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  1. #1
    cncnewbie is offline Plastic
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    Anyone know of any I can print off the Internet?

    Thanks in adavance

  2. #2
    railfancwb is offline Stainless
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  3. #3
    CharlieBiler is offline Hot Rolled
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    Try www.molineparts.com and go to the Links page. There is a tap and drill chart in .pdf format that is downloadable and printable.

    If you have problems call the webmaster at webmaster@molineparts.com .

    Welcome to the party.

    Charlie

  4. #4
    DMF_TomB is offline Titanium
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    Default Excel Tap drill chart for inch and metric

    chart is in Excel file format which the free OpenOffice will open.

    by having chart in Excel format you can check for mistakes and or edit it as you want.

    i keep 8.5"by11" print out by each machine

    of course check each and every line for mistakes and do not use it if you are going to have problems.
    Attached Files Attached Files

  5. #5
    juergenwt is offline Hot Rolled
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    Default

    Off the subject but:
    For metric sizes you don't need a chart. Just subtract the pitch i.e. M10 x 1.5 = 8.5mm tap drill. Same works for inch sizes but gets more complicated because you first need to divide one inch by the number of treads to get the pitch.

  6. #6
    gmatov is offline Diamond
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    Jeurgen,

    Pleas explain this.

    "Same works for inch sizes but gets more complicated because you first need to divide one inch by the number of treads to get the pitch. "

    If I want a 24 TPI thread, what is the divisor of one inch to get the tap drill size?

    If I want a 1/2 -13, how do you decide, by mathematics, what drill I use.

    "to get the pitch. "

    We already know what the pitch is. 13 TPI is pitch. 24 TPI is pitch. Hell, 80 TPI is pitch, and I have a few of them. How are you coming up with that rule to determine drill size?

    Cheers,

    George

    Mebbe Metric IS simpler, but it seems not to cover all situations. .35 MM for lead is simple? .25, .50, .75, 1, 1.25, 1.5, OK. Just don't dump shit on me about how it is "logical". If you had 8 fingers instead of ten, you would be lost. You can always count on them, can't you?

    I teach my grands to count on their fingers. They will be well versed in metric.

  7. #7
    Georgineer is online now Hot Rolled
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    George,

    The confusion comes about because there is no commonly used term for TPI except possibly 'thread count', so people commonly use 'pitch' for it, which it isn't.

    If I may quote: "Lead (pronounced /ˈliːd/) and pitch are closely related concepts. The difference between them can cause confusion, because they are equivalent for most screws. Lead is the distance along the screw's axis that is covered by one complete rotation of the screw (360°). Pitch is the distance from the crest of one thread to the next. Because the vast majority of screw threadforms are single-start threadforms, their lead and pitch are the same. Single-start means that there is only one "ridge" wrapped around the cylinder of the screw's body. Each time that the screw's body rotates one turn (360°), it has advanced axially by the width of one ridge. "Double-start" means that there are two "ridges" wrapped around the cylinder of the screw's body.[4] Each time that the screw's body rotates one turn (360°), it has advanced axially by the width of two ridges. Another way to say the same idea is that lead and pitch are parametrically related, and the parameter that relates them, the number of starts, often has a value of 1, in which case their relationship becomes equivalence.

    While specifying the pitch of a metric thread form is common, inch-based standards usually use threads per inch (TPI), which is how many threads occur per inch of axial screw length. Pitch and TPI describe the same underlying physical property—merely in different terms. When units of measurement are constant TPI is the reciprocal of pitch and vice versa. For example, a 1⁄4-20 thread has 20 TPI, which means that its pitch is 1⁄20 inch (0.050")."
    Screw thread - Wikipedia, the free encyclopedia

    So for 24 TPI you subtract 1/24" from the diameter. For example, take the 3/8-24 UNF thread:

    Tapping drill diam. = 3/8"-1/24"
    converting from fractions to decimals = 0.365"-0.0417" = 0.333"
    Look up the next larger drill size: Q = 0.339". Check against the nearest non-metric tapping drill chart.
    QED, as we were taught to say in school.

    Using the same mathematics, tapping diameter for 1/2-13 is 1/2"-1/13"
    = 0.5"- 0.7629 = 0.4231". I'll leave you to look up the tapping drill gauge, but I believe you will find that it is correct.

