AKA “And you thought handscrews were simple”
For the most part clamps are simple. There is the occasional innovation, but for the most part any style of clamp is interchangeable with any other of the same type. Perhaps the best example is in handscrews. There are really two types: wood thread and metal thread with pivoting nuts.
I spotted this clamp at an estate sale. I almost passed by it as the hundredth odd woodscrew out in the wild. A second look revealed the swiveling jaw and my curiosity was peaked. Of course the lack of threads where the screws were supposed to be nearly stumped me. I threw it in the bag, and since the prices were good, I lugged the rest of the loot back to my car and went home.
I knew that I didn’t recognize the patent so I had to hunt for it. Luckily, there was just enough embossed in the endgrain that I could work out the names enough to start seeing what a search engine would spit out. DATAMP came through after I entered the patentee name. The result:
US 783,502 Clamp or Vise John and William Black
The original patent shows the bars as gear racks of rectangular section. This is also the case in the only other known image in the EAIA Chronicle “Black Clamp”, Vol. 49 No. 1, March 1996.
Mine however has rods, in other words a circular profile, with drilled holes spaced as a rack. The end is marked BLACK BROTHERS MCHY (machinery) CO MENDOTA ILL, PAT APLD FOR. Which would indicate that the clamp may have been produced between 1903 and 1905. There was also a renewal or change made on July 18, 1904. I cannot find any documentation (even in the Patent Office Gazette) that explains if any drawings were changed. Also, it is quite common for tools to be labeled this way even after a patent is granted. Therefore, I cannot conclude whether the revised design was made before or after the patent was granted, at least without inspecting other examples of these clamps.
I also wonder if the swiveling pad is patented. It connects with a groove and a screw. The patent application doesn’t show the swiveling pad but both examples I know of have them.
Additional Resources:
Black Brothers’ History (they’re still in business): https://blackbros.com/timeline/
Clamp Guy entry: http://www.theclampguy.info/mkcc_bbr.htm
Vintage Machinery: http://vintagemachinery.org/mfgindex/detail.aspx?id=1109&tab=0
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