How to use string
slide rule (#1)
Pyramid's string slide rule
(2) Decide the tension you want to use in an unit of Newton (1kg = 2.2lb = 9.8N). Move the wide rule to match the proper tension value, while keeping the narrow one in the same place. For example, if you want to use a tension of 6.5kg (14lb), adjust the wide rule to align 64 on the scale to the arrow for the tension. This also is shown in the photo below.
(3) Let's find the 1st sting, first. Only thing you have to do is to read the scale without moving two rules on it. For example, 1st string of guitar is expressed like e' or e1 in an absolute tone scale. So, take a look at e' on the scale. You may notice that there is numbers written on the both side of the scale and wonder which side should be used. In this slide rule, you should use one number or the other depending on the material of the string you are planning to use.
As you can see in a photo below, an e' string thickness in 6.5kg tension can be found for different material (fluorocarbon, gut, nylon, and metal wound from left to right). The thicknesses it indicates are 0.54mm for fluorocarbon, 0.61mm for gut, and 0.675mm for nylon. There is even metal wound strings shown in further right, so you can try 909Al metal wound, if you can come up with one. In case there is no exact string matched for a tone, one that is the closest should be used. On the right end of the slide rule shows Pyramid product numbers of metal wound strings.
PVF: fluorocarbon ("Seager" etc.) : paper scale pasted on top :-)
Repeat the same procedure, (2) - (3), on the other strings to get the thicknesses. You can find tone names in the reference section of this corner. In case of an usual guitar tuning, the following are the tones for each string,
It's very common to use string(s) on the 1st course in higher tension than others on lute, 19th century guitar, and modern guitar. When the 1st string is used with 6.5 kg tension like the example above, that for the other strings should be around 5.8 kg (or that's what I would do). Of course, this depends on the type and structure of the instrument and personal preferences on sound and playability. Keep in mind, though, not to use too high a tension. It's wrong to think higher tension always guarantee more volume and projection. Strings have to be used in tension properly matched to the instrument to get the best result.
Have you master how to use the string slide rule, yet?
Addendum 1: In the procedure (3), it is also possible to find the string tension with a fixed string thickness. So, you can calculate how much tension a string is under, by using this slide rule and a micrometer. You can find a tension of between 1 and 7 kg, using Pyramid's slide rule.
Addendum 2: By the way, there is a few other features on the back side of the slide rule. "graduation tension" is one of them and a setting of string tension which decreases as the course number becomes larger.
Addendum 3: As I mentioned in the other chapters, appropriate strings may differ even for instruments with the same scale length, depending on their bracing scheme, string bending angle at saddle, etc. The best way is to actually try ones on the instrument with different selection criteria.
Addendum 4: Knowing the character of the strings you usually use is very important, because they can serve as a good reference for changing strings. For example, you want to change tension a little lighter (or harder) or to change from nylon to fluorocarbon. Or you want to change a tension a little after switching to gut string, etc. With this string slide rule, experimenting on strings will gets much easier. You now can explore not only sound of the instrument, but also sustain, projection, balancing all the strings, volume adjustment, etc, etc.
Addendum 5: If you own a 19th century guitar, it's a must to try a set of gut strings. That will open a new horizon on your guitar music experiences.