I don't see the standard states a runout can only be used on a rotating part. But to verify it, you need to rotate it around an axis and read the errors from a dial indicator running through the part's surface. We say inspecting a part is a process of simulating part's function or assembly. We also say a well drafted drawing tells how the part works. So if a part does not rotate, why would anyone put runout control on the drawing? I've always seen drawings of stationary parts have runout control on it's cylinder surface or surface perpendicular to the datum axis. I think it's legal, but is it really good practice?
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runout used on rotating parts only? 3
- Thread starter bxbzq
- Start date
CheckerHater
Mechanical
OP: “…I think it's legal, but is it really good practice?”
Fsincox: “…my vote is NO!”
Am I right?
Fsincox: “…my vote is NO!”
Am I right?
CheckerHater
Mechanical
I feel sorry for the state of the industry where someone is questioning legality of using run-out on round part.
:-(
Is that a position, Frank?
:-(
Is that a position, Frank?
CH,
I didn't realize there was a question on using runout on round parts, it is the not easy to actually rotate parts I was thinking "we" were concerned about. Spindle housing bearing bores is my common example. The bearing manufactures often specify runout tolerances for mating components so I use them even if the part is not easily rotated.
I didn't realize there was a question on using runout on round parts, it is the not easy to actually rotate parts I was thinking "we" were concerned about. Spindle housing bearing bores is my common example. The bearing manufactures often specify runout tolerances for mating components so I use them even if the part is not easily rotated.
- Thread starter
- #29
What about a rectangular block with coaxial holes one of which being datum feature and rest of holes are controlled relative to the datum axis with runout tolerances? In this case you can rotate the dial indicator to check the holes. Good practice?
CheckerHater
Mechanical
Bxbzq,
In your earlier post you appeared like you objected to using runout on the piston.
No, I would normally not specify runout to check counterbore. If you read my post carefully and followed the link, you would see what kind of part will commonly benefit from using layout.
The good rule of thumb will be: if the part rotates during manufacturing (not necessarily during “function”), it may benefit from using runout during inspection. Nevertheless, one can actually devise a fixture to check “not easy to actually rotate parts” as well. Look at this picture:
There is no need to spin engine head.
(It says “concentricity”, but we all know it isn’t
)
In thread about partially-opposed FOS I stated that “Every single dimension, tolerance, or geometrical specification can be applied in the way that’s legal, but useless. Every rule can be misused and abused.”
I stand behind this statement. Nobody is holding gun to your head. You are the one to decide what the best tool for the job is.
In your earlier post you appeared like you objected to using runout on the piston.
No, I would normally not specify runout to check counterbore. If you read my post carefully and followed the link, you would see what kind of part will commonly benefit from using layout.
The good rule of thumb will be: if the part rotates during manufacturing (not necessarily during “function”), it may benefit from using runout during inspection. Nevertheless, one can actually devise a fixture to check “not easy to actually rotate parts” as well. Look at this picture:
There is no need to spin engine head.
(It says “concentricity”, but we all know it isn’t
)In thread about partially-opposed FOS I stated that “Every single dimension, tolerance, or geometrical specification can be applied in the way that’s legal, but useless. Every rule can be misused and abused.”
I stand behind this statement. Nobody is holding gun to your head. You are the one to decide what the best tool for the job is.
CheckerHater
Mechanical
Here is the thing: if your counterbore passes, say, 0.10 runout requirement, it automatically passes 0.10 position requirement, either MMC or RFS (not like I would endorse it as "good practice")
But that's overkill, unless you are also worried about the circularity of the counterbore.
So I don't think we should focus too much on how the part is made, nor on how it's inspected. Stick to function!
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
So I don't think we should focus too much on how the part is made, nor on how it's inspected. Stick to function!
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
CH,
I understand some in the shop may want to check it that way on a coaxial situation, that is fine by me, as long as they only use it to confirm that it meets the position requirement I placed on it. I would not use runout as the callout for it though.
I understand some in the shop may want to check it that way on a coaxial situation, that is fine by me, as long as they only use it to confirm that it meets the position requirement I placed on it. I would not use runout as the callout for it though.
CheckerHater
Mechanical
I agree.
This is why I cannot see why there is so much drama.
If it is your design, you apply requirement that you believe is the best.
If you are manufacturer, and you receive the drawing with runout applied to “counterbore” you have 2 choices:
You device jig similar to the one on the picture and charge customer for it.
In bad case where reliable fixturing is not possible, there still way out. Even though Y14.5 provides no number or formula, it actually has requirement for datum feature to be “sufficient” (sorry, cannot quote exact paragraph right now), so you may claim (rightfully so) that control is not standard compliant.
This is why I cannot see why there is so much drama.
If it is your design, you apply requirement that you believe is the best.
If you are manufacturer, and you receive the drawing with runout applied to “counterbore” you have 2 choices:
You device jig similar to the one on the picture and charge customer for it.
In bad case where reliable fixturing is not possible, there still way out. Even though Y14.5 provides no number or formula, it actually has requirement for datum feature to be “sufficient” (sorry, cannot quote exact paragraph right now), so you may claim (rightfully so) that control is not standard compliant.
Off-topic clarification:
"We also say a well drafted drawing tells how the part works."
I am not among this "we", as I was taught that the purpose of a detail drawing was to completely define a part, not how it works or is to be used, or even how to make it (except in specific cases).
"We say inspecting a part is a process of simulating part's function or assembly."
This is not entirely true, especially if there are simpler methods which can be used to ensure that the part meets its definition.
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
"We also say a well drafted drawing tells how the part works."
I am not among this "we", as I was taught that the purpose of a detail drawing was to completely define a part, not how it works or is to be used, or even how to make it (except in specific cases).
"We say inspecting a part is a process of simulating part's function or assembly."
This is not entirely true, especially if there are simpler methods which can be used to ensure that the part meets its definition.
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
- Thread starter
- #37
If the drawing contains inappropriate specifications, would it be considered complete?
All levels of drawings should completely define the part/assy that they are addressing. Component parts should have already been completely defined, unless further operations are required at the assy level.
The purpose of an engineering drawing is not to tell how the part/assy works, just to fully define the item (so that it will work as designed). How the part/assy works is better accomplished thru separate documentation, such as manuals or instructions.
Of course, different industries tend to follow different practices, but in the more strict sectors such as aerospace, my above comments are accurate. In other sectors, where perhaps manufacturing tends to drive engineering, your position may be valid.
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
All levels of drawings should completely define the part/assy that they are addressing. Component parts should have already been completely defined, unless further operations are required at the assy level.
The purpose of an engineering drawing is not to tell how the part/assy works, just to fully define the item (so that it will work as designed). How the part/assy works is better accomplished thru separate documentation, such as manuals or instructions.
Of course, different industries tend to follow different practices, but in the more strict sectors such as aerospace, my above comments are accurate. In other sectors, where perhaps manufacturing tends to drive engineering, your position may be valid.
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
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