Advice on a thread size and fitting for a Celestron binocular tripod mount I have an older pair (8 years old) of Celestron 10X50 binoculars with what looks like a 0.25" screw hole. The closest product on the Celestron website now is this.

I have taken to looking at the moon and planets lately, with the binoculars handheld. I have a photo tripod. I got an Opticron binocular mount (this one) which fits my quick release plate perfectly. It also claims a 0.25" screw.

The problem is the the screw goes in to the hole (behind the little cap with 10X50 on it) and sticks. It goes in quite easily for 2 threads and stops. I've cleaned both, and used a tiny amount of lubricant on both, but with no joy.. Once in the mount does just about hold the binoculars, although they slew readily around the axis of the screw.

Any suggestions?
The standard thread for these is 1/4 - 20 UNC.  The 20 means 20 threads per inch - you could try measuring that. The same size fastener should be what's on the Opticron, so it should "just work".  It's possible that there is something in the hole in the binocular that's blocking the thread.

However (and if you are not the first owner),  someone might have tried to use the wrong fastener and damaged the thread.  Threads can be recut with the right tool.