By User:LPNalini @timeAndDate(1274121818)
Mechanical pencils are the tool of choice for many engineering design and drawing applications, as well as for a range of other office solutions. When producing drawings by hand it is important to use lead, which has a precise width and hardness in order to maintain conformity throughout the drawing. Using a 0.7 mm pencilsquare, or triangle. A standard pencil, where the core material is bonded to the casing, does not allow for the same uniformity: use will gradually increase the width of the writing tip until the pencil is sharpened again.
Advantages
The mechanical pencil has other advantages besides. First, neatness: accurately placed lines and writing are much neater than those scrawled with a standard pencil. Also, thin lines of uniform thickness tend to be easier to erase, and erasing is what a pencil's all about. Otherwise we'd just be having a discussion about pens. Second, refills: a mechanical pencil will last you much longer than a standard pencil, that may save you money in the long run.
Disadvantages
And there are some disadvantages to a mechanical pencil also. A mechanical pencil is more mechanically complicated than a standard pencil, which means it may break easier. Also, mechanical pencils will be more expensive initially than standard pencils; since most mechanical pencils will only hold one particular lead width, you may have to spend money buying various pencils to accommodate all the different types of lead you intend to use.
A Bit about Lead
Now, let's talk briefly about lead. First, its always important to note that we may call it lead, but almost always it's just graphite which is a lot less dangerous than lead. Lead for mechanical pencils is graded by its width. The most common widths start at about 0.3mm for very fine work and range all the way up to 4mm for heavier, bolder lines. In between, leads are available in increments of 0.2mm, i.e. 0.5mm, 0.7mm, 0.9mm, etc. The most common lead sizes used are 0.5mm and 0.7mm, especially in engineering drawings.
Also, we may talk about lead in terms of hardness. Hardness for lead is rated on a scale that ranges from H values, to F in the middle, to B which are the softest. The softer a lead is, the darker its color will be, but also the faster it will wear and the less accurate its lines. Here's a standard hardness table:
9H 8H 7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B 7B 8B 9B
Hardest <> Darkest
The standard pencil used in most settings is the HB. Other hardnesses are generally used for art and drawings.
Finally, there are two types of mechanical pencils you may consider. We'll talk about those below.
Propelling Mechanical Pencils
Propelling Pencils both hold the lead in place as well as advance it incrementally when the mechanism is activated. These pencils are best for standard office work, like writing. You push a button and it gives you a good, standard amount of more lead. Propelling Pencils will generally hold multiple leads, minimizing how often you'll need to refill them.
Clutch Mechanical Pencils
Clutch Pencils will only hold the lead in place, and do not advance it incrementally. You'll have to use your fingertip or writing surface to stop the lead where you want it. These are generally used for leads with thicker diameters, which are sturdier. Also, in some cases, especially in drawings, you'll want to use a longer writing tip to reach around or under other drawing tools such as t-squares and triangles. Some clutch pencils will accept a small range of different size leads, making them a bit more cost effective, although changing leads out tends to be a hassle. Also, clutch pencils will usually only hold one lead at a time and must be refilled every time that single lead is used up. These pencils are best for drawings and art although, it is also good to keep a 0.5mm Propelling Pencil for the most precise, standard lines you'll draw.
Top Sellers
Here are some of the top-selling mechanical pencils on the market today.
