Am I correct in saying that the rawlbolt specification screwfix use is
( thread x maximum fixture size), e.g. M12 x 60 can fix 60mm thick
fixture. It looks like that from the pictures. The B&Q ones appear to
be (thread x length of bolt) and the back of the pack tells you the
fixture size - since the bolt is usually 50mm, in B&Q, M12 x 110 is
needed for a 60mm fixture.
Does this sound correct ?
(Good news: a local screwfix counter has just opened (Nuneaton))
it's the fixture thickness in Rawlbolt specs.
If you are looking at these kind of fixings, then I've found that
injection fixings are a much better solution.
- There is not the issue of the fixing not gripping properly if the
hole is not quite right or the material a little crumbly
- You can have whatever length you like
- *Very* sturdy fitting.
I gues this is resin and threaded studs.
Re screwfix rawlbolts, any guidelines to the size of hole used with a
certain thread i.e. is it always for example 4mm more than the thread,
so M12 would need a 16mm hole ?
Exactly. Holes for these are always bolt size + 2mm and it's non
critical within reason.
It varies. There are charts on the Rawlplug web site showing that for
Rawlbolts, the hole is 0.5 to 2mm more than bolt size. I found it to
be fairly critical which is one reason I don't use them any more.
Slightly too big and the fitting grip is weakened a lot.
Screwfix do an own brand zinc plated type.
Fischer do passivated ones similar to the yellow appearance of
Rawlbolts - also available from Screwfix.
They also do stainless steel if you want that.
All are in various lengths and sizes, or you can even buy 1 metre
lengths of rod and cut it - frankly I can't be bothered. There are
nuts and washers with the packs.
For resin, I started using the Fischer type with the screw in base that
has a mix of plain resin and resin with mortar. e.g. Screwfix 80157.
These are quite viable for small to medium projects.
I then had a project where I needed to fit over 200 fixings. At that
point, I invested in one of Fischer's special purpose guns (Screwfix
35237). The cartridges for this are about half the price of the screw
base ones, so it was worth it.
There are also resin sleeves. These are used if you are fixing into a
hollow block or a brick with holes through the centre. They retain
the resin around the stud.
The important thing is to make sure that the hole is clean of dust.
Needless to say, Fischer sell some gizmos to do this. I found that
a vacuum cleaner and/or an air jet is perfectly adequate.