Blender Tutorial

Blender Drill Bit Tutorial
 
 
Skill Level:          Beginner (Tutorial assumes that the user knows the basic functions of Blender ).

Blender Version: 2.45

Tutorial Version: February 19, 2008

Resources: drill_bit blend file




Introduction.

This tutorial illustrates a technique of modeling a "semi-realistic" 118° Point Twist drill bit in Blender.

I use the term "semi-realistic" because there are a couple of key features that I won't be including in the model since, although they are important in the proper operation of the drill bit, they aren't really too noticeable in the final model. These features include:



Also, note that I am not modeling to any particular scale. Although, this is easy enough to adjust later. Adjust the scale by the reciprocal of square root 2 (0.7071) (to obtain an unit one radius) and then scale by 0.5 to obtain an one unit diameter.
Then you can scale depending on what size of drill bit you desire in either English or Metric units.


It's always a good idea to collect some reference information on what you're going to model. Here's just a few resources that I found on the Internet:


Drill Bit Anatomy

Drill Bit Geometry

This site has a couple nice and simple diagrams showing the drill bit's major features: Typical Drill Bits

This site contains a nice and simple diagram showing the drill bit's "Angle of Relief" feature (in the 'Wheting of Drill' section): Drilling

Finally, the Wikipedia site on drill bits: Drill Bits




Final Result: Drill Bit.



Step 1. Creating the Drill Bit's Flutes/(Grooves)

Note: I've disabled the Transform Manipulator (Widgets) (Press [Ctrl] + [Space] :: 'Manipulator' Enable/Disable, or press the 'hand' icon button in the 3DWindow header). For a relatively simple mechanical type model like this, I find that it tends to get in the way, but you can leave it on if you prefer.

Delete the default Cube.

Ensure that you are in Top view ( [Num_Pad 7] ), and add a 32 vertice Mesh Circle. Set the 'Radius' parameter to 1.4142136 (square root of 2). (This value was used since, in combination with the settings used for the Screw function, it will produce a Helix Angle of approximately 30°).

In the Edit Buttons Window :: Link and Materials panel, give the mesh circle a more appropriate Mesh and Object name for the final object that we are modeling: 'drill_bit'.

Tip: You can save yourself a bit of typing by using Blender's copy and paste feature. Once you've typed in 'drill_bit' in the "OB:" (OBject) text entry button, position your mouse cursor over the button and press [Ctrl] + [c] to copy the text to the buffer. Then move your mouse cursor over the "ME:" (MEsh) text entry button and press [Ctrl] + [v] to paste the text.


Figure 1. Basic Drill Bit Cross Section.



Set the margin clearance by extruding and scaling ( Press [e] , [s] ) the mesh Circle's vertices by a factor of 0.95 .

Tip: If your goal is mechanical precision, you can set the margin clearance using the formula: Final Margin Clearance = 0.7071 * 0.5 * ( (1.4142136 - (1.4142136 * Scale Percentage) ).


Figure 2. Establishing the Drill Bit Margin Clearances.



Invert the vertice selection by pressing [w] Specials > 'Select Swap'. Then [Shift] + RMB de-select the 4 vertices that will form the drill bit's margins on the outer Mesh Circle. (Refer to Figure 3).
Erase the selected vertices.


Figure 3. Creating the drill bit's Margins.



Select and Erase the internal edges on the margins.


Figure 4. Erasing the Unnecessary Edges.



De-select all vertices, and then select the two vertices on the right half of the circle that lie just inside the major Grid divisions (The 2 vertices on the right shown circled in orange in Figure 5 below), and snap the 3Dcursor to the selection.
Select the vertices lying between the first two that were selected.
Change the scaling mode to 'Scale wrt (with respect to) cursor' mode :: main keyboard dot/period key: [ . ]
Mirror the selected vertices across the X-axis ie. Press [m] Mirror Axis > 'X Global' - you should see the selected vertices flip wrt the cursor across the X-axis.
Repeat this operation for the left hand side.


Figure 5. Defining the lower drill bit Cross Section.



