How to tolerance a cross drilled hole on a cylinder

[ipunkrock]

I have a cylinder with a cross drilled hole that passes through the centerline. The cylinder fits in a hole and a pin goes through the cross drilled hole. I am trying to dimension the allowable deviation from the centerline. The tolerance for the distance from the end of the cylinder to the center of the hole can be much greater than if the cross drilled hole does not intersect the centerline. I have attached what made the most sense to me. I added an ordinate dimension at 0 and gave it a tolerance. Is that allowed? Is there a more correct way to dimension Y14.5?

Thanks! J

 

[powerhound]

You should first call the OD of the cylinder datum A. Then subtract the largest size of the pin that goes through the hole from the smallest size of the hole. Take the difference and that is your diametric tolerance for both the cylinder drawn and for the cross hole position in the hole that it goes into. Be sure to use an MMC modifier on the tolerance as well as on the A datum. The ordinate dimension should be removed.

I used the floating fastener formula for this because it seemed appropriate based on the perceived function of the assembly. Others please chime in if I should ahve used the fixed fastener formula.


Powerhound, GDTP T-0419
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[MechNorth]

Yo iPunk (I feel like Dirty Harry now!), do you feel lucky?

This is a GD&T forum, but your proposal doesn't look like you want to use GD&T. Hence the question, do you feel lucky, iPunk?

With GD&T, you can concisely define your design intent as you wrote it; without GD&T, it will be open to wild interpretations. Your graphic does not provide any valid information required for fabrication. Sorry.

Jim Sykes, P.Eng, GDTP-S
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[ipunkrock]

It is correct that I am not using GD&T in the image provided but I would like to move that direction in order to define the placement of the hole.

Powerhound, I understand your methodology to control the fit if the parts are coaxial. i am concerned with the cross drilled hole placement. I am attaching a better image to hopefully explain my question more thoroughly.

-J

 

[MechNorth]

You're surprisingly close with what you have in the second image. You need a secondary datum (B?), probably the end face of the tube. Next, you need a size tolerance on the .063 diameter to make it a feature of size (that is a requirement if you're going to use a position control). Next, get rid of the sketch showing the acceptable tolerance zone. Then, dimension the height of the hole (i.e. like you have the .070 dimension now), deleting the tolerance value and adding instead a position control with a value of .070 (without a diameter symbol) and a reference to datums A and B. Then, dimension the width of the hole, deleting the dimension again and replacing with a position control with a tolerance value of .250. That's about it.

Oh, and in ASME Y14.5-1994, the thru hole is considered two holes unless you put CONTINUOUS FEATURE on the size callout.

Jim Sykes, P.Eng, GDTP-S
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[ipunkrock]

MechNorth,

Thanks! That makes good sense. Just what I am looking for. Thank you much!

-J