Stainless steel from china...
RUST ALERT!!!
Non-metric screw size
- Thread starter DiyNutJob
- Start date
RUST ALERT!!!
But he said the screws say "top quality" on the box. 
How long for the rust to appear? My direct from china SS roller door catch still looks brand new after a couple months of installation. It is exposed to the exterior because of a big gap in the front door I have yet to fix.
Here, first words are "Top quality". I am guessing you find what I say funny because you don't buy top quality screws much.But he said the screws say "top quality" on the box.
Goldscrew PZ Double-Countersunk Multipurpose Screws 4 x 40mm 200 Pack
Order online at Screwfix.com. Top quality, waxed single thread, multipurpose screw. Popular with the professional. Features a lower screw-in torque and faster drive speed. Suitable for screwdrivers, combi drills and impact drivers. FREE next day delivery available, free collection in 5 minutes.
www.screwfix.com
(4-3.8501) / 4 = 3.75%.
Don't know, but having more time to waste on trivial things I made a little experiment a few years ago.
Took different brand screws and left them outside for roughly 12 months.
Results:
Turbo Silver/Gold by screwfix (no rust at all,not even superficial)
Reisser (no rust at all)
Wickes galvanised (surprisingly some were very corroded, others just superficially rusted)
Toolstation galvanised (superficial rust, especially on heads)
Ultra screws stainless steel from screwfix (like new)
Stainless steel screws from Toolstation (even better than the Ultra because they have a polished finish)
Random stainless steel self tapping screws from ebay (rusted all over superficially and some corroded at the thread)
I had bought these last one to replace some on a metal shed.
I replaced them again.
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Deleted member 174758
Man, I bet you are the life and soul of the kitchen at parties!Just for the giggles
A 100 pack of Turbodrive 4 x 40mm screws.
Random sample of 20 screws.
Measured with an uncalibrated digital caliper.
I have in front of me four screw boxes from Reisser, Spax, ForgeFast and Tite-Fix, yet none of these say "top quality". Have I been sold a pup (or rather four pups?). The Reisser and Spax both state "high peformance", the ForgeFast states "elite performance" and "low torque", whilst the Exterior-Tite states "allows easier insertion and less battery wear". TBH those are all truthful descriptions, but not one claims to be "top quality", which is surely a meaningless description, but beloved of certain Far East manufacturers? BTW the Spax and Reisser screws stand up a lot better to be driven and removed multiple times than any other screws I've ever used and I'm yet to have one snap off on me
Are you gonna use some sealant?
There's time and place for everything. For door gaps, stick on seals are fine. I have got a good supply of those from china. These are more sticky than the local ones I had. China uses american tech.
Despite all the scary stories, I have faith in ebay/china SS. I have some ebay marine grade SS nuts and bolts holding up a fence post for a few years, no problems.
Superficial rust is good performance. The rust on the thread was probably contamination from the shed metal.
Since I am not into mindless torqueing, no ordinary screws would snap. I had house builder screws snapping from their over torqueing.
Not quite, although yes, I should have been more specific.
saying that these screws have a manufacturing variance of ±1%, may have been more appropriate.
There will always be manufacturing tolerances when creating screws.
As a 4mm thread diameter is the absolute maximum allowable width, for a 4mm screw - accounting for this tolerance will mean the thread diameter (in this case) will be at least 1% smaller, plus a safety margin.
Standards for wood screws are a bit difficult to find
- But, just for example, here are some standards under DIN 7998:With an allowable thread diameter of 3.75 to 4mm for a 4mm screw.
....so, I am guessing my screws have a manufacturing tolerance of ±1% with a design offset of 0.112mm (or 2.8%,
....or 1.8% safety margin with 1% manufacturing variance).
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Deleted member 174758
What utter nonesense! You select the screws which are appropriate to the task. If your builders snapped screws it is just as likely to be that you chose some cheapskate bunch who didn't know the difference between a 4in screw and a ring nail, or maybe they were just using your cheap and nasty "ordinary" Chinese screws? Any competent tradesman knows the difference between screw qualities and like it or not, at the speeds tradesmen need to work, tools like impact drivers and appropriate quality screws are a must for some tasks
And just what do you mean by "ordinary screws"? There is no such thing. I've had cheap stainless and brass screws (the type supplied with some ironmongery) snap when being hand screwed into pilot holes in hardwood before now. That is much more down to poor quality screw materials than me having muscles like Garth (for anyone not old enough look up the cartoon chatacter)
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Deleted member 174758
The Construction Information Service (a UK service for architects, specifiers and builders) suggest that BS 1210 (1963), ‘Specification for Wood Screws’ is ‘obsolescent but still relevant’ when specifying screws. This standard specifies that construction screws have a minimum tensile strength of 550N/mm² and apparently British manufacturers work to this or a higher standard, such as the newer BS 1580 (2007). German manufacturers work to similar standards.
Apparently, if the standard is met it should be more than possible to drive a 5.0 x 100mm (#10 x 4in) wood screw into dry C16 timber using a 150Nm impact driver providing the tool and tooling are in good order and the screw is being driven perpendicular to the wood. So if you are snapping screws, throw away the cheap carp and get better screws... because cheap screws won't drive without some failures
Apparently, if the standard is met it should be more than possible to drive a 5.0 x 100mm (#10 x 4in) wood screw into dry C16 timber using a 150Nm impact driver providing the tool and tooling are in good order and the screw is being driven perpendicular to the wood. So if you are snapping screws, throw away the cheap carp and get better screws... because cheap screws won't drive without some failures