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Tool Talk Discussion Forum

Posi-Drive bits

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Eddie in MI

03-09-2005 19:48:24




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I was shooting some screws and realized that the bit that I was using was a posi-drive, not a true phillips. Okay... I'm going to show my ignorance here... what's a posi-drive bit for? They look a lot like phillips bits and they work on phillips fasteners. Is there actually a posi-drive fastener head that they mate up with?

TIA,
Eddie




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Stickler

03-10-2005 20:12:46




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 Re: Posi-Drive bits in reply to Eddie in MI, 03-09-2005 19:48:24  
Harleys used all PosiDriv fasteners an the engine and primary cases in the late 70's. Lots of other applications too.



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Joe Evans

03-09-2005 20:32:42




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 Re: Posi-Drive bits in reply to Eddie in MI, 03-09-2005 19:48:24  
Yes, there are genuine pozi-drive fasteners. A lighting manufacturer I used to work for, used them by the ship load for fixture assembly. I believe the pozi-drive fastener is slightly deeper and has a steeper angle from the outside of slots to the slots' intersection resulting in a more positive bit bite compared to Phillips. I think you'll find that the pozi-drive bit is "pointier" than a Phillips bit.

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JoeK

03-10-2005 01:09:47




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 Re: Posi-Drive bits in reply to Joe Evans, 03-09-2005 20:32:42  
Believe t was an"Improvement" on the Phillips to allow better engagement with less "feel"needed for automated or high speed assembly processes.Now Torx is gaining ground again and square(Reed-Prince??)is making a comeback in torque sensitive applications as a sensor can determine no of turns or torque achieved from a"locked"in bit.(opinion based on observation)Eventually Phillips and Straight will probably join the square nut club.

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Gerald J.

03-10-2005 08:12:14




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 Re: Posi-Drive bits in reply to JoeK, 03-10-2005 01:09:47  
Pozi-drive has an extra notch in the screw between the Phillips slots. The driver fits that to get more drive surfaces.

There are four similar Phillips like drives, US Phillips, metric Phillips, Pozi-drive, and Reed and Prince. Their screws and drivers don't interchange.

Phillips and metric Phillips look the same but are different sizes. Pozi-drive has the extra drive surfaces, sort of a tapered square drive in the middle. Reed and Prince have flat wings, no taper to the wings of the driver.

Then there are three wing variations.

Square drive is known as Robertson.

Gerald J.

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Eddie in MI

03-10-2005 10:31:56




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 Hmmm... in reply to Gerald J., 03-10-2005 08:12:14  
The regular Phillips and the Pozi seemed to interchange just fine for me. I didn't strip any screws, nor did I even notice that I was using a Pozi bit until I finished the project. That's what prompted me to post this question in the first place.

The part about a more confident engagement with automated assemble machines really makes sense.

I'd don't belive I've ever seen a metric Phillips. Are they usually marked? How would you know one if you saw one?

Just curious... I learn more here everyday!
-Eddie

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Gerald J.

03-10-2005 16:29:28




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 Re: Hmmm... in reply to Eddie in MI, 03-10-2005 10:31:56  
Metric Phillips are common parts in electronics made in Japan, Taiwan, and other western Pacific rim countries. Some of the screws in a typical PC box are metric Phillips, some are American Phillips.

They are easily stripped with American Phillips screw drivers. Been there, done that way too often. They are usually on metric screws. They have a little dimple about the size of a period on the head somewhere. They are also known as ISO Phillips. I have a set of Japanese (made for local use, not for export) Phillips and they fit the metric Phillips without rattle. A friend that was running radios on ships traveling around the world a few years back bought them for me. I'm careful to not wear them out.

I have seen ISO Phillips in the Jensen Tools catalog at a fairly high price.

Its possible that the pressure you put on the Pozidrive bits cut some matching notches in your Phillips screws. Generally Pozidrive bits don't fit Phillips screws tightly. Nor do Phillips bits fit Pozidrive screws tightly. When they fit right the screws and drivers don't rattle, and the screws stick to the bits well. When they are mixed, the screw heads generally suffer, sometimes ending up with round divots.

Gerald J.

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