Hot Topics: A Bolt to Go with this Ancient Wrench

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When you’re doing repairs or retrofits, sometimes the old hardware is going to show, so it’s good to have nuts and bolts with old fashioned profiles to match the original look. But how do you fit a square head in a hex hole? The Forum has the answer.

Original Post: Square Headed Lag Bolts

sgull Member

At my work place I came across a bunch of old lag bolts of different lengths and diameter that all have square heads instead of hex. I tried using different normal wrenches and sockets on them but none will fit right. I showed them and asked at the hardware store if they knew of a wrench or socket used for these and they said they said they'd never even seen square headed lag bolts. I Googled a little and found that apparently these are outdated and rarely used nowadays. Any comments appreciated.

Highlights from the Thread

marksr Forum Topic Moderator

An open end wrench should work fine. I've seen/used those types of lag bolts, but it's been awhile. A hammer helps to speed up their installation.

Hal_S Member

You'll want to find an old fashioned square wrench. If you can't get a standard square wrench, I find that a square bolt train wrench will do.

An old train wrench and a modern crescent.

ray2047 Group Moderator

An eight point socket is intended for use on those.

8 point sockets.

Image source: Billings and Spencer

sgull Member

An open end wrench should work fine. I failed to mention I was really hoping to be able to drive these with a socket, not manually turn by turn with an open end or crescent wrench.

“An eight point socket is intended for use on those.”

Good to know. I think I have some of those around, and if not at least I know now that's what's needed. Thanks ray2047!

PJmax Forum Topic Moderator

When you buy a set of sockets, you'll sometimes see two of the 8 point sockets at the low end. Snap On sets all came like that. I have 8 point sockets in all three drive sizes.

the_tow_guy Group Moderator

Hardware guys who've never seen a square-head lag bolt?

aka pedro Member

Yeah, I'm thinking that a hardware guy who has never seen a square head lag bolt should probably be working at one of the big box's instead. I can't recall for sure, but would almost be willing to bet that 30-40 years ago, before certain power tools became prevalent, it was the other way around; you only found square head ones. Today, I have occasionally had to dig a bit deeper or search a bit farther to find the right size square head lag for the sake of maintaining an element of authenticity. Nevertheless, the guy should have known. I don’t know how many lags you have to drive, but you may spend more time and as much money buying the right sockets as you would to simply buy new hex head bolts.

Hal, thank you for the reminder. I have a wrench very much like that in one of my tool boxes, and have used an open end or adjustable wrenches on square head lags for so long that I may have forgotten what it was originally used for.

Find more ways to drive them at: //