Hardness details and marketing suggestions
One reader well-versed in hardness testing writes in to add a few details to a recent article. Meanwhile, some of our more-creative readers suggest some names for a nail-pulling invention featured in Inventor’s Corner. And the inventor chimes in to update us on his progress and the name he chose.
Details, details, details
The recent article on hardness testing was interesting and useful (“Getting Help from Hardness Testing,” July 7). It provides technical information on various types of hardness, one of the important mechanical properties of materials in general, especially for metal cutting.
But there are a few discrepancies:
• The definition of “ANSI” 4130 steel is incorrect. ANSI is an acronym for the American National Standards Institute. Correct definition of this grade of steel is AISI/ASTM 4130 (AISI stands for American Iron and Steel Institute, and ASTM stands for American Society for Testing and Materials).
• The description of the steel heat treatment that increases hardness left out the critical fact that for annealing, the rate of furnace cooling (so many degrees per hour) and the final cooled temperature should be provided. Otherwise, the tensile and yield strengths of a given grade of steel cannot be verified.
• The information on Brinell hardness did not mention the standard ball and standard loads for a Brinell hardness tester. The balls should be 10.0 mm in diameter and made of hardened steel and tungsten carbide. Balls that aren’t 10 mm should meet ASTM E 10 requirements. The test uses loads of 500, 1,000, 1,500, 2,000, 2,500, and 3,000 kgf. And the 500-kgf load is for testing relatively soft metals such as copper and aluminum alloys. The 3,000-kgf load is mainly used to test steels and cast irons.
• The article left out the range of the most accurate readings (the minimum and the maximum values) for Brinell and Rockwell (HRB and HRC) hardness numbers.
• The information in the table “Sample hardness ranges for metals” is inaccurate. A tungsten-carbide ball indenter lets you measure the hardness of heat-treated steels up to a maximum of 627 HB. If the Rockwell hardness is 105 HRB, scale C should be used because numbers higher than 100 are inaccurate. If hardness is less than 20 HRC, scale B should be used for the same reason, i.e., hardness numbers of 19 HRC and lower are inaccurate.
Nail remover update
The Sept. 23 issue from last year featured a nail-pulling gun in the Inventor’s Corner column. It asked readers to suggest names for the soon-to-be-patented invention. Here are some of the letters we received, as well as an update from the inventor.
Nailout, or Nail-out?
How about the “Nail Biter.”
My son and I read the article about the pneumatic nail remover. My 13-year-old son, Wyatt, suggests “NailOut.” He enjoys building with wood but he says removing nails is too much work.
The name “Nail Ripper” would make the tool sound robust, which I think is what you need to encourage sales.
I’m partial to the Anti Nail Gun name.
Name it the DeNailer, or simply Pneumatic Nail Puller.
I recently filed the patent to cover this invention in the U. S. and Canada. And we chose a name from the several hundred suggestions we received mostly due to the magazine article, the “Nail Shark.”
The response I got from the article was really inspiring. I had e-mail from a great number of companies ready to buy several right away. It turns out there is a whole industry that does nothing but take apart old buildings to recycle the wood. They do it mostly by hand. A gentleman I corresponded with from Habitat for Humanity said that they routinely buy and tear down old houses, and if they could more economically take them apart, it would save them millions every year.
The first-round prototype built over this past year pulled out big and small nails and even a few dry wall screws. The second version is just about ready to be prototyped.
I have estimated that there may be a demand for 250,000 or more in the first few years. There are between 1 and 2 million carpenters in the U. S. and Canada, and nearly every one I have spoken with said they would buy one of these the first chance they get.— Jake Kittell
A better way to learn FEA
I wholeheartedly concur with the thrust of the recent FE Update column (“Surface Contact 101: Block and Ramp with Friction,” July 7). However, I think the example chosen was way too difficult for novice FEA users. During the 1980s, I was a structural loads engineer working on the Space Shuttle at Rockwell. The company developed a course for training new users on FEA that contained a series of problems, each progressively more difficult than the previous one, that could be solved by hand. You could then model and solve them using FEA.
In place of the example shown in this article, I would suggest a two-step approach. First, solve a truss that is statically determinate by hand. Then solve it by FEA. Then solve a truss that is not statically determinate (i.e., something that involves additional relationships like Castigliano) before you solve it by FEA. After modeling and solving several simple problems such as this, you can progress to something more difficult such as modeling nonlinear behavior in FEA.
350 psi of vacuum?
In an article on vacuum forming (“Vacuum-Formed Plastics Fool Filmgoers,” July 7), it said the technicians “apply about 350 psi of vacuum.“ This doesn’t really make sense. Maybe someone meant pressure?
Good catch. There’s about 350 lb of air pressure over the area of the sheet. The process applies a vacuum of about 25 in.-Hg. — Jessica Shapiro
Some serious sarcasm
I have been carefully reading all the articles associated with electric vehicles (EVs). There is a way to extend the range of EVs that is so obvious I do not understand how everyone is missing it. All EVs should be designed with motors for propulsion on two wheels and alternators on two wheels to generate electricity. Ergo, we will greatly extend the range of EVs and save a lot of ergs.
I feel sure that when this proposal is turned into law by our Congress, sales of EVs will soar. Having solved this problem, Congress can then address major other issues such as repealing some of those annoying laws of physics and letting us buy incandescent bulbs.