Comments about Swingline� High-Capacity Heavy-Duty 3-Hole Punch, 75 Sheet Capacity:
The plastic rings get gouged quickly and are not easy to turn to a new spot for a cleaner hole punch. The hole punches themselves dull very quickly and become useless. At no time was I ever able to punch 72 pages at once. I spent more to get a better product - it didn't happen. The only good thing I can say about it are the treads on the handle at least make it easier to push down on - which you have to do constantly to get your pages punched.
I would suggest contacting the manufacturer to see if its a part they can get for you. The number for Swingline (800) 820-6220. To better assist you please provide them with the model number of the punch, 74550C