Although we have the right shape now, the web diameter (the distance between the flutes/grooves) is a little wide.
In actual drill bits, this web diameter increases (very slightly) as you go from the bottom (tip) to the shank (top) of the drill bit.
This aids in forcing the material being drilled out of the grooves as it moves upwards, as well as adding strength to the drill bit structure.
Since the variation in the web diameter is very small, we'll forgo this detail and compromise by using a constant average web diameter.
To reduce the web diameter, scale the selected vertices shown in Figure 6 (wrt cursor) by 2. ie. Press [s], [x], [2], and press [Enter].
Repeat for the opposite side.

Tip: You can save a bit of time by performing the scaling operation in combination with the last step (when you already have the 3DCursor's location set for each side).


Figure 6. Reducing the drill bit's Web Diameter.



Now to create the drill bit's 2 cutting edges. Delete the three vertices in the upper part of the inset semi-circular piece on the right side.
Note: It's important to get the right side, because drill bits cut into the material when they are rotated clockwise (when viewed from the top).
Select the two end vertices of the opening and add an edge by pressing [f], then perform a 'Subdivide Multi': [w], [main keyboard 2 (two) ] (ie. select the second menu item) and adjust the default 'Number of Cuts:' value to 3 and press [Enter] or click on [OK].
Do the same for the opposite side of the drill bit cross section.


Figure 7. Adding the Cutting Edges.



Since we created the margin by extruding and scaling wrt the center of the circle and not wrt the cutting edge "base", the vertex lying on the outer corner of the margin is not "in-line" with the cutting edge.
We will correct this now by extending the cutting edge beyond the margin, and then using this edge to cut a vertex that is in-line with the cutting edge.

Snap the cursor to the inner vertex on the cutting edge. (Refer to Figure 8).
Select the inner vertex of the margin (Shown circled in orange in Figure 8 below), and extrude + scale [e], [s] the edge so that it extends beyond the outer edge of the margin.


Figure 8. Setting up the Cutting Edge.



Select the outer edge of the margin and press [k] to bring up the Loop/Cut Menu and select 'Knife (Exact)' from the menu.

Create a cut by first activating the Knife tool by LMB clicking somewhere to the left of the first point being cut in the 3DWindow. (Refer to Figure 9 below).
Hold down [Ctrl] and move the knife cursor icon close to the inner vertex of the drill bit's margin and LMB click.
Hold down [Ctrl] and move the knife cursor icon close to the last vertex on the helper guide line and LMB click. Press [Enter] to perform the cut.


Figure 9. Cutting the Margin.



Select the vertex on the "corner" of the Margin and then the corresponding vertex which was the result of the previous cut and merge them by pressing [Alt] + [m] :: Merge 'At Last'.
Select the vertex at the end of the helper guide line that was created to aid in making the cut in the previous step and erase it.


Figure 10. Correcting the Drill Bit Margin Edge.



Snap the cursor to the vertex on the "corner" and then select and scale the outer margin vertex wrt the cursor by 0.8 .


Figure 11. Adjusting the Margin/Clearance Bevel.



Place the cursor back at the origin ( [Shift] + [c] ).
Delete the outer edge of the Margin which is on the opposite side of the drill bit's cross section where we just adjusted the margin. Then select the 4 vertices forming the corrected margin, duplicate them [Shift] + [d], and rotate them 180 degrees. ie. [r], 180 [Enter]
Select all vertices and Press [w] :: 'Specials' > 'Remove Doubles'.


Figure 12. Adding the Opposite Margin/Clearance.



Ensure that your 3Dcursor is at the origin by pressing Shift + [c], and de-select all vertices.
Note that the 3DCursor location is important, since when we use the Screw function in the next step, it serves as the focal point around which the drill bit's cross sections will be created.
Ctrl + LMB click anywhere in the 3DWindow to create an "orphan" vertex and then snap the vertex to the 3Dcursor.
Switch to Front view, zoom the view out slightly, and extrude the vertex up 15 grid units.
Tip: After starting the extrude, press [Z] to limit the extrusion along the global Z axis, and then enter [15] to move the selected vertex 15 Blender Units (BU) upwards.
The length of this 15 BU line defines the distance for the Screw function to replicate the original drill bit cross section for the defined 1 revolution or 360 degrees (Turns: 1).
Select all vertices.


