aren't torx already metric ??

 

Does Robertson have a metric similar or is there just the one?

 

There probably is no why; It's just the way some things were created or evolved. Robertson (square) are like Philips - they have sizes that don't necessarily correspond to SAE or metric measurements. Lots of things have gauge sizes that just are what they are. I suspect mark sr is correct about torx - the number most likely correspond to tenths of mm (T25 = 2.5mm). Where that's measured to, I have no idea. hex keys, hex socket are dimensioned across the flat sides.

 

I fail to see the logic or reasoning for this question,

Are you looking for a specific tool, and can not find it?

 

Not looking for anything, just a general question.

With Torx or Square bits, I just need two (long bit and short bits) for each size. Easy to manage.

With sockets and allen, I need an SAE set and a metric set. And for Allen, I need allen bits as well as the L shaped keys, then in both SAE and metric. Frankly I can never tell which is which, so I have both sets mixed together in a tray. When I do need it, most of the time I am unable to visually "see" the hex shape socket because most of the time it's recessed deep light in a light fixture or a towel bar, or worse yet in a tub spout it is recessed AND facing down. So your finding the right one is typically done blind, sorting through a bunch of SAE and metric keys and find the right one by feeling out whether it goes into the hex hole or not and how loose. If there is only one standard, then less keys to sort through, same with the hex nut driver.

So the motivation is, why do I need to keep what I considered to be excessive number of allen L keys, allen driver bits, hex socket sets (in SAE, in metric, short ones, deep ones, 1/4 ones, 3/8 ones, 1/2 ones, for socket wrenches, for "driver ready" ones).

 

To the OP . the screw in bit industry has gone crazy in the last 20 years.

 

Welcome to global trade. Even before the current multi-nation manufacturing systems, the British had their own, and even with just SAE, you still needed multiple drive sizes and sockets depending on the application.


Ya, no kidding.