Okay- here's the deal- Torx are six point and torx plus are five. The tamper proof in both have a hole in the center for the corresponding pin in the fastener. Hope this helps.

 

OK, can anyone tell me why, in a system that was designed in modern times, do the sizes go 15, 20, 25, 27, 30, 35?

 

mhmike: I have three sets of torx drivers; all are for 3/8" drive socket. One is Sears standard six points, one is Sears Tamper Proof with the hole in the center and is six point; and the last is Matco Torx Plus six point. The sizing numbers on all of them are the same except the 'Plus' sized set has the word "Plus" before the No. The size of the 'Plus' bit is larger than the standard bit across the flats of four points in all cases. For example: the measurement of the standard No. 45 is .265 inch, while the same measurement of the 'Plus' is .305 inch. I have never seen a five point Torx bit or screw.

I have found that when working with Torx machine screws that are chrome plated that a standard Torx bit is more prone to spall out the recess because chrome is relatively soft. I have got into the habit of using a 'plus' sized torx that has to be gently tapped into the recess before applying any torque to the bit. I have never spalled out a Torx recess in a machine screw while using that technique. Of course, that particular machine screw has to be inserted and removed using the 'Plus' sized Torx bit forever after. ......... BC