General Mechanical Drawing Questions
This page summarizes the general agreement on mechanical drawing as a whole, article by article. Please see each project’s individual page for more details.
paper
Paper Size Use the smallest possible paper size that does not make it difficult to see the image clearly.
Use the long edge of the paper in landscape orientation, but only in A4. You can also use the long edge in portrait orientation.
Please check the drawing style for paper size and format.
linear sum graph
Vertical and horizontal lengths of graphics must maintain a correct proportional relationship. Vertical and horizontal scales must not differ by 1:1, and vertical and horizontal scales must not differ by 1:2.
Even products made from transparent materials are described as opaque.
The lines indicating the appearance of the product are drawn with thick solid lines, and the dimension lines, auxiliary dimension lines, main lines, etc. are drawn. are drawn with thin solid lines.
For the scale of the drawing, please check the scale. For the line, please check the line thickness and type. For graph representation, please check projection diagram etc.
size and shape
Unless otherwise noted, dimensions shown should be indicated by a two-point measurement.
Dimensional tolerances do not limit shape unless otherwise noted. Geometric tolerances are indicated where necessary.
For dimensions, in addition to reference dimensions and theoretically precise dimensions, dimensional tolerances are indicated individually or in batches.
For dimensional tolerances not shown separately, indicate the specification number and grade in the drawing or record the dimensional tolerance table.
Regarding dimensions, please refer to general questions on how to fill in dimensions and dimensional tolerances, etc., regarding shapes, refer to geometric tolerances, etc., and regarding dimensional tolerances which are not shown separately , refer to general tolerances and refer to general geometric tolerances.
surface texture
When it is necessary to indicate surface roughness, surface treatment method, cycle time, etc., the indication should not be ambiguous or the surface properties should be indicated on the basis from JISB0031.
For surface roughness, surface treatment methods, knots, etc., please see Surface Roughness.
welding
In case instructions regarding welding are required, there are no ambiguous expressions for the instructions, or the instructions are given using welding symbols in accordance with JIS Z3021.
screw spring
Special parts such as screws and springs are illustrated using simplified symbols specified in JIS standards.
projection method
Projection method is a word that is not very familiar. In simple terms, it refers to the method of “where is the image when viewed from which direction”.
What is actually made is a three-dimensional solid, but in the drawing, it is a two-dimensional plane, so between the person who draws the drawing and the person who looks at the drawing, three-dimensional (imagining) → two-dimensional (drawing) → three-dimensional conversion ( imagination/creation). That is, the imagination of the person who drew the drawings must be consistent with the imagination of the person who looked at the drawings and realized something.
So that everyone can make the same drawing, the JIS standard regulates where the drawing is drawn when looking at it from which direction.
The basis of projection
Projection drawings are usually drawn using the third angle method, but if they are difficult to understand using the third angle method, or they cannot be drawn according to the layout correct page, they are drawn using the first angle method or the arrow method.
Whether you use the third or first angle method, you must record the symbol for each projection method on or near the title block. If you have a drawing without symbols, this can be considered a third angle method.
Basically the third angle method is the main one, so I think you just need to remember that the first angle method also has such a method.
The more complex the shape, the more difficult it is to understand the drawing, but the arrow method is useful in this case. Although the arrow method can place a figure in any position viewed from a specified direction, to make it easier for people viewing the drawing to understand, place it in the same direction as the third triangle method as much as possible. If it is placed in the exact opposite direction to the third trigonometric method, it will not only hinder the understanding of the shape, but also lead to misunderstandings.
To make it easier to understand the shape of the drawing, you can also draw a three-dimensional diagram. In this case, describing the dimensions in the perspective view may cause misunderstandings. I think it’s good to record the dimensions for reference, but the purpose of drawing a three-dimensional diagram is just to help understand the shape, so basically you shouldn’t record the dimensions.
By the way, many people may have doubts about the correct word between “arrow method” and “arrow aiming method”, but the current JIS standard is “arrow method”. However, I think both can convey meaning, so there is some. no need to be too careful.
third angle method
The third triangle is based on the front view and is surrounded by some or all of the other projections, as shown below. If a third triangle is used, the third triangle symbol appears in or near the title bar.
If the shape can be understood using only the front view, no additional projection drawing is necessary. If it is easier to understand the shape with a projection other than the front view, or if the dimensions cannot be grasped using only the front view, draw another projection.
first angle method
The first angle method uses the front view as a base and places some or all of the other projections around it, but reverses the arrangement of the third angle method with top, bottom, left, and right, as shown below. If the first angle method is used, a first angle symbol appears in or near the title bar.
As with the third angle method, if you can only understand the shape from the front view, no additional projection is necessary.
vector method
If you are using a projection that does not conform to first angle or trigonometry formats, you can use arrows to place the projection in any position viewed from all directions. If arrows are used, they are indicated for identification by an arrow indicating the direction of projection and uppercase Latin letters, with all characters written upwards.
Other projection methods
In order to make it easier to understand the shape of an object, etc., when drawing a three-dimensional view, use isometric projection, oblique projection, perspective projection, etc. for drawing.
Isometric projection
Also known as isometric projection, both coordinate axes are drawn with a 30° tilt, each side is drawn at actual size, but the depth is also at actual size, so it is drawn larger than it n actually appears.
oblique projection
The front view is drawn in the same shape and the depth is drawn in half scale at an angle of 45°.
perspective projection
It is a method of drawing three-dimensional objects based on geometric processes.
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