If I was really needing force fit collars and I still had the old
ones, I would put them in a machinist vise such as a Kurt vise or
use a press to compress the collar so it would be tight again.

Do not press on the round edges but press on the flat area.  Think
of it as if you are trying to press the collar thinner.

Don Teach
Shreveport, Louisiana

 [ Ref.  http://www.kurtworkholding.com/  -- Robbie