Tangent Plane
Tangent Plane
(OP)
The ASME Y14.5-2009 standard embellished the explanation for the "tangent plane" modifier a little. The 1994 edition made it sound like it was only for the three orientation symbols, but now in paragraph 6.5 it has an extra note saying that "it may also have applications using other geometric characteristic symbols..."
I'm trying to think of another GD&T symbol that may use the T modifier, and all I can come up with is profile of a surface (and even then it cannot be a contoured surface, but only flat), and maybe total runout on a flat surface. Any other insights?
I'm trying to think of another GD&T symbol that may use the T modifier, and all I can come up with is profile of a surface (and even then it cannot be a contoured surface, but only flat), and maybe total runout on a flat surface. Any other insights?
John-Paul Belanger
Certified Sr. GD&T Professional
http://www.gdtseminars.com





RE: Tangent Plane
However, we can apply the T modifier on a parallelism callout, for example : Parallelism|.005 circle T|A The tangent plane contacting the high points of the surface must lie within two parallel planes .005 apart which are parallel to datum plane A.
SeasonLee
RE: Tangent Plane
If it's used on total runout, it can only be on a surface that's perpendicular to the datum axis, but it won't control form.
Maybe they just put the note in the standard kind of as a CYA for some of these weird situations which may come up...
John-Paul Belanger
Certified Sr. GD&T Professional
http://www.gdtseminars.com
RE: Tangent Plane
Application to form wouldn't make any sense; you want the actual surface, plus it explicitly states in '09 that it doesn't control the form.
Position? Wouldn't that just be the loc'n of the true geometric counterpart anyway?
Runout? You need to contact the actual surface, but then that's what I thought for orientation too. I'm picturing a knobby cylinder where the indicator is only allowed to touch the tangent end ... that would theoretically just be circularity at a non-continuous diameter, wouldn't it? Same thing for a surface perpendicular to the datum axis.
Orientations & profile controls are all that I can see.
Paul, here's a link to a practical use of (T) with a profile of a surface control. http://www.tec-ease.com/tips/september-06.htm
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Tangent Plane
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Tangent Plane
RE: Tangent Plane
Good to have you back.
The term "tangent" in Y14.5 has a different meaning than it does in geometry. In Y14.5 it means "contacting the high points". So the Y14.5 tangent plane used in orientation tolerances is a perfect plane that contacts the high points of the imperfect actual surface. In general, the unconstrained tangent plane will contact the actual surface at 3 points. See Fig. 6-43 in Y14.5M-1994.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Tangent Plane
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Tangent Plane
Got to ask, but what is an unrestrained tangent plane?