Controlling position of a cross hole on a cylinder 3

[atroy]

I want to control the position of a cross hole on a cylinder.

The tolerance zone I want to create is 2 parallel planes .030" apart (see the blue in the image attached). Basically, I want to make sure the hole goes through the center of the cylinder, but I want to give manufacturing as much tolerance to position that hole left or right.

How do I construct my FCF to control just the position of the thru hole through the center of the cylinder without limiting the location of the hole left or right? Is the drawing I have attached correct?

 

[3DDave]

You want a total of 0.030 and you need to show the position tolerance separately as a width perpendicular to the axis. A second, also separate, position tolerance of the width paralleling the length of the axis will allow separate control in the other direction; you may want to use a separate perpendicularity tolerance to limit the angle of the hole axis to the cylinder axis.

Edit - I originally read it to be .030 on either side of the axis.

 

[atroy]

You want a total of 0.030 and you need to show the position tolerance separately as a width perpendicular to the axis.

That sounds like exactly what I attached, correct?

I guess my broader question is: can I use a tolerance zone constructed of two parallel planes to control the position of a hole? I have this idea in my head the hole positions can only be controlled with cylindrical tolerance zones.

you may want to use a separate perpendicularity tolerance to limit the angle of the hole axis to the cylinder axis.

This is a good point. Without some control like that, the hole could just be coincident with the cylinder and still technically meet the print requirements.

 

[chez311]

atroy,

As 3DDave is suggesting, you're going to want to employ something like Fig. 7-28 bidirectional tolerancing. This will allow you to utilize different sized tolerance zone for difference directions. Note that currently you have not constrained the hole along the cylinder's axis so technically it could be anywhere along that axis - if that is your goal (ie: as you stated, as much tolerance to position it left or right as possible) you've already accomplished it. I assume that in reality this needs to be constrained to some reasonable level between 0.030 and the length of the cylinder.

Additionally, and someone can correct me if I'm wrong here, I know this is a rough sketch however I don't think your application of datum A is technically correct. If your intention is to set Datum A as the axis of the cylindrical feature, to me it seems to be actually suggesting that it is tangent to the surface of the cylinder - which I do not believe would be valid.

 

[chez311]

atroy,

Also to add as I did not see your other post until after I hit submit, a tolerance zone bounded by two parallel planes is entirely possible and allowable - that is what is created by the bidirectional tolerance in Fig. 7-28 that I noted. This is created by the combination of the view in which the tolerance is specified, the direction and application of the leader lines, and very critically the omission of the diameter symbol in the FCF.

 

[atroy]

chez311,

Thanks for confirming. Yes, I intentionally left out the control of the hole along the cylinder axis, but based on this thread I would add in the control as follows (see attached).

And yes my Datum A is incorrectly called out--I was in a rush to post the question. I've also tried to fix that in the new sketch attached.

 

[greenimi]

Here is a thread, where a potential good solution has been discussed. At least at the cursory level. See if it is applicable, again, at least partially.

https://www.eng-tips.com/viewthread.cfm?qid=344419

 

[chez311]

atroy,

Again - I know it is a rough sketch, but the key to bidirectional tolerancing is the view in which the tolerance is applied and the direction of the width leader lines. Attaching both FCF is a single leader line (additionally not a width - only an arrow pointing to the diameter) as you have does not create the tolerance zone you desire. I believe (as opposed to a cylindrical tolerance zone) as you have it shown where your parallel planes bounding the tolerance zone is actually ambiguous in relation to the DRF. Note the DRF can be the same for both [A|B] similar to how it is in 7-28, as long as you follow that dimensioning scheme.

 

[atroy]

Ah I think I understand now. I wasn't aware of the the importance of the direction of the width leader line.

 

[pmarc]

atroy,

Another option is to just add diameter symbols to both tolerance frames in your most recent sketch.

This, of course, does not create rectangular tolerance zone, but might be more functional and will not require addition of extra perpendicularity tolerance (unless the perpendicularity needs to be less than .030).

 

[mkcski]

I don't want to steer to far off course for this post, and please correct me if I wrong. But since one hole is not a pattern of holes, shouldn't the upper FCF (on the second drawing) with only datum A be perpendicularity control and not position? Position that only controls orientation is "misleading". If there were two or more holes, position would be appropriate to control the location "between" the holes.

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[pmarc]

mkcski,
The upper FCF controls location too. It assures that the axis of dia. .030 tolerance zone is (1) perpendicular to the datum axis A and (2) that it crosses the datum axis. If the callout was changed to perpendicularity then only the requirement (1) would have to be met.

 

[mkcski]

pmarc: You are correct. I was focusing on the lower frame of a composite control with patterns of holes and forgot perpendicular only controls rotation and not translation. Thanks again for clarity.


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[greenimi]

I was focusing on the lower frame of a composite control with patterns of holes

Just a slight correction: there is no composite callout in the shown case/sketch.
It is a multi-single segments scenario.

 

[chez311]

pmarc,

Good point, I did not think of the simple solution staring me in the face - partially because OP was asking specifically about a planar/width-shaped tolerance zone, and partially because it is in reference to a single feature instead of a pattern of features. Unless someone else says otherwise, it seems to me like that would also be a viable soltution, while also as you pointed out not requiring an additional perpendicularity tolerance (as the wider bi-directional tolerance along the *datum feature's axis would allow the *hole axis to tilt to the full amount of that wider tolerance zone without perpendicularity refinement) unless better than .03 is required.

It also seems to me that this would only work with Multiple Single Segment, because Composite tolerance for a single feature would only control orientation in the lower frames, right? Maybe that wouldn't be outright invalid but at least perhaps improper.

*edits for clarity, I was talking about two different axes

 

[mkcski]

greenimi:

Yes, but to me, a single feature the two single element FCF's "acts" like composite for a pattern.

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