# Drill Sizes



## rkapuaala (Jan 3, 2008)

Back in the days when I used to do custom cabinetry and carpentry, I use to have this chart I kept taped to my drill bits case that had a table of bits sizes listed in their metric, inches, and numbered equivalents as well as tap sizes for the holes. I never laminated the sucker and depended on it for an interpretation of the puzzeling drill numbers and for tap sizes. It disintegrated finally yesterday when I hurriedly took my bit case out of my tool box and is beyond repair. 
I can probably find one on line, but I guess the question I'd like to put to the expert machinist on this list is,,, what are the rules for:
1. Determining what size bit to use for tapping a threaded hole

2. What is the logic behind the numerical descriptions of certain smaller screws and bolts such as 00-90 and 00-80 etc... (I mean I think I understand that the lowere the last 2 digits are the larger the bolt or screw, but what is the theory behind it. What do the first 2 digits mean and the last 2 digits mean)

I've always been baffled mostly by the criptic (at least to me) descriptions of bolts and would appreciate a good explanation of them. I understand the differences between a coarse thread and fine thread, and can do metric conversions but those numbers confuse me every time and I believe that's due to the fact that I never learned the theory behind them.


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## Mike Reilley (Jan 2, 2008)

Here's drill and tap chart...but there are hundreds on the net. Find the one that fits your needs...or two...or three.

http://www.stanford.edu/group/prl/cgi-bin/wiki/index.php?title=Tapping_and_Threading#Tap_and_Drill_Bit_Size_Table 
Bolt sizes (not screws...screws are tapered and are used in wood/plastic) were defined by the Unified Thread Standard....years ago...and have been replaced by metric sizes lately. In the Unified Thread Standard, there are numbered diameters for bolts, #0 through #10, with 0 the smallest and 10 the largest. The outside diameter of the threads = 0.060" + 0.013"*(numbered diameter). So #2 has a major diameter of 0.060" + 0.013"*2 = 0.086".

The number after the dash is threads per inch....so an 00-80 bolt is 0/.60" in diameter and has 80 threads per inch. A 4-40 bolt would be 0.112" in diameter... with 40 threads per inch.

Lastly....bolts from 1/4" and up..use the diameter outright, followed by the threads per inch.....1/4" 20 bolts are 0.25" in diamter and have 20 threads per inch.


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## DKRickman (Mar 25, 2008)

Posted By rkapuaala on 11/02/2008 12:15 PM
2. What is the logic behind the numerical descriptions of certain smaller screws and bolts such as 00-90 and 00-80 etc... (I mean I think I understand that the lowere the last 2 digits are the larger the bolt or screw, but what is the theory behind it. What do the first 2 digits mean and the last 2 digits mean)







I don't know what the sizes themselves are, or what the logic might have been behind them, but I can tell you a little about the nomenclature.

There are a range of sizes, including 00, 0, (maybe?), and 1-12. Above that, I've always seen them referred to by size (1/4", etc.). The second part of the number is the threads per inch.  So a 00-90 bolt is size 00, 90tpi. It's pretty easy to find 10-24 (coarse thread) and 10-32 (fine thread) bolts in most hardware stores. Both are #10 diameter (whatever the heck that is), but have different threads, different tap diameters, etc.


The reason for the different tap diameters is that the stated bolt diameter refers to the outside of the thread. A 1/4" bolt is cut from 1/4" rod, and will go through a 1/4" hole (in theory, anyway). the thread is a 60 degree V with the top 1/8 and botom 1/8 missing. So, the finer the thread, the shallower that V will be, and the larger the tap drill will need to be.

Aint it fun?!


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## Semper Vaporo (Jan 2, 2008)

The original numbered sizes for rods were based on some fellow's design of a method to make various uniform sizes. He numbered them Number 1, Number 2 and so one for each different size. That caught on as a defacto "standard" nomenclature. Unfortunatel other people did the same... of course, due to the natural entrepreneurship of the human species there were several "standards"... one from each fellow that was selling rods. Then someone made one smaller than the smallest one (that was called a Number 1) so it got called Number Zero (often listed as "0" which many people pronounced as "Oh" or sometimes "ought", instead of "Zero" [this is the same as toy track gauges being #1, #2, #3, etc. and a smaller gauge became "0" which got called "Oh" and when someone made a track one half of that size it got called "Half Zero", or "HO" which people tended to pronounce "Aitch Oh").

