ou'll need to prepare a sheet metal drawing in AutoCAD. This drawing will contain a multiview
drawing and a 3-D model of a custom bracket that will be used in an HVAC system. If you draw
everything correctly, you'll be able to place a flat pattern for this bracket in the same drawing. Here,
you'll start with some rough models and drawings of the bracket, and you'll need to build a
multiview drawing and a flat pattern for this component.
Multiview Drawing of your Bracket
The bracket you are designing in this project will attach to an overhead beam and to the ductwork
using bolts. The bracket will include two bends and will be drawn in Imperial units. In your
multiview drawing, you will need to include holes for these bolts that are drawn to standard sizes.
The bolts that will be used to attach the bracket to the ductwork and the overhead beam are #1/2-13
threaded bolts. Use the link below to find the required hole diameter for this bolt. You will need to
use this hole diameter in your CAD drawing. Take note of the hole size you will need to
accommodate these bolts.
To find specifications for Imperial and metric bolts, use the Guide for Specification of Imperial
Bolts, Threads and Hole Fits in Advanced LIGO Parts.
To get started, open a new drawing in AutoCAD. Type the UNITS command into the command
prompt to bring up the Drawing Units dialog box. Change the decimal precision and make sure the
units are set to inches. You can reduce the precision to three decimal places. Also, check that the
angle units are set to degrees. Click on the Direction button to open the Direction Control dialog
box. By default, east should be specified as 0° for angular measurements. On the Home tab, select
the Annotation drop-down box and select Manage Annotation Styles under the standard style. Set
the font of your annotations to Courier New. Finally, you'll need to define an appropriate scale for
your drawing.
Next, you'll need to define the paper size you want to use for your drawing. Switch to your Layout,
delete any content that appears in the layout, and turn off the grid. Click on the Output tab, and then
select the Page Manager button. The Page Setup Manager dialog will appear; select the Modify
button to change the page size. Another dialog will open, and you'll see a list of paper sizes on the
left side of the dialog. Select the ANSI B paper size.
A screenshot of the title block that will be used in the drawings for this project.FIGURE 1—A
screenshot of the title block.
Now go back to your layout and start adding a title block and a window that will show your
drawing. Make sure that you draw your title block in the paper space, not in the model space. The
title block will be 1 inch tall and should be split into five boxes. Your title block should have two
rows, each 0.5 inches in height. The boxes showing your student name, ID number, a box with
“Graded Project”, and a box for your scale should be 4 inches wide. The final box will contain the
title of your drawing. Leave approximately 0.25 inches for the top and bottom margins, and leave
approximately 0.75 inches for the left and right margins. Figure 1 shows how your title block
should look. This title block will be used for all the drawings you create in this project.
One of the best habits you can develop when using AutoCAD is to carefully define your layers. The
layer names should be descriptive. Developing the habit of assigning color and linetype by layer
and using only descriptive layer names will help you keep track of the various elements in your
drawings. As you start building your drawing, you'll need to create new layers for hidden lines,
bend lines, bolt holes, center lines, and annotations. Go to the Home tab and choose the Layer Properties button to bring up the Layer Properties Manager. In this project, you'll need to start by
defining six layers. The names of these six layers should be “Bracket,” “BoltHoles,"
"HiddenLines," "CenterLines,” and “Annotations.” Change line color in each layer to match the
following color scheme in the Color Scheme for Layers table.
Color Scheme for Layers
Layer Color
Bracket White
BoleHoles Yellow
HiddenLines Magenta
CenterLines Cyan
Annotations White
Once you've created your layers, you'll need to define linetypes for each layer that match the
standard conventions for the different types of lines. To do this, go to the Properties box on the
Home tab. Select the drop-down box for linetypes and choose Other. From here, you can load
standard linetypes and add them to the linetype drop-down list. Select the Load button; you'll need
to add the "ISO dash space” and “ISO long-dash short-dash” linetypes. Finally, you'll need to
define a linetype scale so that you can properly see these linetypes. To do this, use the LTSCALE
command and set the scale to 0.02.
Now that you've defined your layers and linetypes, you're ready to start drawing your bracket. This
particular bracket is a U-shaped metal hanger. This bracket will be made from soft aluminum that is
0.25 inches thick. The bend radius for all bends will be 0.1 inches. If you look up a K-factor for this
material and bend radius, you will find that the K-factor is 0.33. All bends in this drawing will be
90° bends. You'll need to use this to calculate the bend deduction and the bend allowance.
