tolerance of position (top) - 2

7/28/2019 Tolerance of Position (TOP) - 2

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Tolerance Of Position,part-2


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TOLERANCE OF POSITION (TOP)SPECIAL APPLICATIONS:

Bi-Directional TOP (Locating a Hole in Two Directions).TOP with Zero Tolerance at MMC.

Using TOP to Control Spacing and Orientation of aPattern of Holes.

TOP with the LMC Modifier.

Using TOP to Control Symmetrical Relationships.Top Using a Projected Tolerance Zone.

Using TOP to locate an elongated hole.


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Bi-Directional TOP(Locating a Hole in two directions):

In this application, the following conditions apply;-The tolerance zones are parallel boundaries in thedirection of the TOP control.

-The shape of tolerance zone is _________.


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Bi-Directional TOP(Locating a Hole in Two Directions):

In this application, the following conditions apply;-The tolerance zones are parallel boundaries in thedirection of the TOP control.

-The shape of tolerance zone is rectangular .


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-The tolerance zones are located by the basicdimensions relative to the datums reference. -Bonus tolerances are permissible.

Interpret the drawing and design a gauge pin?

Bi-Directional TOP (Locating a Hole in Two Directions)


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Bi-Directional TOP (Locating a Hole in Two Directions)


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Using TOP to locate an elongated hole:In this application, the following conditions apply;

-The tolerance zone shape is a boundary of identicalshape as the elongated hole, minus the positiontolerance value in each direction.


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-There is no axis interpretation.

-The tolerance zones are located by basic dimensionrelative to datum's referenced.

Using TOP to locate an elongated hole


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-Bonus tolerance are permissible.-The elongated hole must also meet its sizerequirements.

Using TOP to locate an elongated hole (Contd..)

Interpret the drawing and design a gauge pin?


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Using TOP to locate an elongatedhole (Contd..)


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Note-1:

When the word boundary is placed beneath a TOP

callout, the following conditions apply: The tolerance zone shape is virtual conditionboundary.

There is no axis interpretation for the application.

Using TOP to locate an elongated

hole (Contd..)


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Note-2:If the same positional tolerance is desired in bothdirections, a single positional tolerance feature

control frame may be used. In this instance, thefeature control frame is directed to the elongatedhole with a leader line.

Using TOP to locate an elongatedhole (Contd..)


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Top Using a Projected Tolerance Zone A projected tolerance zone is a tolerance zonethat is projected above the part surface. A projected tolerance zone modifier is specifiedas P


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A projected tolerance zone is used to limit theperpendicularity of a hole to ensure assembly withmating part.

Top Using a Projected Tolerance Zone(Contd..)


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Top Using a Projected Tolerance Zone(contd.)


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Using TOP to Control SymmetricalRelationshipsIn this application the following conditions apply:- The tolerance zone shape is two parallel planes.


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-The tolerance zone is located by' an impliedbasic zero dimension relative to the datumreferenced.- A bonus tolerance is permissible

Using TOP to Control SymmetricalRelationships (contd.)

Gauge for thiscomponent?


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Using TOP to Control SymmetricalRelationships (contd.)

The example shown, involves using TOP MMC, whichcontrols a symmetrical relationship to ensure that thepart can be assembled.


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TOP with the LMC Modifier

The LMC modifier is used in a TOP control when thefunctional consideration is to control a minimumdistance on a part.

The minimum distance can be a minimum wallthickness, a minimum part distance, or minimummachine stock on a casting.

A bonus tolerance is permissible when the toleranceof an FOS depart from LMC towards MMC.


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In this application, the following conditions apply:The shape of the tolerance zone is a cylindricalboundaryThe dimension between the centerline of the diameter and the datum axis is an implied basic zero.

TOP with the LMC Modifier (contd.)


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A bonus tolerance is permissible.The minimum wall is l.6 (24.2-20.8 - 0.2) -:- 2 = 1.6].Perfect form at LMC applies (perfect form at MMC isnot required)

TOP with the LMC Modifier (contd.)


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Using TOP to Control Spacing andOrientation of a Pattern of Holes

Desired to control only the spacing and orientation of holes in a pattern.

This can be accomplished by using a TOP control with

a single datum reference.


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In this figure, the TOP control limits the spacing betweenthe holes and the square ness of the holes relative to

datum plane A, but the TOP control does not control thelocation of the hole pattern



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The designer typically uses a TOP control on a holepattern with a single datum reference in two cases:

when the hole pattern is used as a datum feature,and only the spacing and perpendicularity need tobe defined.

when a hole pattern is toleranced with a multiplesingle-segment TOP control.



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When a hole pattern is used as a datum feature, it doesnot have to be located from outside edges of the part.

The outside edges of the part can be defined from thehole pattern and toleranced with a profile control.

Using TOP to Control Spacing and

Orientation of a Pattern of Holes


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Multiple single segment TOP controlsA multiple single-segment TOP control is when two

(or more) single segment TOP call outs are used todefine the location, spacing, and orientation of a patternof features of size.


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The upper segment of the TOP control providestolerance for the location of the pattern of holes relativeto the outside of the part.The lower segment of the TOP control providestolerance for the spacing between the holes and theorientation of the holes relative to datum A.Each segment of the TOP control is an independentrequirement

Multiple single segment TOP controls


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Multiple single segment TOP controls(contd.)

This type of control when a hole pattern can have a largetolerance with respect to the outside edges of the pan,

but requires a tighter tolerance for square ness and/or

spacing within the hole pattern.


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TOP with zero tolerance at MMC.

There are three primary benefits to ZT at MMC:1. It provides flexibility for manufacturing.

2. It prevents the rejection of usable parts.3. It reduces manufacturing costs.

Zero Tolerance (ZT) at MMC is a method of tolerancingpart features that includes the geometric tolerancevalue with the FOS tolerance and states a zerotolerance at MMC in the feature control frame.


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76 12

12

CONVENTIONAL POSITIONAL TOLERANCING AT MMC


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76 12

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ZERO POSITIONAL TOLERANCING AT MMC


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44

M16X2 -6g

MAJOR DIA

SPHERICAL FEATURE LOCATED BYPOSITIONAL TOLERANCING

S


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Datum plane A

Spherical feature

Datum axis B

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True position

0.8 diameter sphericaltolerance zone

SPHERICAL FEATURE LOCATED BYPOSITIONAL TOLERANCING


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Position - Location of Irregular Feature

Position can Control Location of Irregular Features


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The figure shown below is a possible gage that might be used to inspect theposition tolerance. The values shown are theoretical design values, which do noti l d l d ll

tolerance of position (top) - 2

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