Dear ASTE:

The world seems to be closing in on me. Everyone with less seniority than me has been laid off. They announced it one day by marching all those to be laid off into the auditorium and telling them they were to be immediately escorted off the premises. They justified it by telling them they were afraid of tactics like revenge, espionage, theft and violence. One minute they were valuable employees, part of the team, part of the family, and the next they were criminals capable of acts of murder and mayhem. What if I'm next? I always thought I would work here my whole life, but now I'm not so sure. It's all so depressing that everyone around me is stunned, incapable of getting past it and going back to work. The résumés are appearing from every workstation. It's like rats deserting a sinking ship or clinging to the last bit of driftwood once it's gone down. What should I do?

Dear Writer:

The world can be an uncertain and cruel place. Just when we are starting to feel fat and secure, along comes the reality police wearing hobnailed boots. The truth is there is no such thing as a secure life or job. It is just a false sense of security that we allow ourselves to feel so that we can get through the days. All we can ever do is be ready. Educate yourself.

Educate yourself in new technical areas and to the politics of your situation and to the other companies that might need you when you are treated like so much raw sewage floating on the sea of life. Be afraid and paranoid and cautious. They might be out to get you, but even if they aren't, you might get swept up in a wave of cost cutting that begins with some bean counter you have never even seen who rouses from his catatonic state long enough to say ``Hey, I've got a great idea! Let's send all these jobs to Haiti and pay the workers in chicken feet.

Dear ASTE:

At my company all we ever do is fight over our measurement techniques and their validity to inspect everything from size to form, orientation and location. In recent years, we have thrown out all our inspection equipment except the CMM (coordinate measurement machine). We sold off our surface plates, height gages, vernier calipers, micrometers, fixtures, gages. . . everything. Now, we are finding gross errors in what the CMM's do to establish datums (average planes and axes instead of high point planes and axes) and check form (not nearly enough points are taken with our touch probes), orientation and position (probing the actual surfaces with only a few points where, according to the Dimensioning and Tolerancing Y14.5 standard, we should be probing a gage pin for holes that is the maximum inscribed cylinder--now called the mating size). We know what the software is doing is not correct, and we know we are being told to use no fixtures to establish the datums, and we know we aren't probing correctly. What can we do to get our confidence in our measurement procedure back?

Dear Writer:

You can plan a more balanced attack. Your measurement procedure is too reliant on the mystical abilities of the CMM. If your procedures need more points to gain confidence in checking form, then take more points, either with the probe you have or with a probe you buy that is designed to drag along the surface and take hundreds of points. If your software won't form high point datum planes and axes, then get a software program that will-- or better yet, fixture your parts to establish datums and probe the fixtures since fixtures will touch the work piece's high points. If you have low confidence in the validity and functionality of the data you are collecting, then augment it with surface plate equipment or with dedicated receiver-type gages (GO gages to inspect maximum material condition envelopes and Functional gages to inspect geometric tolerances such as perpendicularity and position controlled at maximum material condition). 

Notice that unlike many CMM (coordinate measurement machine) zealots, I did not say use only the one tool. I said use a more balanced approach that takes the attributes of all the tools available and forms a more technically correct measurement procedure. These tools augment one another. Each is made better by the other and gives us more confidence in the final inspection data. Lately, it seems like those of us suggesting the use of anything other than the CMM have come under attack by the CMM drones. All measurement equipment has flaws and a great way to overcome these flaws is to collect data in a variety of ways. Some of these ways will be slow, but give you valuable variables data for the improvement of manufacturing. These slower techniques, like the surface plate and the coordinate measurement machine, should be used optimally, like with fixtures for proper datum establishment, and with enough points to reach an acceptable level of certainty about things like form. Faster techniques like GO gages and Functional gages may be used to inspect a lot of parts very quickly for attribute (good vs. bad) data. These faster techniques, since they often simulate the worst mating condition of an assembly, will give you a good deal of confidence on simply whether or not your workpieces will assemble. Again, remember it's not use one measurement piece of equipment exclusively, but use as many as are needed to give you the data and the confidence you need to sleep well at night.

Dear Jim:

I understand that this newsletter will contain the particulars about what percentage of people taking the Y14.5.2 certification exam passed, but I would like to know something else. Since you have taken and passed the exam, what were your impressions about the way it was administered and the mood of the group taking it?