Figure 13. Mesh Preparation



Adjust the settings shown hi-lited below in Figure 14 (Edit buttons window :: Mesh Tools panel)
Then press the 'Screw' button.
(If you happen to have more than one 3DWindow open, your mouse cursor will turn into a '?' requestor. In this case, just click on a Front view 3DWindow).

Note that the final cross section count will actually equal 16 - the original cross section + 15 created by the (Steps: 15) setting; though the individual "tubes" created will equal the Steps setting '15'.

Also note that the 'Degree:' setting is only used with the Spin and Spin Dup functions. If you require a fractional Screw operation, say 1.5 for example (and still maintain the vertical "thread" spacing which is established by the length of the line segment), you will need to adjust the 'Turns:' value to the next highest value '2', press the Screw button, and then delete the excess '7' cross sections created on top.
Also, since each cross section is being rotated 24° (360° / 15), you will notice that the top cross section doesn't lie at the right angle. Hence, you will need to make a knife cut 22.5 BU up from the origin. 22.5 BU because the drill bit's lands (the raised surfaces) spirals around the Z axis every 15 BU; therefore the next half rotation will occur at 15/2 or 7.5 BU higher than the first complete rotation.

Finally, if you don't like the results of the Screw function, you can always 'Undo' Ctrl + [z] the results, change the settings (including the length of the extruded line segment) and try again.


Figure 14. Adjusting 'Screw' Settings.



De-select all of the vertices [a], then link select (press [l] with your mouse cursor over one of the vertices in the center line) and delete the center line of vertices.
Select all of the vertices, and move the mesh vertically 15 BU, so that the bottom of the mesh is located at the origin.
Activate the 'Depth Buffer Clipping' icon shown hi-lited in orange below in Figure 15 to "hide" the geometry on the back side of the drill bit in order to make it easier to view the object as well as limit vertex/edge/face selection to the ones visible in your current view. Vertex/Edge/Face selection mode may be selected via the hotkey: [Ctrl] + [Tab] + main keyboard [1], [2], or [3].

Note: Switching to Wireframe view mode by pressing [z] , de-activates the 'Depth Buffer Clipping' feature allowing you to select "back-side" vertices (vertices positioned in behind other vertices). Also, in Wireframe view mode, the 'Depth Buffer Clipping' icon disappears since it is irrelevant.


Figure 15. Creating the Drill Bit Grooves.



Step 2. Making the Drill Bit's Pointy End

Switch to the Right Side view.
Since the lower part of the drill bit is symmetrical about the Y axis, there is no sense modeling both sides. So we will save ourselves some time and effort by deleting the lower left side vertices of the drill bit as shown below in Figure 16.


Figure 16. Deleting Drill Bit Mesh Redundant Vertices.



Standard 118° Point drill bit ends form an internal angle of 59° wrt the major axis of the drill bit (118° / 2). This means that if you were to stand the drill bit up on a table top, the angle between the table top and the bottom end of each drill bit face would be 31° (90° - 59°).

To create this 31° angle, we will use a helper object to guide our knife cut.
Ensure all vertices are unselected and Ctrl + LMB click somewhere in the 3D Window. Snap the lone vertex to the origin - Shift + [s] > 'Selected to Cursor'.
Extrude the vertex to the right about 3 B.U.
Rotate the vertex wrt the cursor -31°.


Figure 17. Creating a helper (Guide) Object.



De-select all of the vertices.
Switch to face select mode and select all of the faces to be cut excluding the two next to the origin. This is because the knife tool can have problems splitting vertices that are coincident to the cutting edge. Sometimes, in this case, it can create a new face with vertices that are slightly offset, so it's best to avoid this situation altogether.
If you check the Face count in the top Information header, you should see a total of 16 faces selected (Fa: 16 - 540).

