Thinking of signing up for the community college Tuesday night GD&T course; I run a Bridgeport and a 13" LeBlond all day, holding ±0.0005 with an indicator and sine bar, but some newer prints with true position callouts slow me down. For those who took a class, did it sharpen your inspection and setup decisions on the floor, or was a stack of prints and a surface plate at home just as effective?
I took the Tuesday night class at our CC and it paid off the first week when ‘true position @ MMC’ stopped being voodoo and I quit over-inspecting. Practical tip: stick a snug dowel in the bore and use an angle plate to simulate A/B datums, sweep the pin with your tenths indicator, and remember the bonus buys you clearance so you can green‑light parts faster. If you can’t swing the class, skim the position section on https://www.gdandtbasics.com, but the live Q&A with your own prints was the real win.
Worth it for me — stopped clocking holes and started doing functional checks: gauge pins plus a drill bushing to verify true position at MMC and take the “bonus tolerance” instead of chasing tenths. Just make sure the instructor ties datums to how you’d fixture; if not, this primer helps: True Position – Position Tolerance | GD&T Basics. Think of MMC like free clearance you get to spend on location, not a trick question.
Biggest win from the night class: I learned to turn the callout into a functional gauge — calculate the virtual condition, bore a ring to that size in an aluminum plate, and use it as a slip check on the mill; “measure for function,” and I stopped sweeping every pattern. First week after, a bolt-circle job went from 25 min inspect to 5 because the ring and a pin told me go/no-go off my datums. If you’re already solid on basics, a quick pass through https://www.gdandtbasics.com helps, but the walkthroughs beat self-study for me, @alerodr.
Quick example: the class got me building a simple “datum target” block — three skimmed pads for A, a slot for B, a pin for C — so I set parts up the same way they’re checked and stopped chasing edge math. @alexander_and67’s pin trick pairs well, but if you’re mostly doing one-offs, machining that block per print can be a time sink — still worth it for your mix?
Took the Tuesday GD&T at Clark; what sped me up was “set it how they check it” — I zero the DRO off a pin in the primary hole and a skimmed pad instead of an edge, and my position rechecks stopped arguing with the print. I also keep a tiny phone calc that does 2*sqrt(dx^2+dy^2) so I know if a bore’s in the zone without a surface plate run, which feels silly but saves time. Worth it if they cover datum precedence and derived features; otherwise it’s mostly symbols with not much floor change.
And i did the Tuesday night CC GD&T last fall; the best payoff was learning to use “virtual condition” to build a quick check plate — calculated VC for a bolt circle, pressed dowel pins into a scrap plate at the basic locations, and now I drop parts on it to sanity-check true position before I even touch the indicators on the Bridgeport. It’s worth it, but if they don’t cover projected tolerance zones for tapped holes you’ll still be guessing on tall standoffs.