seventy-five cent uni-bearing hinge...
I make a lot of decorative boxes. They're a good way to hone my skills (small boxes are pretty darn unforgiving when it comes to fit and finish). They're also a good way to use-up all those small pieces of stock that are too small for just about anything else.
In the past, I've used pieces of brass rod as pivots for a top. There is a certain amount of trial and error to get the length of the rods just right on each side so you have an even reveal all around the top. And there is little chance to make adjustments once you've hammered the pins home.
So I came up with this little scheme.
I use four 10-24 (3/8" long in this case) stainless set screws, and two 5/32" steel balls. That is enough stuff for two "hinges," and all the gear is available at any well-stocked hardware store. Total cost per side is about $.75, about $1.50 per box.
The set screws need to have the cup ends (this is the typical set screw that you see in hardware stores, but there are other types of set screws so I thought I'd mention it).
The technique requires four holes: Two 5/32" through-holes (one on each side of the box) and two 5/32" 1" deep holes (one on each side of the top).
Each hole receives a 10-24 3/8" set screw. The set screws in the top are buried such that the steel balls that ride on top of them are just a tiny bit proud of the holes.
Once the set screws are installed, the steel balls are placed, and then the top is set in position. Finally, the set screws on the sides of the box are turned in until they engage the steel balls. Don't overtighten them. I get it close, and then I just lightly wiggle the lid as I slowly turn the final set screw home. Once all the play is removed, the top won't wiggle any more and I'm done.
You can make adjustments to move the top left/right by adjusting the set screws in the box sides. Just make sure you loosen one side before you tighten the other. Fine adjustments are the key here, turn the screws in fractions of a revolution.
The open/close action of the top is very smooth.
And, the top can be removed for adjustments, finishing, etc.
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