I own and use a lot of umbrellas brackets. Some are definitely better than the others. In an earlier post, I found one iteration that was significantly better than the others I own. And when I get past that irksome short-spigot requirement, this umbrella bracket will become one of those things I no longer have to think about.
These fine threads did finally strip out on one of my bracket bodies. I decided that if I could get some thumbscrews with a larger shaft diameter and a coarser thread, I could improve the practical retention and regain some functionality. I chose 1/4 x 20 (1/4" shaft diameter with 20 threads per inch) as the thread size, since it happens to be the same thread size as the tripod socket in the bottom of the camera. I found some plastic thumbscrews with a large knurled head and a 1" shaft through Amazon. For ordering information (#4715), click here. They're somewhat expensive, but beauty sometimes hurts.
To start the project, I first disassembled the umbrella bracket to make it easier to handle. Next, I got out the old Sears Roebuck Tap and Die set that my father purchased many, many years ago. You don't need to purchase an entire set for this project, only a 1/4 x 20 taper tap and the proper size drill. You can use a small crescent wrench to hold the tap. Now before we go further, we need to talk about tools.
Tap: The tap cuts the threads on the inside of the drilled hole. (The cutter that makes threads on the outside of a shaft is called a die). Taper taps are the easiest to use, as long as the hole you're threading is drilled completely through, as it is here. If the hole is "blind" (one that doesn't go all the way through), you'll need to tap it in stages, starting with the taper tap and finishing with a bottoming tap. TMI.
Drill Press: A drill press is a belt-driven power drill mounted in a housing that allows the drill, held in place by a chuck, to be lowered onto the workpiece in perfect vertical alignment. It makes the job easier, but isn't essential if you're a careful worker. If you have several flash brackets, you can probably bring them to somebody who has a drill press and get them drilled all at once, so long as you provide the proper size of drill and bring the "driller" a bag of cookies.
Since our hole goes all the way through, keep turning the tap as far as it will go. This allows the clean, sharp edges at the back end of the tap to cut the threads to their proper depth. In Photo #3, you can see the flute,or groove, along the side of the tap. Chips will collect in the flutes and must be eliminated to prevent tearing. Unless you're working with a blind hole, the chips should fall through the flutes and out the bottom. Here, slow and steady does the job. After the hole is completely tapped, I use compressed air to blow the chips clear.
I'm probably going to buy more thumbscrews, gather up the rest of my Photoflex and Impact brackets, and start drilling and tapping them for this larger 1/4 x 20 thumbscrew.
And I'll get to keep the cookies for myself.
One suggestion: When not in use, turn the umbrella retaining screw as far in as it will go. This will protect the threads and prevent the screw shaft from being bent or damaged.
Afterthoughts - Umbrella Shaft Filler: I mentioned in an earlier post that a pencil can be pushed up the hollow umbrella shaft to minimize damage from the clamping action of the thumbscrew. When I first read it, I didn't believe it. If you don't, here's a photo of my newly modified bracket with an umbrella shaft so modified. Yes Virginia, that little beige blob is indeed a pencil.
Other Thumbscrew Sources: Since writing this posting, I found some e-Bay sources of steel shaft-plastic thumb piece screws for less than I paid for the all-nylon ones. Check these out it they're still available. I wasn't too wild about the steel shaft (black nylon is just cooler looking) but they are cheaper. I bought some anyway. Whatever style you choose, just be sure that the threads extend right up to the base of the thumb piece.
Drills with Taps: A recent visit to a hardware store chain showed that individual taps can be purchased with the proper sized drill included. Sweet!