Then someone made a rod smaller than "0" (zero) that and decided that "-1" or "minus 1" (the next logical (to me, anyway) number on the numerical scale) was bad because someone might not see or understand the dash ("-") before the number and so it was decided to call it a "00" size, (sometimes pronounced as Double-ought or Double Oh or Double Zero... all are the same). Even smaller sizes became "000" and "0000" (Triple Ought and Quadruple Ought).


Others developed sizes based on a descending number sequence where "100" was the smallest (smaller than human hair) and "1" WAS the biggest, and then it got bigger so it became "0" and "00" and "000" etc. (Electrical wire sizes follow this nomenclature.)


Still some others assigned letters to the sizes, "A", "B", "C" etc.


As these various size rods are used as threaded bolts, multiple drill sizes had to be developed to handle a size for a hole to be a through hold without threads (and as things began to need to be more precise then holes needed to be "close fit", "loose fit" and more precise nomenclature, more drill sizes were needed). Also, holes needed to be different sizes based on how thick a thread was to be tapped in a hole, (90% engagement, 70%, 50%, etc.) based on the strength needed vs difficulty in doing the tapping.


All of this created the hodge-podge of drill bit sizes and the need for tables to know which size drill for which size hole for which purpose.


There were "standardizing" committees that sought (and sometimes found) mathematical relationships between the various defacto "standards" and some of the standards were modified slightly to account for slight errors in the mathematical relationships. The defacto "Standard" was "Standardized" on the mathematical value and the original value was slowly eliminated over time as parts already built to the original sizes were replaced/repaired with the new sizes.
If you work with or repair old machinery you will still sometimes run into a bolt size that you have to make yourself if it needs replaced since you cannot get stock or find taps and dies that particular size anymore.


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## rkapuaala (Jan 3, 2008)

Thanks guys. No wonder I had/have to rely on a chart. At least now, I understand the 00-XX nomenclature


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## John J (Dec 29, 2007)

Now that I read this I have a head ach. I think I will run down to the Tracks Tresteles and Road Bed forum and see what's going on there 

It is interesting information.


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## SteveC (Jan 2, 2008)

Richard

You may find the following of interest.

[url]http://www.osv.org/explore_learn/document_viewer.php?Action=View&DocID=1973[/b][/url]

[url]http://en.wikipedia.org/wiki/Screw#Unified_Thread_Standard[/b][/url]


Here's a couple of tips I found at the below listed link.

*Newman Tool's handy hint.

*For Metric sizes only. Diameter of thread minus the pitch equals the tap drill size. 
eg. M6 x 1 
6 - 1 = 5mm
and you thought metric was difficult ;-) 




thanks to Jay Steinbuchel of Barksdale Control Products for the following:


This works for all 75% threads, not just metric.


For example, the tap drill for 3/8-16 is 5/16.


The pitch is 1/16". (1 / threads per inch = inches per thread)


3/8 - 1/16 = 5/16.


For other sizes that don't work out so nicely, just use the closest drill size.

*http://www.newmantools.com/tapdrill.htmhttp://www.newmantools.com/tapdrill.htm*http://www.newmantools.com/tapdrill.htm


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## rkapuaala (Jan 3, 2008)

I can see I'm going to have to read this thread over and over again a few times before I really get, but I'm closer now than I ever was


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## Semper Vaporo (Jan 2, 2008)

Posted By SteveC on 11/02/2008 5:40 PM
Richard

snip

For other sizes that don't work out so nicely, just use the closest drill size.

snip 



Hmmmm... unless you have a HUGE collection of drill bits, that is: the whole fractional drill bit set, plus the numbered drill bits AND the lettered drill bits... THEN... well...

you just use the closest drill bit size anyway... (usually the next larger size in my meager little 24 bit set...) and really, really hope for the best. Sometimes the next larger size is just too much the next larger size, so then I use the next smaller size and run the bit in and out of the hole a dozen times to try to ream out the hole a bit more! And use lots of oil to try to keep from breaking the tap! (Starting with too small of a hole means the tap is having to drill out the hole as well as cut the threads... hard on taps! But if you start with too large of a hole, then there may not be enough material left to actually form threads or what is left does not support the threads of the bolt and the threads will strip off the bolt under pressure as the bolt is tightened.) I have, a few times, decided that my selection of bolt size was wrong and I find a bolt size that I have drill bits for instead.

