dimensioning questions

[d.evans]

I have a part that is intended to be measured in the free state, but during the machining process, so much material was removed from the base material, that the finished piece has some "bowing-in" of the side walls. These walls are now only .035" thick (+/-.005") and the distance across the long and short (inside) ends of the part have an extremely tight tolerance (.001"). There is at least .002" to .003" of bowing-in on both of the long walls. These walls will flex out when the mating interference-fit part is installed. Knowing that they are bowed-in and by how much, AND that it will flex into tolerance, do I reject the part based on its free-state measurements?

[kbotta]

So, there is no 'restraining' note on the drawing right? And no use of circle (F) right? And we know that all dims apply in freestate unless otherwise spec. right?
Is this a rigid material?

Honestly, I report it as is, and worst condition. But I would make a note on the report of the condition that you have pointed out. So someone else can 'see' what you 'see'.
Does this help?
Kev

[kbotta]

Oh, do you have a check fixture for the piece?
Just checking. What does it look like on that?

[d.evans]

notes

there are no restraining notes. There is no check fixture either. The only thing I have is the mating part. It will be a press/interference fit. If it gets installed to do a "fit-check", we could easily damage the parts and ruin the ones of which I sent a .pdf.
The mating part will be braised into the ones I have to measure.
I'm just trying to avoid producing a "non-conformance report" on a part that may not measure in-tol to the letter of the law, but is going to work in the real world.

[bw_bob]

I'm with kbotta. The dimensions are what they are and just note your concerns....cover thy butt

[Snaggy]

Having been told in the past that I am just an inspector, I would tell it like it is, make my observations and then let someone else (who gets paid to do it)make the decision! C.Y.A

[John Kingston]

I agree, no note about restrained, measure in free state. Not sure if you can, but I would take it to our Engineering department before getting too far. We are not a real big company (200 people), so it isn't too hard for me to do. If you're part of a huge place, might be better to just verify and report.

[Paul Sarrach]

The part only has to be restrained if it calls it out.
The part only has to be in the free state if it call it out.
You can restrain it, if you understand how it will be mated.

I would do a freestate. Report that
I would do a it restrained, and Report that.
Then let them decide how the would like you to procede.
then give it a little help

[Jan d.]

It seems to me you must report the free state. To assume that you know exactly how the part is used, can sometimes lead to embarrasment. Trust me, it happened to me. They said they explained it all to me, then when I reported the part in spec, I got blamed when the part did not work. Never again! If the engineer wants it reported differently, have him put that in writing.

I do not agree with Paul. Just report per the print, and if they want it differently, have them put it in writing. If they do that, just follow their instructions. But make sure you CYA!!!


Jan.

[Paul Sarrach]

You dont have to agree with me.

What checking it restrained will show how its being machined correctly, just that it loses its integrity after it is released from the machine.

You can never give too much information. If I know that it is a good part, I may even old school it and do a plate layout, which means you may have to use blocks and sine plates, which will hold it into position, Which is acceptable method.

A CMM can check a good part and say its bad, by the same token it can check bad part and say its good. What my job as an inspector is to report what is coming off the Machine. And then let the powers to be make a desection on what to do next.

I am proud of my work and I will give the extra effort. I tell them what the part is. I would never give a cmm report and say " "I think its good but, I dont know for sure, I only checked it out in freestate, the print did not call out what to do, and the report says its bad, its a flimsy part, what do I do now"

[kbotta]

If your drawing says to interpret per asme y14.5m-1994, then the letter of the law is FREESTATE (unless noted otherwise on the drawing). You can add as much info as you want - however, lets just say this was for a customer, and you went to court over bad parts (I know extreme- but it serves the case) and someone from say ASME committee was brought in to defend your customer (this does happen, ALL the time). You know what one of the 1st questions they would ask? How did you set up the part? And if you say " I restrained it", guess what?
I understand where you are coming from Paul, and you should be proud if your work! I know I am, and thats what makes us 'special'
If you really want to show 'something' in your report, show it reatrained, and in freestate. Then let the powers that be decide "what the customer will see".
My best advice? CYA...
Kev

[carpentj]

ALWAYS document a nonconformance to specification regardless if the part may or may not be "suitable for use" and you will never be in the wrong! If you have a material review board or something similar, it is their responsibility to make the decision, that's why they get the big $$. If the decision is yours alone to make, I would still document the nonconformance and also all reasoning for making the decision to use, scrap or repair it.

[Paul Sarrach]

Thats what I am saying. If you think its a good part, but you think it takes another shape after its released from the chuck. Inspect for that. I was not suggesting that you say a warped part is good, just that the machine is making good parts. Its bad now, what do we do?