BMW R1200RT/R1250RT Forum

Just back from Machine Mart where I have purchased a small Socket Set. On the package the description states "Flat Drive" Allows up to 30% more Torque by Gripping the "Flat Sides" of the Nut and Not the Corners". Must admit this a new one on me and I just can't see what they are getting at.
Any idea's anyone ?.

Its not a new thing, the likes of Snap on have been on this for a while, they call it 'Flank Drive', see below. Basically a slight change in profile that shifts the contact point further down the flat and away from the corner, reducing the risk of rounding.

Also known as surface drive.  They work well.

Thanks for the replies Chaps, although it does seem that there different things here. The Sockets I have just acquired are of a full hexagon type, hence the description "Flat Drive". The picture of the "Flank Drive" posted by Graham is different. What originally concerned me was the statement "Allows 30% more Torque" which I probably and mistakenly understood to mean that 30% more torque was being applied than was set on my wrench. However after giving this some thought I now see that this would not be possible. (I hope !!).

You are right, the torque is a product of the force applied and the distance it is applied from. A socket on its own cannot increase the applied torque although torque multipliers are a thing. The claim is that you can increase the torque by 30% without the fastener rounding.

As for your sockets they are a 6 point and the one in my picture is a 12 point, both work in the same way and flank drive is available on 6 and 12 point sockets, ring spanners, open ended spanners and even adjustable spanners now (I think), flank drive is just a snap on trademark - I'm sure if you tried you could find plenty of other names for essentially the same thing.

Nicely explained Graham. Cheers.