I interpreted 'Specially designed Flat Drive sockets allow up to 30% more torque to be applied.' on Machinemarts web site and on the sealed packaging of a set of sockets to mean they were hex, rather than bi-hex sockets - then found they were bi-hex. So what does 'Flat Drive' actually mean please.
Harry Bloomfield gurgled happily, sounding much like they were saying:
Normal sockets drive the corners of the nut, which is great until you need to remove one that's a bit mullered.
Wall/Flat-drive sockets are kinda-hex, but I can see why you'd think they're bi-hex. Each wall is curved, so the force is applied nearer the centre of each of the flats of the fastener, rather than the corners.
A good illustration...
In message , Adrian writes
About 25 year ago, Snap-On pioneered the concept with their "Flank Drive" range. I remember the Snap-On guy had a bolt screwed tightly into a thread and the bolt head had all the corners machined off. A standard socket just spun round but the flank drive socket got the bolt out.
Why don't you phone them and ask? "Surface drive" is the normal term for hex sockets that bear on the centre of the flat of the nut. "Flat drive" means anything they want it to which I suspect is "normal bi-hex socket" with our own meaningless name applied to it.
Hmm not so sure about that, i have a set of metrinch sockets dating from the late 70s
It happens that Adrian formulated :
Take a look at the actual item description and see what you think...
I have just tried a nut in one of my old 1/2" bi-hex sockets and an identical nut in one of the MM sockets. The fit is identical, catching just the corners of the nut - so I am very disappointed.
I think that is correct don't recall Snap on inventing it but they may have a modified design.
You can also get open end spanners which have a raised bit at the front opening and sloppy at the back which gives more purchase on the nut with out rounding it off.
Harry Bloomfield gurgled happily, sounding much like they were saying:
Hmm. Can't quite see from that pic, and the description is very non- committal.
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I have the Machine Mart version and the difference is that the sockets have two slightly curved convex protuberances and a concave area between the two on each 'flat' making it a twelve point socket with curves.
This differs from the example (borrowed and repeated here) which has a central bearing point making it the opposite configuration from the Machine Mart version:
Cic.
The set you link to is METRIC. A 1/2" nut has flats just a bit under
12.7mm across. The closest sizes in your METRIC flat drive set are 12mm and 13mm A/F sockets. The 12mm socket is designed for 12mm A/F so unless you use a big hammer won't fit a 12.7mm A/F nut. The 13mm is for 13mm A/F and has 0.3mm slop on a 12.7mm nut. To as you have found it won't touch the flats properly but contact too close to the corners and will simply round the corners off.Go get an imperial set for your imperial nuts.
"Snap-On" type bi-hex flank drive will be an even worst fit when miss used.
he was talking about the drive size, not the nut size.
go to ebay and get something like:
320547326120 which is a set of 3/8 drive impact single hex sockets at 9.95 plus 3.50 deliveryMrcheerful brought next idea :
I was referring to the drive size - sorry if I didn't make it clear.
I have had an acknowledgement to my email of complaint to MM, I'm just waiting for their response now.
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