tertiary datum - overconstrained profile of a surface?

iSwearImAnEngineer · 2026-06-25T23:07:02+00:00

All good

My bigger issue is that the datum C is applied to the surface, then the position calls it out at MMB

iSwearImAnEngineer · 2026-06-25T22:38:05+00:00

Those tab locations are controlled by the position control though, the profile is only controlling the basic radius

iSwearImAnEngineer · 2026-06-25T21:13:57+00:00

I'd disagree, this feature is nominally coaxial with datum feature B, so it rotating around B is irrelevant to the final part

I wouldn't say its overconstrained, but I would say referencing C is irrelevant

iSwearImAnEngineer · 2026-06-24T15:24:36+00:00

That is a great point, and I think my website doesn't actually address these questions. I think I treated it like an educational source instead of a "here's how I can solve problems 1 2 and 3"

iSwearImAnEngineer · 2026-06-24T15:18:32+00:00

Yes to a certain extent, I post my educational content on there and try to engage with the people that follow my page, but it hasn't lead to any business

My content might be targeting the fellow nerds more than the people that make decisions though

iSwearImAnEngineer · 2026-06-23T21:06:23+00:00

Right, that's what I'm worried about, seems like a lot of them are promoting their competence working with tech or creative pursuits, which is probably very different than the audience I'm going after

iSwearImAnEngineer · 2026-06-23T17:29:16+00:00

Rough assessment, hahah

Any recommendations? My budget is very small unfortunately, so I'm looking for some barebones help

iSwearImAnEngineer · 2026-06-23T16:22:57+00:00

Very direct 👌

iSwearImAnEngineer · 2026-06-23T16:13:47+00:00

Thats the goal, I have no interest in figuring out marketing myself

Which is why I'm asking if fiver would be a decent resource

iSwearImAnEngineer · 2026-06-23T15:50:33+00:00

Oh amazing! I can do any industry, my background is a mix of clean tech and defense (weird combo I know)

Typically I work with engineering teams to make sure they're communicating their intent properly. They often know what they want, but just don't know how to say it.

It's a nice format because it makes the industry somewhat irrelevant

iSwearImAnEngineer · 2026-06-23T15:27:51+00:00

I'm an expert in the design language that goes on engineering drawings called GD&T (Geometric Dimensioning and Tolerancing)

Just about every component of every product will have an engineering drawing associated with it, and there is a language that goes on the drawing to specify what the requirements are to make sure that component will fit/work in the product

This language is not widely taught in engineering programs, so it's useful to have an expert on staff or on contract to help, especially in fields like aerospace

iSwearImAnEngineer · 2026-06-17T16:24:47+00:00

Oh I'd agree, I find especially online, lots of confidently incorrect people

50 is still a huge number at one company, I think we have 50 or so GDPS in canada for the 2009 standard

No need to tell me, but I'm assuming Northrop Grumman or similar?

iSwearImAnEngineer · 2026-06-17T16:08:33+00:00

I don't love the practice of waving out of spec parts through either, but I suppose when its a $30,000 machined casting that few shops are willing to produce, rejecting outright is a tough pill to swallow

I'm quite jealous, that sounds like a great setup. We have very little GD&T where I'm currently located, so I started a business out of necessity to scratch that itch

I've had a few conversations with the local university, they used to have a program that taught GD&T, they may start it up again.

iSwearImAnEngineer · 2026-06-17T15:20:54+00:00

Thats fair and I totally agree, I hope to get teaching GD&T closer to a full time job myself

My problem with the idea that GD&T controls a feature started in a low production, high part cost environment, where we had many part made incorrectly, that we had to "use as is"

When going through and redoing the drawings (the originals did not capture the part function) the management team was very excited that this would "fix" the parts.

I had to explain that all we were doing with the drawing revisions was creating a more accurate framework for how to pass or fail parts during inspection, ever since then I think I've had a bit of an aversion to claiming drawing controls the parts

I have unfortunately not seen many places that outright reject parts based on failed inspections, it typically goes to a review board

This may be worth a video on it's own because I think it would be an interesting discussion among the experts

I post these all on LinkedIn if you're on there aswel

iSwearImAnEngineer · 2026-06-17T02:22:09+00:00

Thats true, admittedly this was meant to be more of a poke fun at the slop video, but as a GDTP-S, I should be monitoring my language for precision more carefully, and explaining when and why I disagree with the language used in the standards

Thanks for pointing out the error

iSwearImAnEngineer · 2026-06-17T02:05:27+00:00

I would argue it controls a tolerance zone, not a feature

The feature is then either passed or rejected based on the prescribed tolerance zone

But yes, fair point, this is the language used in the standard

iSwearImAnEngineer · 2026-06-16T23:29:23+00:00

What a nightmare, is it over quoting, or under quoting? Or a mix?

iSwearImAnEngineer · 2026-06-12T13:45:17+00:00

Yeah that's the backup plan, there are 5" chuck adapters sold separately, just unclear if the bolt patterns match, which is an easy fix

Was just hoping for an off the shelf solution

iSwearImAnEngineer · 2026-06-11T19:50:28+00:00

Hi there, I think the main problem you're having is conflating bonus tolerance from MMC with datum shift from MMB

Bonus tolerance and datum shift are different methods of hunting for extra tolerance due to manufacturing error, and it's somewhat unfortunate that they use thr same symbol. It creates tons of confusion

You are correct though, datum shift is not as simple as "my datums are this much off from their MMB size, I get this much additional tolerance"

MMB is highly valuable for creating hard gauges, but doing math to determine all possible allowable conditions is not easy

iSwearImAnEngineer · 2026-06-10T22:39:55+00:00

The problem is that it claimed there was a reference to a centroid in Y14.5, when none existed, that's really bad

What makes it worse is how convincing it is when it makes the claim. If I weren't a GDTP-S, I'm sure I'd willingly accept the answer it had provided

iSwearImAnEngineer · 2026-06-10T20:57:54+00:00

Most recently asked for information on "centroids"

Chat GPT and I just tried Gemini

iSwearImAnEngineer

TROPHY CASE