I'm building an ice jigging rod and the tiny diameter of the rod blank is much smaller than the hole in the standard size cork ring. I thought about building up the handle area with epoxy finish in thick coats until it was a snug fit with the cork, but this seems like it would take awhile. I also thought about using some skinny masking tape to build up a couple well spaced arbors and really load the u40 rodbond between them. Any ideas would be greatly appreciated. Thanks,
Joe

if the space is not to great you can run thread up and down the blank to build it up

Is it a preformed grip? If so it will work, but you just need to encapulate the tape arbors in the rod bond, a bunch of epoxy in between will do nothing but waste your epoxy and add weight. If it's seperate rings and your building the grip than a long lengthwise strip of fiberglass dry wall tape wrapped on the blank impregnated with epoxy will make a good arbor to build up your blank to the OD you need. You can use it also under a preformed grip. Lengthwise paper tape may work if you can encapsulate it fully to keep the water, etc. off it for obvious reasons.

That is a problem with building ice rods. With the preformed handles I get the hole is only 3/16s of an inch so there is usually not that much to build up maybe 3 layers of tape, and yes you really have to seal them in the rod bond or whatever epoxy you are using to glue everything together or they will fail.

Jann's Netcraft has cork with 1/8" holes in them that I used for my ice fishing rods, 1/8" was about perfect for the St Croix blanks

What I like to do is to use a sleeve of rod section that is a good fit inside the rings (or preformed grip if that is being used). Sometimes no shimming is required, but if it is, I will use tape arbors as above to build up the blank in 4 to 8 places to fit the sleeve. When it all fits together to my liking, I seal the arbors with 5 minute epoxy and let them dry, then load the blank with rod bond and seat it inside the sleeve. When dry, mount to grip and reel seat as usual.

What everybody said. Sometimes, your local sport shop will have some donor rods in the back....one nice thing sbout lifetime warranties on rods is: lots of breakers available.
My local sports shop permits me to take away all the broken rods, for re-cycle.
You should be able to find a short section of fly rod tip that will mate tightly with the butt section of your project rod....with a diameter that make your corkwork lass of a hassle.