Screwing and pilot holes
Fuoleum
I'm laying some oak floorboards so I will have to drill pilots for my
screws (OK so far!).
Problem is I don't have any tools for the job so I need to know what to
buy. If I get 3.5mm screws, does that mean I need to drill a 3.5mm
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 much
--
Fuoleum
Phil Anthropist
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.
Lobster
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
TheScullster
"Fuoleum" wrote
> Problem is I don't have any tools for the job so I need to know what to
> buy. If I get 3.5mm screws, does that mean I need to drill a 3.5mm
> pilot hole, or a smaller one?
>
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
meow...@care2.com
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
nightjar
"Fuoleum" <Fuoleum...@diybanter.com> wrote in message
news:Fuoleum...@diybanter.com...
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
d...@gglz.com
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:
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=100089&ts=72295&id=11092
- but this is hard work, and they may cause black "iron stains" in oak
if they get damp.
The easiest/simplest thing to use is:
http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=72483&id=12110
Pilot drill the oak at slightly less than the screw size, screw it
straight into the softwood joist - but these will leave a very modern
looking screwhead exposed.
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:
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=102076&ts=72941&id=50439
- again, you can hire these.
Whatever you do, practice on some scrap first, and try not to go
through pipes or power cables.
Darryl Bailie
<meow...@care2.com> wrote in message
news:1152172394.4...@j8g2000cwa.googlegroups.com...
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
Lobster
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: http://tinyurl.com/pvxgy (or
<http://www.broadleaf-timber.co.uk/floors/technicalinfo/ftechnicalinfo41.html>)
David
d...@gglz.com
http://www.britishhardwoods.co.uk/flooring/fitting_floor.html
Matt
>
>Or you can use a nailer capable of pushing the nail under the surface:
>http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=102076&ts=72941&id=50439
>- again, you can hire these.
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.
--
Dave Plowman (News)
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.
--
*If you think nobody cares about you, try missing a couple of payments *
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
