, but modern lathes tend to be somewhatly standardized, especially Chinese lathes which is what you have. Which means that your measurement doesn't need to be extremely precise because you only need to determine which of the standards you are dealing with.
First, measure the outside diameter of the spindle (over the threads). There are four standard diameters - 3/4", 1", 1 1/4" and 33mm.
Second, measure the length of the threaded portion of the spindle, and then count the number of threads in that length to determine the thread count. Again, there are a few standards on modern lathes - 16tpi, 10tpi, 8tpi, etc.
This is a small lathe with an MT-2 spindle bore - my guess is that the threading is 1"x8tpi.
Here's a reference that lists spindle specs for various lathes. Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to
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; Unfortunately, they don't cover Harbor Freight.