scooby
Established Member
When I got my Senco drywall driver about 20 years ago, I bought a box of timber screws with square drives. Think I bought them as a curiosity as I've still got the almost full box.
Confused about screws
- Thread starter civvywood
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Thats the way engineering has gone, to much freedom of choice has been given to designers rather than the tried and tested parts bin approach that maintained some control over types, without it so much machinery and vehicles could potentially have had every size and type of fastener available to mankind used somewhere just because all the engineers had their preference.
I think they are called a Robinson drive, used on Kreg pocket hole screws and require good location and angle of drive otherwise they do slip and drivebit jumps out.
JobandKnock
Amateur curmudgeon
You get square drive screws quite a bit in collated flooring (wood) screws. AFAIK they are square drives, not Robertsons. When driving into dense plywood or chipboard they pick up.the screws more cleanly and drive in better than the Pozi screws we can get, but then that is a true straight drive application with no cam out
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TheTiddles
Established Member
Robertson drive is about 115 years old, one of the main reasons it’s not used more is due to Mr Robertson’s desire to not licence his design out to other manufacturers, having been stung once, which allowed other deigns to take large contracts in new mass produced items and in markets outside Canada.
Slavish dedication to one head type can leave you paying a lot of money for a particular fastener when another configuration is cheaper and more available, bits are cheap and since the invention of the computer managing lots of things has presented less of a problem. A single fastener type on your rifle to allow front-line servicing is sensible, other people usually have more than one screwdriver to hand, sometimes three or more.
Slavish dedication to one head type can leave you paying a lot of money for a particular fastener when another configuration is cheaper and more available, bits are cheap and since the invention of the computer managing lots of things has presented less of a problem. A single fastener type on your rifle to allow front-line servicing is sensible, other people usually have more than one screwdriver to hand, sometimes three or more.
scooby
Established Member
Yeah, that's them. I added them to an order of drywall screws when I got the driver. I've done quite of a bit of chipboard flooring since I got the driver but I always just used an impact driver. I bought the Senco as I used to do all the boarding and my mate would plaster. He does all the boarding now, so sold it last year. Still got that damn box of screws in the garage though somewhere.
Vann
Established Member
They will cam out, but they're not as fussy as ps/pz, and can take more angle misalignment.
I can never remember if they're Robinson or Robertson (the latter I think), so they're square drive to me.
Cheers, Vann.
Jonm
Established Member
With regard to Phillips vs pozi, my understanding is that Phillips were developed to be used on assembly lines with power screwdrivers in the early 1930’s. I think this would generally be working with metal, tapped threads etc. At the time most power screw drivers did not have a torque limiter so the screw head was designed so that at high torque the bit would force its way out of the screw head, rather than break the screw (cam out).
When torque limiters came along the “cam out” function was not required, better to have a design where the bit stayed in the screw head, then tighten the screw to the correct torque using the torque setting on the screw gun. Hence pozi drive, hex, torx etc.
I may be incorrect in the above, if so I am sure someone will tell me.
When torque limiters came along the “cam out” function was not required, better to have a design where the bit stayed in the screw head, then tighten the screw to the correct torque using the torque setting on the screw gun. Hence pozi drive, hex, torx etc.
I may be incorrect in the above, if so I am sure someone will tell me.
MorrisWoodman12
Established Member
Slightly off topic though with strong connotations. Using screws which are self drilling causes some users grief because they don't clamp the two parts being joined up tight. The screw cuts it's own thread into both parts so they cannot be pulled together. So either clamp tightly before screwing or drill a clearance hole in the first part so that the screw is able to pull the joint together tightly.
This was why cross head screws were developed, I think principally for use in car production initially. I agree that Torx is definitely the best but to be fair if your bits are in decent condition then cam out shouldn't really be a big issue with Pozi, unless they are very tight. If you need to remove pozi screws and suspect they may be an issue, rust etc, then always use a manual driver to start them off, you can feel if they are starting to slip.
civvywood
New member
Thanks everyone for your replies, I didn't know a thread about screws could be so interesting and useful LOL.
I ended up buying some Goldscrew Plus PZ from Screwfix in the sizes I need and will buy other sizes as and when.
I ended up buying some Goldscrew Plus PZ from Screwfix in the sizes I need and will buy other sizes as and when.
Woody2Shoes
Impressive Member
I would say that - intuitively - this doesn't seem right. Cam out is an uncontrolled process - when the drive bit slips out of position in the screw head - and there is often damage to screw head, drive bit, and sometimes other parts of the workpiece. I can't think of a situation where cam out is a good thing, and it seems to me that all these different shapes are efforts to reduce it.
J-G
Established Member
Not quite - specifically the Supadriv rather than Pozidriv was to improve the 'accessability' - regarding alignment of driver and socket/recess - many others were/are ways to promote/circumvent proprietry design and yet others are based upon security issues.
