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.
Some humanoid walking robots are also good at running, balancing, and coordinated movements in group settings. Several of our sports robots have won regional or worldwide acclaim in the RoboCup soccer World Cup, or FIRST Robotics competitions. Others include the world's first hockey-playing robot and a trash-talking Scrabble player.
A recent example of a major CAE revamp is MSC Apex, released last month by MSC Software Corp. In a discussion with Design News, MSC executives noted that its next-generation platform is designed to substantially reduce CAE modeling and process time, “in some cases from weeks down to hours.”
The Thames Deckway would run for eight miles close to the river’s edge, rising and falling slightly with the tidal cycle. It will generate its own energy from a series of devices that will line the pathway and use a combination of sources to make the path self-sustaining.
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