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Using an engineering scale

and drawing scale

Common Engineering Scales

Most CAD systems allow the drafter to draw at whatever scale he or she feels like. However, if fabrication shops are going to be using your drawings you will help them far more by drawing views to commonly accepted engineering and architectural scales.

Many shops like to keep drawings to a consistent scale so fabricators get used to knowing how drawings are laid out. This is just as important in plant layout and architectural drawings where 1/8"=1'-0" and 1/4"=1'-0" are standards for construction and building permit work.

In machine design 3"=1'-0" and 1-1/2"=1'-0" are very commonly used in weldments and small assemblies. Details can be full size or half size.

Drawing to scale is also important since the CAD system can make scale templates more accurately than ever before. Drawings can be plotted at full scale and parts can be checked against them simply by placing them on the drawing. Paper plots can be glued to wooden forms and templates can be sawn to shape with minimal layout time.

The following table shows typical engineering scales and useful data to help set up your sheet layout.

RATIO DWG. SCALE DECIMAL RECIPROCAL
1:1 FULL 1 1x
1:2 6"=1'-0" 0.5 2x
1:4 3"=1'-0" 0.25 4x
1:8 1-1/2"=1'-0" 0.125 8x
1:16 3/4"=1'-0" 0.0625 16x
1:24 1/2"=1'-0" 0.0417 24x
1:32 3/8"=1'-0" 0.03125 32x
1:48 1/4"=1'-0" 0.0208 48x
1:64 3/16"=1'-0" 0.0156 64x
1:96 1/8"=1'-0" 0.0104 96x
1:128 3/32"=1'-0" 0.0078 128x

There is also a small engineering scales power point presentation with sound that I put together about this subject. It's worth a listen if you are just learning the process of setting up drawings to scale.

You can use this chart in many different ways. Most often you would be starting off with an autocad file that was drawn full size in model space and now needs to have a drawing border to a specific drawing scale placed around it.

How to Scale a drawing to make sure it is accurate

Scaling off a drawing 1
  • You can use this technique to check if you have the scale set correctly for your printed drawings
  • Check the drawing scale, in the example at the left, the scale is 1" = 1'-0"
  • Use a engineering scale. The number 1 means 1 graduation of 1 inch represents 1 foot
  • Find an even whole number dimension on the drawing and check it with the scale
  • Read the graduations on the scale, you should get the same dimension
  • Check several other dimensions on the drawing to be sure the drawing is to scale
  • Scaling off a drawing 2
  • This is how you cheque the size of an object that is not dimensioned
  • First check the drawing scale is accurate as above
  • Use a engineering scale. The number 1 means 1 graduation of 1 inch represents 1 foot
  • The smallest division on the scale is 1/4"
  • Here the plate thickness is not dimensioned, but the scale reads 2 divisions or 1/2"
  • Check several other dimensions on the drawing to be sure the drawing is to scale

  • Simply draw your drawing border actual size and scale it up using the reciprocal numbers until your object fits nicely within the drawing border. Under drawing scale in the title block, label the scale from the chart whose reciprocal created the best fitting border

    Also if you have a drawing border that is 3/4"=1'-0" and you want to make it 1/2"=1'-0" look up the reciprocals for both scales. Since you are making your drawing border smaller in this case you need to divide 16/24 = .6666667. Scale the original border down by this amount and your scale is changed.

    The Ratio and Decimal numbers can be helpful if you are working in paper space and need to know what the scale factors are for window resizing in order to create the proper scale.

    Purchasing an engineering scale or an architectural scale is important should you need to measure off drawings in order to verify that they have been made properly to scale. eBay is a good source to find used and new scales. Here are some of the latest listings for drafting scales occuring on eBay right now...



    > Using a scle to read an engineering drawing

     
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    A SolidWorks designer talks about stuff related to CAD and mechanical design
    • Sketching on a SolidWorks drawing

      If you are new to SolidWorks, there can be times when things are a little frustrating. One of those simple things is adding notes or sketching lines on an exisiting drawing with several views.

      You add your note or centerline and then move one of the views but the note you added stays where it is and you end up having to move it seperately.

      Or you have a note that belongs somewhere else in the drawing that gets moved when you are rearranging views when you dont want it to.

      The solution to these problems is found in these excerpts from the SolidWorks help section.
       
      Lock View Focus.
      Allows you to add sketch entities to views, even when the pointer is close to another view. You can be sure that the items you are adding belong to the views you want. You can also double-click views to lock the focus.
      So if you want to add a note or a line to views and have them move when you move the view, click in the views, right click and lock the view focus, then add the items you want.

      Once you are finished just click the views and unselect the lock view focus. Now your items should move in lock step with the views.

      What about notes that you want to be part of the sheet. Say you have some general material or heat treatment notes that you dont want to have moved when views are manipulated. You need to use lock sheet focus.

      Lock Sheet Focus.
      Allows you to add sketch entities to the sheet. Otherwise, the sketch entities belong to the view that is closest to where you begin sketching. You can also double-click a sheet to lock the focus. Lock Sheet Focus is available when at least one drawing view is present. When Lock Sheet Focus is enabled, the drawing sheet border is pink.

      Finally if you are in a situation where you want to lock certain projections in postion use lock view position. I find this useful when I want to use a single projection to show an open or closed position by superimposing views on top of each other:

      Create two views of the same part or assembly. Align them horizontally or vertically as required. Right-click anywhere in the desired view and select Lock View Position. Then you can line up the copied views right over top of the original, making it look as if both are the same.
      Following these directions should help so that notes and sketched lines dont end up where they are not supposed to be!