THRU-HOLE - completely through the material of an object.
I agree with Daniel. But, what is the smaller hole in the center?
The motor shaft. The thru hole is most likely for an adapter flange.
It could also be the 5/16-18 Tap depending on which hole you're referring to ... Regardless, there are two diameters inside of the "Thru Hole" that was initially questioned. The shaft (with Keyway) and threaded hole (Tap) ...
The diameter the thru hole is pointing to, the smaller circle inside it would not exist.
Keep in mind this is an assembly, not a part. There is a motor, with a shaft. The shaft has a tapped hole in it. Attached to the front face of the motor is an adapter flange with a 2.500 hole through it to get over the motor shaft.
If it's an assy, the dim's should be ref, unless you're machining the holes at assy.
Either way, the smaller hole should not exist.
It's a vendor cutsheet drawing, like this:
It's not a drawing to actually manufacture or assemble something.
Wow, that's busy
It's most e-drawings not getting the font right. The original probably looks better.
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