NEED PULLEY REMOVAL HELP

I AM TRYING TO REMOVE THE DRIVE BELT PULLEY FROM MY 1968 SUBURBAN. LOOKS LIKE TWO HOLES IN THE PULLEY FOR SET SCREWS. I ASSUME THEY WERE ALLEN SCREWS. THEY APPEAR TO BE ROUNDED OUT OR SOMEONE STARTED TO DRILL THEM OUT. LOOKS LIKE I WILL HAVE TO DRILL THEM. CAN SOMEONE TELL ME WHAT SIZE DRILL BIT TO USE SO I WONT RUIN SOMETHING. I KNOW I WILL HAVE TO TAPP NEW THREADS. ANY OTHER IDEAS WELCOME.

THANKS MUCH

I'd suggest spraying some penetrating oil in the set screw holes and let it work for a day or two. Try to slip several drill bits into the hole in the set-screw until you find the one that fits firmly. Then drill the holes in the screw(s). When deep enough try an easy-out . As to the size of the set screw, if the screws are in deeply, you may be able to try several sizes of screws 'til you find one that will fit the threads. I would only drill and tap as a last resort.

Thanks Cavry. My problem is there is no setscrew head to guage drill size. I think I start with very small and work up as needed.

I'll remove the set-screw from mine about 1:00 today and let you know what size it is. Interestingly, apparently the hole for the set screw is drillled in two stages. The first, or outer, diameter is unthreaded and large enough for the set-screw to go into the hole without touching, and then a smaller dia. for the threaded portion. Whatever happens, I would think that you would not need to drill larger than the outer diameter under most circumstances.

My pulley has a 5/16 USS x 1/2 set screw and took a 9/64 allen wrench. So I'd start with a 9/64 or 5/32 bit, if I needed to drill it out.

There are not many folks who would go out to their tractor, remove a pully allen screw just to measure and communiccate the sizes to a total stranger.

Thanks Cavry, that is the info I needed.

My pleasure. Not being snide but Whoopee, it took all of 5 minutes. I've been in the situation where I needed help or info more times than I can remember. I'm glad to be able to return prior favors.

I had the same problem. I took the unit to a clever friend who had a welding shop.
He used a stick welder and struck an arc inside the set screw and welded the welding rod to the inside of the screw. He then welded a piece of welding rod to form a "T" at the top of the rod. He then just backed the screw out using the welding rod "T" as the tool. When he welded the rod to the inside of the set screw, it got real hot and turned out very easily.
The whole process took about 5 minutes and did not involve any drilling or tapping. It was pretty slick. All you need is an experienced welder.
Good luck !