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Hex-Head Screw

It’s been just more than a month since my backside found its way back into an editorial chair here at Popular Woodworking Magazine. We are about to wrap up the first issue since my return. That means the articles are in our binder and we read everything one additional time to make sure there are as few mistakes as possible before it goes to press then to you for your reading pleasure. (It’s your duty to find the one mistake we left in the magazine and that can only be accomplished if your read the entire issue from front to back.)

Reading binder is totally different for me this time around. My duties and responsibilities are different. But there are things that stay the same. As we read, we also discuss any concerns we find. Yesterday there were a few discussions, but the one that fascinated me the most was about hardware for a portable workbench top.

In the article text, the author, Christopher Schwarz, writes that the above-picture hardware is a hex-head bolt. Of course, with each round that label is challenged. We all call it a lag screw. Bob Lang and I say a bolt has a nut involved to make a connection and that a lag screw is what was used.

Via e-mail, Chris again defended his label and directed us to a home center to confirm – he used the term by which the piece was listed at the store at which he bought it. (The goal is to make it easy for readers to find the exact piece – be it screws, nails or drawer pulls – used in the article.) So check we did. Do you think you know the answer? Be careful.

Online at one store we found the terms “hex-head screw” and “lag screw” intermixed. At a second store, we found similar terminology and we found the hardware item pictured below.

Lag Bolt ?

Chris wasn’t wrong in how he listed the piece.

Is this what happens when store inventory is labeled by folks who don’t really know what the item is called? Or is this known as a hex-head bolt? Are the terms hex-head and lag, and bolt and screw interchangeable? Comments are open. Let’s hear your thoughts.

— Glen D. Huey

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Showing 67 comments
  • NoelNNY

    The Lady Megan hath not offered her wise words of what the ol’ bard would recount on the matter – could this topic be retitled “The Turning of the Screw” ?

    What say ye Fair Lady of Auburn Loc’s???

  • Jeff Ward

    Having worked in retail for many years, I would suggest that if bin tags are evidence for terminology, there would be many more conflicts about proper names for things. Beyond terminology, it’s nearly as bad to assume that what is in the bin matches the tag.

    Ultimately, I’ve got to agree with Jack on this one. Lag bolt or lag screw? The only possible answer is yes.

  • A Tinkers Dam

    I am a retired machinist (30+yrs) and a past instructor of manufacturing and engineering. I hung up my machinist career some years ago, retired and now pursue my serious woodworking “hobby”.

    Terminology / Nomenclature in threaded fastenters is very improtant in the field of manufacturing. The go-to source around the world is the Machinery’s Handbook” printed by Industrial Press. Another referance source are the Audell’s Manuals of old. I will provide (from Machinery’s Handbook) the distinctions between the threaded fasteners in question.
    “Differentation between Bolt and Screw:
    -A bolt is an externaly threaded fastener disigned for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut.
    -A screw is an externally threaded fastener capable of being inserted into holes in assembled parts,of mating with a preformed internal thread or forming its own thread and of being tightened or released by torquing the head.”
    -An externaly threaded fastener that has a thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is a SCREW. (Example: wood screws, tapping screws)
    -An externally threaded fastener that must be assymbled with a nut to perform its intended service is a BOLT.
    -An externally threaded fastener that must be torqued by its head into a tapped or other preformed hole to perform its intended service is a SCREW. (example square head set screw).
    Specification for manufacture of fasteners such as that pictured are found in the table “American National Standard Hex Lag Screws (ANSI B18.2.1-1981, R1992)

    The general definition of a “lag screw” is:
    lag screw
    (Miscellaneous Technologies / Building) a woodscrew with a square head
    [from lag3; the screw was originally used to fasten barrel staves] (lagging)
    Collins English Dictionary – Complete and Unabridged © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003
    (The referance to “square head” stems from the original head form of a lag. Modern lags now are available with hex heads.)

    So this is a VERY long way to explain the the fastener in question is technically refered to as a “Hex Lag SCREW”. If it were to have a square head it would be refered to as a “Square Lag SCREW”.

    No such thing as a Lag BOLT, if threaded into a pre-threaded hole, it would simply be refered to as a Screw, Cap SCREW or Machine SCREW (that’s another long winded discussion).

    Sorry if I seem overly anal about the terminology but after many, many years of experiancing confusion when correct terminology is not used I have seen the benifits of using the correct terms to identify fasteners.