I use Thomas J Glover's "Pocket Ref"... (the little black book available at most hardware stores) page 598 to determine the tap drill, but I don't know what thread depth of penetration that set of numbers is attempting to reach, but it seems to work fairly well. but then... I don't have the sizes it lists so in using the bits I do have I will get some other thread depth value anyway! I also check page 431 for the size of the bolt and the "Close Clearance" size to be sure my selected drill bit is not too close that that number such that all I end up with is a hole the tap will just fall through!









I suppose that if what I was making had some bearing on life and limb then it would be best to consult a more complete chart such as is probably in "Machinery's Handbook", but I don't got one of them. I do have a copy of Modern Machine Shop "Handbook for the Metalworking Industries" but it has so many pages describing threads that I am not sure what chart I should use, then use the "correct" tap drill!

It is also important to know what materials are involved. Strong materials do not need as much thread depth as soft materials to be strong enough for various applications.


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## SteveC (Jan 2, 2008)

Well Charles,

Invest $40 and buy a cheap 115 piece drill set from Harbor Freight. While the drills aren't anything to write home about, the hinged cover index itself is worth the money and you could always upgrade the drills as they wear out or break.









*115 Piece High Speed Drill Bit Set with Index*
29 fractional sizes 1/16'' to 1/2''
26 letter sizes A to Z
60 numbered wire gauge sizes 1 to 60


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## rkapuaala (Jan 3, 2008)

Wow, thats a really cool box. Most of the stuff I do is using the 0 size bits. I have a pretty good set of wood drill bits and all I need for the steel bits in 1 sizes and up. I resolved the issue with tap sizes long ago by not buying bolts that I didn't have the correct bit and tap size for. I learned that after snapping a few taps


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## Semper Vaporo (Jan 2, 2008)

I can't speak as to the quality of HF drill bits as I don't have a set, BUT I will say that I have over the years had many sets of cheap bits and I have learned that I regret very much having wasted my money on them. I have dulled a cheap "Titanium coated" bit trying to drill just one hole in Oak wood!

A few years ago at the Midwest Old Settlers and Threshers Reunion at Mt. Pleasant, Iowa, I broke down and bought a 10 bit set from the Winter's Drill Bit City tool tent because I watched the guy drill holes in hardened bolts without prepping the ROUND bolt, and his bits went in like the bolt was softened butter.

The next summer I was trying to drill a hole in my concrete porch to install a weather vane post and could not get into the 3-inch thick slab more than just shy of half way. I was using a brand new 1/2 inch carbide bit and I thought maybe I had hit a piece of re-rod, so I moved over about an inch in each X/Y direction and tried again... and again got stopped just shy of half way through... consternations! I got the 1/4 inch bit from the set from the tool tent and tried it again. Breezed trough it! I then went back to the carbide bit and finished the hole properly. I pretty well ruined that non-carbide bit from the set, as one would expect in concrete. But I was so impressed with the way it worked I decided to buy a bigger set at the next "Reunion".

I also decided to kid the proprietor about it. I took the 1/4 inch bit with me and was prepared to "complain" about how the tip was so chewed up!







I had to stand in line to get his attention and unfortunately, the fellow in front of me was a bit of a weirdo and was complaining that he had tried to sharpen the bits he had purchased the year before, using what he admitted was a cheap sharpener, and had ruined the bits and wanted a refund. The proprietor was not in a good mood at that point, but I handed him the bit I had and asked him what he thought of the tip. He sighed heavily,took the bit and scrutinized the tip. His eyes bugged out and he did a double take, then a triple take. "What have you been drilling?"

I said, "A concrete porch slab."

He rolled his eyes and said he could not replace a bit that I had used to do that. I said (in a loud voice), "I know that! I would not expect you to! But I had to show you the reason I am here to buy a bigger set... those are GOOD bits!". I bought a bigger set (cannot afford the 115 bit set as it is several hundred dollars), but after using them for a year, at the next Reunion, I bought 3 more sets as Christmas presents for my 2 sons and son-in-law. When I walked up to make that purchase the proprietor recognized me and wanted to know if I had been drilling concrete recently!

I am sure you can get similar bits from other places, but I HIGHLY recommend this guy's stuff. Expensive? Yes, but after using them I don't even SEE the cheap bits at the hardware store, HF or anyplace else anymore.

