With the current state of CAD software, picking between the two is as easy as picking between the two buttons. The increasing gap between designers and machinist makes it easy to pick one over the other without really thinking about it. I will try to shed some light on the issue and help you choose the best one for the situation.
In machining and design, a chamfer is a sloped or angled corner or edge, and a fillet is a rounded corner or edge. Of course you can use them on exterior and interior edges. Both exist because of the impossibility to machine a part to perfection with ease. The sharp edge left in the corners is a risk to the hand that tries to move the component.
Benefits of chamfers
one tool can be used to machine chamfers of different sizes. If you have edges with 1×45° and edges where you need a 2×45° chamfer it is pretty safe to assume that you can use the same tool for both thus saving machine time
it is less expensive and faster to apply chamfers. This is especially true with manually machined parts
reduces the stress concentration of the edge (in smaller amounts than fillets)
extremely useful for complementary parts (parts that should fit in holes/pockets)
Cons of chamfers
not really used or recommended for interior edges
chamfer edges are the first to lose paint
Advantages of fillets
removes stress concentration from the corner (in higher proportion compared to chamfers)
has the advantage of completely removing the corners which is especially beneficial for painted parts
contributes to the aesthetics of the part
Cons of fillets
internal edges decide the maximum diameter of the tool that can be used
more expensive/take more time compared to chamfers
In conclusion I think that fillets should be used where chamfers are just not enough. If you have a visible part or where the ergonomic of the component is very important fillets should be preferred when a slight increase in price is not a problem. For everything else, chamfers are usually enough, and applying them to most of the corners of your part when you are finished with your design should become second nature. Your shop colleagues will thank you!
I firmly believe that being able to create and control complex sketches is where the bread and butter of the design engineer is. It all starts from the bottom, and if you are comfortable creating sketches that do what you want them to do then you are half way to the finish line. Let us capitalize on that. Try to build the following model with as few sketches as possible.
Regular geometrical shapes where invented by the ancient Greeks and although they might seem simple for the human mind if we know the rules that govern them, it is sometimes hard to build them in a CAD system. Let’s try to build a regular octahedron with a 10mm edge. Making it with as few features as possible earns you extra points for this challenge.
The secret to complex models is the ability to decompose a design into smaller pieces. Build them together like puzzle pieces and you should be able to obtain pretty complex manufacturing parts. If you combine the features from previous challenges like extrude, revolve and holes you can easily obtain the model below.
Holes with threads are the easiest way of fixing parts together. They also have some advantages of being removable, as opposed to welding for example. For this challenge you should try to make a hole and add a standard metric thread to it and also add one external thread. If you manage to do that, you will have another very important tool in you CAD belt.
Pad/Extruding is not the only operation you can use on sketches. The revolve feature is extremely useful for axis symmetric parts, manufacturing them on a lathe is really easy to imagine. Again, you have a choice, either bring the radii directly in the sketch, or add some fillets afterwards. While drawing, why not try to add some tolerances to our dimensions.
After we started with a simple sketch-extrude/pad design in the first challenge let us now learn how we can reuse the same geometry in different places with patterns. You could either complicate the same sketch by drawing all of the four pockets, or you could just build one and reuse the pattern, I would recommend the latter.
I want to start a series of daily CAD Challenges for the beginners in the field of design engineering. For each new challenge I will supply the 3D model in STEP format and also the drawing as PDF. Today we will start with a basic model that I created in Fusion 360.
The sketch is the first building block of every 3D model. Let’s start with a simple sketch that we can extrude/pad for 20mm to obtain our model, and while we learn how to do that, adding some holes in the same sketch should not be that difficult. The outer radii could be added inside the same sketch or afterwards as fillets, your choice.
I will provide Google Drive and DropBox links for each challenge. Good luck!
If you are like me, then you feel that what you learned about machining in school might not be enough for your daily activities. This channel is exactly what is needed to understand the day to day activities of a machine shop. Tips, how to videos and also Fusion 360 tutorials, you can see the whole life of a part, from CAD to the finished product on this channel.
Thank you John Saunders for sharing your experience in your awesome machine shop!
I just finished this course on Material Behavior on Coursera and I can say that it was a great experience. If you want to freshen up on your materials knowledge or you are currently studying this and want a different perspective, I recommend you take this course.
The course is offered by Georgia Tech and it is taught by Thomas H. Sanders, Jr. (Regents Professor). I have to be honest: although the course is full of information, it might seem rather slow and boring sometimes and if you do not pay attention or even write down the important topics, it will be hard to pass the tests at the end of every week. The course goes through the most important aspects of materials like atomic structure, crystalline structure, defects etc.
We all know that these massive online open courses are sometimes just marketing schemes for unknown universities from around the world that do not offer a lot of value. This course is not like that, and everyone that will make it through to the sixth week will have a deeper knowledge of materials.
The student effort is listed at about 2 hours and 30 minutes for most weeks, and I have to say that was not enough for me, I guess for someone new to the material behavior, this course might well take up 4 or 5 hours a week with a little internet search on different topics mentioned by the professor.
In conclusion, I highly recommend this course and I found it to be one of the best open courses floating around on the internet.