    One advantage of this approach is that it works for non-standard threads such as those found on lathe mandrels. I have no idea how well it works for thread profiles other than 60*, such as Whitworth.

    George

  8. #8
    juergenwt is offline Hot Rolled
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    Thanks Georgineer for explaining to Gematov. Juergen

  9. #9
    drylakemachine is online now Cast Iron
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    georgineer,need to edit your samples..
    jim

  10. #10
    Georgineer is online now Hot Rolled
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    Quote Originally Posted by drylakemachine View Post
    georgineer,need to edit your samples..
    jim
    Have I made a mistake? If so I apologise. Will you point me to it?

    George

  11. #11
    DMF_TomB is offline Titanium
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    Default using tap drill chart or doing the math

    yes you can calculate a tap drill size. for myself i prefer to use a chart and also see where number, letter, mm, fraction drills are. sometimes i only want a size or 2 larger for tapping stainless steel.
    ........most work i do if i make a math error i could be in serious trouble. i prefer using a chart and not wasting time or material.
    ........ i keep the same excel chart next to my computers for doing CAD CAM work. if i want to know a drill bit size to 4 decimal places inch or 3 decimal mm i can find it fast while programming for CNC or calculating CAD distances.
    .........when doing a job alone (as a master machinist i often am working alone) i have to double and triple check for mistakes. Finding out I made a mistake and have to do a job over is getting rarer and less often. Which is a good thing as it is embarrassing to admit to my boss i made a mistake and have to do a job over.
    ........Occasionally a part 0.0015" out of tolerance is used for a few weeks (or risk production lost for weeks) as i make another part to within 0.0003" or tighter. I rarely miss measuring a part when cooled down to room temperature and or measured to a proper finish and not measured to a rough surface.
    ........still i admit using charts and any other help, to avoid mistakes i highly recommend. it maybe why when i lost my job in 2005 (production line closed down) and i got a new job on supporting different types of production machines and the majority of workers took pay cuts of 30% or more i instead go a raise when hired for new job. and got raise a year later and another raise 2 years after that during one of the worst recessions since the Great Depression.

  12. #12
    Bob E is online now Cast Iron
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    ...Will you point me to it?
    Quote Originally Posted by Georgineer View Post
    ....
    Tapping drill diam. = 3/8"-1/24"
    converting from fractions to decimals = 0.365"-0.0417" = 0.333"
    ....
    If I may jump in here...

  13. #13
    Georgineer is online now Hot Rolled
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    Thanks Bob - my bad, I should have typed 0.375". I believe I came to the right answer though, it was just Fat Finger Syndrome.

    As it happens DMF_TomB I also prefer to use charts for all these things (always assuming the compiler of the chart hasn't got fat fingers too; I found a mistake in a table of American Wire Gauge diameters on the internet this week). However, I have found that it's worth knowing how these things can be worked out from first principles, when faced with a thread that isn't in the charts.

    George

  14. #14
    juergenwt is offline Hot Rolled
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    Tom - I just pointed to a simple way to find the correct tap drill if a chart is not available. I use a chart for all my inch tap drills even if after many years of working I know many of the most common size by heart.
    For metric tap drills I hardly ever use a chart since there a only a few thread sizes commonly used. M3, M4, M5, M6, M8, M19, M12 will cover (depending on your work) 99% of your need. Remember - metric fine is for specials only. Metric coarse was designed to cover almost all of your everyday need. In shops using metric threads only coarse is being kept in store.
    As far as making a mistake - I have seen people walk over to a wall displaying a thread chart and returning to their work bench only to remember the wrong number. Ah-old age! For inch sizes I prefer pocket cards. I am sure they are available from many tap suppliers.
    As far as knowing tap drills to four decimals for inch and three decimals for metric - I don't thing so. Three for inch and one decimal for metric. ( Inch size drills are in fractions, numbers ore letter sizes listed in 0.001 inch and metric drills are in sizes 0.1 mm apart.)
    One more easy way to calculate your metric tap drill. Learned this one as an apprentice and it works good for everyday usage. Take the thread size and multiply by 0.8.
    (M4 x .8 = 3.2, M5 x .8 = 4.0mm). Over M5 add 0.2 and over M10 add 0.3. (M10 x 0.8 = 8 + 0.3 = 8.3mm). Again, this is for everyday shop use only!

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