GD&T Help

[Lewis.Young]

Hi All,

I've been trying to learn the in's and out's of GD&T recently, as I've only touched upon it in the past.

Can anyone help to explain what's being said below in the paragraph and the image? I think I understand the concept of bonus tolerance in MMC and LMC (a 10mm +-0.2 shaft made at 0.3mm MMC will give extra bonus tolerance at a rate directly proportional to the shaft diameter as it decreases to the lower limit of 9.8mm), but i'm struggling to understand why RFS doesn't have this. Especially the part in the image where it says "it may act like 9.5mm to 10.5mm", what is that supposed to mean?

Any help or extra learning info would be greatly appreciated

Thanks

Lewis Young
Windows 7 x64 - 32GB Ram
Intel Xeon E5-1620 v2 @ 3.70GHz
nVidia Quadro M2000 - 4GB
Inventor Professional 2017.3
Vault Basic 2017
3ds Max 2018

[Frederick_Law]

There are companies that do GD&T training.

We had one came to our company and train everyone.

Check with quality control and ISO companies.

[Lewis.Young]

That would be the ideal situation, but because my company hardly uses tolerancing they're not willing to pay for the training

I'm actually looking for a new job at the moment, so this GD&T study is more to build my personal knowledge in case my new job requires it. Hopefully I can get some proper training somewhere down the line with a company who sees the benefits.

Lewis Young
Windows 7 x64 - 32GB Ram
Intel Xeon E5-1620 v2 @ 3.70GHz
nVidia Quadro M2000 - 4GB
Inventor Professional 2017.3
Vault Basic 2017
3ds Max 2018

[Frederick_Law]

There are info online but its better with someone who understand GD&T explain with sample drawing and part.

I need to read my notes again to see how to answer this which means I shouldn't 

[Lewis.Young]

Yeah i get what you mean, I've found a few free resources online but it feels like i'm missing out information.

Anyway I appreciate the feedback, if nobody else can help i might just try a few libraries and see if they have an edition of ASME Y14.5

Thanks

Lewis Young
Windows 7 x64 - 32GB Ram
Intel Xeon E5-1620 v2 @ 3.70GHz
nVidia Quadro M2000 - 4GB
Inventor Professional 2017.3
Vault Basic 2017
3ds Max 2018

[Anonymous]

RFS means you do not get the additional tolerance MMC or LMC would give you.

[Anonymous]

Hi Lewis.Young

Look up GD&T rule1 and rule2 (Taylor Priciple). Theres lots on google.

I have a few books that explaine the priniples but cant photo copy them (copy right etc...)

A pocket guide "Geo-Metrics III" by Lowell W Foster is also a handy reference booklet.

[Curtis_W]

Another resource in case it helps someone in the future:
https://www.youtube.com/playlist?list=PLKaojPU8IOnHU75NcH7Muq7K92rTNekXI

[shawonhabijabi]

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I had the same confusion with RFS vs MMC bonus tolerance. Tbh reading alone didn’t help much, I needed visual examples Excedify.com helped a lot with that