# So, what exactly do I search for to find a #21 Hex Key Driver? **URL:** \ **Category:** Factual Questions\ **Created:** [September 1, 2013, 12:22am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701 "2013-09-01T00:22:36Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [September 1, 2013, 12:22am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/1 "2013-09-01T00:22:36Z")
I’m servicing equipment that requires fine adjustments to be made to a mechanical part using a #21 hex key driver. How do I find one of those, exactly? I want one that comes with, or can be attached to, a handle of some kind. ---
**Author:** ![JBDivmstr](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@JBDivmstr](https://boards.straightdope.com/u/JBDivmstr)\ **Post date:** [September 1, 2013, 12:36am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/2 "2013-09-01T00:36:10Z")
#21? By hex key driver, do you mean an allen wrench? Allen wrenches (usually “L” shaped, with 6 sides) normally come in ‘standard’ and ‘metric’ sizes. Question… Approximately how big is the hole that this ‘hex key driver’ needs to fit into? 😕 (It does need to fit into a hole, doesn’t it?) A picture would simplify matters immensely, as far as determining exactly what kind of tool you are trying to find. If it’s a 21mm, that’s a pretty large allen wrench/hex key. ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [September 1, 2013, 12:42am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/3 "2013-09-01T00:42:32Z")
> [@JBDivmstr](#): > > #21? By hex key driver, do you mean an allen wrench? Allen wrenches (usually “L” shaped, with 6 sides) normally come in ‘standard’ and ‘metric’ sizes. This does, in fact, go into a 6-sided hole. > [@JBDivmstr](#): > > Question… Approximately how big is the hole that this ‘hex key driver’ needs to fit into? 😕 A 1/16th inch key seems to fit, but I see some wear on the key after use that suggests to me that it’s ever so slightly the wrong size. Also, I’ll need something that fits into a driver of some kind, as these things have a ton of tension on them from the factory. When I was using a short 1/16th inch key and trying to twist sideways, I barely have the hand strength to loosen it, and it hurts my fingers. > [@JBDivmstr](#): > > (It does need to fit into a hole, doesn’t it?) A picture would simplify matters immensely, as far as determining exactly what kind of tool you are trying to find. > If it’s a 21mm, that’s a pretty large allen wrench/hex key. It does go into a hole. If I showed a picture, it would disclose my employer, which isn’t something I’m comfy doing on here. Of course, it certainly isn’t 21mm. It’s close to 1/16th. ---
**Author:** ![JBDivmstr](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@JBDivmstr](https://boards.straightdope.com/u/JBDivmstr)\ **Post date:** [September 1, 2013, 12:45am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/4 "2013-09-01T00:45:10Z")
As far as variety is concerned, [Grainger](http://www.grainger.com/Grainger/hand-tools/ecatalog/K-16/N-bia/No-0/Ntt-allen+wrench%7Callen+wrench+sets?Ndr=textsearchesinbase%2Btrue&sst=All) probably has the widest selection of hand tools. (The link will take you to the first of the ‘allen wrench’ pages.) Hope that helps. ---
**Author:** ![ombre12](https://avatars.discourse-cdn.com/v4/letter/o/d26b3c/32.png) [@ombre12](https://boards.straightdope.com/u/ombre12)\ **Post date:** [September 1, 2013, 12:51am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/5 "2013-09-01T00:51:03Z")
Allen wrenches do come in both SAE and metric sizes. (As against Torx and a few others that are solely metric) . Annoying as hell when you don’t know what you are dealing with. You can have an almost fit that will strip out the Allen screw and then you are screwed. ---
**Author:** ![JerrySTL](https://avatars.discourse-cdn.com/v4/letter/j/e274bd/32.png) [@JerrySTL](https://boards.straightdope.com/u/JerrySTL)\ **Post date:** [September 1, 2013, 12:57am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/6 "2013-09-01T00:57:49Z")
It wouldn’t be a Torx T-20 would it? Google turned up this: [http://www.waltonsinc.com/p-1978-hex-key-21.aspx](http://www.waltonsinc.com/p-1978-hex-key-21.aspx) The #21 is the illustration part number. ---
**Author:** ![Glazer](https://avatars.discourse-cdn.com/v4/letter/g/a88e57/32.png) [@Glazer](https://boards.straightdope.com/u/Glazer)\ **Post date:** [September 1, 2013, 12:58am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/7 "2013-09-01T00:58:51Z")
[Eklind](http://www.ebay.com/bhp/eklind-tool) Long shaft T handle. About half way down the page. Sounds like you need a 3/32 or a 1mm. The long shaft gives you lots of torque and the plastic dipped handle is comfortable on the fingers. I have seen Socket adapters in various hex key sizes if you need even more torque. Or you could try a shot of penetrating oil. ---
