I think he's asking the same question I have. How did you acquire that main bar with nice accurate graduations? Donor tool? Likewise for the vernier scale. And, if you made the vernier, I think he's asking how you worked out the spacing. Though I've never made one, there are a references online and in books that explain how to make a vernier scale.
There's no secret! I made the graduations using a tool (see photo) attached to the chuck of the milling machine. The divisions were made with the aid of the graduated ring and a dial indicator. That simple!
The vernier was even easier to do. I observed what the divisions of a common caliper look like and made it the same way. The distance between divisions of the vernier is 3.9 mm (because the zero of the fixed scale coincides with the zero of the sliding scale and the tenth division of the sliding scale coincides with 39 mm of the fixed scale), when the caliper is closed.
Last edited by machining 4 all; 11-24-2020 at 10:54 AM.
I didn't notice it before, but looking at the images enlarged, I can see the slight buildup at the top of the lines that informs on the method of creation. I think it actually makes a very nice effect. I've done graduations the same way (nothing like yours, but just visual alignment references), but my ability to provide nice looking stamped letters/numbers like yours is far short of the task. Great work!
For scales divided into sensible decimal values, designing a vernier isn't very difficult.
Decide the smallest interval on the main scale you wish to further subdivide using the vernier. As an example we'll use the vernier designed in the OP so this value is 1 mm.
Decide the approximate length you wish the vernier to span; this value affects how easily it can be read. In the OP the approximate length of the vernier scale is 40 mm.
Subtract the first value from the second... 40 - 1 = 39 mm
Divide that length into ten units. Thus each interval on the vernier is 39 / 10 = 3.9 mm. Examination of the photographs in the OP shows this to be correct.
A further example... If the vernier were chosen to span a more conventional 10 mm then 10 - 1 = 9 and the vernier would have ten divisions, each 0.9 mm long for a span of 9 mm, or about a centimeter (0.4") which might be hard for old guys with less than perfect vision to read.
If your ruler is one of those wacky inferial ones graduated in fractions, the same approach I outlined above can be used, though the ensuing confusion it will provoke is another kick in the a.. to adopt metric.
There is a free program, LVERN, on my page for designing linear verniers but it's not one of my best efforts. It's mathematically correct but the user interface isn't something of which I'm proud.
Last edited by mklotz; 11-24-2020 at 12:21 PM.
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