I know "the tool does not the Craftsman make", but a quality tool makes it a lot easier for the Craftsman, or the duffer, to make a quality result.

Buy quality... you WILL NOT regret it.


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## rkapuaala (Jan 3, 2008)

I use to do remodels and a lot of them were on slab foundations. There are two ways to install a wall, and one of them is to use a hammer drill and sleeve anchor bolts. You can't get very deep on a cut with a regular drill without ruining the bits. I have hammer drill bits that I've used a hundred times, and I still use them when the rare occasion arrives. 
You can use the same concrete bits in a regular drill,,,, I had to do that a couple of times when I forgot my hammer drill or lent it out,,, but its slow. You need a small cold chisel and a lot of determination. But it will save your good concrete bits which tend to heat up if you use them incorrectly on a drill.


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## Semper Vaporo (Jan 2, 2008)

Posted By rkapuaala on 11/03/2008 5:32 PM
I use to do remodels and a lot of them were on slab foundations. There are two ways to install a wall, and one of them is to use a hammer drill and sleeve anchor bolts. You can't get very deep on a cut with a regular drill without ruining the bits. I have hammer drill bits that I've used a hundred times, and I still use them when the rare occasion arrives. 
You can use the same concrete bits in a regular drill,,,, I had to do that a couple of times when I forgot my hammer drill or lent it out,,, but its slow. You need a small cold chisel and a lot of determination. But it will save your good concrete bits which tend to heat up if you use them incorrectly on a drill. 


Yes, I have used a hammer drill for going into concrete.

Carbide Masonry bits usually just chew right through concrete, unless you hit a particularly hard rock (which a hammer drill will punch through) or if you hit a re-rod... and Murphy says you will always hit a re-rod "square on" at least once in any set of holes you are in need of drilling! And, when you hit re-rod the tip is not sharp enough to shear metal at the tip.

Once before I tried to force a carbide Masonry bit into a stubborn hole and managed to MELT the bit! I was really leaning on the drill to drill a hole in the basement wall. It just would not go in any farther and when I pulled the drill away a pretty silvery glob rolled out of the hole and splattered on the floor... REALLY glad it didn't hit my hands or feet! For that one I just moved over 1/2 inch and, with a new bit, drilled the hole with no problems, unfortunately it was the last of 4 holes for a surface mount electrical switch box and I had to drill all 4 of them again, 1/2 inch to the side!


This time I was using a carbide masonry bit and it went 1/2 way in quite easily. But I have no idea what is in this slab that I hit it twice like that... moving over diagonally should have allowed me to miss a re-rod. I knew enough this time to not melt the bit! The think there may have been a metal plate at the corner where I was drilling. once I penetrated the metal then the carbide bit could pare away metal from the sides of the hole formed by that poor bit that got chewed up in the concrete dust that was in the hole started by the carbide bit as well as the concrete below the metal when it went through.

I had considered using a hammer and star drill but figured that was a bad idea hammering on a thin concrete slab that close to the corner (8 inches from each edge), I feared it might break the whole corner off.


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## Don Howard (Jan 2, 2008)

Used Viewzi to find: 
http://www.wintersdrillbitcity.com/ 
Under construction, but there is an 800 # 
800-950-3938


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## stanman (Jan 4, 2008)

FYI, the _Handy Converter_ program has a whole tab devoted to drill and screw sizes.

http://www.stanstrains.com/HC12DrlScreenLg.htm


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## rkapuaala (Jan 3, 2008)

I know what you mean about having to move the bit around. It could have just been a river rock. I've had to bust some of those suckers up with a combination of hammer drill and cold chisel alternating from one to the other. Re-bar is usually pretty soft here on the west cost, and the grid that its laid out in makes it hard to hit. I've only hit it occasionally, and since its soft here, the bits on chewed right through, although I have to switch the hammer drill over to drill when I encounter it. 
Stan, 
Is that just and image of some software you're selling? If so what language is it writen in and what O.S. does it work on?


