The main telescope Kim uses for solar observing is a Bausch & Lomb 4000 Schmidt-Cass. She uses it to make daily (if at all possible) observations of sunspots with a thousand oaks filter. The scope itself is a little large and heavy for a photo tripod mount, so a wooden tripod mount was built and a longer 1/4×20 bolt was used to secure it. Over the years the threads have stripped off the telescope base and the scope is no longer safe (or even really attached at all) on the tripod.
So to be sure, we tried other larger bolts in imperial and metric and all did not fit. That only left enlarging the existing thread hole from 1/4 to 5/16 using a tap tool. Perchance, Canadian Tire had a tap and die set on a huge sale, so we picked one up last night. In the end the telescope repair took about 30 seconds.
It now fits securely on the tripod with the new 5/16 eyehook bolt.
Below are images of the repair process, in case this happens to you.

The wooden tripod with the original 1/4 x20 x 4″ bolt with two nuts to shorten up the portion screwing into the base

The Bausch and Lomb 4000 telescope

The new 5/16 x 18 eyehook bolt

The tap and die tool set. On sale at Canadian Tire for approx $40 this week.

The 5/16 tap tool applied to the telescope base thread hole and the new eyehook.

The 5/16 bolt test threaded into the telescope base.

The telescope secured to the tripod

The telescope secured to the tripod from another angle.