Whoever told you it would be OK to take it on the plane possibly did not know that you were NOT talking about a modern, compact, sewing machine. An older machine, needing to be heavily padded and wrapped, will not fit in the overhead! I would be concerned about having it go as cargo...can't think of the right word for that...but if it is heavily padded and double boxed it might be OK.
checked baggage...that's the word...