Talk:List of drill and tap sizes

Slash-Not-Slash Fractions?

Fractions in this list use the format "​15⁄16" which, oddly enough, is a problem, as my keyboard (and those of nearly everyone else in the US) lack a "⁄" key - possessing, instead, the subtly different "/" key. It wasn't until I dug into the source that I understood why I couldn't do a ctrl-f search for anything involving (what appeared to be) a forward slash.

I don't want to take it upon myself to change them all (not knowing if there was a good reason they were made that way in the first place), but being this list used to be a frequent resource for me, and it's significantly less helpful without the ability to search.

(speaking of not knowing things, I have no clue what I'm doing with the new edit interface, and couldn't figure out how to create a new section without shoving it into an existing one. hopefully it won't break anything important) - 71.234.116.22 (talk) 03:01, 27 May 2020 (UTC)

Organization

This chart is rather confused. It's very unclear what the key diameter columns down the left mean, especially when compared with the clearance and tap diameters to the right.

I'm guessing that the left column is supposed to be major pitch diameter, but it's quite unclear. Pstemari (talk) 21:24, 25 November 2011 (UTC)

I agree it's confused as it has two "root" columns: drill dimensions, and screw sizes (diameter and thread pitch) for which a listed drill might be used as to drill for a tapped hole. The two columns following the screw/tap size give the sizes of drills used to make clearance holes for that screw size; and while they list decimal diameters, what they should list is the nomenclature of the indicated drill: it's far more useful to know that a clearance drill is #73 than that it is .024 inches in diameter.

Leftmost column is a metric drill size to four decimal places, followed by the same size in decimal inches to five places. Drills of a given size may be available in metric series or one of the three inch series (fractional, letter, number) and the number in the other column is simply the actual equivalent in the other measuring system. Drills in the fractional inch series are called out in the third column.

The next column indicates a particular screw size/thread that the given drill might be useful to drill holes for tapping. Skipping two columns, the next shows how much oversize the tap drill is compared to the theoretical minor diameter for the given thread; but it's expressed as what percentage of the theoretical thread depth will be represented by metal rather than by the air in the hole. People might typically choose 75% of theoretical depth for soft metals, and 60% for steel and other strong metals. This eases the load on the tap, decreasing breakage, while only slightly reducing the thread strength from its theoretical value.

The final column appears to be intended to show the actual major diameter for threads which aren't designated directly by size (#6-32 machine screw, for example) but hardly any values are filled in.

The two columns after the screw/tap size indicate the size of drill to use to drill holes that the screw can fit through closely or with a bit of slack; but the drill sizes have been converted to their decimal-inch equivalents which isn't useful. This should be fixed.

I believe I can come up with a better organization of columns; I'll think about it.

Dbeierl (talk) 01:08, 4 October 2014 (UTC)

Can someone come up with a better way of presenting this information. This is a miss mass of numbering type # number - that mean nothing to most. Also, it is just ridiculous to have decimal equivaluent for fractions - the standard is 5/16 not the decimal equivalent. Good God - what an absolute mess!!!! - this page undermines the value of Wikipedia....it really does. —121.220.134.226

There's a difference between one's own knowledge gaps and what is standard in industry among knowledgeable people. Wikipedia does not delete the info of the latter in the mistaken belief that it serves the former pedagogically. The pedagogical win comes with having all of the deep info while also spoon-feeding limited slices of it as needed, allowing each user to get what they need while having the drill-down to more info being optional (speaking of drills). Although we have a long way to go before masterly pedagogy of that type (because it is trivial easily to cry out for, but tremendously hard to build, across all of human knowledge), deleting all good info because some users didn't understand what to do with it is not the answer. Regarding "it is just ridiculous to have decimal equivaluent [sic] for fractions": in fact, doing so is a universal standard in the machining industries and in engineering drawings that engineers produce for them, for various valid and useful reasons. Machining in the Imperial and US customary measurement systems uses thousandths of an inch and thus works in a decimal format, regardless of anyone's initial personal fear of it upon encountering it for the first time. As for number drill series 0 to 60, as well as letter drill series A to Z, again, this is the widespread norm of machining in the Imperial/US systems. The idea that it "mean nothing [sic]" is, again, initial personal fear of it upon encountering it for the first time—not an objective measurement of its importance or value. Take a deep breath, pace yourself, hang in there. Learning isn't always easy or fun, but it's sometimes necessary.

