Cone ; Profile Measurement

[Madhu454]

Hi All,
I need a favour. Please see the attached drawing. (Drawing is created as per ISO std)
Could anybody suggest me how to measure the "profile of a surface" which is applied for the cone surface.
We don't have a sophisticated machines like CMM in our factory. Can this be measured using any other simple tools or equipments. Please suggest.

 

[drawoh]

Madhu454,

I do not like your datum[ ]A. If you cannot measure it, you cannot fixture to it. I strongly suggest you pick some standard surfaces for this.

Once you have a standard surface, you can make some fixtures that pick up your datums, and line up with your angled surface. Based on your tolerances, even a cardboard cut-out should work.

--
JHG

 

[CheckerHater]

I do not like (F) symbol everywhere. Is part really flexible?

 

[btrueblood]

Agree with drawoh, I would reverse the datum references, i.e. use a cylindrical surface as datum, and check the conical surface for runout relative to the datum. Profile would be checked with simple go/no-go (MMB and LMB) gages, or optical comparator.

 

[SeasonLee]

If the part consists of the tip conical feature only, then the profile control is fine for me; but the part actually consists of several features, it’s a coaxial part instead, so I also think a runout control is a right choice.

For the same reason, I will recommend to use total runout to replace the perpendicularity control, please ref to the Fig. 6-50 on 1994 standard or Fig.9-6 on 2009 standard for more details.

Its not practical to choose the conical feature as a primary datum feature, (If the part is rigid enough and if datum B were the primary datum feature),it will be easy to use the open set up method and measure the profile.

SeasonLee

 

[pmarc]

Madhu,
There are ways to verify this profile callout without using CMM or a dial indicator type equipment.

You could for example use a chuck and grab the part as close to the cone as possible. Then place a surface plate at certain distance from the cone (on your picture this would be a horizonal line placed above or below the cone) and using simple caliper measure distances between surface plate and the cone along cone's slope. Next you would have rotate the part by certain angle and take measurements again and again, until full 360 degrees rotation of the part is done. Since profile of surface tolerance zone is mathematically defined by basic diameter and basic angle (plus probably there has to be a length of the cone given somewhere), you should be able to calculate ranges within which measured distances between surface plate and surface of the cone should fall.

This isn't of course the most accurate method, but may work as a decent work-around if everything is done properly and carefully.

-------

As for other comments given so far, unless I misunderstood something, allow me to respectfully disagree with some.

First, I do not see a reason why the cone should not be used as primary datum feature. If this is trully functional primary datum feature, I would say that using other feature as datum feature and controlling the cone relative to it is "cardinal sin" from GD&T standpoint. This may significantly change geometrical requirements for the part. Look at fig. 4-44 in Y14.5-2009 - conical feature is used as primary datum feature without any problems there. The newest version of ISO 5459 allows it too and offers description in appendix C.

Second, for the same reasons as mentioned above, I think that hints like: "If you cannot measure datum feature, you cannot fixture to it, so pick some standard surface for this" leads to nothing but verification of totally unfunctional geometrical requirements. In my opinion, instead of changing datum features just like that, all the effort should be made to find out how to verify existing requirements. If I were designer of the part, I would not be happy if suddenly someone changed or reqested to change my functional requirements just because he did not have equipment to verify them.

Third, I would like to see a no-go gage used for verification of LMB defined by profile callout.

 

[CheckerHater]

There are several things that I would love to see:

Since pmarc believes ASME references are appropriate, I would like to quote from Y14.5-2009 Para.4.8:

“To ensure proper assembly, corresponding interfacing features of mating parts should be selected as datum features. However, a datum feature should be accessible on the part and of sufficient size to permit its use.”

I wouldn’t make far-fetched decisions until I can see:
a) Entire part
b) Mating part / parts

Also I didn’t get the answer if (F) symbol placed all over the drawing actually means “free state”

Until then, I believe that grabbing conical tip of (possibly) long rubber stick is sufficient to establish (possibly) primary datum

 

[CheckerHater]

Stand corrected: I DON'T belive it.

Posting from work...

 

[fsincox]

If the cone is the functional datum us it. Let the inspection people use the "substitue datum" if they need. Keep the functional intent clear, JMHO!
Frank

 

[pmarc]

CH,
Presence of (F) modifier all over the picture does not automatically mean the part is rubber or made of any other flexible material.

 

[CheckerHater]

Fsincox,

When you say “functional datum” you imply that there are some other datums out there and you are right.
They exist by the name of “datum”, or are hiding under nicknames as “bases”, “origins”, “0-lines”, etc., etc., etc.
Datum is simply something you measure from; and yes, different kinds of them exist, or at least existed until “functional” crowd took over.

Look at the picture: The rule of thumb is (or was) to combine all kinds of datums whenever possible; and, if not possible, resort to substitute.

Unfortunately in the modern world “functional” became politically correct word for “I don’t care how part will be produced and / or inspected”.

As long as you do care – I am with you.

 

[CheckerHater]

pmarc,

I agree. It probably means "revision F", or "functional"

But in both ISO and ASME it means "free state"

 

[fsincox]

CH,
I mean datum in the formal (ASME/ISO) sense, let them use centers as "substitute datums" but keep the functional design intent clear. This is what the text of the standards say to me.
Frank

 

[pmarc]

CH,

The graphics attached by you really intrigued me. I think I know what you meant by saying: "The rule of thumb is (or was) to combine all kinds of datums whenever possible; and, if not possible, resort to substitute.", however have no idea what you wanted to prove by showing these 4 pictures. I will not nitpick on incorrect terminology used (datums vs. datum features). I just wanted to understand it.

And another thing, I hope you realize that by saying: <<... in the modern world “functional” became politically correct word for “I don’t care how part will be produced and / or inspected”>>, you oversimplify the problem. Manufacturing and inspection should always be a concern when applying GD&T to a part. The thing is, you have to be aware that if you use other than functional datum feature(s) on a print, you may end up with good parts being scrapped or bad part being accepted, because you will inspect relative to features that are not the most important for how a part really works.

 

[CheckerHater]

Pmarc,

I intentionally mixed terminology applied to datums, features, and simulators in order to illustrate my point that the idea of datum, as origin of measurement, is universal.

Is this datum, or datum feature?

And when it comes to what I wanted to prove, it is also clear: in my picture datums (in all senses) are meaningful, in terms of either function, manufacturing or inspection.

I still see no proof that OP’s datum [A] has any meaning, or that part, that has different size / shape when restrained or free, is not flexible.