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## Semper Vaporo (Jan 2, 2008)

Posted By stanman on 11/04/2008 9:15 PM
FYI, the _Handy Converter_ program has a whole tab devoted to drill and screw sizes.

http://www.stanstrains.com/HC12DrlScreenLg.htm



http://www.stanstrains.com is Stan's home page where you can find the link to get his converter program. It is a handy program... unfortunately for me, I don't usually have my PC down it the dungeon where the machine tools are to use the drill look-up feature. I have used it several times while cogitating on design whilst sitting in my easy chair. I don't remember how long I have had this version 12, but I don't remember ever seeing the drill tab! I have used the scale conversions LOTS as well as the Metric to English stuff and speed stuff. The little calculator in the corner has been handy a couple of times too.


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## stanman (Jan 4, 2008)

Richard - _Handy Converter for Model Railroaders_ is software I've been offering for a while. It's evolved considerably over the years. Many of the additions were suggested by users - of which there are now thousands worldwide. It runs on any version of Windows from Win 95 through Vista.

Charles - the current version of the program is 12.4. I think the Drills and Screws tab was added in version 12.0, so I'll bet you have it!


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## rkapuaala (Jan 3, 2008)

Stan, 
If it's writen in Java you should be able to port it over to a palm O.S. with a few tweaks. I would love to have that sw on my Palm Treo, sure beats using the calculator all the time. I was thinking of writing the sw myself and installing on my treo, but hey, why reinvent the wheel


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## Mike Reilley (Jan 2, 2008)

Posted By rkapuaala on 11/05/2008 9:14 AM
Stan, 
If it's writen in Java you should be able to port it over to a palm O.S. with a few tweaks. I would love to have that sw on my Palm Treo, sure beats using the calculator all the time. I was thinking of writing the sw myself and installing on my treo, but hey, why reinvent the wheel







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Porting the software to a handheld devices would be fantastic. Like others...I don't keep the computer handy in my shop...nor outside. But...if Handy Converter were to run on the mobile operating systems you find in cell phones....I'd download it in a heartbeat.


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## Semper Vaporo (Jan 2, 2008)

Stan: Yep, I have the feature, but even though I have used the program many times, I don't remember EVER seeing it before!









I was a programmer and features that I have built-in to the original version of a program would often solicit the comment from long time users of, "I didn't know it could do that! When did you add it?"









But the real shocker was when a user would show me something my program could do that "I" didn't know about!









The problem with porting any program to a different platform is the need to have said platform in hand to do the debug on. I bet Stan would be happy to attempt to port it to another OS/Hardware if someone were to buy him the necessary platform to see how to do so!


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## rkapuaala (Jan 3, 2008)

"But the real shocker was when a user would show me something my program could do that "I" didn't know about! " 

Remember this line "Oh, that feature wasn't in the documentation!?"


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## rkapuaala (Jan 3, 2008)

BTW, if stan wants to open source his code, I'll port it to the palm o.s. for him


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## stanman (Jan 4, 2008)

Sorry - not Java. I was using good old Visual Studio 97 when I wrote the first version, so I've just continued using it. I've considered porting it to .NET, but the benefits seem to be lacking.

BTW, the program has a nice undocumented feature or two (actually documented with tool tips), such as - you may enter fractions in most of the fields (example: you can enter either 12.75 or 12 3/4).

I wrote a German language version too, and it also has undocumented features. It allows you to use either the comma or period for the decimal point. Example: you can enter either 12,75 or 12.75. It's always been hard for me to avoid including "goodies". The problem is you never know what's going to turn out to benefit the user...


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## rkapuaala (Jan 3, 2008)

VS 97 is an IDE, what language did you write it in?


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## stanman (Jan 4, 2008)

Posted By rkapuaala on 11/05/2008 5:53 PM
VS 97 is an IDE, what language did you write it in?

VB6


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## rkapuaala (Jan 3, 2008)

Hum,,, I'm not real good with VB. Can you port it to c++ or javascript?


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## stanman (Jan 4, 2008)

Posted By rkapuaala on 11/05/2008 10:50 PM
Hum,,, I'm not real good with VB. Can you port it to c++ or javascript?

Nah - it'a a complete rewrite...


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## chrisb (Jan 3, 2008)

I got lost with the software part of this thread. I have several of the smaller size bits. Of most importants are the ones that go with taps that I use. When I need a #53 bit, I check the chart for diameter and check the bits with a dial caliper. I find that I actually only use a few sizes for the most part. A good tap and drill chat is handy. I laminated mine. Also to go along with drill size, I find its better to built with components that will match your tooling.


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