Now, all that duly said, I agree that it would be nice for this list to have a simple cheat sheet for those users who can't handle the main list. This would be a simple table where the topic of percentage of thread was not even broached and which simply told the target user subaudience (i.e., those doing hobbyist, DIY, or non-critical garden-variety maintenance work) that, "hey, if you want a 3/8 coarse thread, drill a 5/16 hole, end of story", or, "if you want a 1/2 coarse thread, drill a 7/16 hole, end of story". I may add such a little table if I get time to spend on it. And that right there (time to spend) is the thing about complaining about anything on Wikipedia. It's easy to complain, but anyone who's going to actually provide a solution has to invest their own time in doing so.

In the meantime, here's an example of such a usefully simple table. That one tells you at the bottom in a footnote that ~75% threads are assumed. — ¾-10 17:31, 22 March 2015 (UTC)

I do apologise for my over reaction - it just seems to me that it is impossible to a method of communicating this important data in a way that is easily comprehensible by the people that study this and those that need to use it. I probably can't contribute much but I am close to putting together something that I find useful that is easily cross references - depending on your preferences. But I suppose that would be criticised as well. Thanks for trying. — Preceding unsigned comment added by 121.220.134.226 (talk) 10:52, 23 March 2015 (UTC)

Why do we have things like M2.2x0.45 in the column marked drill tap sizes? The drill tap size is a column for drill tap sizes either in metric or imperial (just be consistent). Thread diameters and pitches should be in the horizontal row. This is probably the issue with the whole organisation of these tables - be consistent and you won't have the majority of the table with colours and empty cells.. — Preceding unsigned comment added by 121.220.134.226 (talk) 06:50, 24 March 2015 (UTC)

UNF vs UNC

The tap sizes need to have separate columns for UNC, UNF, & METRIC. — Preceding unsigned comment added by 192.104.67.121 (talk) 13:53, 6 May 2013 (UTC)

On the Drill and tap size chart, the chart shows a 10-24 tap uses a #25 drill. I am using a 10-23NF tap and both the tap and drill indes and a drill and tap set I bought from Home Depot made by Irvin use a #21 dirll. Is the difference because of the threading???

Robert Heard <email removed>

Yes. See here --Coolhandscot 07:36, 19 August 2006 (UTC)

Robert,

That is an awesome table which explains the standards really well. I like the table interlaced like it is with metric because I have to use both systems, and I am reprogramming my brain.

It is confusing to me why I could drill a M 2.0500 hole and then tap with either metric (M2.5×0.45) or a #3-48 or #3-56 that result in different % of depth threads. But only the metric use is in accordance with STANDARDS.

Just like the #12-24 was commercially available in the recent past but is not so much any more. Moshmm82 (talk) 18:45, 31 March 2022 (UTC)

If I am correct in assuming the tabulated "Theoretical percentage of thread" figures are based upon the 60 degree included thread angle used for US and Metric threads it should be remembered that legacy standard threads e.g. Whitworth, British Association etc. will be significantly different from those tabulated figures. 7severn7 (talk) 18:44, 19 November 2007 (UTC)

Number sizes

I think the heading "Drill wire gauge" in the table may be incorrect. Surely gauge sizes for drills are not the same as American wire gauge? Biscuittin (talk) 13:23, 26 August 2009 (UTC)

It's not saying that the drill bit gauges are exactly the same, it is just drawing an analogy to wire gauges. (The exact text is: "Number drill bit gauge sizes are analogous to, but different from, American wire gauge.") Wizard191 (talk) 20:41, 27 August 2009 (UTC)

Number (and letter) drill bits are commonly referred to as "wire gauge" bits, although it's not even close. Pstemari (talk) 21:24, 25 November 2011 (UTC)

Complete rubbish

If you are working in imperial, all measurements want to be the same.

Its pointless expressing the clearance hole for a 5/32" whitworth tap in millimtres!!! If you working in imperial, you primarily need to know the clearance drill is 5/32" and the tapping hole is 1/8". People who work in imperial do not work in imperial in one direction and metric the other.

You need two separate tables, one for metric in mm's and one for imperial, in 64ths and thousands.

82.21.204.60 (talk) 13:34, 18 August 2011 (UTC)

This is essentially the two separate tables in one table...with measurements in both mm and inches so they are easily compared. Coolhandscot (talk) 22:24, 19 August 2011 (UTC)

It's still a mess as is. Getting the nearest US size for a metric size and vice versa is a useful purpose, but the organzation here doesn't make that easy. --Pstemari (talk) 07:04, 17 June 2012 (UTC)

Yes, being able to figure out the closest wire gauge drill bit for a metric tap is exactly why this table is so valuable to me. I don't seem to have trouble with the organization, except that I lose track of the table columns while scrolling. Any suggestion about how to improve the organization? Butchwax (talk) 15:36, 17 June 2012 (UTC)

