I'm laying some oak floorboards so I will have to drill pilots for m
screws (OK so far!).
Problem is I don't have any tools for the job so I need to know what t buy. If I get 3.5mm screws, does that mean I need to drill a 3.5m pilot hole, or a smaller one?
I'd just have a go if I had loads of drill bits, but I don't!
Thanks very muc
-- Fuoleum
I don't know whether the 3.5mm refers to the diameter of the screw shaft (un-threaded part) or not; if it does then a 3.5mm drill bit for the floorboard pilot might be too big. I would try a 3.2 or 3mm drill bit first. The drill bit for the un-threaded part of the screw, which will mostly be in the floor board, needs to be a similar diameter to the un-threaded part of the screw, to allow you to sink the screws fully home without chewing up the screw head or being too slack. But the drill bit for the threaded part of the screw, which will mostly be in the floor joist, needs to be a smaller diameter than the threaded part of the screw, to ensure that the screw thread bites into the joist enough to fix the floorboards firmly in place. Try a 2mm drill bit, but if too tight then try a 2.5mm. Presumably you are using countersink screws so will also need a countersink drill bit. You might want to consider precautions to prevents creaks.
It's kind of "suck it and see" - depends on exactly which type of screws you're using (there are very many) plus the type of wood, and its moisture content.
However, if you have to buy a drill, chances are it may come with a selection of drill bits; even if it doesn't, you can buy a whole set for just a few quid. (if you can afford oak floorboards I'm sure that isn't going to blow your budget!
David
"Fuoleum" wrote
From your questions, it would appear you are a relative newbie to the DIY lark! One piece of advice that most in this group will give you - don't buy the cheapest. This goes for drills, drill bits and screws as well (or any other tools come to that).
I inherited most of my drills and have an ageing B&D drill so can't advise on good current makes, but I'm sure someone will oblige.
Phil
The best answer is to find a proper tool shop or traditional ironmongers, take a screw in with you and ask for the drills you need. However...
Oak contains tannin, which rusts steel and causes blackening of the oak around steel fixings, so use you should use stainless steel or brass screws. The problem with these is that, particularly with brass, it is easier to shear the screw, so the hole through the oak (the clearance hole) needs to be large enough to allow the screw to slide freely in it. With a softwood, the clearance hole would be slightly smaller, but oak will not give as much and the screw will bind in an undersize hole. I have seen as much a millimetre clearance suggested for oak, but for 3.5mm screws, I would use a
4mm wood drill for the clearance hole. However, I would probably use a larger screw than a No 6 in the first place, probably about a No10 (5mm) for brass, in a 5.5mm hole.You will also need a 90 degree countersink. The screw will not pull down into oak, as it will with some woods, so you need to create the recess for the head. You can get one that fits to the wood drill, allowing you to drill and countersink in one go. More work, but a much nicer finish, is to use a pair of special tools, one of which counterbores the hole (i.e. produces a flat-bottomed hole large enough to take the screw head - use round head screws in this case) while the other is used to cut wood plugs from a matching piece of oak. The wood plugs are fitted after the screw, hiding the heads and, if you match the wood and grain direction properly, are almost invisible after sanding.
Finally, you will need a drill for the pilot hole, which is the one that you make in the wood you are screwing into. If the wood you are screwing into is a hardwood, you would use a 2.4mm drill for a 3.5mm screw or 3.5mm drill for a 5mm screw. If it is softwood, use a 2mm drill for the 3.5mm screw or a
2.8mm drill for a 5mm screw. A light application of soap to the thread helps to make it easier to screw in.Colin Bignell
I thought I had a table somewhere for these things, but cant find it. Generally speaking, softwood pilot holes should be about the width of the central solid bit of the screw, hardwood pilots should be a fraction bigger. Clearance holes, its obvious enough what size those need to be. If you have an angle grinder you can get a long bit and grind it so it drills both holes in one, clearance and pilot. And with a bit more work, countersink too. This is well worth doing if youve got a lot of holes to do, and it sounds like you have. Dont be tempted to buy those drill & countersink in one things from screwfix, theyre as much use as a dead rat.
NT
Things we need to know:
What kind of screws you want to use. What kind of visual effect you want on the finished boards (screw heads showing etc) What your screwing the boards to (softwood joists?) How thick the boards are
Trditionally, cut clasp nails would have been used:
The easiest/simplest thing to use is:
However there are "secret nail" systems that will insert the nail in a way that ensures it won't be visible - you can get these from tool hire shops.
Or you can use a nailer capable of pushing the nail under the surface:
Whatever you do, practice on some scrap first, and try not to go through pipes or power cables.
The British Standard states that pilot holes should be between 0.4 and 0.6 times the diameter of the shank depending on density. The table referred to above is probably the one from the Timber Designers manual which gives a
2.1mm diameter pilot hole for a 3.4mm ordinary screw in hardwood, the pilot hole should be 4mm shallower than the embedment of the screw.Darryl
Hang on, I'm backtracking having read a couple of other comments! I missed the bigger picture - why are you using screws in the first place? Are your boards tongued and grooved? The usual method of fixing these is 'secret nailing', which means you don't get to see the heads of the nails:
David
A guide to your options:
While the nail can be sunk below the surface a nailer like that is really only suitable for framing purposes, the main reason being there are always indent marks from the nailer foot that are clearly visible from 20 feet away. The nail heads on the Paslode compatible nails are also relatively huge and the nail heads for the smaller Paslode nailer are non existent (they are just brads).
Basically the nails you would preferably use on (cheap) floorboards such as oval or lost head ones aren't available for use with nailers.
As Prescott once said, screwing is best.
You can buy combination bits that do pilot clearance and countersink all in one go. They come in various screw sizes. The twist drill (which does the pilot part) can be replaced separately.
The pilot hole should be 1.0mm smaller than your chosen screw size ie using 3.5mm screws you want a 2.5mm pilot drill you are screwing Down and you want the run out of the scew thread to catch the wood as it pulls it down to the board otherwise the load will be on the scew head and not the scew.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.