Pre-Flank-Drive Sockets

[T45]

Do you use 'em? Do you prefer them to "lesser-brand" modern sockets?

If so, which ones/?

 

[toolaholic]

I have a hazet 20x22 deep offset wrench that doesn't have flank drive. Worked well to remove the 22mm pivot shaft to frame nut underneath the passenger side exhaust manifold Dakota r/t. Oddly hazet double box wrenches are flank drive. I do not own non flank drive sockets.

 

[Al Borland]

Has anyone ever read the patent application for the flank drive?
What the main purpose/improvement was supposed to be was reducing stress risers in the sockets and reducing warranty costs.

 

[Schurkey]

Link?



I have a bunch of old Craftsman sharp-corner sockets. I use them when I need to. Same with my elderly sharp-corner Wright impact sockets.

The non-Flank-Drive sockets function well enough; but I prefer a radiused-corner socket (or wrench) in general.

 

[stage20]

It's to keep from rounding bolts. Flank sits on the flats of bolts and nuts instead of the corners....can still break the sockets. Doesn't make them stronger.

 

[Packard V8]

First patent 1966

https://www.google.com/patents/US3495485

If one believes the patent, flank drive might be the answer for rusted fasteners; however, I've got Blue Point combination wrenches from the 1930s/'40s/'50s which have served me well for fifty years. I really don't notice any difference in normal use.

Back in the '60s-70s, Bonney Loc-Rite wrenches and sockets claimed a similar technology and I remember really liking them. Loc-Rite patent #3,125,910, inventor was A. Kavalar,

jack vines

 

[Adam.C]

It's to keep from rounding bolts. Flank sits on the flats of bolts and nuts instead of the corners....can still break the sockets. Doesn't make them stronger.

It does make them stronger. Exactly as Al wrote above.

 

[dutchgray]

It does make them stronger. Exactly as Al wrote above.

When everything else is equal they are definitely stronger, however I think the average quality socket aimed at automotive use today is thinner walled which helps with access but reduces strength a bit, consistency in manufacturing is better now than in the past which helps also.
I have some old sockets, I generally use modern ones but if the old design is what I have at hand I will use them. I think it matters more in 12 point than 6 and I mostly use 6.

 

[gdocktor3]

The only flank drive sockets I have are my snap on impact sockets and I only own them because I picked them up really cheap. My 1/4" set is Gearwrench, my 3/8" is SK, and my 1/2" are a mix of older snap on, Blackhawk USA and craftsman USA. My point is I get along just fine with or without flank drive or like design, but it certainly does help make things easier in many cases.

 

[Al Borland]

The aid you get from flank-drive is this:
1. With the radiused/overbored corners, you can get on a fastener that already has minor damage to the corners.
2. Since you have wiggle room in the corners, you can tighten up your clearances on the sides. The closer you can keep point of contact to center of the flat, the better for torque transfer, which will help to not break fasteners.
3. By moving the contact point away from the thinnest point in the socket wall, and eliminating a sharp angle, you increase socket strength and reduce breakage.

In no way was I trying to knock Flank drive, it's just funny to me that what makes it work better is actually a side-effect of a reduction in warranty costs.
As far as rounding off corners, how loose would a socket (especially 6-point) have to be to round off a nut? Flat sides would have to pass over/tear off the corners. That's a lot of metal to move.

 

[bob15]

Kelsey-Hayes original 1961 Loc-Rite patent:

http://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US3125910.pdf

Here is an early Bonney ad with a good history of the company and a great explanation of their Loc-Rite design:

http://vespags.web.fc2.com/up/utica.pdf

 

[Sam'sAutoParts]

I only have 3/8" drive 6pts at work that are pre-off corner. Everything else is modern. If the bolt strips, out comes the big red wrench.

Home I I have.a mix, if they are handy I grab the modern sockets, but if not I will use the older ones. My junkyard box had a bunch of the older stuff, and some was even import stuff and it usually was not a problem.

 

[Wakefield]

Kelsey-Hayes original 1961 Loc-Rite patent:

http://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US3125910.pdf

Here is an early Bonney ad with a good history of the company and a great explanation of their Loc-Rite design:

http://vespags.web.fc2.com/up/utica.pdf

They first only put the rounded corners on their 12 point stuff?
Some Bonney 6 point might have small radius in their corners that are so small that they can only be seen with a magnifying glass.

 

[Adam.C]

The closer you can keep point of contact to center of the flat, the better for torque transfer, which will help to not break fasteners.