    If I may be so bold, the definative answer to your question is: The fastener shown is indeed a “Hex Head Lag SCREW”. Sorry Chris, but I will bow to you on all things “WOOD”.
    Mike W.

  • chodgkin

    The Complete Illustrated Guide to Everything Sold in Hardware Stores, by Tom Philbin & Steve Ettlinger quite simply calls it “Lag Bolt (or Screw)”

    Their buying tip is “Lag screws are cheaper than carriage bolts, so if you have a choice, use a lag screw.”

    I’ve built a number of raised bed gardens, have used these extensively, and when I order them for delivery with the lumber I always order them as lag bolts and always get what I want.

  • MikeyD

    Omitting the word “lag” and calling it a hex head bolt would lead one to believe it is the type that uses a nut. That’s the problem I have with the wording. It’s misleading.

  • dbulissa

    Lag bolts use to be 4 sided hence the new tag of hex


    I am an old retired electric utility phart and specified may things for the construction crews where I got to know hardware. The lag screws (bolts) used by the utility `15 years ago were all square heads, like wise for Mark and those trying to hammer in a lag screw there are different threads for hammering in a lag screw. the link below is to a supplier of pole line hardware, scroll down to near the bottom of the page and several different types of lag screws (bolts) are shown.

    Various Trades have products that are unique to their needs but frequently used by other trades also and called by different names.

  • rrich

    I’m an old phart and growing up on the water in Brooklyn, they were called Lag Bolts. (Stainless steel we would have killed for) Like many things, the name changes between the East and West coasts. Here on the West coast, the term Lag Screw seems to be more popular. So, what is your orientation, Left or Right?

    Generally speaking, when a hex head is attached to a threaded shaft, the term “Lag” also seems to be attached to almost anything except machine threads. One other interesting fact, McFeely’s seems to have far more “Lag Screws” than “Lag Bolts”.

    It appears that the non-machine thread threaded device fitted with a hexagonal head is somewhat lagging in an official definition. What more can one say?

  • MarkSchreiber

    Whatever you call it, they are sure hard to pound in with a hammer.

  • johnmoran

    It’s a screw – Chris is just being stubborn … for a change.

    If he was an engineer, he would call it a screw.

    Just because he’s a stubborn woodworker doesn’t mean it’s a bolt.

    tgoplin has already quoted the definitive test – Machinery’s Handbook.

    Give in Chris.

    Kind regards – John

  • lhowland

    I would always refer to that type of fastener as a lag screw. That differentiates the thread type from something used on a machine or my automobile. I would assume that the hex head just further defines it. But, I have never held a lag screw in my hand that had a philips head or a slotted head. Might be a little difficult to install.
    With respect to the packaging of these fasteners. Are we seeing a majority of these coming from overseas and the precise description we would use is muddied up by someone else attempting to translate a dictionary definition with their interpretation?

  • tgoplin

    According to the Machinery’s Handbook you have a lag screw. If a fastener is normally intended to be tightened or released by a nut it is a bolt. If a fastener is inserted into a preformed thread or forms it’s own thread and can be tightened or released by torquing the head it is a screw. It goes on to say that an externally threaded fastener that has a thread form which prohibits assembly with a nut having a straight thread of mulitple pitch length is a screw (Example: wood screws, tapping screws.) An externally threaded fastener that must be assembled with a nut to perform its inteded service is a bolt. (Example: heavy hex structural bolt.) No offense to the kind folks at the hardware store but I’m going with the handbook.

  • Jack

    Bolts, with machine type threads, are also referred to as ‘machine screws’.

    Screws (wood screws mainly, but near the point even ‘deck screws’) seem to have ‘tapered’ threads. Even sheet metal screws taper from either a blunt point (for use where there are pre-drilled and possibly threaded holes) or sharp point to ‘self thread’.

    It appears that hardware of various kinds are not universally known by a single name, plus regional names. At times it appears they are all regional names.

    So it is a lag bolt or lag screw? The correct answer is: Yes.

  • hharr40

    In my experience “Bolts” have machine threads and “Screws” have the more agressive wood cutting threads. While a Bolt must have a mating threaded partner – nut or threaded hole, a Screw makes its own way into the material being fastened – albeit sometimes with a pilot hole to ease insertion.

