Rockwell mentions, in the passage quoted by Pete above, that you are supposed to drill clearance holes in the battens (not pilot holes). So far as I know, a clearance hole is one which permits the screw thread to pass through. That is, you do not let the screw thread bite into the batten material. The batten is held in place by the screw heads. Joe explained that there is a mechanical reason why it is undesirable for the thread to bite into the batten.
Make The Space – Sunday 20th December 2015
Yes, that was never in question, but surely not 8mm holes?
It comes down to what is an acceptable fixing method.
A hole big enough to push a wall plug through is also big enough to pull a wall plug back through, and would only be considered a secure fixing with plugs designed to be used that way.
My understanding is that these plugs aren’t. I wish they were, as it would hurry things up no end. Which is why I suggested another check with Rockwell. Just in case we got it wrong last time.
I am not sure I understand the relevance of that. After all, the batten does not keep the plug in the wall, rather the plug keeps the batten on the wall. If the plug could fall out through the hole in the batten, it is not fixed into the wall properly and is offering no support regardless of the size of the clearance hole in the batten.
The only question to my mind is whether the heads of the provided screws provide adequate security with an 8mm clearance hole in the batten. From grabbing the battens in place, they would seem to be secure.
The long and the short: I think we’re okay. It would be worth checking with Rockwell to be sure.
It stands to sensible reasons that a plug that needs a 8mm hole to comfortably enter, will need more than an 8mm hole to get back out, the point of plugs being to expand In the hole within which they fit.
Tl; Dr, check with Rockwell that 8mm is the sensible hole to put the plugs in. We worked that out by trial / error (and I’d be happy to carry on like that) but if there’s regs, there’s regs. We should do the right thing.
Yes. you’re right, of course!
There was just something nagging about this and I didn’t have time to think it through at a distance…
If it works and the screw head is big enough then it’s all good. If it was a timber batten the screw would likely pull through a hole this size…it’s not timber though. So we may have found a major advantage in using this expensive material. Clear guidance from Rockwell would have helped!
8mm still sounds big. But same again: if it’s the smallest drill that works, it must be the right one.
Well, a bunch of SDS bits and chisels just arrived on my desk. I’ll try and swing by the space with them before Xmas…
I think 8mm is sensible in the wall given that the plugs are solidly in the brick. We should rather ask whether it is also a sensibly-sized clearance hole in the batten with the provided screws. It would seem fine to me, given that the battens already in place seem very firm with them (although we did not use this method with the first one that we put in, which is the northwest-most batten, nearest the kitchen).
Also, I do not think it is an especially important point, given the function of the plugs, but Pete and I could not push the plugs through the battens into the wall, rather we had to pull the batten back away from the wall to get the plug in the hole we had just made.