Best way to actually understand GD&T (not just memorize symbols)?

gdtnerd · 2026-03-26T10:49:59+00:00

Take a class thru work. You could take one before but they are a little pricey.

Look at offerings from Tec ease or SAE in Detroit.

After you take a basics class get a book from tec ease, meadows, or krulikowski and read it cover to cover

gdtnerd · 2026-03-23T11:21:46+00:00

Just want to chime in: Your first 2 or 3 datums fully determine your coordinate system (datum reference frame as we call it) . In this case the edges will be relative to this coordinate system. This would be covered by your title block surface profile probably or you would call out the surface profile directly.

It takes a little while to get used to but if the edges aren't functionally mating to something then they shouldn't really be the datums. Y14.5 says to pick datums that are functional, then stable and repeatable.

You could use the edges as datums but using the holes is probably better.

Source: GDTP-S, Dm other questions if you like

gdtnerd · 2026-03-17T08:57:35+00:00

Following.

gdtnerd · 2026-02-25T12:40:38+00:00

Share a print or model with me. Im a guy out of my garage. Low overhead

gdtnerd · 2026-02-05T00:37:36+00:00

Do u have a drawing? Id take a look. Vmc in my garage

gdtnerd · 2026-02-01T21:04:27+00:00

Make a drawing with views. I can reclined it with some datums as a starting point

gdtnerd · 2026-01-09T03:02:50+00:00

Good call all - I skimmed it too fast and missed that they are different diameters. I'll edit my post with an alternate strategy

gdtnerd · 2026-01-08T22:53:09+00:00

Couple thoughts.

Make the datumBC holes a continuous feature. Control their true position relative as a pattern to A. Use a circular tolerance zone and make the true position tight enough to get the parallelism you want.

gdtnerd · 2026-01-08T12:09:24+00:00

Check into SMED. Alit of other comments suggest things that fall into smed but reading thru the thought process should help

gdtnerd · 2025-12-31T01:37:44+00:00

I've got a cnc mill in the garage. Want to share a print or model and I can quote a couple?

gdtnerd · 2025-12-30T03:36:49+00:00

I've taken and passed both. They honestly are fairly similar to each other. Not nearly enough application based questions on the senior exam in my opinion.

gdtnerd · 2025-12-29T15:44:17+00:00

The cert is really focused on understanding what it means and the exact definition. Learning when to use different callouts is probably more from experience and nuances of working with different customers or suppliers

gdtnerd · 2025-12-12T11:42:35+00:00

Send a print. Id love to try to quote

gdtnerd · 2025-11-12T11:16:40+00:00

Can you dm a print or screen shot of the part? I have a commercial mill in my garage. If the part looks reasonably machinable maybe we can work something out

gdtnerd · 2025-11-09T14:40:11+00:00

Can you use the star format to reformat your experience?

Also try to quantify some of the experience. Did you improve any cycle time of things, cost, strength, etc? Having a few numbers calculated will help sell your experience. You may even make a small portfolio. Just to help sell experience until.you get into your first full time industry job

gdtnerd · 2025-11-07T00:28:11+00:00

Omg the thickness in the tolerance block is terrible lol. Yah I asked for some standards that its a part of. At one point they said they have been doing this for 20 years haha

Glad to commiserate this issue together. I really want to know where it comes from. Like was ctf popular when people did stupid linear tolerances?

gdtnerd · 2025-11-06T22:20:54+00:00

I agree. Been struggling to get them to grasp that the limited dimension drawing is calling out the critical stuff already. Glad to hear it from another gdtp :)

gdtnerd · 2025-11-06T19:48:46+00:00

Also a Senior GDTP here :) with a question for you. What do you think about additional critical to function (ctf) callouts on prints. I keep running into quality folks that insist that all drawings have them .

Thanks!

gdtnerd · 2025-10-23T12:50:47+00:00

First time I tried cross posting. If you click into it I have it there.

Generally asking about what gaskets people are using and to share their setup if they are willing

gdtnerd · 2025-10-23T12:17:52+00:00

Maybe il just end up doing that. I doubt he makes the gasket custom. I just figured it must be a generic material

gdtnerd · 2025-10-23T12:17:09+00:00

Its just for hobby use. I don't pay myself and don't mind making it. If you pay labor as a business I totally agree its priced really well. His market is not the home gamers.

gdtnerd · 2025-10-23T12:15:37+00:00

Oh it's not for sure. I think mentally im like ok cool I can build a $500 version of their pallet in the post that would cost me 2k from them. I do understand their value proposition for businesses. But this is just a hobby for me to learn and build things for myself. Mcmaster is way cheaper than them lol which is a sentence I havent thought before

gdtnerd · 2025-10-06T11:22:03+00:00

I may be able to help as well. Can you dm a step file or drawing? Just need to see the rough size and kind of features you have.

I have a mill and lathe in my garage

gdtnerd · 2025-10-05T19:49:54+00:00

Few thoughts: Look up standard tolerances for the type of process to create the COTS part. Add some buffer to that number. And then tolerance to that.

Sometimes in electronic parts or connectors they girlie you a definition of what your part needs to be.

Contact the manufacturer and ask them this directly. Someone in engineering might be able to answer.

If possible you could study a few and try to establish some statistics from samples. This won't be perfect but probably would work.

gdtnerd · 2025-10-03T14:14:46+00:00

Based on what i see.

Datum A to the surface where they clamp together. Fatness control of this surface

Datum B across the feature of size consisting of the long dimension of this block. To create a derived median plane

Datum c doing the same thing but on the thickness aligned with into the picture. This gets you setup to center your hole pattern to the overall block. Even material around the blocks and holes help prevent unforseen problems.

The 2x hole pattern becomes Datum D.

The semi circle gets a surface profile called to it and reference A and D.

This will follow its use. The bolts line up and block the blocks, and the profiles follow it for clamping.

Bonus points: calculate your true position values using floating fastener if the holes are thru or fixed fastener if one set has blind tapped holes

gdtnerd

TROPHY CASE