I need some knobs etc for a few jigs.
I am in a metric country and cannot get knobs etc like your mail order
companies have and need to order.
I know what 1/4-20 and 5/16-18 means in Imp terms but what is a 10-24
Tom and Wilson gave good links.
History, As I Know It To Be:
Early in 20th Century, machine tool industry and automobile companies
needing machine tools developed a new screw bolt system (along with drill
sizes with numbers and letters) for their needs. This need had to do with
the torque applied to the machine bolts, which in turn required greater
holding power on the threads before the threads failed. Bolts in the new
standard had improved thread dimensions with complex relationships between
pitch, depth, and other factors (like the steel used.) Out of that need
came the Unified Thread Standard
This is from a book for introduction to Machine Shop:
"The term 'machine screw' refers to a system of numbering used to identify
machine screws smaller than 1/4 of an inch. The number system refers to a
series of individual screw sizes within both the Unified National Coarse
(UNC, or NC) and Unified National Fine (UNF, or NF) Series..... <for
example> is identified by the number 12-28. The First part for he number
specified the gage size of the body of the screw. The second part of the
number specifies the number of the threads per inch. ... For Machine screw
0-80, 0 specifies the size (diameter, 0.060 inches) of the screw, and the 80
specifies the number of threads per inch.... In the number series, diameters
range from 0.060 to 0.216 inches (for the UNF standard.)"
Another article at www.wikipedia.org stated that in 1949, British, Canadian,
and USA merged tread standards and included the imperial measurements bolt
sizes into the UNC, and UNF threading standard for pitch, depth, and so
Way more than you asked, I know.
I live in the US and purchase Metric handles from time to time for my tools,
(Grizzly jointer), etc. that have metric fittings.
I get them from Reid Tool supply,
I dont know if they will ship ex-US, but they get there supply from
somewhere. Many of the items seem to come from Italian and German
companies. So you might scan Reids catalog and search out the company names
and see if they can provide local supplies. What part of the world do you
live? I dont recognize the .za.
I would just order one of the assortment kits and when you see it you
will know more than we can tell you.
You will also have a handy supply, just remember to mind your stock. I
had to do the same thing for metric hardware many years ago.
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