What size of steel pipe will slide into a 1-7/8" O.D. pipe, and fit snug ample while sliding freely satisfactory? ...
Answers: Your pipe is a nominal 1 1/2" diameter, The next size is a 1 1/4" and tag on 3/8" for the pipe wall so a OD on the 1 1/4" is 1 5/8 " too large to fit contained by the 1 1/2" pipe There is no pipe size of standard diameter that will fit tight and slide freely. A 1" pipe size is 1 3/8" OD, it will fit in the 1 1/2" pipe but not a tight fit. You might try this for size.
2" pipe will adopt 1-1/2" pipe. Not sure how snug you need it to be though.