Having 5 pages of microscopic drills at the top in 0.01 mm increments doesn't help. Perhaps slice out three additional tables: one with UNC/UNF sizes, one with metric sizes, and a third that pairs up UNC/UNF with the nearest metric size and vice versa. Pstemari (talk) 04:36, 5 July 2012 (UTC)

The integrated table certainly is useful. Butchwax mentioned finding a number drill for an ISO thread. A mm drill for Unified or a Whitworth thread might also be required. Given that drill sets in 0.1 mm increments are readily available now, both number gauge and ISO drill sets are not necessary in a shop. Complaints against the integrated table can be answered by providing strictly Unified and strictly Whitworth tables separately. That should almost everyone. Regards, ... PeterEasthope (talk) 14:52, 16 July 2020 (UTC)

Unrubbish-ification

I would find the table less confusing if the 4 colors were explained in a legend.

I wonder if Pstemari's objections would diminish if such a legend were up top and had checkboxes to hide/show the various subtables. I believe this is rather easily doable in JavaScript, though I'm not familiar with Wikipedia ways to do it.

Personally I like all the subtables (metric, imperial, gauge, etc.) interleaved into one combined table. As Butchwax says it aids comparison. Bob Stein - VisiBone (talk) 01:33, 18 July 2012 (UTC)

It would be great if there was a table header every 40 lines or so. It's a pain to scroll up to the top if you forget which column is which. I also second the notion that the Imperial and metric should be interleaved. It might be over kill but having the decimal AND metric equivalent would be pretty handy. It's actually why I came here today, to see how close in size 6-32 and M3 are.(Drive by Talker) — Preceding unsigned comment added by 98.230.52.31 (talk) 19:02, 11 January 2013 (UTC)

Forty rows is too many for at least one instance of headings on most screens. I've added four repetitions of the headings at intervals of 24 rows. Let's see how that is accepted. If most readers accept the arrangement, I can add more headings. This problem has been recognized but no automated solution is documented yet. Ref. Help_talk:Table#Sticky_table_headers?. A difficulty with repeated headings as I've done is that any change in heading will require multiple edits. That is error prone. Automation of the sticky heading will solve that. Regards, ... PeterEasthope (talk) 15:53, 16 July 2020 (UTC)

I agree with Bob Stein above - one advantage of this chart is that it shows all subtables together in one chart. I came here today seeking to see what is closest Imperial screw size to M4. I also agree with unsigned above that table headers are good. I dont know if it's possible, but it would be great if the data could scroll, but not the headers (similar to how MS Excel does it with "freeze panes") or have the headers repeated every 30 lines or so.Bmeyette (talk) 17:34, 10 March 2014 (UTC)

I agree with Bob Stein and Bmeyette. I've added a color code: Color Code: Green lines represent inch-sized drills, increments of 1/64". Tan lines represent drills in the number (1-80) and letter (A-Z) series which are specified in decimal inches. White lines are standard metric drill sizes. Blue lines are standard metric drill sizes used for metric taps of the size indicated in the Tap Size column.

The clearance sizes need to be left as drill nomenclature (3/64, 6.5 mm, #37) rather than converting to decimal dimensions since having that dimension you have to chase down the table to find the actual drill that it represents.

I believe I can come up with a column arrangement that's easier to understand. Dbeierl (talk) 01:14, 4 October 2014 (UTC)

Errors in M6

I think the correct drill size for M6 should be 5.0 mm, I've always used a drill size that is the thread diameter minus the thread pitch.

That's what these tables specifies: http://www.newmantools.com/tapdrill.htm and http://www.shender4.com/metric_thread_chart.htm and http://www.engineershandbook.com/Tables/tapdrill.htm

Note that the link to engineers handbook dot com is broken .. the server no longer exists — vulcan_ (talk contrib) 20:53, 10 April 2020 (UTC)

There appear to be other errors in this table, too. --Janke | Talk 18:46, 31 May 2012 (UTC)

The chart is mostly good, but it isn't great yet. The 5.2mm row does contain an error, although not quite the one you thought. A 5.2mm drill is indeed an acceptable tap drill for M6-1.0, and so is 5.0mm, *but* each yields a different percentage of thread (5.2→~60%, 5.0→~75%). So in the cell where that 5.2mm row now shows "75", it should say "60". One of the things going on in this chart, as of this writing, is that it shows only a one-to-one relationship of thread size to tap drill, when that relationship is actually one-to-several. Right now the chart doesn't reflect the fact that there are several acceptable tap drills for each thread size, with each giving a different percentage of thread between 60% to 75%. For example, for a 1/4-28 thread, any of these 3 tap drills may be acceptable: #3 (~75% thread), #2 (~60% thread), or 7/32 (~68% thread). In the case of M6-1.0, the rule of thumb that you mentioned, major minus pitch, yields a 5mm tap drill at ~75% thread. However, the tap drill that the chart mentions, 5.2mm, will give a ~60% thread, which is also acceptable, provided that a 60% thread is what the user wants. But the chart does have an error in that row, because it says "75" in the "percentage of thread column". It should say "60" there, and M6-1.0 should be entered also up above in the 5.0 drill row, with "75" as percentage of thread. I may edit the whole chart someday to reflect the one-to-several relationships, but it will depend on having a big chunk of free time with no higher priorities (story of life!). What I will do right now, though, is at least fix the two rows that we just talked about. — ¾-10 15:09, 18 November 2012 (UTC)

