Matthew Boyden
2/12/2016
MEC 1011
P Johnson
RECTANGULAR vs POSITIONAL TOLERANCING
MINIMUM CLEARANCE FOR HOLES IS 0.007”
POSITIONAL TOLERANCING
 Min hole size of 0.257” Diameter
 Has “Zero Tolerance” at MMC
 Has an 0.009” radius for allowed positions at LMC
 Accepts only good parts
 Throws out no bad parts
RECTANGULAR TOLERANCING
 Min hole size of .264”
 Has Tolerance of +-0.0024”
 Accepts only good parts
 Throws out some good parts
The rectangular toleranced assembly throws out good parts because it uses a rectangle to
tolerance, and the hole size is independent of the hole location. To insure that we don’t
accept bad parts with the rectangular toleranced assembly, we must limit the tolerance
rectangle so that no matter how small the hole is, it will still fit. However, this throws out
some good parts because if the hole is larger than the minimum size, it should be able to
allow for larger location tolerances.
The postionally toleranced assembly throws out no good parts because it uses a circle to
define the tolerance, and as the hole gets larger, the position can be off farther. This
means that if the hole is the smallest possible, the positioning of the hole must be perfect,
but as the hole gets larger, so does the tolerance on the position.
Matthew Boyden
2/12/2016
FIGURE 1
This figure shows the difference in allowed
hole location when the hole size is 0.264”.
The square on the left is the allowed area for
rectangular tolerancing, while the circle on the right
is the allowed area for positional tolerancing.
The shaded area on the left shows all of the locations
that would be good parts that get thrown out with
rectangular tolerancing.
MEC 1011
P Johnson