Tip: The hotkey combination: Shift + [c] (Place 3DCursor at the origin), followed by pressing [c] (Center the 3DWindow view at the 3DCursor) can make it a little easier to select the faces when you rotate the view.


Figure 18. Selecting the Faces to Cut.



Switch back to vertex selection mode.
Press [k] to bring up the Loop/Cut Popup and select 'Knife (Exact)' from the menu.

Create a cut by first activating the Knife tool by LMB clicking somewhere to the left of the first point being cut in the 3DWindow. (Refer to Figure 19 below).
Hold down [Ctrl] and move the knife cursor icon close to the vertex at the middle of the drill bit (at the origin) and LMB click.
Hold down [Ctrl] and move the knife cursor icon close to the last vertex on the helper guide line and LMB click. Press [Enter] to perform the cut.


Figure 19. Making the Cut.



Switch to wire frame view mode OR de-activate the 'Depth Buffer Clipping' feature.
De-select all vertices.
Do a Border or Circular select of the vertices below where we made the knife cut in the last step, but do NOT include the two vertices at the tip near the origin. (Refer to Figure 20 below). Also, link select the 2 vertices of the helper guide line object. Delete the selected vertices.


Figure 20. Deleting the Lower Vertices.



Press [z] to return to Solid view mode OR re-activate the 'Depth Buffer Clipping' feature.
Four triangles were produced by the knife cut on the faces near the origin during the previous step. Switch to Face select mode and select the triangles and then press [Alt] + [j] to convert them to quads.


Figure 21. Converting Triangles to Quads.



Switch back to Vertex select mode.

Select the four vertices forming the margin/clearance protrusion of the drill bit and create a face by pressing [f].


Figure 22. Filling in the Margin/Clearance.



Before we perform the task of filling in the lower drill bit land surface, there is an issue that we need to address.
When you use the Screw tool, since the faces produced aren't flat (ie. the vertices of the face don't lie on a plane) an edge that was perfectly straight (when viewed in top view) may produce a slightly offset/curved result. This is because the faces produced by the Screw tool are actually folded or twisted a bit. Similiar to holding a piece of paper with one hand on the top and the other hand on the bottom of the paper and then twisting it. When a cut is performed across this "distorted" face, the vertices produced are "placed" on the slightly contorted surface.
As you can see in Figure 23 below, where the drill bit's cutting edge should be perfectly straight, there is a slight arc.
Create the "straight edge" shown below in Figure 23 by selecting the 2 outer vertices and pressing [f].


Figure 23. Drill Bit Cutting Edge Issue.



To fix this issue, first we will transfer the inner vertex on the margin to the straight edge by making a cut across the currently selected edge using the knife tool to snap to the existing vertex.
Switch to Right Side view. Press [k] to bring up the 'Loop/Cut Menu' and select 'Knife (Exact)'.
LMB click to activate the knife tool, then press [Ctrl] to snap to the vertex on the inner margin. MMB click and draw a line straight down over the selected straight edge, LMB click and press [Enter] to perform the cut.


Figure 24. Tranferring the inner Margin vertex to the Straight Cutting Edge.


Select the inner vertex on the Margin and then the corresponding vertex which was the result of the previous cut and merge them by pressing [Alt] + [m] :: Merge 'At Last'.


Figure 25. Merging the inner Margin vertex to the Vertex on the Straight Cutting Edge.


Select the 2 outer vertices of the remaining straight edge, and then press [w] :: 'Subdivide Multi' with a 'Number of Cuts' setting of 3.
Merge the corresponding vertices from the slight arc to their corresponding partner on the straight edge in the same manner as in the previous step.


Figure 26. Merging the Arc Vertices to the Straight Cutting Edge.



Starting from the origin, and selecting 4 vertices at a time, create 4 faces (by pressing [f]) that span the bottom of the drill bit from the curved flutes to the straight cutting edge.
Place your mouse cursor over one of the interior edges of the faces that were just created, press [Ctrl] + [r], and roll your Mouse Wheel forward until you see the 'Number of Cuts' setting equal to 7 in the 3DWindow header. Press LMB to create the cuts.

