Thanks for the information, I fully understand the MMC issue, but in LMC, what would the concept be and where or how would it be used? Again, thank you very much, greetings from Tijuana MX
The MMC modifier protects that inner boundary of the hole and outer boundary of the pin. This ensures the fit while maximizing the allowable tolerance. LMC modifiers protect the opposite boundaries. Applications could be min wall thicknesses and cast features that need proper machine allowances. Keep in mind RFS does all of this but just does not allow that extra "bonus tolerance". When in doubt, always go RFS as the default.
Can we say then a nonzero tolerancing at MMC is just a bad practice because it hurts manufacturing or is there any situation that necessitates using nonzero tolerance at MMC ? Thanks in advance
Good question. I usually don't put zero at MMC on bolt holes. As you know, the GTol of zero at MMC design technique allows the hole to be smaller. A small hole may be difficult to put a bolt in with a line-line fit. I like to stick with standard drill sizes for the hole and use a regular (fastener formula calculated) position tolerance at MMC. Sometimes small holes can hurt another aspect of the design.
@GeoTolPro. So you can't use zero tolerance when you say have a shaft at 1.003 MMC and a hole at 1.005 MMC, so that when both are produced with the zero tolerance at MMC modifier, you preserve a non-zero clearance fit of 0.002 between the parts while giving manufacturing more room on tolerance for each?
You’re the best instructor
I had taking GD&T training and you are the best instractor/teacher.
The way you explain GD&T is amazing. You have the best explanations and way of talking. I could listen to you all day even if it's about GD&T. LOL!
Wow, thank you!
Your videos are the best
Thanks for the information, I fully understand the MMC issue, but in LMC, what would the concept be and where or how would it be used?
Again, thank you very much, greetings from Tijuana MX
The MMC modifier protects that inner boundary of the hole and outer boundary of the pin. This ensures the fit while maximizing the allowable tolerance. LMC modifiers protect the opposite boundaries. Applications could be min wall thicknesses and cast features that need proper machine allowances.
Keep in mind RFS does all of this but just does not allow that extra "bonus tolerance". When in doubt, always go RFS as the default.
Can we say then a nonzero tolerancing at MMC is just a bad practice because it hurts manufacturing or is there any situation that necessitates using nonzero tolerance at MMC ? Thanks in advance
Good question. I usually don't put zero at MMC on bolt holes. As you know, the GTol of zero at MMC design technique allows the hole to be smaller. A small hole may be difficult to put a bolt in with a line-line fit. I like to stick with standard drill sizes for the hole and use a regular (fastener formula calculated) position tolerance at MMC. Sometimes small holes can hurt another aspect of the design.
@GeoTolPro. So you can't use zero tolerance when you say have a shaft at 1.003 MMC and a hole at 1.005 MMC, so that when both are produced with the zero tolerance at MMC modifier, you preserve a non-zero clearance fit of 0.002 between the parts while giving manufacturing more room on tolerance for each?