Antique Curved head screw

[Roger Feeley]

I picked up an old oak office chair from a neighbors garbage. It was the victim of many botched repairs. In one case, a steam bent half round arm had split and had been repaired with a bolt with a peculiar curved head like the ones shown below. All I could find are some vague statements about the bolts being used to hold chair legs.

470045
Anyone know more?

[Jim Becker]

Those kinda look like the same idea as a "Chicago bolt", but with a head that has fangs. :) I suspect that the idea is that as you tighten the hex bolt, the other end gets drawn very positively "into" the wood which locks the component into place so it cannot twist/rotate. I'm making that guess purely from what I see in your photo.

[Steve Rozmiarek]

You see those on wood components on old farm equipment. They attach a half rounded something to a flat surface. The wings match the rounded part. Bat spokes in binder headers for example. I don't know what the proper name is.

[Bill Dufour]

Similar to a plow bolt or elevator bolt but bigger head.
Bill D

Similar on Amazon. search term seems to be curved head screw
https://www.amazon.com/Hillman-Group-58474-Curved-4-Inch/dp/B00NWJFEZ2

[Paul F Franklin]

Nowadays, I'd call them a saddle bolt...intended to fasten a tube or other curved component to something else...

[Roger Feeley]

Steve,
Thats exactly how this was used. The round steam bent arms on the chair fasten to the flat seat. To make a good joint, they flattened to half round. That’s the part that split. So, rather than fix the split, they replaced the screw with this bolt. It had the dual purpose of holding the arm and preventing further splitting.