A drawing showing a rough sketch of the bracket you will create in this project. The end face and a
view of the base are shown. FIGURE 2-A rough sketch of the bracket for this project. Note that
this sketch is not drawn to any scale.
First, draw the outside face, a top view, and a side view of the bracket. You'll often need to prepare
a fabrication drawing from a rough sketch prepared by a colleague. Figure 2 shows a rough sketch
of this bracket with the location of the drill holes. If you look at the left side of Figure 2, the center
of the lower hole is 1.5 inches above the bottom of the base. The next hole is 1.5 inches above the
first hole. If you look at the top view, each hole is 1.5 inches from the outside edge. The holes are
aligned along the center of the base and the edges.
In total, each face and the base of the bracket will have two drill holes. The holes on the base and on
the faces should be centered along the length of the bracket. The dimensions in the above figure
refer to the total length and width, meaning that these measurements include the thickness of the
sheet metal used to form the bracket.
A drawing showing a sketch of the bracket you will create in this project. The end view, top view,
and side view are shown. FIGURE 3—A sketch of the bracket for this project in AutoCAD.
When building your multiview drawing, you'll need to place the end view of the bracket shown in
Figure 3 in the bottom left portion of the drawing. You'll show a top view above this, and a side
view should appear to the right. Start by drawing the outline for each view, either as lines or
polylines. Make sure to place each type of line (hidden, bolt holes, and center lines) in the appropriate layer. Placing these center lines and hidden lines will help you create your drawing very
quickly.
In order to properly align the drill holes, you should manually enter offsets for your lines and circles
as you draw them. The easiest way to draw the bolt holes is to use the Circle (Center, Diameter)
tool.
A screenshot in AutoCAD of the bracket in 3D. This model is shown in an isometric view.FIGURE
4 A 3-D drawing of the bracket.
Now, you'll create a 3-D model of this bracket in the same drawing. Create a new layer, and name it
Model. Switch to this layer and start drawing out a 3-D model for the bracket. For this model, you
should use lines to draw your bracket as this will make it easier to erase overlapping lines in your
model. Keep in mind that you'll need to rotate the bracket to an isometric view after it is finished.
Draw your model from the top view in the X-Y plane. Figure 4 shows a 3-D view of the bracket in
an isometric view.
After you have finished your model, you will need to rotate it to an isometric view. To do this,
select the model and type the ROTATE3D command. In total, you'll need to rotate the model three
times. You'll see several options in the command line. These commands allow you to select the axis
about which the model will rotate. After you choose an axis, you will need to select a reference
point on the 3-D model. It's best to choose one of the corners of the model. Try to choose the same
corner for each rotation, otherwise, the model may move to a strange location and it might overlap
with your multiview drawing. You'll perform the following three 3-D rotations:
X axis, -90 degrees
Y axis, 45 degrees
X axis, -35.2466 degrees
You should now see an isometric view of your model next to a 2-D view of your multiview
drawing. Note that a 3-D perspective in a multiview drawing should not have any overlapping lines,
and hidden lines are not normally used in these models. Once you get to this point, you'll need to
start removing overlapping lines that would normally be shown as hidden lines. Some lines can be
selected and deleted, but other lines may have to be extended or shrunk so that they do not appear
behind one face of the bracket.
For the bolt holes, show only the circles that can be seen from the isometric view and delete any of
the circles that would appear as hidden lines. If you rotated the model correctly, you'll that there is
one circle in the base that is cut in half by the end of the bracket. This circle needs to be replaced
with an arc. The easiest way to draw this arc is to use the Center-Start-End setting. Rotate the view
so that the viewport to the top view so that you are looking at the bracket from above. Follow the
instructions below to set the isoplane so it matches the rotated viewport.
If you need to draw a line in a rotated drawing, you'll need to change the isoplane you're working
in to match the current view in AutoCAD. By default, the isoplane is the X-Y plane when you begin
a new drawing.
One easy way to change the isoplane is to rotate so that you are facing the plane in which you
would like to draw. Once you rotate to the desired plane, use the UCS command and select the View
option. The isoplane will now patch your view and you can start drawing 2-D lines and curve. To
reset back to the original isoplane, type the UCS command and select the World option. A screenshot in AutoCAD of the finished multiview drawing. The upper right portion of the
drawing shows the 3D model in isometric view.FIGURE 5—A multiview drawing with a 3-D
model of the bracket.
