Your Basic Compass: Care and Feeding.
Good quality compasses are not easy to find. When you find a good one, you still need to take some basic steps to get the best results from it.
The compass has two jobs. A compass sets two points, a steel point and a marking point, at a constant opening. It can transfer a measurement from a center point to a new point, marked by the lead. It can mark two or more points exactly the same distance from a center point. The definition of a circle is the set of all points exactly the same distance from some center point— a compass can draw circles.
Thinking about this definition, we will always be talking about 1) a center locator and 2) something to do the marking. Both of these working points are something to maintain and care for.
Shouldered Needles; Finding Center
Measuring from a center means locating that center very precisely. That is the job of the steel point of the compass. It should be good quality and sharp.
If it is painful when pressed against the back of your thumb, but doesn’t draw blood, it is just about right.
Alvin 2mm Shouldered center and
Keuffel & Esser 1.5 mm Shouldered double end compass center
The two needles shown here are “shouldered” and doubled ended. The shouldered point (facing up) is the point used to center the compass on a drawing. The tapered needle point has a different purpose which will come up later. If the point is too rounded or if it is bent it must be sharpened or replaced. Availability is the same story as compasses. These are no longer commonly available in good quality. Treat them with care if you find good ones. If you find good quality steel points, buy several.
The second part of the compass’ job is to mark off a distance, an arc, or a circle. That usually needs a pencil lead or a pen. I will have a separate sections on “steel pens” and adapters for pens or mechanical pencils, but first we need to talk about the lead. First Problem: The lead sold with your compass is too soft for layout work. It is almost always HB. Drafting leads have hardness labels from HB and 1H to 9H. The higher the number- the harder the lead. HB is the softest common drafting lead. You can still buy good leads in most hardness grades. To get successful layouts with good symmetry and not make a mess smearing lines, 2H or even better 3H lead is recommended. I use 4H because I don’t mind sharpening. To get those good results, your lead needs to be sharp. This is not difficult.
It is quite difficult to get a good round point, like a typical wooden pencil, on compass leads. It is not really practical at all with softer leads. It requires a special “lead pointer.” They are irritating to use for compass leads. Round points also dull very rapidly. The shape below works better.
As Always: One Man’s Opinion. For Layout Work
Compass leads sold as replacements have the profile in the 1st picture. This will work for about 10 seconds. This tends to chip and it dulls very quickly.
The solution is to change this to a chisel point. The back of the lead is flattened to meet at a nice strong point.
This also tends to chip at the corners and is sharp enough to cause problems with 3H or harder lead.
The answer is to take off a bit of each corner to give the four sided chisel profile shown. I find that this works well for 2H to 5H lead. 3H and 4H are best.
Getting to a good strong point that will last for a reasonable amount of time takes about 30 seconds. Practice Practice.
The smaller the compass, the narrower the final chisel point is made.
The tools are in the next picture. A common Swiss file is nicest, but most professionals just use fingernail files.
The traditional tool, a 4 inch file, was once included in a compass set but it is easy enough to find an inexpensive “Swiss needle” file or fingernail files. The “sandpaper paddles” sold by art and drafting supply houses are actually harder to use than finger nail files for the compass point and I have never found an advantage for the compass. They are intended for shaping pencil points.
Sharpening Tools
Finally, something easy to find.
Carry a dedicated container for whatever you use. These make a mess.
A different lead shape is easiest to use to use to give a final dark pattern line with a compass. It simply shapes the lead to the desired line thickness. This will give a consistent line weight for the complete drawing session. This only works well with soft leads. I usually use 4 H lead for constructing the geometric layout and then HB lead to draw pattern lines. After the HB leads are used, the drawing must be handled with care. It smudges easily.
Constant Line Weight Point
This is shaped with the same files in the obvious way.
The desired width is left to run across the full width of the 2mm point. As for the chisel, take the sharp edge off the corners.
The result is long lasting and gives nice line quality.
0.3mm Shown
Everyone asks about mechanical pencil adapters for the compass, so I will comment on them in a separate post. I do not think that mechanical pencil adapters are a good idea. It is better to learn to sharpen your compass lead. It’s not that hard.
A Complex Story
This needs its own post
The last thing within your control is lubrication. If you use a compass for years, you will need to lubricate a couple of points. The thread on the adjustment wheel is the biggest worry. Many newer compasses have plastic parts and they will wear rapidly. Lubricating the thread with beeswax will extend their life. Never use oil on drawing instruments, specially around plastic. If you cannot find beeswax, hard paraffin wax works.
If you treat a professional compass well, it will last longer than you do. I used the same compass for a few years 10 hours a day and I still have it. The chrome is worn through but it still performs well.