Datum Planes
Datum Planes
(OP)
Hello to everyone!
I apologize for the question....but I have never understood this issue
If I have a flatness surface (datum A) e the I use two holes for Datum B and Datum C, which mutually normal planes I must consider?
Could you help me, please?
Thanks in advance
Luke
I apologize for the question....but I have never understood this issue
If I have a flatness surface (datum A) e the I use two holes for Datum B and Datum C, which mutually normal planes I must consider?
Could you help me, please?
Thanks in advance
Luke





RE: Datum Planes
Perhaps a sketch of your problem.
RE: Datum Planes
If that is the case, then datum A is a plane and datum B is the intersecting point of 2 perpendicular planes while datum C only orients the part. Now we have 3 mutually perpendicular planes - one created from datum A and 2 more from datum B.
Hope this helps.
Dave D.
www.qmsi.ca
RE: Datum Planes
KENAT,
Have you reminded yourself of FAQ731-376: Eng-Tips.com Forum Policies recently, or taken a look at http://eng-tips.com/market.cfm?
RE: Datum Planes
Last week I started to study the ASME Y14.5.M-19 and, with the help of this forum, I have understood the main issue.
Now, when I have a drawing with three datum planes it's clear the meaning but, when I have a different drawing it's not clear the meaning for me.....
Can I have always three mutually perpendicular planes also when in the drawing I have, for instance, a flatness plane (datum plane A) and two holes (Datum B and Datum C)?
Also three holes can "fix" my part in the space but which planes I must consider like "Datum Planes"?
In attachment a drawing of the situation.
Luke
RE: Datum Planes
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Datum Planes
On your sketch though, the holes aren't perpendicular to your primary 'A' datum which changes things. In fact, as set up I don't believe your datum structure works. You'd have to look at it again based on function to try and determine what's really required.
KENAT,
Have you reminded yourself of FAQ731-376: Eng-Tips.com Forum Policies recently, or taken a look at http://eng-tips.com/market.cfm?
RE: Datum Planes
Which datum planes (secondary and thirtiary) I can use if I have a surface with only a little flatness face?
in addition.....(I don't have a big practical experience about it)....for every part I produce should I have a specific tool that simulate the datum planes re-called in the drawing part?
Is also for this reason that is better to have three mutually perpendicular planes?(reduce cost linked to a lower number of tools)
Thanks
Luke
RE: Datum Planes
If you part does not have holes used for assembly, then the primary datum is the largest surface while the secondary datum will be the longest side and the tertiary datum will be the end of the part.
Dave D.
www.qmsi.ca
RE: Datum Planes
A minor clarification, if I may, to your previous. Two planes will intersect in a line and not a point.
However, the line (secondary datum) is the AXIS of the hole thru which a set of mutually perpendicular planes may be passed.
RE: Datum Planes
Right on - I stand corrected since it is an an "axis" per 4.4.2 page 55 rather than a point.
Dave D.
www.qmsi.ca