Bad GD&T prints

Bad GD&T is where I live.

Most of the prints from our customers are 30+ years old. On those ones, we work with customer to convert them to modern day notes. Can be pretty interesting sometimes!

Another big thing I run into is that GD&T was not properly taught at the college level until about 10 years ago. All of the "big dogs" (60 year old dudes with two masters degrees) who have been at the shop for 30 years don't really understand GD&T and they have to go to someone like me (30 year old with barely an associates) who is the expert. The ones who cared to learn this stuff do great but there are definitely a group of those guys who don't/won't care about it at all.

The medical industry is the worst I have ever experienced in 38+ years that I've been programming CMMs

My favorite project of all time..

A local college was repairing an engine from a u-boat and they needed some gears. They had schematics from 1942 in German. We had to translate, reverse engineer, and then create new prints with modern GD&T. My family has a large connection with WW2 (specifically sinking these SOBs) so it was cool to be a part of this process

XxXxXx has done some interesting work with their GD&T process. They don't mark up any kind of a print anymore. Part of the part cad data surface is some wireframe, which outlines all mating surfaces. They issue a single spec for all stampings (GLOBAL GENERIC TOLERANCES FOR SHEET METAL COMPONENTS). They make a 3D PDF file that calls out the functions and sizes of all holes, you reference the specs, you program. Outline surfaces are mating tol, non-outline surface are non-mating tol, 15 different hole type callouts, 4 surface callouts, 5 trim callouts.

Only problem is, you have no way of knowing which of the 5 possible types of trim it is, unless you are an XxXxXx engineer as these are not called out on the PDF, the PDF only shows hole type/size, none of the other 2 possible surfaces are ever called out on the PDF (again, without being an XxXxXx engineer, you don't know).

Everything is called out to A|B|C, but some fixtures will have 'D' nets as well (but only sometimes and only if there are more than 3 "A" nets, but I've seen them with 5 nets, all "A").

Oh, and they do NOT allow MMC for any position callout anymore, haven't for a few years, but you are allowed it for the "B" and "C" locators, but the fixtures are made with RFS pins, so you don't get that either.

So, it was a great start, but kinda not as great on the followup. CAD is always master (except for hole sizes, called out on the PDF), all 'basics' come from the CAD file.

I'm constantly programming parts where the part can measure good, have all finishes (like paint) applied, and be installed, but if you add a coat of paint after that the part will be "bad". It's still in the assembly, but because someone decided that edges that will sit in clearance and be painted are acceptable datums you've got CMM programmers spending, literally, 4 extra hours on a part program to apply the correct tolerances for paint. 4½ if they browse the forums while they should be doing the above.

Other than being tedious af, this company is paying way more for their parts than they need to because of these crappy callouts. And their vendors are losing personnel (like me) who don't have the patience for stupid bs. And that's just one of the many items on my list of grievances with these... be nice....

Sweet project. I have been inside the one in Chicago that was the only captured 1 during the war. Movies make them look like cavern.... more like a gopher hole...

I do enjoy conversations with engineers when they tell me whats what and when I ask them where in the standard I can reference what they are saying and they refer to some random text book...... Then I quote them the section / subsection and page # ( no , not from memory you nerds ... ) I am talking about and then refer to me actually having my Y14.5 certification it gets kind of fun.

I have to do that a lot with a Black Oxide coating super annoying.

That IS a cool project.

I've been in the U-boat in Chicago too. What really impressed me was just how complicated it was on the inside, lots of complex curves and components. It is really impressive what could be made before the days of CAD and CMMs.