Join Paul F. Aubin for an in-depth discussion in this video Other line forms, shapes, and edits, part of Drafting Foundations.
- Simple straight lines are the first thing that you'll need to practice and master, to be sure. But there are many other types of lines and shapes that we'll need to draw. Things like circles, arcs, freeform curves, or mark out equal spacings in many cases. So, let's explore a few of the common shapes and techniques that you'll want to also master. Let's start with some parallel lines. Now, you may not have access to a T-square, or a parallel bar, or maybe you're in the shop or something. So, the first technique I want to show you is something really simple just using two triangles. What you do is you take the first triangle, and you kind of hold that steady off to the side, and you take the second triangle and you put it up against the first one.
Now, this allows you to just move that triangle along the first edge, and it will always keep a parallel edge. So, I'm going to just position this where I want it to go. And then I'll just come in here and draw my first line. And then, as I move the first triangle along the edge of the second one, you'll see that I've creating some parallel lines. Now, of course, if I want to control the distance between those lines, I can come in with my scale and mark off where I need that line to go.
Just put a little dot right there. And then I just line up my triangle with that dot, and then draw in my new parallel line. And it maintains those lines as parallel. Now, the trickiest thing about this technique is, of course, if you accidentally move the first triangle, then it will be difficult to match it up again. So, having a T-square or a parallel bar is certainly preferable if you have one at your disposal. The way this works is you put it along the edge of your drawing board.
And then as you're moving the T-square, you get a little bit more control over the parallel lines. And also, if you need to mark off distance, you don't have to worry so much if this has to move out of the way. You can simply move it out of the way, mark off the distance that you need, and then when you put this pack on the same edge, you know that it's parallel, and you don't have to worry as much about moving that other triangle out of the way. But as I mentioned before, if you don't have access to these tools, or if you're out in the field, then the two triangle approach can certainly be helpful.
Now, when it comes to other shapes, things like circles or curves, there's a few different options that you have. So, a circle template is the easiest way to create circles if they're standard sizes. So, all I have to do is locate the size circle that I want, and then just simply put my pencil in that shape, and make sure that I'm putting equal pressure all the way around the template. And I'm still trying to roll my pencil, if I can, like I talked about in the previous video with you, so I get a nice continuous smooth curve there.
It takes a little practice to do that even in pressure all the way around without making a mistake. Now, we have templates for all different types of shapes that are common in drafting. So, I have an architectural template right here. So, perhaps I needed to draw some standard symbol like this toilet symbol. Once again, I just provide even pressure all the way around the symbol, and just sort of trace it like so to create that standard shape. And it's quicker, and it's obviously more consistent if you use a template to create those common shapes.
Now, when you need a circle or an arc that's a size that's not in your template, or that needs to fit a very specific circumstance, you can use a compass. Now, I have a nice set of compasses here that can either do ink or pencil. And I actually have a few different sizes here. So, this one is for very large radii. And we've got this one here which is for a smaller radius. Now, this is slightly more precise because I have the dial here, where I can open it up to exactly the size I want.
And once again, I can use my scale ruler here and open this up so that it matches exactly the distance that I'm looking for for the radius. So, it makes this a little bit more precise than the one that doesn't have that wheel in there. There's a needle on this side, and the lead is on this side. Now, you may notice that the point varies a little bit here between the lead holder point, which is pointed all the way around, and the compass point, which is more of a chisel. We do that because we're moving around the circle.
That point works a little bit better. And we're going to use our sandpaper here to keep that sharp. And you just sort of file off a little chisel shape, like so, in order to get that kind of a point. Then you just put the needle point into the paper, and I'm doing this at a slight angle here. That allows me to get the pressure that I need as I draw this around. Now, I've got a pretty hard lead in there right now, so it's a fairly light line that I'm getting. So, you can use a softer lead if you need to get a darker line.
You can also use this to get an arc. So, you can just stop at where you need the arc to go. Now, it's a little easier if you've got to do a tangent to a point like that. So, if I've drawn the curve first and then I come in with the straight edge, it's a little bit easier to make sure that you're getting that point exactly tangent to that existing curved line by drawing the curve first. It's a lot tougher to get that curve to match the existing straight line that's already there. You, certainly, can do it with practice, but it does take a decent amount of practice to do that.
