Best screw head that won't strip

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On Thu, 31 Jul 2014 16:54:55 +0000 (UTC), Larry Blanchard

Torx will do it too - bit not quite as well as the Robertson.
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wrote:

(when, not if!!)
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On Thu, 31 Jul 2014 22:25:50 -0400, snipped-for-privacy@snyder.on.ca wrote:

I find exactly the opposite. Torx (star) are much better. I find the screws aren't nearly precise enough for the Robertson (or "square head recess") to work as well as it should.
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On 8/1/14, 3:45 PM, whit3rd wrote:

I don't get this. Why not push when removing?
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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-MIKE- wrote:

For the same reason you lift your feet when you walk.

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On 8/1/14, 5:20 PM, Bill wrote:

I don't get that either. A screw is a helical ramp, more or less. You turn it to go in and come out. The farther the screw is in, the more friction/resistance there is in both directions. Most often, I find it necessary to push on a screw when removing it, at least until it's a good deal out.
What am I missing?
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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-MIKE- wrote:

Well, I should clarify my remark, since there appears to be at least 2 factors: 1. The friction (between the bottom of the screw head, and the workpiece) that I alluded to. 2. The fact that you are pushing "down" when you wish for the screw to come "up", that has been mentioned.
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Because the objective is to _raise_ the screw. Pusing down on it makes that harder to do and thus requires more torque to raise it. To get more torque without cam-out yout have to push harder, which then requires more torque to raise the screw, which requires you to push harder...
--
Grant



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On 8/1/2014 8:25 PM, Grant Edwards wrote:

Theory aside, when the head is buggered, pushing gets it out, not pushing makes the bit slip. One law of physics out does the other.
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On 8/1/14, 7:25 PM, Grant Edwards wrote:

Yeeeeeeeaaaahh, OK. wow
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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True. But the point is you're better off using a screw head and bit design that minimizes the amount of pushing required -- especially when removing a screw since the pushing is forcing the screw in the "wrong" direction.
--
Grant

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Grant Edwards wrote:

Since the amount that you wish to raise the screw head with a twist of the wrist is very, very, small, I think the effect you describe may be negligible. Of course, the wider the threads, the greater the effect. I could probably design a screw that would be difficult to unscrew by pushing down on it! ; )
Bill
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That doesn't mean pushing down is making it easier (than it would be were a different head chosen up-front).
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On 8/1/2014 10:33 PM, snipped-for-privacy@attt.bizz wrote:

In a perfect world. . .
If you are removing screws above you, you can defy gravity and push "up" to get the screws out.
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On Friday, August 1, 2014 8:12:41 PM UTC-7, Ed Pawlowski wrote:

Yeah, there IS a screw head design that allows you to pull. The screw has a dovetail slot, curved so the driver can be positioned at one edge and rocked into the slot. This scheme is not compatible with magnet-held hex shank bits.
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On Fri, 01 Aug 2014 12:55:57 -0400, snipped-for-privacy@attt.bizz wrote:

I guess there is a difference between the generic "square-drive" now being sold in the USA and the original Canadian Robertson (or Scrulox) screws and screwdrivers. I know I've seen a lot af really crappy square drive screwdrivers recently, and a lot of REALLY crappy screws of all types with Chinese lettering on the boxes.. And the difference between pozi-drive, Reed and Prince (aka Freerson), and Philips screws and drivers causes a LOT of problems because they look so similar but are virtually incompatible.
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wrote:

I smell a scarlet colored fish.
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On Fri, 01 Aug 2014 22:33:16 -0400, snipped-for-privacy@attt.bizz wrote:

Anyone with a torque screw driver want to do a test? Drive several identical screws into severel peices of different woods then read the torque required to remove them with no downward force, and with , say, 5, 10, and 15 lbs of force pressing on the screw and tabulate the results? In both hard wood and soft wood - and using both steel and brass screws. I'd be willing to bet the difference in torque required would be within the limits of the torque required to lift the downward force treating the screw as a simple inclined plane. (in other words, insignificant).
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wrote in message

I think the initial "breaking loose" of the screw to get it to turn requires more down pressure and torque than does the following turns... I think back to the days of working on motorcycles and using an impact driver that was hit with a hammer to break Phillips head screws free as an extreme example. A less extreme example is when I've hit the handle of the screw driver with a hammer as I put rotational force upon it to break the screw free. More typically I push down hard with the screw driver to break the screw free and them use primarily rotational torque to remove them. When using a powered driver (usually my PC drywall driver) with various bits the same dynamic occurs... I need a lot more down pressure to break the screws loose than to remove them.
John
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wrote:

Like I said - a scarlet fish -(red herring)
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