Tapered Slide Ring

There was a discussion on the rod makers list recently about the angle that should be used to taper a slide ring. Most rings that I've seen are jammed up onto the reel foot. The ring and the foot make contact only at the edges of the foot. It's a poorly engineered component, but it's simple and traditional.

About the only thing that can be done to improve the fit is to taper the inside diameter of the ring. That can be done a couple different ways. A swage was explained on the rod makers list. It's a steel mandrel with one end tapered to the desired angle. The ring is pounded onto the mandrel to expand the ring to fit the taper. The other method is to turn the taper on a lathe.

The question that emerged from the discussion on the rod makers list was what angle to use. As I understand it, the foot of most fly reels has a 7 degree taper. Brent Nickerson, a retired engineer and machinist from Alberta Canada, suggested a 7 degree angle about half way into the ring. Several replies to his post recommended a 3 1/2 degree angle because the ring would have a combined 7 degree taper.

So...I just happened to have a couple discarded rings in the shop to experiment with. I turned one with each of the two suggested angles and mounted a reel to see how they fit. The ring in the first picture has a 3 1/2 degree angle. The second picture is a 7 degree angle. Click on the pictures to enlarge them and take a look at the position of the rings relative to the insert. The 3 1/2 degree ring leans forward into the reel seat insert. That makes sense given that the reel foot has a 7 degree taper. The reel foot is going to force the ring to lean into the insert.

For me, the primary reason for tapering the ring is to minimize or eliminate scaring the insert with normal use. I would prefer for the ring to fit flush with the insert. Take a look at the second picture. That's the 7 degree ring. The tapered half of the ring fits flush with the reel foot and the flat half of the ring fits flush with the insert. The ring fits square with the insert...perfect!

I'm not an engineer or machinist. But apparently it took a combination of both to solve this riddle. Kudos to Brent Nickerson! I'm putting this one in the secret stuff file.

Here's a link to some CAD drawings that Brent provided. There are three PDF files for bored 3.5 and 7 degree rings and a 7 degree swaged ring. Shared with his permission: SLIDE RING DRAWINGS