Depth of a CB hole on a incline
Depth of a CB hole on a incline
(OP)
Hello all,
I am looking for standard definition of depth of a CB hole on a inclined surface.
For e.g., I have a triangular gusset. I have a CB hole on the inclined surface parallel to the base. So the depth of the CB hole varies from a min. value to a max. value. So when I do a hole callout annonation in a drawing for a CB hole what should the depth be? Min. value, max. value or value at the center? What is the standard manufacturing practice?
And is there any standard that defines this and what is it? Any help would be really appreciated.
Regards,
I am looking for standard definition of depth of a CB hole on a inclined surface.
For e.g., I have a triangular gusset. I have a CB hole on the inclined surface parallel to the base. So the depth of the CB hole varies from a min. value to a max. value. So when I do a hole callout annonation in a drawing for a CB hole what should the depth be? Min. value, max. value or value at the center? What is the standard manufacturing practice?
And is there any standard that defines this and what is it? Any help would be really appreciated.
Regards,





RE: Depth of a CB hole on a incline
RE: Depth of a CB hole on a incline
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline
Thanks for the quick replies. Section view makes sense.
So a regular CB hole callout using a CAD software would be ambiguous and incomplete?
If not how is the machinist going to interpret it?
Regards,
PS: I have used "a" instead of "an" before an vowel in my previous post. Sorry, it was a typo
RE: Depth of a CB hole on a incline
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline
The callout is as follows:
<dia sym>hole thru
<CB sym>CB hole <depth sym> depth of CB head.
The depth you obtain is the max depth by default(If no subsequent operation is performed on HW hole).
But some machinists I talked to say that the depth should have been "Value @ Center of CB" not min or max.
Hope this clarifies.
RE: Depth of a CB hole on a incline
But, depending on your design, it could be called out as min or max. I don't know what the CB is used for.
Create your holes, make a sect view, then dim dia and depth.
Your callout looks good to me. Draw a centerline thru the center of the hole on the dwg. The machinist should never have a problem with it.
I hope I understood you correctly and I made sense.
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline
This is one of those situations that are not always covered by today's cad packages.
RE: Depth of a CB hole on a incline
1. The CB is for a socket head cap screw, and you do not want the head exposed, well then, a Min Depth will be your guide.
2. You are using the CB to fit a bushing. You don't require an amt lenght of bushing, but you must maintain a minimum wall thickness on the machined part... then you should specify a max depth, and trim the bushing.
there are numerous examples where only experience will tell you which way to go... but hey, that why we get paid the Big Bucks right?
Wes C.
------------------------------
When they broke open molecules, they found they were only stuffed with atoms. But when they broke open atoms, they found them stuffed with explosions...
RE: Depth of a CB hole on a incline
My question relates to a depth callout of a "Variable Depth CB hole" and how does one interpret it.
I have obtained 3 different answers and unable to find a standard definition of depth in case of a variable depth hole.
Here are the three answers:
1. Depth is measured from the point where a full cylinder of the feature is defined aka Min Value of the depth ( Not tolerance).
2. Depth is measured from the center of the CB hole cause it is to where the location of the hole is measured.
3. Depth is measured from the point the probe makes initial contact aka Max value of the depth.
So my questions are "If I specify the CB depth (of a variable depth hole)o n my print how is the machinist/inspector going to interpret it? Min value, Max value or the Mean value. Or the callout incomplete without a section view? And what standard defines it and where can I find it?"
I appreciate the discussion guys. Thanks a lot.
RE: Depth of a CB hole on a incline
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RE: Depth of a CB hole on a incline
Mike Halloran
Pembroke Pines, FL, USA
RE: Depth of a CB hole on a incline
I agreed to it already. I am asking about the scenario where the section view was not created. How does one deal with such situation?
Is the callout completely illegal without a section view or section view just adds clarity to drawing. IMO both are completely different scenarios. And I am looking for Standard which addresses the issue.
Regards
RE: Depth of a CB hole on a incline
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline
RE: Depth of a CB hole on a incline
One problem becomes apparent immediately, even beyond the nonexistence of your datum:
- The usual tools for measuring cbore depth intrinsically assume the existence of a datum surface normal to the hole axis.
The problem gets worse if your angled surface is also nonplanar.
Mike Halloran
Pembroke Pines, FL, USA
RE: Depth of a CB hole on a incline
RE: Depth of a CB hole on a incline
What if I take away the vertical surfaces i.e. that if I have a part shaped like a rhombus or a parallelogram then my problem surfaces again.
Also if ones dimensions like MikeHalloran asks, then one can accumulate the tolerances! And you will loose design intent.The problem is not just restricted to CB holes but can include tapped holes also.
Whats scary is that I was not able to find a theoritical definition of the depth of the CB hole anywhere in the literature so that I can extrapolate.
Yes I can make my "Local standard". But the problem is it will be not be interpreted like that in all cases and I have to communicate the standard each and every time. And that really baffles me cos this should be part of the standard literature somewhere. I don't think this is a trivial issue. And I really appreciate the discussion.
Regards,
RE: Depth of a CB hole on a incline
Why would anyone devote any effort to producing a standard for a bad practice?
Mike Halloran
Pembroke Pines, FL, USA
RE: Depth of a CB hole on a incline
But what about a threaded hole. Is it still called a threaded hole?
Thanx for the info
RE: Depth of a CB hole on a incline
For a threaded hole? A thd is a thd. Yes, it is a threaded hole. It can be tapped or turned, but is still a thread.
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline
I have seen a lot of steels that have full 3D form on the top and counter bores are always dimensioned from the bottom face (I have no idea if this is a correct standard) but it is very easy for the machinist to use the flat bottom face as a datum.
Now what about the chamfer around the counter bore?
RE: Depth of a CB hole on a incline
Can you show us a pic of your CB? Maybe it would clear up for most of us.
thanks
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline
[URL=http://imageshack.us][IMG]h
Regards
RE: Depth of a CB hole on a incline
RE: Depth of a CB hole on a incline
Regards
RE: Depth of a CB hole on a incline
There are no hard and fast proceedures for dimensioning this type of hole. You need to find a feature from which you can relate back to the hole. In the case of a rhombus where the hole is not normal to any side, I would dimension from the intersection of two sides, using both linear and angular dimensions.
RE: Depth of a CB hole on a incline
If the shape is different...it depends on your design. If it is important where the screw head is in relation to the outer surface, you need to find a point or surface to dim from to the bottom of the CB.
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline
Probably this is what I was looking for. Some standard hard and fast procedure to dimension this type of hole. And it does not exist.
I really appreciate all your help. Its been very illuminating.
Regards,
RE: Depth of a CB hole on a incline
Counterbores are really intended to be used in something like a turret drill, at cycle times governed by how fast the operator can cycle the turret, and feedrates governed by how hard (s)he can lean on the handle.
Mike Halloran
Pembroke Pines, FL, USA
RE: Depth of a CB hole on a incline
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline
RE: Depth of a CB hole on a incline
Am I missing something? I am confused.
Regards,
RE: Depth of a CB hole on a incline
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Depth of a CB hole on a incline