09-13-2012, 12:48 PM
Hello Again, I should have looked at the PDF before rattling on about the virtues of vernier scales, From what I make of the PDF it's not quite right, it seems that you may have confused decimals and minutes, with 10 vernier graduations over 7 degree graduations, rather than 11 degree graduations for decimal or 6 vernier graduations over 7 degree graduations for 10 minute increments.
The trick with vernier scales is to have ten graduations so 0 thru 9 just as you have, but the total length of these should be the same as eleven of the degree wheel graduations, I think you can also use nine but eleven is bigger so more accurate and easier to read, This will give you your 0.1 degree measure.
For minutes use 60 graduations over 61 on the degree wheel for minutes, or 30:31 for 2 minute increments, 20:21 for 3 minute increments, 12:13 for five minute increments or back to 10:11 for 6 minute increments(the same as decimal) and finally 6:7 for ten minute increments.
The beauty of vernier scales is that you can achieve really good accuracy without terribly expensive machinery.
On rotating vernier scales it is customary to use two scales one to the left and one to the right of the origin mark (the zero) so for decimal 0.1 degrees, that is a total of 19 graduations instead of ten, Zero as the centre mark with a 9 at each end of the scale, in truth 9 of these marks are duplicates and not really required but it looks nice and is easier to use.
Oh and one last thing, If you feel that it's all getting too tight to read which is common when you want to read minutes directly you can "Double size" the scale which does make it far easier to read, If you want to know how just ask, I've already taken up half the page and it is a bit of off topic.
Best regards
Rick
I can feel another how to thread coming on
The trick with vernier scales is to have ten graduations so 0 thru 9 just as you have, but the total length of these should be the same as eleven of the degree wheel graduations, I think you can also use nine but eleven is bigger so more accurate and easier to read, This will give you your 0.1 degree measure.
For minutes use 60 graduations over 61 on the degree wheel for minutes, or 30:31 for 2 minute increments, 20:21 for 3 minute increments, 12:13 for five minute increments or back to 10:11 for 6 minute increments(the same as decimal) and finally 6:7 for ten minute increments.
The beauty of vernier scales is that you can achieve really good accuracy without terribly expensive machinery.
On rotating vernier scales it is customary to use two scales one to the left and one to the right of the origin mark (the zero) so for decimal 0.1 degrees, that is a total of 19 graduations instead of ten, Zero as the centre mark with a 9 at each end of the scale, in truth 9 of these marks are duplicates and not really required but it looks nice and is easier to use.
Oh and one last thing, If you feel that it's all getting too tight to read which is common when you want to read minutes directly you can "Double size" the scale which does make it far easier to read, If you want to know how just ask, I've already taken up half the page and it is a bit of off topic.
Best regards
Rick
I can feel another how to thread coming on
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