OK, who came up with the number and letter drill sizes anyway?
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    Default OK, who came up with the number and letter drill sizes anyway?

    Ok, metric sizing is better but we have fractions here is the US. At least they're consistent in there sizing increments. But, who came up with the number and letter sizes? There is no consistent dimensions increments between sizes and in the case of letters the "F" and 1/4" are the same. WTF is up with that?? It has never made any sense whatsoever. How about a drill set that starts at .015" and goes to .505" in .01" increments? Much more useful.

    Don't even get me started on tap shank sizes!!

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    Number drills originated with wire gauge sizes and I think the letter drills are an extension of that system.

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    There was a thread here not too long ago where someone answered that very question quite well. It made a lot of sense. I haven't got time to search it, but if you find it you may be surprised.

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    I did a search and found this on Wikipedia. It pretty well coincides with what I was told many, many years ago.

    Drill bit sizes - Wikipedia

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    it could have been worse... if you lived in the pre revolution era in France, thousands of units of measurement were in daily use...

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    Quote Originally Posted by Wild West View Post
    ...and in the case of letters the "F" and 1/4" are the same.
    You're thinking of an "E" drill. The F is .257 and is the tap drill for 5/18-18.

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    Quote Originally Posted by Oldwrench View Post
    You're thinking of an "E" drill. The F is .257 and is the tap drill for 5/18-18.
    That would be 5/16-18.

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    Quote Originally Posted by Wild West View Post
    Ok, metric sizing is better but we have fractions here is the US. At least they're consistent in there sizing increments. But, who came up with the number and letter sizes? There is no consistent dimensions increments between sizes and in the case of letters the "F" and 1/4" are the same. WTF is up with that?? It has never made any sense whatsoever. How about a drill set that starts at .015" and goes to .505" in .01" increments? Much more useful.

    Don't even get me started on tap shank sizes!!


    well you can start by sending me all of your letter,number, and fraction sizes i just love them.
    then you could buy all metric sizes it will make life much easier for you.

    i have nothing against metric when i need one i buy one and use it.

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    If I was wanting do draw wire 200 years ago to the most commonly used standard, I would need to make a wire-sized hole in a drawing die.
    Some of them are fairly small.
    I would have been delighted if I could have purchased a twist drill that was the correct size as the wire so I could finish the draw-die button with a simple operation.

    If only someone made wire-sized drills.

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    A few years back on the AltCNC newsgroup (remember them?) a member wrote a fantastic fictional story about ww2 prisoners of war working in german military factories coming up with the system so that secret messages could be passed to the outside world by ordering drills. He did a really great job on the story and it was perfectly believable. Wish I could find it.

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    Quote Originally Posted by Wild West View Post
    Ok, metric sizing is better but we have fractions here is the US. At least they're consistent in there sizing increments. But, who came up with the number and letter sizes? There is no consistent dimensions increments between sizes and in the case of letters the "F" and 1/4" are the same. WTF is up with that??
    Whoa whoa whoa, hang on there cow boy. 0.250" and 0.257" is the same? I thought this was a website for machinists.

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    Here you go....the perfect place for your....uhm question ?

    The Hobby-Machinist Forums

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    Quote Originally Posted by Wild West View Post
    Ok, metric sizing is better
    Not in my eyes.

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    Quote Originally Posted by Mtndew View Post
    Not in my eyes.
    ditto.........

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    Those praising metric do realize that metric sizes fasteners are not the stated diameter don't they? It is called a m8 bolt not an 8mm bolt because it is not 8mm in diameter. that 8mm is just the closest round number to the true diameter.
    Bill D.

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    The drill system was designed by the inventor of the twist drill, Stephen A. Morse. Morse also designed the Morse Taper system. Morse also founded the firm of Morse and Williams, an important manufacturers of freight elevators. Morse began his career as a journeyman machinist working for Isaac Singer (the inventor of the sewing machine). Morse invented the twist drill in 1861 and patented it shortly thereafter. The Morse Twist Drill and Machine Company operated in New Bedford, Massachusetts, from 1864 to 1990.

    Stephen A. Morse was born in Holderness, New Hampshire, on May 28, 1827, and died December 22, 1898, in Philadelphia.

    stephen_a_morse.jpg

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    Quote Originally Posted by RC Mech View Post
    Whoa whoa whoa, hang on there cow boy. 0.250" and 0.257" is the same? I thought this was a website for machinists.
    Ok, ok, I got it wrong. My bad. I do know the difference.

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    Quote Originally Posted by Bill D View Post
    Those praising metric do realize that metric sizes fasteners are not the stated diameter don't they? It is called a m8 bolt not an 8mm bolt because it is not 8mm in diameter. that 8mm is just the closest round number to the true diameter.
    Bill D.
    Last time I checked a UNC/UNF thread it wasn't the same diameter as the nominal diameter either, so not sure what your point is.

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    a lot of machining technology came about cause it was better that what was available at the time, majority agreed to standardization for things and its benefits. some standards were started by manufacturers who were not eager to always share details as they worried about others copying their methods
    .
    many do not realize early nuts and bolts were made to fit each other in sets. if you had 100 screws and nuts quite often they had to be checked so they were not too tight or loose and tolerances were all over the place.
    .
    measuring tools are relatively cheap today. imagine having to buy micrometers at $5000. each. or put another way if it cost 10 days labor at $200/day thats $2000.
    .
    you try making anything custom in small quantities and normally will find it takes a lot of time and expense. like getting a custom tap made over $100. cost not unusual. try making a drill bit. not as easy as some assume


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