Can a datum be a centerline?

Datum can indeed be a centerline, but it is never to be labeled as such on a drawing. A centerline you can talk about it, but not call it out as a datum on the drawing. A centerline is imaginary and that they should specify the centerline of a feature and then associate other features.

Can a datum be an edge?

As stated before, datums can be located on points, axes,edges, and surfaces. It is important though that they is called out correctly on the drawing to control the right type of feature.

What makes a good datum?

Datum features must be easily identifiable on the part. Datum A makes a good primary datum for the four holes because the primary datum controls orientation, and it is desirable to have bolt holes perpendicular to mating surfaces. The hole locations are dimensioned from the bottom and left edges of the part.

Can a threaded hole be a datum?

When we have done this, we place the datum symbol on the shoulder of the threaded hole callout and the words “MINOR DIA” next to the symbol, indicating that the minor diameter of the thread is the feature to be used as the datum feature. The FCF for the datum hole is RFS as we do for all threaded holes.

Does positional tolerance need a datum?

Tolerance Of Position must always have one or more datum references except for two exceptions: Coaxial cylinders and a pattern of features of size used as a primary datum.

How do you mark out datum lines?

Marking out lines This could be the use of one straight edge of a sheet of metal as the datum for marking out a square or a specific corner of the material. To measure a point on a marked line use a V marking. Scribing a line through the point of the V will give an accurate position of the marked line.

How do you set a datum point?

Creating a datum point by projecting a point onto a face. Select a point on the model and an edge or datum axis on which to project the point. Abaqus/CAE creates the datum point where the edge or datum axis intersects a line that is normal to it and passing through the selected point, as shown in Figure 7.

Do datums have to be perpendicular?

The standard defines a datum as a theoretically exact point, axis, or plane. It may require using datum targets, but a theoretical plane can still be constructed from those targets. So again, it’s true that the theoretical datums mentioned in a feature control frame are perpendicular to each other.

Can a datum have a tolerance?

Tolerance Of Position must always be located by Basic Dimensions. The Basic Dimensions may be explicitly called out or implied. 3. Tolerance Of Position must always have one or more datum references except for two exceptions: Coaxial cylinders and a pattern of features of size used as a primary datum.

How do you call a threaded hole in a drawing?

Click Hole Callout (Annotation toolbar), or click Insert > Annotations > Hole Callout. The pointer changes to . Click the edge of a hole, then click in the graphics area to place the hole callout.

What is a datum line?

A datum line can be a datum axis or datum axis line. A datum line is generally established on the center of a target’s cylinder bore or cylinder shaft, and is rarely established on a ridge.

Where is a datum axis established?

A datum line is generally established on the center of a target’s cylinder bore or cylinder shaft, and is rarely established on a ridge. This section explains cases where a datum axis is established on a cylinder bore and on a cylinder axis.

How do you find the datum of a cylinder?

We can place the datum symbol either on the surface or on one extension line from the surface. For any surface other than a round cylinder, the datum is strictly on the side where the symbol is shown. However, for a round cylinder, the datum is the entire round surface. On an Axis

How do you use a flat surface as a datum?

To use a flat surface as a datum, the following indication symbol is used: The surface of the target (datum feature) indicated as the datum may be uneven or warped. Datum plane A can be established by supporting the surface set up as a datum using a surface plate or other higher precision plane.