**Author:** ![JBDivmstr](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@JBDivmstr](https://boards.straightdope.com/u/JBDivmstr)\ **Post date:** [September 1, 2013, 1:01am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/8 "2013-09-01T01:01:22Z")
Sorry, but I’m not familiar with tools that small, or the ‘numbering/sizing’ system that you’ve described. If the size is smaller than 1/16", (or it’s metric equivalent) then that would explain the number ‘21’, indicating the size. FWIW, I’m a carpenter and General Contractor by trade. (And a fairly decent ‘shade tree’ mechanic, when I have to be. ;)) If you’re unable to find it at the site I provided a link to, then perhaps one of the other Dopers will be more familiar with what you’re looking for. Sorry I couldn’t be of more help. Good luck! (At least you’ve come to the right place to ask for help, the ‘Dope’ has people from just about every ‘walk of life’, you could imagine! 🆒) Looks like you already knew that, though! ---
**Author:** ![Glazer](https://avatars.discourse-cdn.com/v4/letter/g/a88e57/32.png) [@Glazer](https://boards.straightdope.com/u/Glazer)\ **Post date:** [September 1, 2013, 1:05am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/9 "2013-09-01T01:05:43Z")
> [@JerrySTL](#): > > It wouldn’t be a Torx T-20 would it? > > Google turned up this: > [http://www.waltonsinc.com/p-1978-hex-key-21.aspx](http://www.waltonsinc.com/p-1978-hex-key-21.aspx) > > The #21 is the illustration part number. I throw those away on a regular basis and I still have at least a dozen in the bottom of my bag. They come with every door hinge, pivot, closer or lock set as well as dozen of other products I use regularly. I keep a bunch of the set screws in my parts box. Quicker than searching the floor for the tiny bastards. The larger 10-22 set screws too. ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [September 1, 2013, 1:13am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/10 "2013-09-01T01:13:14Z")
> [@JerrySTL](#): > > It wouldn’t be a Torx T-20 would it? > > Google turned up this: > [http://www.waltonsinc.com/p-1978-hex-key-21.aspx](http://www.waltonsinc.com/p-1978-hex-key-21.aspx) > > The #21 is the illustration part number. Probably not, unless the item being illustrated is under extreme zoom… the ends are way too fat. ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [September 1, 2013, 1:14am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/11 "2013-09-01T01:14:27Z")
> [@Glazer](#): > > [Eklind](http://www.ebay.com/bhp/eklind-tool) Long shaft T handle. About half way down the page. Sounds like you need a 3/32 or a 1mm. The long shaft gives you lots of torque and the plastic dipped handle is comfortable on the fingers. I have seen Socket adapters in various hex key sizes if you need even more torque. Or you could try a shot of penetrating oil. A T Handle looks like exactly what I’m wanting, thanks for that. ---
**Author:** ![zoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zoid/32/336_2.png) [@zoid](https://boards.straightdope.com/u/zoid)\ **Post date:** [September 1, 2013, 1:16am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/12 "2013-09-01T01:16:22Z")
[Hex key insert bit.](https://www.google.com/search?newwindow=1&biw=1600&bih=719&tbm=isch&sa=1&q=hex+key+insert+bit&oq=hex+key+insert+bit&gs_l=img.3...65306.65884.0.66289.4.4.0.0.0.0.118.273.3j1.4.0....0...1c.1.26.img..4.0.0.zOy_xjNhN4g#facrc=_&imgdii=_&imgrc=-On9AL6945NZxM%3A%3BZ8BrvXcgl1XtCM%3Bhttp%253A%252F%252Fc.shld.net%252Frpx%252Fi%252Fs%252Fpi%252Fmp%252F16772%252F114345707%253Fsrc%253Dhttp%25253A%25252F%25252Fwww.hudsonmayor.com%25252Fimages%25252F41NvDtOMktL.jpg%2526d%253Da278441afee6c4752a3ca4409a358c8d92cd8da6%3Bhttp%253A%252F%252Fwww.sears.com%252Fcentury-drill-and-tool-68455-hex-key-insert%252Fp-SPM5849703207P%3B315%3B315) Stick it into a screwdriver that takes bits or get an extension and use it with your drill. ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [September 1, 2013, 1:21am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/13 "2013-09-01T01:21:24Z")
By the way, here’s the verbatim text from the training manual that I’m reading: “Adjust if necessary using a #21 hex key driver in hole . . .” ---
**Author:** ![zoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zoid/32/336_2.png) [@zoid](https://boards.straightdope.com/u/zoid)\ **Post date:** [September 1, 2013, 1:24am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/14 "2013-09-01T01:24:29Z")
[This site](http://www.carbidedepot.com/formulas-drillsize.htm) says a #21 is 0.1590 inches if that helps at all. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [September 1, 2013, 1:31am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/15 "2013-09-01T01:31:31Z")
