Browse through a machine-tool catalog and you’ll find many sets of jobber-length drill bits. I’ve often wondered what jobber-length meant and after seeing yet another flyer from Travers or Enco, I decided to find out. Although you can find many mentions of jobber-length bits, it’s difficult to locate a clear definition. The Wikipedia defines jobber-length bits as those for which the length of the flute (the twisted part) is 10 times the diameter of the bit. Thus, a 0.25-inch drill bit should have a flute length of 2.5 inches.
But it turns out that’s just a crude rule of thumb. The definitions (note the plural) of “jobber length” comes from ANSI/ASME B94.11M-1993. As far as I can tell, without buying a copy of the standard, the ratios of flute length to drill-bit diameter vary. The standard defines lengths, not a fixed ratio. A #60 drill, for example, has a ratio of 16.7 to 1, while a #10 drill has a ratio of 12.6 to 1. What about the quarter-inch drill? It comes in at 11 to 1. (My drill dimensions come from the 26th edition of “Machinery’s Handbook,” a fine reference.)
While doing my research, I found an interesting and helpful article on drilling, center drilling, and spot drilling; “Get it Straight,” by Kip Hanson. Although 10 years old, this article remains relevant. You’ll find it here: www.ctemag.com/dynamic.articles.php?id=31.
Robots that walk have come a long way from simple barebones walking machines or pairs of legs without an upper body and head. Much of the research these days focuses on making more humanoid robots. But they are not all created equal.
The IEEE Computer Society has named the top 10 trends for 2014. You can expect the convergence of cloud computing and mobile devices, advances in health care data and devices, as well as privacy issues in social media to make the headlines. And 3D printing came out of nowhere to make a big splash.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.