Once you're finished, your multiview drawing and your 3-D model should look similar to Figure 5.
Drawing Your Flat Pattern
Now you are ready to draw your flat pattern. If you look at the rough sketch in Figure 1, the
dimensions are given as the outer dimensions of the bracket. In order to draw the flat pattern, you
will need to calculate the bend deduction. You'll need to calculate the bend deduction for each bend.
Use the formulas to calculate the bend allowance and the bend deduction before you start drawing
your flat pattern:
You should find that the bend deduction is 0.0633 inches and the bend allowance is 0.2867 inches.
Once you've calculated the bend deduction, you can calculate the total length of the sheet. If you
add up the total length of the sheet and subtract the bend deduction for each bend, you'll find that
the length of the sheet is 13.8733 inches. This is long enough that it's better to draw the flat pattern
vertically. Draw the outline of the flat pattern in your Model view.
Because of the bend in this bracket, you'll need to place bolt holes from the edge of the flat pattern.
Remember that the bolts are defined based on the location of the center of the bolt hole; draw in
your circles while carefully paying attention to the distance from the edge. Just like with drawing
lines in your multiview drawing, this will be easiest if you type in the distances for your endpoints
while you are drawing.
To place the two holes that will appear in the base of the bracket, you'll need to offset the center of
the bolt hole from the middle of the flat pattern. The total length of the sheet, including the bend
deduction, is 13.873 inches, so the distance to the middle of the sheet is 6.9365 inches. The holes in
the base of the bracket are separated by 3 inches. Therefore, each hole will need to be offset from
the center of the sheet by 1.5 inches.
A screenshot in AutoCAD showing the location of one of the bend lines.FIGURE 6—The process
for placing a bend line.
The last step is to draw your bend lines. Normally, you would need to calculate this location based
on the bend allowance and bend deduction. However, there's a very easy way to place the bend line
in this flat pattern by using the location of the holes on the base and the end. If you take a moment
to draw a dimension line across the bend region connecting two holes, you should find that the
distance is 2.9365 inches. This is shown in Figure 6.
The bend line should be placed in the middle of these two holes. Because you now have a
measurement for the distance between these two holes, you can easily calculate the distance to the
midpoint. This is the location where you should draw your bend line. This is shown in the green line
in the above figure. Repeat this process for the other bend line.
At this point, you have drawn all the important portions of this drawing and you can start creating a
final draft.
Moving Your Model to Paper
Add a table with two rows to your layout in the upper right corner. Make sure you add this to the
paper space and not the model space. Each row should be 0.5 inches tall and 7 inches long. Add the
following information to your table: Thickness Bolt size Bend R Material
0.25 in. #1/2-13 0.1 in. Soft Al
Place this table so that it lines up with the upper right corner of the drawing. This should connect to
the outline on your paper.
Switch to Model space and arrange your model so that it sits in the lower left portion of the paper.
Place the flat pattern in the right side of the paper. If everything was drawn correctly, you'll be able
to use a 1:2 scale.
At this point, you should start adding dimension lines in the Annotations layer. Note that you don't
need to add every single dimension to this drawing. This should show you the advantages of using a
multiview drawing; the various portions of the drawing are aligned with each other, and this reduces
the number of annotations required to indicate dimensions. As a final step, select everything in the
drawing and change all of your lines to black. Your finished drawing should look like Figure 7.
The finished sheet metal drawing for this graded project.FIGURE 7—The finished sheet metal
drawing.
Inspecting Your Work
Before sending your drawings for grading, examine your drawings for any errors. Make sure your
name and student number appear on every drawing, and in the filename. As part of your inspection,
consider the following points:
Check for correct shape, size, and placement of entities. Exact placement can be confirmed by
checking the coordinates of all lines, points, and arcs.
Check that the entities are on the right layers.
Check to ensure your blocks are the correct size, if you have used any blocks.
Use the ERASE command to delete any unwanted marks.
Make sure your name and student number appear on the drawing title blocks and in the filename
(for instance, John Smith HVAC Sheet 1.dwg).
When you feel confident that your work is complete, submit your work. Send in this material as
soon as you complete the project. Don't wait until your work on the next project is finished