Allen wrenches have 6 flat sides. Torx have 6 points and curved sides. Look at this picture for the difference. A very small Allen wrench would fit in a T20 screw but if you try to tighten you will strip the screw. [https://www.google.com/search?q=allen+or+torx&client=safari&hl=en&source=lnms&tbm=isch&sa=X&ei=-5ciUvzzNIKOigLm0ICoAg&ved=0CAgQ\_AUoAA&biw=320&bih=416#biv=i|13%3Bd|w0kZiX\_5AFykZM%3A](https://www.google.com/search?q=allen+or+torx&client=safari&hl=en&source=lnms&tbm=isch&sa=X&ei=-5ciUvzzNIKOigLm0ICoAg&ved=0CAgQ_AUoAA&biw=320&bih=416#biv=i%7C13%3Bd%7Cw0kZiX_5AFykZM%3A) ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [September 1, 2013, 1:44am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/16 "2013-09-01T01:44:56Z")
Rick, Pretty sure we’re on hex here rather than torx, based on the docs. Pretty sure torx would have been a better choice, too, given how big of a pain this application is. Little tiny adjustment, would be good to be able to torque the crap out of it. If this guy works his way out of adjustment somehow, I get a phone call at 3 in the morning telling me to drive an hour each way and put it back in adjustment. There are, however, two of the screw in question holding a shaft in place, and in theory both have to work their way loose before I get that phone call. ---
**Author:** ![Gbro](https://avatars.discourse-cdn.com/v4/letter/g/c6cbf5/32.png) [@Gbro](https://boards.straightdope.com/u/Gbro)\ **Post date:** [September 1, 2013, 2:11am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/17 "2013-09-01T02:11:59Z")
> [@Mr.Slant](#): > > Rick, > > Pretty sure we’re on hex here rather than torx, based on the docs. > Pretty sure torx would have been a better choice, too, given how big of a pain this application is. > Little tiny adjustment, would be good to be able to torque the crap out of it. > If this guy works his way out of adjustment somehow, I get a phone call at 3 in the morning telling me to drive an hour each way and put it back in adjustment. > There are, however, two of the screw in question holding a shaft in place, and in theory both have to work their way loose before I get that phone call. Then you should be thinking about using a thread lock product. Loctite blue is for parts you want to fiddle with and Loctite Red is a high strength product that may require heat to loosen. And there is also nylon screws where a small button of nylon will interfere with the threads thereby holding position well in many applications. And when I use any socket or bit that feels loose but is the correct tool I will when able use a shop rag or something similar to tighten the connection. ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [September 1, 2013, 2:37am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/18 "2013-09-01T02:37:51Z")
> [@Gbro](#): > > Then you should be thinking about using a thread lock product. Loctite blue is for parts you want to fiddle with and Loctite Red is a high strength product that may require heat to loosen. The shaft these screws tighten holds in yet another shaft that has a PM interval of 90 days. I’m new in this position, though, so I’ll play it by ear with your suggestion. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [September 1, 2013, 4:29am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/19 "2013-09-01T04:29:07Z")
> [@zoid](#): > > [This site](http://www.carbidedepot.com/formulas-drillsize.htm) says a #21 is 0.1590 inches if that helps at all. This is a good try as it has #21 as a size, but unfortunately it only applies to nomenclature for drill sizes. You can see that the #21 is over twice the size of the 1/16" that is said to fit. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [September 1, 2013, 4:45am UTC](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701/20 "2013-09-01T04:45:10Z")
> [@Mr.Slant](#): > > By the way, here’s the verbatim text from the training manual that I’m reading: > “Adjust if necessary using a #21 hex key driver in hole . . .” I’ve been working with Allen wrenches for over 40 years. I can see one being called a “hex key driver,” but I have **never** heard of any sizing nomenclature for them other than the actual size in millimeters or inches. “#21” just doesn’t compute for this. I wonder if it’s a reference an “official factory tool” with a number used only by your company. > [@](#): > > Little tiny adjustment, would be good to be able to torque the crap out of it…There are, however, two of the screw in question holding a shaft in place, and in theory both have to work their way loose before I get that phone call. I’m confused by the use of the word “adjust” here. You adjust something that has a range of settings, like a volume knob. It sounds to me like this is a matter of getting something tight enough. If so, I’d use the word “tighten.” > [@](#): > > When I was using a short 1/16th inch key and trying to twist sideways, I barely have the hand strength to loosen it, and it hurts my fingers. You can improvise a handle of some sort or use pliers to turn the thing with some oomph. I’d be careful about using a threadlocker product. It conceivably could hold the screw so well that you’d strip out its hex in a removal attempt. [Next page](https://boards.straightdope.com/t/so-what-exactly-do-i-search-for-to-find-a-21-hex-key-driver/667701.md?page=2)