    Perhaps the confusion occurs because the “Lag Bolt/Screw” has a machine bolt hex head but wood cutting threads whilst Wood Screws (with wood cutting threads) have provision to be driven by a “Screw Driver” as opposed to a Wrench. Now throw in the term “Machine Screw” – screwdriver head but machine threads – and we’ve quite a goulash of terminology.

    “A picture is worth a thousand words”

  • msiemsen

    Most workmen would call them “lags”, as in “hand me one of theose !/4 inch lags”. When they are used in conjunction with a lead or plastic “shield” in masonary they would be called a lag and shield. A shield could be reasonably compared to a nut. I find it odd that no one has mentioned that a bolt without a nut on it is properly called a machine screw, there is no point on the end of a 1/4-20 machine screw. Try posting a picture of a machine screw and see what response you get as to it’s proper name, screw or bolt.

  • kct3937

    For 50 plus years, I have known these items as “Lag Bolts”. Sometimes today, you have to ask a youngster at the supply yard for a lag screw and many times it depends on the size of the item you are requesting. Never ask for it at Home Depot, unless you like blank stares. IMHO hex head has nothing to do with it as they have always been made that way and have alway been tightened with a socket drive or a wrench …which is not a place where jewish cowboys keep their cattle.

    Now if you want to call a square drive screw by it’s real name…Robertson things will be all right in the world 🙂

    May the scwartz be with you!

  • marmadoon

    I would suggest that you separate the replies and see if there are differences in terminology by region.

  • fltckr

    I did a search for USA made fasteners, and I found the following on a supplier’s site: “Hex Lag Screws (Bolts)”. So I guess they are bowing to the public’s perception of how they are described – smart choice. However, the American National Standards Institute (ANSI) and the American Society of Mechanical Engineers (ASME) call them “hex” or “square lag screws” – no compromising from the smart guys (since 1914 no less). I will personally think “screw” when I see a box of “hex lag screws (bolts)” from a USA manufacturer, or a box of “lag bolts” from a foreign maker. Does it matter? To me it does a little bit because there is a good reason for standardization, and it should not be ignored. Now, the comment about using wooden pegs instead of lag screws/bolts has me wondering. Should we use ANSI approved pegs/dowels or foreign made wood formed cylindrical fasteners? Seriously, I’m not being serious here….I’m not going to re-label my supply drawer.

  • fltckr

    For what its worth: Machinery’s Handbook, 26th edition (2000) calls it a “Hex Lag screw” and the square head a “Sqare Lag Screw”, both with accompanying illustrations that leave no doubt of what they are describing . This is according to ANSI and ASME standards. The 1914 edition of Machinery’s handbook has a table of “Lag Screw Thread Sizes in Common Use”, and lists the same shank size and number of threads for a 1/4″ Lag screw as the 26th edition, so I don’t think anything has changed much since then except today most are made in China out of inferior steel and to much lower standards. So why did I label my supply drawer “Lag Bolts”? I think it is because the foreign manufacturer labeled the box according to their understanding. Had they been made in America, I’m willing to bet the box would have been labeled in accordance with ANSI/ASME standards e.g., “Hex Lag Screws”.
    My two cents…

  • abt

    I’ve been labeling drawers for hardware and came across both label names for the same type of hardware when in the original bags. Both packages were vendor labeled, so even vendors may be confused.

  • ronwood72

    I went with lag bolt, because you turn it with a wrench, any thing turned with a screw driver was a screw. I am betting this wasn’t the tie breaker.

  • Richard Dawson

    In reference to Glen’s discussion of changing the clutterhead on a jointer, were there any lag bolts damaged in the filming of his enlightening video? (I always called it a planer.)

    Inquiring minds need to know.



  • bubbainmiss

    Lag Screw or Lag Bolt–either one. Specifying “hex head” is both redundant and implies that it is a machine thread. What somebody at a home center chose to call it makes no difference. If they hung claw hammers under a sign that said “crowbars” would you tell your readers to drive their clinch nails home with their crowbars? Just show a picture of the correct fastener in the article.

  • vdepauw

    Sorry but describing this as a hex headed bolt is totally wrong. The bolt would indicate a staright threaded shaft ment to screw or turn into a matching threaded hole and would need to be identified also by the threads per inch. This could be of any material wood throuh metal. The item illustrated has a shaft with a taper and is ment to turn into a non threaded hole in a softer material. It does not really cut a thread. Calling it a hex head is proper as the head has 6 flat sides. This screw can also come swith a square head, 4 flat sides.
    Vic De Pauw

  • gdblake


    You and Bob are correct, screws have points, bolts tighten down via a nut. I don’t care what some back office idiot who doesn’t know what the item really is labels them for display or catalog purposes. Language is fluid and the meanings of words change over time because of ignorance and general disregard for convention. Words only mean things when the definitions stay constant. I find it odd that Chris would defend the use of bolt in this case when he is usually a stickler for using the proper term. Or does he only cut grooves now and done away with dados, rabbits, and filisters?