M4

The entry for M4x0.70 shows only 1 entry, presumably for a "default" thread %, but it calls for metric 3.5 drill. Every other chart I've ever seen calls for a 3.3mm drill for M4x0.70 tap. This may be same as M6 example above, where entry in chart is actually a 60% thread, but it's claiming 75% and does not list the 75% thread drill bit size of 3.3mm.Bmeyette (talk) 17:26, 10 March 2014 (UTC)

Added the M4 heading to help people following the multiple errors and corrections. Regards, ... PeterEasthope (talk) 15:05, 16 July 2020 (UTC)

hi , this will probably sound really stupid to you folks but I've been having difficulty figuring out what taps to use for my rc builds amd the screws are m4 and m3 I believe but I bought a 4-.70 tap and the m4 screws didn't work so I found an m4-40 and they worked but barely , I had to run the screws in and out like the tap to get them to finally go. I don't understand the huge difference in m4-40 and the 4-.70 either I thought they were both 4mm taps. Anyhow can you either direct me as to what taps I should use for 4mm machine screws and possibly a link to an actual complete chart with tap and screw sizes ? If one is available. My favorite part the rc hobby is building my own stuff as much as possible and being able to tap my own screw holes and maybe even make the odd threaded pieces would be an amazing addition to the endless number of skills to learn . Thanks and sorry for the long winded response , I try to get as much info in as I can and I tend to over explain myself lmao 🤣 😅 cheers Daveovington (talk) 03:44, 6 August 2023 (UTC)

Explanation

This table is really useful, but hard to understand for someone unfamiliar with drills and taps. It would be really nice if the opening paragraph were expanded to explain what purpose of the table is, and what the columns mean.

The first two columns give diameters: diameters of what? What does "fractional" mean? What does "tap size" refer to? — Preceding unsigned comment added by 129.215.138.131 (talk) 13:44, 17 June 2013 (UTC)

I added some lede content that explains. HTH. — ¾-10 00:53, 18 June 2013 (UTC)

Metric drill sizes for tap and clearance are missing, incorrect, thread % does not consider material

   The metric screw tap and clearance sizes are largely missing, and those clearance hole sizes that are present are more often incorrect; e.g. M5 x 0.8 has 5.1 mm as close fit, but this would be an interference fit, all sources have 5.3 mm. (0.1 mm is below the sum of surface roughness and tolerance of the screw and clearance drill diameter.) (The source cited for the table - SmallParts.com no longer exists.

  The article should clarify that this is a tabulation of drill size recommendations including tolerances, not the precise minimum or maximum diameter of the required hole. 

  The following sources appear to be reliable based on a few entries, but have not been verified in detail;

https://littlemachineshop.com/Reference/TapDrillSizes.pdf http://www.draughtsman.co.uk/information_images/mechanical/clearance_holes.htm http://www.calculatoredge.com/charts/mmetricthreads.htm

   I am no longer current, but the chart most often seen on the wall in machine shops in the USA using imperial tooling was supplied by Starret. It looked like this recent version; https://forum.solidworks.com/servlet/JiveServlet/downloadBody/2791-102-1-3184/starrett-inch-metric-tap-drill.pdf  More complete information from the Starret catalog looked like this; http://www.jwdonchin.com/Starrett/Catalog/pdf/647.pdf
     As of this date both of these links are dead.  — vulcan_ (talk contrib) 19:43, 22 April 2021 (UTC)

   The application of thread depth assumptions of 60%, 75% etc. should be corrected. Preferred thread depth is material dependent as well as cost vs strength dependent. The tips of the thread offer progressively less benefit and begin to cause fastener failure as softer materials are considered. Soft materials do not benefit from the tips the thread profile, it deflects and does not contribute to the clamping force developed, and it may separate and cause lockup. i.e. gall and jam. The choice of thread depth in a hard material trades additional cost to form or cut a deeper profile for increased ultimate yield strength of the fastener. The topic would need a Wikipedia article of its own.  — Preceding unsigned comment added by PolychromePlatypus (talk • contribs) 15:03, 7 July 2015 (UTC) 

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