Can i use a point as my datum?
Can i use a point as my datum?
(OP)
Im new to this Gd&T stuff and have only had a couple courses on it. I know that you can't use imaginary points as datums... the drawing attached has a datum "A" we want to use but I am unsure if its allowed?
Any help would be great.
Thanks in advanced,
Red.
Any help would be great.
Thanks in advanced,
Red.





RE: Can i use a point as my datum?
Additional thing to consider - a feature which has been defined/ selected/agreed as a critical one does not have to be a datum feature straight away.
RE: Can i use a point as my datum?
There are a couple other things, if you are open to critique :)
Such as using flatness on the .118 dim. Did you mean for just the top surface of the .118 to be flat?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Can i use a point as my datum?
I would say OP's datum A is rather a straight line, though drawing presentation is not clear enough to be 100% sure sbout that.
RE: Can i use a point as my datum?
Welcome,
I really doubt the part will be stabilized for manufacturing or in it's final assembly, captured solely on those "points". Those "points" are really 2 lines on tapered faces and while they could be defined as datum targets lines, I suspect it may not really function that way, Ask yourself how does the part function?
The interesting thing here is I suspect the radius may come into play in the actual assembly but our current standard does not recommend using a radius as a datum a practice I cannot support. If it functions like a datum, it is one, whether the book allows it or not, It is the standards problem not the parts, INHO
Also, the flatness callout is incorrect, while the 2009 standard now allows flatness on features of size the depth you show cannot correctly be called a feature of size as the surfaces are not directly opposing faces.
Frank
RE: Can i use a point as my datum?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Can i use a point as my datum?
Frank
RE: Can i use a point as my datum?
thanks for the help.
Red.
RE: Can i use a point as my datum?
Frank
RE: Can i use a point as my datum?
RE: Can i use a point as my datum?
Frank
RE: Can i use a point as my datum?
I'm confused by the 45º ... I see only 4 of those diagonal surfaces. But why is it even basic?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Can i use a point as my datum?
If all your guys are concerned with is whether or not something is legal, there's a whole lot of that to go around with this print without even talking about the question about datum A.
Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Can i use a point as my datum?
No standard is referenced, about half of the characteristics of most features are left uncontrolled, and datum feature A is unclear.
Dean
www.d3w-engineering.com
RE: Can i use a point as my datum?
BTW, I'm assuming '82 (or earlier) because of the datum callout symbol.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Can i use a point as my datum?
I have questioned this drawing and have proposed it be re-dawin with proper GD&T but this well not happen. We have received parts that we excepted and work does not want any changes to be made to drawing in fear of a product problem...
I know this could become a future problem but the guys above me want nothing to do with change.
again thank all you for the help.
Red
RE: Can i use a point as my datum?
I still feel that the datum concept shown, if it is correct to the intent, needs at least an opposing datum to capture the part. I suspect the "shaft dia" would does that nicely in the real function.
Frank
RE: Can i use a point as my datum?
Frank
RE: Can i use a point as my datum?
You can be assured of two things with this drawing:
1. If you have received good parts in the past, it is not because of this print, it is in spite of it.
2. If you don't get this print right, there will come a day when your company is going to have to shell out some bucks on parts that don't work.
Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Can i use a point as my datum?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Can i use a point as my datum?
Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion
RE: Can i use a point as my datum?
I think we all would agree on that, too.
I just want to know if it is sufficient. I don't think any of us wants to be around the machine restraining this part only on those knife edges, I know I do not.
Frank