You got that backwards. When the socket contacts the bolt closer to the corners, you get less stress (trying to split the socket or rounding the bolt head) for a given torque input. Snap On Flank drive sockets hit pretty close to the corners.

Other sockets fit looser and contact further in from the corners (nearer the centerline). This results in much higher stress. Just a tiny fraction of an inch can greatly increase the stress since the force is equal to the input torque/distance from fastener centerline to the point of contact. I think Snap On has said 20% less stress in the past. It could be something like that (compared to craftsman for example). A few thousandths of an inch could make an appreciable difference.

By moving the contact point away from the thinnest point in the socket wall, and eliminating a sharp angle, you increase socket strength and reduce breakage.

Not quite right either. If the load at the contact patch was the same, this would be true. But it's not. The closer you get to the actual corner of the bolt head, the lower the stress, the lighter and thinner you can make the socket.

As far as rounding off corners, how loose would a socket (especially 6-point) have to be to round off a nut? Flat sides would have to pass over/tear off the corners. That's a lot of metal to move.

Not that loose. All sockets contact hex heads with a very thin line on each face of the hex. When you apply a load to a surface, the resulting stress equals load/area. We can assume, due to the manufacturing tolerances of a bolt head, that most sockets will only touch 2 flats (initially). So the area of contact is TINY- like the breadth of a human hair. As contact area decreases, stress increases. So it's not hard to generate enough stress to plastically deform soft metal. So a std grade fastener is fairly easy to round over. The other issue is the orientation of the socket flat - the angle between that and the bolt hex. As that angle increases (due to a sloppy fit or pre-rounded corners), the chance of rounding the head increases dramatically.

When a fastener rusts, it looses metal. The rust initially increases the dimension, then rubs or flakes off leaving less hard material. This allows a socket to rotate more and present the corner of the hex head bolt with an angled surface (for normal pre-FD sockets). The corner has less material behind it, so less strength. As it yields the contact patch becomes closer to the center of the fastener, so stress increases, more yielding etc.

The flank drive socket actually works like a Flank Drive Plus wrench. The contact point inside the socket is a sharp edge that actually bites into the socket (instead of the angled surface above) like a tooth. This creates a lot of friction which helps the socket grab on.

Here's one more thing to think about:

When you apply torque to a bolt via a wrench, in Freshman physics we learned that that same torque must be reacted by the bolt (in friction for example). But in the real world, that isn't true.

Every part in that system bends and flexes elastically. The ratchet bends, the pawls inside its head compress slightly, and the bolt head is squeezed. If the socket contacts the fastener just a tiny bit closer to the fastener centerline, you get more stress so more elastic deformation of the bolt head. This means you actually need more effort to remove a bolt with a lower quality socket.

We hear stories from old pros all the time about how their Snap On socket removed a fastener others' could not. Or that they can remove stubborn bolts with less torque. This is why.

Just to put this in perspective, I'm not sure how much additional torque is required to crack a stuck bolt free using a craftsman socket versus a Snap On. It could be fairly small which also explains why guys can get by using regular grade tools. But to respond directly to the OP, why would one choose an inferior socket to a modern FD style version? FD sockets do a better job of removing stuck fasteners and do it with less effort.

 

[bmwpowere36m3]

Can you even still buy corner engagement sockets? All my SO, SK and CMan are off-corner... I have a few older CMan 6-pt that aren't (maybe mid 80's).

I don't know why you'd prefer the corner engagement... sockets or wrenches. That said, I've used those and non-flank drive open end wrenches and they work for the most part. They only struggle on really tight or corroded hardware and I've rounded a few heads in my time.

All my current tools are off-corner, flank, grip, "whatever" drive.

 

[MShaw]

And then there are those of us that bought Snap on and other premium brands in the 1950s and 1960s before flank drive was available. I don't know if flank drive would work better as I have never owned any. Logic says they would but , to me, not enough to be worth retooling at my age.

 

[gdocktor3]

And then there are those of us that bought Snap on and other premium brands in the 1950s and 1960s before flank drive was available. I don't know if flank drive would work better as I have never owned any. Logic says they would but , to me, not enough to be worth retooling at my age.

The biggest benefit, I think, is saving time. Where now you, and I, sometimes take a few extra seconds persuading and caressing some real stubborn fasteners, the flank drive stuff "bites" almost immediately, reassuring you that you will get the fastener off without rounding it off.