Great overview! Very clear demonstrations. Thanks.

You need to have the part mounted on three points on the surface plate (gauge or 1-2-3 blocks) for flatness as 3 points make a plane, see GD&T Y14.5-2018 setup processes.

@GeoTolPro

5 ай бұрын

The video mark 6:06 explains the three gage block method. However, this is a terrible way to check sheet metal or a large heavy part (gravity causes the part to sag). ASME Y14.5-2018 does not define how to measure tolerances! It only defines the theoretical tolerance zone. The part's quality plan defines the inspection method based the situation (risk vs. cost analysis). That's what the video is about.

@mscscambodia

5 ай бұрын

Two points is never acceptable, putting on the surface plate is not flatness check, part will be reject by any metrologist if this is how you set it up for flatness. @@GeoTolPro

@mscscambodia

5 ай бұрын

The risk is you put a company out of business for what you are showing as a way to check the parts for flatness, not worth it.@@GeoTolPro

As always a great video.

Really good explanation, keep up the excellent work!

Thank you for the video. It's very helpful. Keep posting such contents. Wish you good luck...😉

Great video

Thank you sir

very clear and informative video 😁👍

Great explanation! Could you also explain the difference between regular flatness and a flatness with CZ? How the tolerance zones would be in these two cases?

@GeoTolPro

7 күн бұрын

Flatness "combined zone" is an ISO-GPS concept. The CZ modifier locates the flatness tolerance zones together to also control location between the surfaces (usually to control coplanarity). ASME would instead switch to a profile tolerance to control location between multiple surfaces.

@mahanteshhindiholi432

7 күн бұрын

@@GeoTolPro Understood. Thank you very much!

It is my goal to learn GD& but so many caveats and definitions and interpretations makes my head spin. Difficult subject, great video!

@GeoTolPro

Жыл бұрын

Yes, there is a lot to learn with GD&T. Its just like learning a CAD system. It ranges from casual users of the program who can make a few simple parts all the way to the experts who can model the most complex assemblies. Good luck and keep at it!

@ganeshshenoy2615

2 ай бұрын

And just when you think you get it, one query can throw you off.

Seen scenarios where large plates get stacked directly onto one another and slide/shuffle around during shipping and are left with scratches. Usually parts are still functional even though they would fail a flatness check because of a scratch. How would you specify that indented scratches/gouges are allowable on let's say 5% of the surface as long as the other 95% of the surface is flat within the specified tolerance zone? Add a note on the drawing?

@GeoTolPro

Жыл бұрын

There is nothing in Y14.5 like that requirement. A note sounds like the best method here.

in the starting, does flatness of 0.1 means it is controlling Ra(Surface roughness) or Ra is further refinement of flatness. Size->Flatness->Ra ??

@GeoTolPro

Жыл бұрын

Surface roughness is a much smaller scale than flatness. It is a localized peak to valley. Surface roughness also applies to curved surfaces where flatness does not. Not sure I would call roughness a refinement, its just a totally different jurisdiction. But geometric tolerances do control "all elements" of the feature.

Hey thanks for this explanation! Question 0:15: Is there a difference for the manufactured part to inspect if you: 1) Datum A onto the flatness callout itself (like in the video), or if you put: 2) Datum A on directly the surface Does it matter or is it actually the same? Thanks :)

@GeoTolPro

7 күн бұрын

No difference there. The surface must be flat. Then it is also named "datum feature A". Personally, I like to have the symbols together.

Try that on a 2.0 wide flange that is 333.5 diameter.

@GeoTolPro

5 ай бұрын

Sounds like a good one for a CMM!

Umm...I don't think adding some random size shim under a side @4:40 gets you to correctly measure flatness. All you're doing is adding another unknown 'parallel' surface to the mix. To measure flatness of that part I was taught to turn the surface to be measured upside down and support the part at tool points spaced as far apart as possible to limit their effects, like shown at 6:15. Showing the method at 4:40 I think is misleading but I'd like to hear the reasons why it's not.

@GeoTolPro

Жыл бұрын

There is never a "perfect way" to measure flatness. Instead, there are different levels of risk vs. cost. Feeler gage check for flatness is common for large plates with say a 2mm flatness requirement. Feeler gages are cheap and quick way to verify this. However, feeler gages would be terrible for a machined part with a 0.05 flatness. A more precise (and expensive) measurement with a dial indicator (or CMM) would be needed.

@GeoTolPro

Жыл бұрын

Also, supporting off tool points would not be good for a heavy part or sheet metal that sags under its own weight. Again, there is no perfect way to measure flatness. There are different techniques for different scenarios with the need to balance risk vs cost.