Thread: Removing screws under wooden plugs

Is there any chance of people just agreeing to disagree on this ?
cheers
AJ

It's not a matter of agreeing or disagreeing, it's a matter of tight, not quite tight or slightly stripped.

Originally Posted by PAR

It's not a matter of agreeing or disagreeing, it's a matter of tight, not quite tight or slightly stripped.

If it is not practical to use a torque wrench on each screw (and it's not) , you will not be able to seat the screw perfectly simply by feel, every time , so , if the screws are just below surface level , it is advisable to align the slot with the grain . The reason is both cosmetic and functional. If the screws are to be covered with a plug, there seems to be no reason to align the slot. ....still, without using a torque wrench on every screw it is impossible to be sure that each screw is tightened to the correct torque , better to give each screw an extra tweak , to make sure.....or have the torque wrench on hand at all times !........

No one has ever suggested using a torque wrench. Again there is "home", under tight and partly stripping. In some softwoods or with the use of especially aggressive threads, like those found on bugle headed deck and drywall screws, yes you can drive the head right down with little worry about stripping or even a pilot hole for that matter, but this is also as wrong as over or under tightening a fastener. The bottom line is a fastener has a point where it's head, regardless of the type, lands on the surface. This is easily noticed because a dramatic increase in torque is required to drive it further (softwoods) or the actual threads begin to strip.

Look I'm talking about doing it (all of it) right, which means a clearance and a pilot hole are predrilled. In softwood this isn't always done, though it should be, but in reasonably dense hardwood, you don't have a choice, other wise you'll split or crack the wood or can't drive the screw. When the head bottoms in the counter sink or on the surface, that's it, it's done and no additional tightening or loosening is required, for any reason, including under putty (no one has yet to explain why it's needed to be with the grain). This under putty thing, is purely a left over from a day when everyone used rosin based putties, which very few still use. I still use it very occasionally (once or twice a year) and have a cast iron skillet hanging on the shop wall with several ounces in it, waiting for the next time I need some. I've removed countless tens of thousands of putty covered fasteners and never has the slot orientation caused any issue that couldn't be attributed to something else. Since the invention of cross point and other drive arrangements on fasteners, slots have all but gone the way of the Dodo bird anyway.

I've heard all sorts of silliness about this old wives tail, how the horizontal slot helps hold the putty in (they don't know chemistry apparently), it's permits the dent to orient with the grain lines, so it's less objectionable, etc., etc., etc. Again, after 30+ years of removing every screw and fastener imaginable on every type of boat, never has the slot orientation been more then wishful thinking. Nor has anyone been able to substantiate the claim with physics or chemistry. I'm a double engineer and if you can't explain why something should be done one way or the other, then I'm usually not going to buy into wives tails.

should have stayed shut up...
for the record, I agree with you PAR.
It's just that sometimes, the WWW simply isn't more than a discussion tool.
Certainly not an effective place to challenge long-held beliefs.
Desiderata & all that...
cheers
AJ

Well, I for one found the whole back 'n forth quite fascinating. I'm not a boat person at all. Know nothing about building or restoring them. But clocking the screws was something I was taught by my original mentor.
I never really gave it any thought, just did it because that was how I was taught.
I did always assume it was a purely aesthetic thing and never really considered the engineering behind it.
I thank both of you for challenging my thinking.

Hmm.. quite a bit of polarity in this debate.

Problem is that there is a lot more to the issue than has been expressed. It is not just a case of "screw head bottoms" followed by "now the thread strips". Quite a few variables involved, including how compressable & elastic the wood, surface area of the head vs total surface area of the threads, ductility of the screw, angle of countersink (if any) vs angle of screw head etc etc. etc. Experience will show that in many (if not most) timbers, the head will simply pull into the timber, rather than the thread stripping out. I suspect there is likely to be some deformation of the timber against the thread, but this does not necessarily constitute "stripping".

A maximum of a quarter turn in most timber, using a typical countersing head, is unlikely to do any stripping of threads. It is likely to pull the head a fraction deeper into the timber. Is this a problem? Probably not in most cases.

If you have a big washer under the screw (e.g. a butt hinge) & a very short screw, you might start to strip the timber. Using a longer screw, you might also start to stretch the screw.

Using cheap screw made (e.g. Bunnings stuff) I have, on occasion, managed to break the heads off by over tightening in hardwood- no thread stripping in evidence. I have also, once, managed to torque the head off a 12mm coach bolt! Again, no sign of the threads stripping & pulling out of the timber.

Bottom line - I don't think that a maximum quarter turn tighter will have any material effect on strength in most applications.. But be carefull with short screw, or where the screw head can't pull into the wood. I do agree - not such a good idea to loosen the screw to align it.

Originally Posted by PAR

No one has ever suggested using a torque wrench. Again there is "home", under tight and partly stripping. In some softwoods or with the use of especially aggressive threads, like those found on bugle headed deck and drywall screws, yes you can drive the head right down with little worry about stripping or even a pilot hole for that matter, but this is also as wrong as over or under tightening a fastener. The bottom line is a fastener has a point where it's head, regardless of the type, lands on the surface. This is easily noticed because a dramatic increase in torque is required to drive it further (softwoods) or the actual threads begin to strip.

Look I'm talking about doing it (all of it) right, which means a clearance and a pilot hole are predrilled. In softwood this isn't always done, though it should be, but in reasonably dense hardwood, you don't have a choice, other wise you'll split or crack the wood or can't drive the screw. When the head bottoms in the counter sink or on the surface, that's it, it's done and no additional tightening or loosening is required, for any reason, including under putty (no one has yet to explain why it's needed to be with the grain). This under putty thing, is purely a left over from a day when everyone used rosin based putties, which very few still use. I still use it very occasionally (once or twice a year) and have a cast iron skillet hanging on the shop wall with several ounces in it, waiting for the next time I need some. I've removed countless tens of thousands of putty covered fasteners and never has the slot orientation caused any issue that couldn't be attributed to something else. Since the invention of cross point and other drive arrangements on fasteners, slots have all but gone the way of the Dodo bird anyway.

I've heard all sorts of silliness about this old wives tail, how the horizontal slot helps hold the putty in (they don't know chemistry apparently), it's permits the dent to orient with the grain lines, so it's less objectionable, etc., etc., etc. Again, after 30+ years of removing every screw and fastener imaginable on every type of boat, never has the slot orientation been more then wishful thinking. Nor has anyone been able to substantiate the claim with physics or chemistry. I'm a double engineer and if you can't explain why something should be done one way or the other, then I'm usually not going to buy into wives tails.

...you don't like to be questioned apparently Par....in that case we shall agree to disagree.......being a double engineer , you should realise that I have as much chance of proving you incorrect , as you have of proving me wrong !