  • oakripper

    I have always called this a lag screw because the threaded part comes to a point. When referring to the fastener with the eye or ring on the end, if it has a threaded end that comes to a point it is referred to as a eye-screw and if it uses a nut then it is referred to as a eye-bolt. just my 2 cents worth.

  • Bernard Naish

    Traditionally called a coach screw here in England. Coach bolt has threaded portion to take a nut and a domed head with a square section under it that stops it turning. Lag screw not a description known here. Keep up the interest or all this will be lost. Regards to all.

  • Ron 1

    I think number of years us old-timers have in the Trade should pretty much count towards the correct name. I have 50 years calling it a “Lag Bolt” or may have even called it a “Lag Screw”. Hell I don’t remember, the important thing is I know what I need, and that gets to be very important as you get older.

  • Sawduster

    As a similar convention, when does the size and or thread count change its name from a machine screw which also includes a nut for closure to a bolt? Have just wondered and never gotten an answer.

  • gazpal

    The piece of hardware pictured is a lag/coach/hex screw – it works in the same manner as a screw but you use a spanner or socket to turn it. A lag/coach/hex bolt passes all the way through the work piece and is secured using a nut.

  • 7-Thumbs

    I’ve always called this a lag bolt. Personally, I wouldn’t trust any name a big box store put on their hardware.

  • GregM

    My opinion is that this item is *correctly* called a “lag screw” but – in North America at least – also *commonly* called a “lag bolt”. I think the key word to include here is “lag”. If you ask for a “lag screw” or “lag bolt” you will most likely leave the store with the appropriate item. Readers in the UK or Australia may need a “coach bolt”, but here in the US that wouldn’t get you far since our coach bolts have round, domed heads that cannot be gripped or turned by a wrench (spanner).

  • Bob Miller

    I read the magazine back to front and then to the back again. Is this still an acceptable method? Or am I skating my duty to find that one error by reading in reverse article order?

    I would if not thinking about it call it a “lag bolt” this is also what the rest of my family does. I think “hex head” is an acceptable prefix because regardless of its bold/screw/swirlything status it does have a hex head.

    I wonder are different naming conventions a regional thing and you would get 6 different answers from hardware stores in 6 different places.

  • renaissanceww

    Sounds like a perfect opportunity to sidestep the whole issue and use a wooden peg. Then you can call us Lie Nielsen or Veritas and pitch them on some ad space highlighting their dowel maker solutions conveniently placed adjacent to the article.

  • icmguy

    Here in the northeast we call them lag bolts. They’re usually used with “lead” shields to attach equipment or wood ledgers to concrete. So I suppose you could consider the shield to be the “nut” in the bolt assembly. The screw threads certainly grab the soft metal better than any other thread you might use. I expect it all boils down to how you use it. Perhaps the hex head is a redundancy since the majority of modern bolts have a hex head rather than the square (old) or twelve point(newer) you see on occasion.

  • keithm

    I’ve always called them “lag bolts” It may be a regional thing like soda, pop, soda pop, coke, etc.

    Where it gets fuzzy is
    * Hanger bolt (half machine thread, half screw thread)
    * Dowel screw (double screw thread)
    * Dowel pin (a wooden piece cut to length, often spiraled or fluted)

  • Narayan

    You all are crazy.

    It’s called a doohickey and you use a turnthingy to fasten it to the whatzit.

  • almartin

    Since you brought it up…

    1st paragraph, last sentence: you, not your
    Last paragraph: Chris’, not Chrirs’.

    Now to wait for the magazine. 😉

  • Nick Webb

    And in the UK it’s called a coach screw. As others have said, call it what you want but show a picture.

  • Village Carpenter

    I had a guy at a home center yell at me one time when I called these lag screws. “They’re lag BOLTS!” he said. He may have been a bit unhinged. Or had a screw loose. Your choice.

  • tms

    I call it a lag screw.

    For me, a screw is held in tension by the contact of its threads to the wood. A bolt is held in tension by a nut.