Note: If you don't have a Mouse Wheel, you can simply press main keyboard [7] and press [Enter].


Figure 27. Filling in the Drill Bit Tip Faces.



Merge the vertices on the outer edges of the faces created in the last step to the outer drill profile.


Figure 28. Filling in the Drill Bit Tip Faces.


Box select the vertices shown below in Figure 29.
Remember to de-activate 'Depth Buffer Clipping' and check to ensure that no extra vertices were selected.


Figure 29. Selecting vertices to Mirror.


Make a duplicate ( [Shift] + [d] ) of the selected vertices.
Press [r], [z], [180], [Enter].


Figure 30. Rotate duplicate vertices 180°.


Select all vertices.
Press [w] 'Specials' :: 'Remove Doubles' to "join" the duplicate vertices to the main mesh.


Figure 31. Removing Doubles.



Select all the vertices of the drill bit and press [Ctrl] + [n] to recalculate the normals.
Press 'Set Smooth' in the Edit Buttons window :: 'Link and Materials' panel.
Press the 'Add Modifier' button in the Edit Buttons window :: 'Modifiers' panel and select 'Subsurf' from the popup menu. Also, set the 'Levels:' to 2 (or lower if your display response time becomes unacceptably slow) and the 'Render Levels:' to 3.

Tip: A fast way to add a Subsurf Modifier is by pressing [Ctrl] + the main keyboard number key corresponding to the Subsurf level you want; [2] for example.


Figure 32. Adding a Subsurf Modifier.



The drill bit will, for the most part, look alot nicer with all the added smoothness. Though, if you look at the cutting edges of the drill bit, they don't look very sharp.


Figure 33. Subsurf Effect on the Cutting Edges.



To sharpen it up again, we need to adjust the crease setting to 1 for the edges shown selected below in Figure 34.
Select the edges shown below, and press [Shift] + [e]. Move the mouse pointer away from the median center of the selected edges until you obtain a crease value of +1 as shown in the 3DWindow header.

Note: To have the crease value displayed visually as an increasing thickness edge (dependent on the applied crease value), press the 'Draw Creases' button located in the Edit Buttons Window :: 'Mesh Tools 1' panel.


Figure 34. Adjusting the Cutting Edges Sharpness.



Also, adjust the edge creasing for the edges shown selected below (plus the complementary edges on the opposite side of the drill bit) to +0.5 .


Figure 35. Adjusting the Trailing Edges Sharpness.



Step 3. Finishing the Top of the Drill Bit


Switch to Right Side view.
Select the top 'ring' of 36 vertices (ie. the 32 vertices which were part of the original 32 vertices mesh circle + the 4 margin vertices), and extrude them up one grid unit.

Tip: To quickly select the vertices, use vertex loop selection: Ensure all vertices are first unselected, place your mouse cursor over an edge along the lower vertex loop and press [Alt] + RMB click.


Figure 36. Extruding Top Ring of Vertices.



Hide all of the unselected vertices - [Shift] + [h].
Switch to Top view.

We need to return the cutting edges to their original curvature, so select the 3 vertices in the center of each of the straight cutting edges of the drill bit and delete them.
Place the cursor in the center of the narrowest part of the groove (the center of the drill bit profile) and ensure you are in 'Scale wrt Cursor' mode.
Select the vertices on the curved part of the flutes/grooves (up to and including the corner), duplicate ([Shift] + [d]) them, and mirror [m] the duplicated vertices across the Global Y axis.


Figure 37. Reshaping the Flutes/Grooves.


Select all the vertices and perform a [w] :: 'Remove Doubles'.
Reveal all of the vertices once again - [Alt] + [h], and replace the faces that were deleted due to deleting the vertices earlier.
Select the top 'ring' of 36 vertices once again and extrude them upwards by 1 grid unit a total of two times.
Close off the top margins/clearance part of the drill bit, so that they don't extend to the completely round cross section part at the top of the drill bit.


Figure 38. Extruded Vertices.