Dear Writer:

The air was filled with the stench of fear. It sounds like the beginning of a bad novel, but it's the truth. The people in that room were so afraid I thought a few were going to have heart attacks. The older man next to me lamented why he would put himself through such a torture. When I finished the exam and rose to leave, I wished him luck. He stared back at me looking a sickly shade of green. I hope he made it out alive. I thought the people who administered the exam were unqualified to do so. They were not subject matter experts. They were virtually useless in clarifying the content of questions that badly needed clarifying. Many questions on the exam were vague-- not difficult, just vague. I've been teaching this stuff for a long time and have been involved in the ANSI meetings since 1982, and I felt that had I not known the personalities of many of the members of the committee who wrote the exam, I could not have easily figured out which answer that they would think was most correct. This exam, had it been clearly written, would have been far too easy. But just the fact that it wasn't clearly written and that some of the questions were simply incomplete, made it an interesting experience in test taking. As mentioned elsewhere in this newsletter, only 13 of 64 people passed the Technologist level exam and only 64 of 129 people passed the Senior level exam. It doesn't take a psychic to realize that many of the people were too confused by the wording to answer correctly, and many were simply too afraid of the consequences of failing to even spell their name correctly. I'm not kidding when I say that there was a reason most of the members of the Y14.5 committee stayed away. Only the very brave or the very deluded took that exam. I'm not certain which category I fell into, but I am grateful I didn't stumble under the pressure as did many others in that testing room. When it was over, I saw grown people who at least thought they had done well actually prance out of that room, their arms held overhead in a victory pose. Others, however, sat with their heads barely off the table, their eyes empty and pleading for some sort of help, when none was to be had. It was a sad and pitiful sight to behold. To all those who tried and failed, I can only say that at least you had the courage to try.

Dear ASTE:

I am interested in getting some feedback on how you dimension screw threads at your companies, or other companies you have seen in your work. It seems that every few years, we get into huge discussion on whether to dimension/tolerance threads functionally (pitch diameter) or non-functionally (minor diameter for internal threads). As you might have guessed, the design folks are on the functional side of the fence, and the fab folks are on the non-functional side of the fence. Our fab producibility engineers are pushing strongly to dimension/tolerance internal threads to the minor diameter because it saves ``a lot" more to inspect threads to the minor diameter than to the pitch diameter. Several of our programs do this and we usually don't have problems. I am not inquiring about what is the ``right" thing to do, nor what Y14.5 says to do. I believe I understand all the issues. 

My questions to you are simple:

1) How do you dimension screw threads?
2) How do you generally inspect them?
3) Is this issue an isolated incident at my company, or do you have similar discussions in your companies?

Thanks in advance for your response. If you can let me know something I will use it in some discussions we plan.

Dear Writer:

My opinion on dimensioning and tolerancing screw threads has always been the functional one. If concessions must be made because of limitations in equipment or time, they should be made at the time of inspection. To actually imply that the designer wants the inspector to inspect in a nonfunctional manner is against my beliefs. We, as dimensioning and tolerancing engineers, are tellers of physical truths. If the screw engages the pitch cylinder, we simply describe that on the drawings. If I was inspecting the threaded holes and was unable to comply with inspecting the axis of the pitch cylinder, I would do the best I could, with the equipment I had at the time, and if that meant estimating the location by using the minor diameter, so be it. But I would never put that on the design drawing, because then we lose the goal altogether. That goal should always be to, at least suggest that the feature is only optimally inspected if it is inspected as it functions. And even if we can't inspect it that way today, we will remember that we should try to increase our measurement capability in the future to do a better (more functional) job. 

As long as the requirement is on the drawing, we keep it in mind as our goal, and strive to achieve it. Besides, threaded gage plugs for inspecting projected tolerance zones on threaded holes are available in many different varieties out there. You just need to buy a few sets. Another problem with designating that threaded features be inspected by using the nonfunctional minor diameter is that people often also don't use a projected tolerance zone on the minor diameter. Unless the zone is projected, we don't stand much of a chance of even making a wild guess as to whether or not the parts will assemble. I have seen many inspectors jam an unthreaded gage pin into the minor diameter of a threaded hole and then inspect only one circle on the gage pin (close to the surface of the primary datum feature).

Then, knowing only where one point on the hole's nonfunctional minor diameter axis is, they announce that the hole has met its design requirements. This is wasted motion on their part. They convince themselves that by taking this little bit of completely nonfunctional two-dimensional information that they have complied with the drawing requirements which were nonfunctional to begin with. It's error compounded by error. Starting down that road, I think, is a huge mistake.

Dear ASTE Reader:

In response to our request for GD&T Certification test results for the November 8, 1997, testing dates, the ASME staff has responded with the following information: In order to pass the examination, a candidate must achieve an 85% overall score and at least 50% in each category. 

The overall results to the November 8, 1997 ASME GDTP Exam:

Technologist Level :
 64 candidates for certification took the examination
 The average score was 73%
 13 individuals achieved Technologist Level GDTP Certification

Senior Level:
 129 candidates for certification took the examination
 The average score was 82%
 64 individuals achieved Senior Level GDTP Certification.
 

The content validity of the ASME test has been established. Content validity refers to the extent that the test is a relevant and representative sample of the knowledge (the knowledge outlined in the ASME Y14.5.2 standard) an individual should possess to be certified as a geometric dimensioning and tolerancing professional.

The following dates and locations have been established for the 1998 exams: May 16, 1998: Cleveland, OH; San Jose, CA; Dallas, Tx; Atlanta, GA; Minneapolis, MN; and Grand Rapids, MI. November 14, 1998: Seattle, WA; Rochester, NY; Detroit, MI; Nashville, TN; Phoenix, AZ; and Baltimore, Md.

Thank you for your interest.