Now, if you need a curve that's not an arc or any of the template shapes that you have, you can use a French curve. This is great if your drawing roads, or railroads, or things like that, where the curves kind of are much bigger and more freeform. So, what you do is you find a portion of the French curve that matches the curve you're trying to create, and then you just draw a long that piece. And then by moving the French curve, you can actually change the shape of the curve and draw it in segments that are sort of tangent to the existing curve and kind of create a more continuous curve that way from different portions along the French curve.
Now, when you have a line and you need to divide it into portions, so perhaps you want to bisect a line into two equal segments, or perhaps, you want to take a line and break it into a series of divisions, there's a few techniques we can use there. So, with a simple straight line, if I wanted to bisect it, I actually can do that either with a compass or with a triangle. So, using my compass, actually, I'll use the larger one in this case, what I can do is just open it up to a radius that's maybe a little bit more than half of this, put the point on one endpoint of the line, and just sort of mark a light arc out here, and then do a second one at the other endpoint of the line, like so, and then I come back in now with my T-square, and pick up that point, and just kind of bring it in.
And that, right there, is the midpoint of that line. Now, you could do the same thing, actually, with two 45 degree angles. So, find that endpoint right there, strike a small line, take this end point right here, strike another 45, and then, of course, mark that point right there. And that will give us the midpoint of this line. Now, we do something similar if we need several divisions along a straight line.
Now, that line right there that I was dividing, actually, might have been the one I drew with the two triangles originally. So, I'm going to draw a new line over here using the T-square, just so I can make sure I'm staying parallel. And then, what we can do is draw another line off of this. It doesn't matter what angle you draw this on, so I just did a 45. I'm going to take my scale now, and you look for a convenient set of markings. So, I'm just going to use the inch markings in this case, and start right at the beginning.
And since we know that these divisions are equally spaced on the ruler, all we have to do is mark them off on the diagonal line, and then we can draw parallel lines from those points. And this is where we can use the technique that we did earlier. Since this is going to be a random angle, what I'm going to do is like up the first point with the endpoint of the line I'm trying to divide. So, this point right here, I want to line up with the first point that I indicated on the diagonal line.
And then I'll use that trick that I showed you with the two parallel triangles. And I'll mark this one, slid it along the parallel line. And as I mark each of these lines, it will intersect the line that we're trying to divide, and create the equal segments. Now, of course, if you have your adjustable triangle, you could use your T-square in this case and find that angle, and use the adjustable triangle to achieve the same thing. But the two parallel triangles works just as well, as long as you maintain a steady hand.
So, what about cases where you make a mistake? Well, naturally, you've got your eraser that you can use to correct things. Or it may just be that in some cases it's not so much of a mistake, but rather, you just need to kind of clean things up a little bit. You know, so you obviously, can just come in here and use a regular eraser, and kind of remove the bits that aren't required. But in some cases, when you do that, you might actually take away some of the required line. So, there's another tool here called an erasing shield.
And this is just a really thin piece of metal that has all these cutouts on here. And what we can do is, actually, position this over the portion of the drawing that we don't want to erase. And then, when we erase up against that shield, it removes that little excess piece of arch, for example, and give me a much cleaner connection there between those two edges. Now, in a previous video, you saw me do a dash line, where I painstakingly laid out each of the individual dashes.
Well, here on the erasing shield, I have a series of circles that are all lined up in equal spacing. So, you can actually use this to create a dash line by first creating the line. Let me find a nice dark one here, maybe that one right there. Put the erasing shield over that, and then this is where if you happen to have an electric eraser, it will be much easier to do this, because this will allow you... To very quickly remove those negative spaces there and create that dash line.
Now, you might also want a drafting brush. That allows you to very quickly clear away all the debris from the eraser. And you can see that we end up with a nice dash line. So, it's best to think of your eraser as not just something you use to correct mistakes. It's actually one of your editing tools as well. Now, as you might expect, you can perform all of these previous examples on a computer also. I'll use AutoCAD in the demonstration for this, and I'll show you some of those techniques in the next video.
- Drafting equipment and materials
- Drawing lines by hand
- CAD drawing
- Looking at line weight
- Multiview drawings
- Adding details: sections, symbols, and more