Slide the outer edge of the margin/clearance protrusion in slightly in order to produce a smooth tapering off effect of the margin to the side of the drill bit.
Rotate the view so that you are looking fairly aligned to the side of the margin as shown below in Figure 39.
Switch to edge select mode, and select the top outer edge of the margin.
Press [Ctrl] + [e] :: 'Edge Slide' and slide the edge inwards by a percentage of -0.5 , so as to decrease the width of the margin towards the top of the drill bit.
Be carefull to slide the edge inwards and not vertically along the side of the drill bit.
Repeat this step for the Margin on the opposite side of the drill bit.


Figure 39. Tapering Off the Margin.



To produce a smoother fall off to the margin, snap the 3DCursor to the inner vertex on Margin at the edge loop below the one we were just working on.
Then select the corresponding vertex on the outer margin and scale it wrt the cursor by a factor of 0.7 .
Repeat this for the vertices on the other side of the same margin, and then perform the operation for the margin on the other side of the drill bit.


Figure 40. Adjusting the Margin Taper.


Switch to Right Side or Front view.
Select the top 'ring' of 32 vertices (ie. the 32 vertices which were part of the original 32 vertices mesh circle), and extrude them up one grid unit a total of two times.


Figure 41. Extruded Vertices.


Select the first "ring" of vertices that were extruded (the first one from the start of extrusion which is not rotated; ie. the 5th ring from the top), and hide the rest of the unselected vertices ([Shift] + [h]).


Figure 42. Vertice Selection.



Now we start to bring the internal flutes/grooves back out to form a "perfect" circle that we started from.
We'll perform this in 5 steps. I'll show you how for the first one, the rest you can do given the values that I'll supply.
Switch to Top view and select the 2 rightmost vertices and snap the cursor to them.
select the rest of the vertices contained in the right hand groove.
Scale, [X], 0.7, [Enter].
Repeat for the opposite side.


Figure 43. Restoring the Profile Circle.



Ensure the cursor is at the center of the vertices and then rotate them wrt to the Z axis by -24 degrees.


Figure 44. Rotating the Profile.



Repeat the operation for each "ring" of vertices, moving upwards from the one we just did, using the following values:


You should end up with the following:


Figure 45. Transition to a Circular Profile.



The rest is very simple. Select the top circle of vertices and extrude upwards by 10 grid units.
[Optional]: To add a little more style, make a second extrusion up about 0.3 grid unit and then scale these vertices inwards by a factor of 0.7 .
Snap the cursor to the top vertices and switch to 'Scale wrt cursor' mode.
In top view, add a 9 by 9 mesh grid and scale it down so it fits within the mesh circle.
Select just the outer border vertices of the mesh (Unselect the "middle" vertices by pressing [b] and RMB drag over the inner vertices) and press [Ctrl] + [Shift] + [s] 'To Sphere' and use a value of 0.7.
Bridge the gap with faces. ( ie. select both "rings" of vertices to connect, press [f] and from the 'Make Faces' menu, select :: 'Skin Faces/Edge-Loops' )

Select all vertices and press [Ctrl] + [n] :: 'Recalculate normals outside' and also press 'Set Smooth'.

To sharpen the top circular edges, select the top circle of vertices (the 'edge' at the bottom of the beveled top), and set the crease value to approximately 0.9 and set the 'edge' at the top to something like 0.7 to give it a somewhat smoother edge.


Figure 46. Finishing off the Top.



Step 4. Final Details

To complete the drill bit model we'll do a couple of scaling operations, so that it can be easily scaled to whatever dimensions are required.
Since drill bits are sized according to the diameter of hole they create (which is established by the diameter between the drill bit's margins), setting the drill bit's diameter to 1 BU will make it easier in the future to create a drill bit of any size dependent on the scale being used in the Blender Scene.

Place the cursor at the origin by pressing [Shift] + [c] and select all of the vertices.
Ensure that you are in "scale wrt cursor" mode.
Scale by a factor of 0.7071 (inverse of square root 2) to remove the square root 2 scale. (Making the drill bit diameter = 2 BU).
Scale by a factor of 0.5, so that the diameter of the drill bit is equal to 1 BU.


Figure 47. Final Mesh.