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Incorrect Calculation of an Imperial Dimension
peter_morris
Member Posts: 43 ✭✭
I'm currently drawing the headstock of a very old lathe (simply because I can!). I want the dimensions to show as "Inches Fractions", but when I do the figure is incorrect. When I use either inches or metric the dimension is correct. For example the conversion from 15.88mm results in 3/4 when it should be 5/8. I suspect this is a flaw in the conversion routine, but if you're going to offer Inches Fractions then they absolutely must be correct - a tolerance of a 1/4" is dreadful. The resolution should be at least 1/128" and probably less.
Ohh, I've just found the problem - the default setting of the precision was too course. The situation is now much improved as I found I could select a precision of 1/64", but I would propose that the maximum precision is still too course, as mentioned above 1/128 would be better.
(I've left the first part of this question as I wrote it as this may be of use to other users).
Ohh, I've just found the problem - the default setting of the precision was too course. The situation is now much improved as I found I could select a precision of 1/64", but I would propose that the maximum precision is still too course, as mentioned above 1/128 would be better.
(I've left the first part of this question as I wrote it as this may be of use to other users).
0
Best Answer
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peter_morris
Member Posts: 43 ✭✭
metric is useful when doing metric drawings, but when trying to draw an old lathe that was built to imperial measurements its much simpler to use that system.
Your question: 7/64 and 17/128 are proportions of an inch. One advantage of the imperial system is its actually much simpler to be pretty accurate when using a ruler. For example a rule with graduations in 1/64ths can easily be used to measure 1/128ths and possibly even 1/256 because the latter two measurements are a half and a quarter of the graduation which is relatively easy on the eye. Its much more difficult to do the same in a metric system.
Finally, there's an awful lot of quaint Americans who persist in using the Imperial system (even if they don't know how many ounces there are in a pint!).
All the best.
6
Answers
quick, what's 7/64th? or 17/128th?
I need to get back to work, as I'm not making any friends today.....
Your question: 7/64 and 17/128 are proportions of an inch. One advantage of the imperial system is its actually much simpler to be pretty accurate when using a ruler. For example a rule with graduations in 1/64ths can easily be used to measure 1/128ths and possibly even 1/256 because the latter two measurements are a half and a quarter of the graduation which is relatively easy on the eye. Its much more difficult to do the same in a metric system.
Finally, there's an awful lot of quaint Americans who persist in using the Imperial system (even if they don't know how many ounces there are in a pint!).
All the best.