Monday, March 15, 2010

Drills and Drivers, Screws and Screwdrivers

I got to thinking about this last night - yesterday I was driving some Phillips head screws using an impact driver - if you haven't had a chance to use one then you don't know what you're missing. I was at a friend's shop when I spotted his Makita driver and asked him about it - wanting to demonstrate, he quickly grabbed the driver and a 4" decking screw, threw a 1" board on top of a 4x4 chunk of pressure treated and drove the screw in just a few seconds, without stopping or doing short bursts (which is what i usually do) - the screw went in like butter. The difference is the super short ratcheting that the impact driver supplies (just like an pneumatic impact wrench) - the clutch for the ratcheting doesn't kick in until the drive feels resistance - then it ups the torque value exponentially (my own Dewalt driver delivers 2700 lbs of torque according to specs). The result is that the screw drives very smoothly and the tip doesn't strip (at least it doesn't if the tip is 'fresh'). Other advantages of these impact drivers: they're lightweight (not needing the other functions of a drill they don't have multiple clutches or mechanisms for drill, hammer, clutch, etc); they have shorter barrels so your hand is closer to the work and they fit in smaller spaces; they have a built in light that shines on what you're driving (many newer screw-guns and drills now have this feature as well). Disadvantages include: you're more apt to break a screw off in your work (extreme torque can work both ways); one can't use these to drill holes very well (the chuck is a locking type for a hex-shaped shaft, that doesn't include any type of Jacobs style gripping action for round drill bits); non-impact bits pretty much disintegrate with use.

Another reason I thought of all this has to do with my having to remove some hinges and latches from some old cabinet doors - these doors had about upteen coats of paint on them so it was quite a task - it was also away from my shop so I was wishing I had a brace with me. Why a brace? One sort of forgotten advantage of the brace is for the amount of torque that can be applied to a slotted screw using a flat-tip screw brace bit. Using a large brace (12" swing), plus with the amount of pressure you can exert on the pad, you can worry off just about any slotted screw - which is what these old hinges had under all the paint. As it was I managed to remove them all but it took much more time than it normally would have had a brace and flat-tip bit been involved.

So last night the thoughts of the day ran through my head and I started thinking about drivers and screws - this naturally (at least for me) got me thinking about different types of screw head-types and what I knew about the flat tip, Phillips and square drive. So this is what I knew (through anecdote, discussion, etc):

  1. The square drive and screw was actually patented by a Canadian named Robertson – thus it’s called the Robertson drive in Canada and it’s ubiquitous in use north of our borders – this drive actually pre-dates the Phillips drive and screw in the US.
  2. The Phillips drive and screw was invented by someone in the US who sold the rights to a company who marketed it under the Phillips name. Initially there wasn’t a good way to manufacture the screw heard (and there are variations with up to 6 or 8 vanes/slots) so the patent pre-dates the actual manufacture by some years. I had also heard that the Phillips bit was developed for the manufacture of airplanes (something to do with the attachment of the aluminum skin – the recessed head discouraged drag and the shape of the slots allowed for the head to “cam out” rather than the screw being over-torqued and the threads being stripped).
  3. According to what I’ve heard, the Phillips screw and drive owes its use in the US to Henry Ford, who wanted to use a product in his vehicles that was patented and owned by a US company rather than one outside our borders.
  4. It’s obvious in retrospect that the Phillips drive is inferior to the Robertson’s drive due to the built-in design (the desire to cam out instead of stripping). Strange that it’s used on everything and has pretty much replaced the slotted screw and driver – well it is easier to register and use than a slotted fastener. But why has it taken so long for the Robertson drive to gain popularity among US users? I first saw the Robertson screw being used by outdoor deck builders – makes sense as the drive head doesn’t strip – the worst thing about a stripped head when building decks is that it takes off the coating that prevents rust – once the head starts to go the coating causes rusty spots that are very un-slightly, in a very short time.
So what of the above is true and what isn’t? Doing a little research it appears that these same stories are found and accepted all over the web. A bit more research will be needed before anything conclusive can be ascertained – however one thing is indeed certain – the Phillips drive and bit for most woodworking is indeed inferior for many reasons.

Next topic: the Monkey Wrench!

-- John

1 comment:

Chuck said...

Robertson head screws are really the easiest to work with for a lot of reasons. I had no idea they weren't common outside of Canada. Thanks for the post.