Drawing a standard M20 hex bolt from scratch is a foundational skill for any mechanical drafter or engineer. Whether you are using AutoCAD or a DWG-compatible alternative, mastering the correct sequence of commands—from setting up your layers to applying precise chamfers—will drastically speed up your drafting process.

How to Draw a Hex Bolt in AutoCAD (Step-by-Step)

In this guide, we will walk you through the exact steps to draft both the top and side views of an M20 hex bolt, complete with thread details and centerlines.

目次

• Step 1: Set Up Layers and Guidelines
• Step 2: Draw the Top View (Hexagon Profile)
• Step 3: Draft the Side View and Thread Profile
• Step 4: Shape the Bolt Head Arcs
• Step 5: Apply Centerlines and Save
• Simplify Your CAD Workflow with DARE

Step 1: Set Up Layers and Guidelines

Proper layer management prevents headaches later when you need to hide or modify specific parts of your geometry.

1. Create New Layers Open your Layer Properties Manager and create three distinct layers:

Guidelines: Set the color to Red. (Make this your active layer).

Outline: Set the color to White.

Centerline: Set the color to Cyan.

2. Adjust Your Grid Set your Grid and Snap spacing to 2mm for precise manual snapping during this exercise.
   You can access this by right-clicking the Grid Mode icon and selecting Settings.
   
   

3. Draw Construction Lines Use the XLINE (Construction Line) command to create intersecting horizontal and vertical construction lines.
   
   These will serve as the center point for your bolt.
   
   Add an additional vertical line to the right to mark the side view position.
   
   

Step 2: Draw the Top View (Hexagon Profile)

Next, we will draw the top-down view of the bolt head. Switch your active layer to Outline.

1. Draft the Base Circle and Hexagon Select the CIRCLE command.
   
   Specify the intersection of your guidelines as the center point and enter a radius of 15.
   
   

Select the POLYGON command.

Enter 6 for the number of sides, specify the same center point, and choose Circumscribed about circle.

Snap the radius to the right quadrant of your circle.


2. Project Guidelines for the Side View Switch back to your Guidelines layer.

Ensure your End Point and Intersection Object Snaps (OSNAP) are turned on.

Use the XLINE command to project horizontal lines from the key endpoints and intersections of your hexagon.

Use the OFFSET command to create vertical boundaries for your side view (e.g., offset by 13mm, 14mm, and 60mm to define the bolt head and shaft lengths).

Step 3: Draft the Side View and Thread Profile

With your guidelines projected, switch your active layer back to Outline to draw the side profile of the bolt body and threads.

1. Define the Shaft and Threads Use the RECTANGLE or LINE command to define the main body of the bolt using the projected intersections.
   
   
   
   
   
   
   
   
   

To create the thread, use the OFFSET command to offset the outer shaft line inward by 2mm.

Use the LINE command to draw a 60-degree angled line at the tip of the bolt for the standard thread runout (type 240 degrees in your dynamic input).

Change the thread line color to Magenta for clarity (optional, but good practice for plotting).

2. Mirror and Chamfer the Tip Use the MIRROR command to duplicate the thread profile to the other side of the shaft.
   
   
   　
   
   

Use the CHAMFER command on the bottom tip of the bolt shaft.

Set your distance to 2.5mm and select the intersecting corner lines.

Use TRIM to clean up any overlapping lines.

Step 4: Shape the Bolt Head Arcs

The trickiest part of drawing a hex bolt is accurately representing the curved chamfers on the bolt head.

1. Draft the Head Arcs Using your guidelines, define a 30mm width for the bolt head.
   
   
   

Switch to the Outline layer. Use the CIRCLE command with a 30mm radius from the center top of the bolt head to create the main center arc.

Use the ARC command (Start, End, Radius) to create the smaller side arcs, specifying an 8mm radius.

2. Add Chamfer Lines and Clean Up Draw lines extending at a 60-degree angle from the top corners of the bolt head to simulate the machined edges.
   
   
   

Hide your Guidelines layer temporarily.

Use TRIM to cut away the excess circle and arc geometry, leaving only the characteristic curved bolt head profile.

MIRROR these features to the opposite side to ensure perfect symmetry, and trim any remaining excess lines.

Step 5: Apply Centerlines and Save

To finalize your engineering drawing, you need standard centerlines.

Open your Layer Properties Manager, select your Centerline layer, and click on the linetype.

Click Load and select a standard ISO or Center linetype (e.g., CENTER or ISO dash dot).

Switch to the Centerline layer and draw lines vertically and horizontally through the exact centers of your top and side views.

Hide or freeze your Guidelines layer. Save your file as M20_Hex_Bolt.dwg.

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