Square head capscrew are useful for what these days?

Cannonmn · Dec 24, 2017

Recently we received many long heavy thick plastic drawers of fasteners, all with Fastenal labels. One drawer was full of 3/8” x 2” square head capscrew (yes, capscrew with integral head-washer and tapered start threads.). Another drawer held similar items but configured as bolts. I rarely see square-head fasteners and I’m interested in what they are usually used for. I know they can be useful when a row of fasteners adjacent to a raised edge allows the edge to prevent head rotation, but that doesn’t happen too often. Is their some other role where square-heads are particularly useful or are they nearly obsolete?

Monarchist · Dec 24, 2017

Cannonmn said:
Is their some other role where square-heads are particularly useful or are they nearly obsolete?

The ONLY saving-grace those have ever demonstrated to me is that one can see at a glance if they are damaged.
As they often are, given that the only weaker shape is triangular, and 5, 6, or more sides are all improvements.

They can be nicer to deal with than a buggered straight screwdriver slot, for-sure, and a Philips, maybe, but not much else.

jhruska · Dec 24, 2017

Square head non-capscrews sometimes referred to as square head set screws with cup or point on the end are usually hardened.
This property makes them ideal for locking assemblies on location.
John

magneticanomaly · Dec 24, 2017

Photos would help. The commonest product these days with a square head is a set-screw. Distance across flats usually equal to nominal thread diameter, so there's no room for a washer-face under the head to make it a capscrew. Square-head USS bolts were pretty common on all sorts of assemblies 60 or more years ago. The only recent square-head bolts I have seen are track pad bolts on a John Deere dozer, b ut I am pretty sure these were 1/2" or larger.

Square heads or nuts are less likely to round-off under high torque with loose wrenches, probably slower to become unremovable due to rust. But they take up more space, take more material to cold-head, and require wider flanges and access room for bulkier wrenches, hence their recent disfavor.

Photos? Fastenal part numbers?

gmach10 · Dec 24, 2017

jhruska said:
Square head non-capscrews sometimes referred to as square head set screws with cup or point on the end are usually hardened.
This property makes them ideal for locking assemblies on location.
John

The type you just described make for great jacking bolts.

JST · Dec 24, 2017

They are good for assemblies that need to look older.

They work well for places where access is hard, and the head will jam against a boss etc and not rotate (if not integral washer).

Tyrone Shoelaces · Dec 24, 2017

Square headed set screws are usually used in four way lathe tool posts.

Regards Tyrone.

adama · Dec 24, 2017

They see common use in rail applications, dont know why but there commonly used in track work.

M.B. Naegle · Dec 24, 2017

Kinda falls into the self-jamming category, but I've seen them used as a sort of "captive" fastener in stepped slots. They seem to take a beating better than hex head bolts. I've opted to use square headed set screws in designs where it would be helpful to get to the screw from the top with a T wrench, OR get to it from the side (something you don't always have the head-room for with hex set screws. I think the one thing getting rarer than the bolts themselves are 4 and 8 point socket drivers!

I'll add too, that square head cap screws typically have a little wider shoulder under the head than their hex counterparts in that the corners stick out farther (short of using an actual flange head bolt).

Monarchist · Dec 24, 2017

M.B. Naegle said:
I think the one thing getting rarer than the bolts themselves are 4 and 8 point socket drivers!

"I got mine", but only ceased worrying about the scarcity when I realized my habit of throwing the 4-sideds away, often in favour of male Torx when not male hex or female Allen, meant I hadn't had cause to use 'em in Donkey's Years.

randyc · Dec 24, 2017

There are a few in my old Sheldon:

1 for the lantern
(8 for the 4-way)
2 for a boring bar holder
1 for a parting tool holder

1 carriage lock
2 taper attachment locks
2 for tailstock setover
maybe a couple of more that I've forgotten in the gear train.

alskdjfhg · Dec 24, 2017

Old school Budd lug nuts (think that's the name), one part is a square head. The lug nut within a lug nut type.

M.B. Naegle said:
I think the one thing getting rarer than the bolts themselves are 4 and 8 point socket drivers!

I bought a new 8 point impact socket set not too long ago, 3/8-1" or so. Wasn't too expensive, was Taiwanese off Ebay.

WHHJR · Dec 24, 2017

Used in conjunction with #9 wire in farmer engineering and rigging applications.

5¢

winger · Dec 24, 2017

Around here they were called grub screws,was common on farm equipment as well as square headed bolts.
Dave

Cannonmn · Dec 24, 2017

Here’s a slightly bigger one from same Fastenal set, is 1/2 x 1 1/2”, happened to have it in pocket where others still at work. Sry 4 blurred pic of top, mark is grade 5 plus “E5” with degree sign over the E.

manualmachinist · Dec 24, 2017

Square head would be superior in captive situations by providing a large bearing on the flats, much less apt to spin and loose the locking force to remove the nut.

gbent · Dec 24, 2017

That is the first time I've ever seen grade markings on a square headed bolt.

randyc · Dec 24, 2017

Reminds me: I made two of these things coupla' months ago ("collar-head screws" according to Machinery's Handbook). These were small ones needing #7-32 threads, to fit a toolmaker's vise.

billmac · Dec 25, 2017

Tyrone Shoelaces said:
Square headed set screws are usually used in four way lathe tool posts.

Regards Tyrone.

Also in other tool holding applications,for example tool holders for quick chnage tool posts. I have some tool holders with socket head cap screws and some with square heads. The socket heads tend to get chips in the sockets which means that you need to blow them out before you can adjust them. The square heads don't suffer from this problem.

Jay_Rogers · Sep 7, 2018

Generally, Square Head Cap Screws have the high tensile strength to hold objects together. They are used where greater resistance to seawater, abrasion as well as higher mechanical properties required. Square Head Cap Screws are also used where precise tolerances are required for installation and disconnection! Hence, There are other application and uses also!

Square head capscrew are useful for what these days?

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