End of Slot as Datums? 7

[SDETERS]

I have a part that has two protuding slot features on it. The part is made of Rubber. The two protruded slots are what locates this part in the assembly. I want to call out a profile of these slots but I also want to call the end radius as y and z datum Please See PDF. What is the proper way of doing this? Will the R.16 be basic or have a tolerance? Should I say three surfaces on the profile instead of all around? Suggestions. Wow two questions from me in same day. Sorry.

 

[KENAT]

Well, while you most likely have a point as you most likely know more about it than I...

If the outside profile is truly relatively non critical then I'd hope it would have a tolerance that reflects this and that is well within process capability and so chances of one being far enough off to be rejected is correspondingly small. Or something like that.

If there is some other interface or functional concern that the OP hasn't shared with us (or I missed) then I'd look more closely.

I sometimes wonder if, especially on non critical parts, we spend too much time trying to find the 100% correct, all things considered solution, when a 99+% solution could be found for a lot less time and effort.

I think most people I work with don't go far enough, but I sometimes wonder if on here we don't get a bit carried away occasionally.

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[MechNorth]

Really like your last 2 pts, Kenat. I look at this forum as an opportunity to go to the N'th degree in a theoretical discussion. Exposure over time to (decent) design, manufacturing and inspection can help guide us toward the practical and away from the impossible perfect.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[fsincox]

Participation is voluntary; I like exploring ideas with people who seem to be well versed on the subject.
I spent a half hour today arguing with a guy (the chief representative of quality and head of our new GD&T “A” list, we are currently preparing to adopt the 1994 standard) who insisted the standard requires datums to be in alphabetical order ABC, DEF, primary, secondary, and tertiary “the don’t have to start with “A” but they have to be in order, that is the way they show it in the book and it’s supported by 4.4”. I was shocked, I couldn’t believe my ears. I finally found the statement in 3.4.3 “datum reference letters need not be in alphabetical order”. I said: “if what you say is true, they would always be in order”. After reading and thinking he said: “oh, I don’t have time to argue about this anymore”.
My point is some of us need to have a place were we can discuss issues.

 

[MechNorth]

To add to the last point of Fsincox, an increasing number of companies have only one or two GD&T SMEs these days, and almost none have GDTPs, so it's especially important that a forum like this exists for them.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[NormCrawford]

There are other forums too.
This is a good one.

But man it can eat up some time. lol
I would list others but I don't wnat to break any rules or step on toes.

Norm Crawford
GDTP-S
Applied Geometrics, Inc.

http://www.GDandT.com

 

[axym]

No doubt that these forums eat up a lot of time. The reasons that I justify spending the time are that I learn a lot from the other members, that I think I can be help them learn as well, that I find out what issues people are facing, and that trying to explain myself sharpens my own understanding as well as my ability to communicate it. I've had a lot of "aha" moments thinking through issues that were brought up on this forum.

It might also be that I'm one of those freaks who actually enjoys debating Y14.5 minutiae for it's own sake. Sad but true.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[MechNorth]

You attend the Y14.5 meetings, Evan...yes, you are one of those freaks. Add to that the fact that you're from Vancouver, and whoa Nelly! Norm and I (and a few others here that attend the meetings) aren't freaks of course, because we're from the extended rust belt where people are well grounded.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[KENAT]

When the OP is a fairly direct question, not an invitation to discuss or debate a topic, and especially if they appear relatively inexperienced in GD&T I try to give a fairly direct answer and not get too caught up in intricacies. To do this I will sometimes make some assumptions (yes at the risk of making an ass…), although I try and qualify these to some extent.

When it is more of a discuss/debate question or just very complex then I tend to just let you smart folks with GD&T letters after your name have at it and just follow along till my brain starts to smoke (usually about ½ way through the OP).

I can’t claim to stick rigidly to either of these principles but try to generally follow them.

That’s not to say others approaches are wrong, however I know I have got frustrated when my threads have been taken off on a tangent or gone into much greater detail etc. than I desired/needed, so I try to “do as you would be done by”.

Now I've gone and taken this off track though, doh!

Posting guidelines faq731-376

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(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​