AFFF
Established Member
All the above posts offer good advice. I personally avoid using phillips as they are designed to "cam out" at set torque loads. Pozi drive heads are much more secure. If you want a screw thats almost impossible to rip the head on then torx are brilliant. Interestingly there is another type of cross head screw that often turns up in japanese and far eastern engineering - JIS (japanese industry standard) it looks very similar to phillips but the slots are narrower. Found a lot on japanese motorbikes. Don't try to use a phillips driver on these, you will wreck the head. Its worth having at least one JIS driver in your toolbox just incase you come across one that you want to remove.
Another bit of advice especially when driving screws into hardwood is to drill a pilot hole (as mentioned) but also to lubricate the screw. You can buy specific lubricants to do this but I just use petroleum jelly. Only needs a little dab on the tip of the screw but makes driving so much easier.
Brass screws have a really bad tendency to get ripped heads. A good trick is to buy some steel screws of the same size and use these first to secure the hinge/fitting etc. Then take them out and replace with the brass ones - the heads don't get ripped
Another bit of advice especially when driving screws into hardwood is to drill a pilot hole (as mentioned) but also to lubricate the screw. You can buy specific lubricants to do this but I just use petroleum jelly. Only needs a little dab on the tip of the screw but makes driving so much easier.
Brass screws have a really bad tendency to get ripped heads. A good trick is to buy some steel screws of the same size and use these first to secure the hinge/fitting etc. Then take them out and replace with the brass ones - the heads don't get ripped
guineafowl21
Established Member
According to James May(!), the Philips head was developed for production lines, and designed to cam out at a specified torque.
Most of the tools I have seen on production lines are set to the right torque so no cam out, not good if the screws are a nice matt black.
Jonm
Established Member
I had a further look at this, apparently the original patent did not refer to “cam out” or “throw out” and opinions vary as to whether it was a design feature to prevent damage to expensive components and delays removing snapped screws or an advertising ploy to justify a design flaw.
There was an improved version of the phillips screw patented in 1942
https://pdfpiw.uspto.gov/.piw?PageN...1=2474994.PN.%26OS=PN/2474994%26RS=PN/2474994
I include an extract in the attached photo and that clearly states that “throw out” is a design feature and the reasons why. On the left of the page there are toggles to take you to the front cover which gives dates, title and refers to Phillips screw head.
Apparently henry ford adopted phillips screws, (apparently robertson would not sell his patent to ford) hence their popularity.
If cam out is an advertising ploy it is still being used, here is an aircraft industry supplier advert
https://eumro.co.uk/zephyr-phillips-screwdriver-bits.aspx
JobandKnock
Amateur curmudgeon
In constructuon one of the best known uses of Phillips screws is for drywall fixing - task for which collated screwguns are used which use the cam out/throw out feature when a specific depth is reached
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JobandKnock
Amateur curmudgeon
Japanese power tools use them quite a bit, in particular Makita, but also Hitachi/Hikoki. Worth having at least a JIS size 2 to deal with them (sold on Amazon, etc)
AES
Established Member
Interesting thread this. I have a couple of comments re the above Jonm:
1. After over 50 years in aviation (military and large civil - 20 pax and up, mainly but not exclusively maintenance), I have "almost never" seen PH heads used (and definitely never re the square drive Robertson - also a claim sometimes made for those - IMO - horrible things)!
2. MAYBE in "light/sports/general aviation" aeroplanes but not on big-uns IME;
3. If you read the EUMRO text above, it "smacks" of America and not "English English". For example I've NEVER heard of "cam out" being called "throw-out" in English, and in line 5 of the blurb, one reads "most" and not almost, which is what yer average English speaker would write. Just saying that EUMRO is clearly a supplier and NOT a manufacturer (of tools or fasteners it seems) so I think they're pushing some US stuff. Not necessarily a bad thing at all, but not "standard English practice" either in my experience - even though most big commercial aircraft (apart from Airbus) come from N. America these days;
4. Still re EUMRO, IME, maintainers aren't so interested in cam out damaging the screwdriver/bit, but definitely about bloody great scratches on aircraft skins (skins are, generally speaking, depending on exactly where they are, are an integral part of the whole load-bearing structure. Scratches in load-bearing skins are generally speaking NOT to be tolerated at all.
Not saying any of the above is all definitely wrong Jonm, but definitely doesn't jibe with my own experience.
P.S. There's a member here "Inspector" who if I remember is a Canadian working/has worked in aviation. I wonder what his take is on the above - especially "cam-out" v "throw-out"?
But separately, isn't it "interesting" that so many of us have our own opinions "prejudices" (?) re screw heads? (Personally - Robertson? I hate the bloody things and only use them because of my Kreg Pocket Hole jig)!
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