    There is an old adage in wooden boat building:
    Nail where you can,
    screw were you must,
    and bolt where you have to.

  • Jonas Jensen

    What does the American Standardisation Society call it?
    I agree with jmoorse, that a picture could be nice, but usually I am able to get an idea of the hardware when I go to the site you reccomend in the article.

  • John Vernier

    Sounds like a decent topic for a short article. Isn’t Hillman group based in Cincinnati? Maybe you should do lunch with somebody over there and see if they have the same problems with different retailers or regional variant terms. FWIW growing up in Michigan these were always lag bolts, but I think the distinction between bolts and screws is a good one, and worth fighting for.

  • brownkm52

    I’ve always called that a lag bolt. My after-the fact explanation:

    If you turn it with a screwdriver, it’s a screw.
    If you turn it with a wrench, it’s a bolt.
    If it’s a bolt with screw threads, then it’s a lag bolt.
    If it’s a bolt with a domed head and a nut, then it’s a carriage bolt.

  • Bill Lattanzio

    A good rule of thumb may be that a screw can thread itself and a bolt cannot. Even so, one of my distributors calls it a hex lag screw, the other a hex lag bolt. So I can see where all of the confusion comes from.

  • jmoorse

    That object is technically a hex head lag screw for wood. I buy mine from McMaster-Carr, whose catalog description shows the relevant ASME, ASTM and SAE standards. The nice folks at hardware and big-box stores aren’t technical experts and the signs and labels are often incorrect. I’m usually happy if they can tell a nut from a bolt. Don’t bother asking the guy in the tool department for a brace.
    The best way to make sure that your readers can identify the correct hardware is to show a clear picture of it. That way even those in other cultures, or whose first language is not english, can understand. While I love PWW magazine, I usually find your drawings incomplete. But that’s just me, an engineer but not a writer. I tend to improvise anyway.

  • AL

    I am a big folder of Chris, but Glen I agree with you and Bob. When I saw the photo, the first thing that popped into my head was “lag screw.”

  • iwigle

    In Canada I’ve always known these as lag bolts. And when I check the Canadian sites for Home Depot or Lowes, they call them lag bolts as well. If you search for lag screws, you find no lag bolts.

    No argument with the “bolt needs a second (female) device”, I agree with the discussion about “lag screw”. But this does raise a more generic editorial challenge: When something is properly called a widget, but virtually the entire world calls it a doodad, what’s an editor to do???

  • Peter

    OK, to add more monkeys the barrel: calls this thing a ‘coach screw’ and call it a ‘coach or carriage bolt’. Don’t think that helps!


  • Jonas Jensen

    In Denmark it is called a French screw.
    But I guess that I would call it a lag screw as well. A bolt needs either a nut or a threaded hole in my opinion.

  • jrfuda

    I too vote “Lag Screw.” When you talk to folk in the construction trade, that’s what they call it. When you watch a DIY show where the seem to be building a deck every week on one or an other of them, they always talk about attaching the ledger with lag screws unless they have the ability to attach with bolts (access to the interior side where the ledger in mounted). I, personally, have used them most recently to attach my lumber rack to studs in my shop and to mount an antenna to the rear gable of my home. Both times I went looking for lag screws, not bolts.

  • danoelke

    Its a lag screw (adding “hex headed” is optional). As you say – a bolt is threaded to have a nut put on it. While I know that terminology shifts over time – I think those who know that there is a better / more correct term to use have a duty to educate others.

    Edivince that some online retailers got it wrong is not a good excuse to further corrupt the language. There are other examples (probably many more) of retailers that get it right. To use Chris’s reasoning against him – if more & bigger retailers get it right, then more readers will find what they need by using the correct terms. I think you will steer more readers towards finding the right piece of hardware by using the right name. For example – Home Depot does get it right. If you search “hex bolt” you see bolts. If you search “lag screw” you see lag screws. And if you search for “hex lag bolt” you see lag screws – *and* the title for each item says “lag screw”

  • jte9999

    I’m with you, Mr. Lang, and Bill. I’ve never heard of an ‘Archimedean Bolt’. A bolt is a fastener which requires a second part. That’s my story and I’m sticking to it.

  • Bill Lattanzio

    If you want my two cents. That is a hex lag screw. Screws are tapped into wood or metal, or what have you. Bolts are fastened through using nuts or threads. I’m not just guessing blindly, I use and sell hardware for a living.

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