30 April 2019 _ PopularMechanics.com/BY ROY BERENDSOHN/↓ASK ROY
30 April 2019 _ PopularMechanics.comCOLUMNSMy daughter
asked me why
nails bend, and
I was stumped.
What should I
tell her?
Aaron T., Bowling Green, KentuckyThat’s a good question, and kind
of a tough one to simplify. Nails
bend when they’re not struck
square on the head. How much
they bend depends on two factors. The first
is the slenderness ratio. That’s the length
of the nail relative to its diameter. When
there’s more nail sticking out of the wood,
the slenderness ratio is higher, and it’s
more likely to bend when you hit it with
your hammer. It might help for her to
picture a soda straw. A long straw bends
easily, and a short one does not.
The other factor to consider is the stiff-
ness of the material used to make the nail.
If a nail isn’t very stiff, it’s going to bend
easily, whereas stiff nails, such as the ones
made from high-carbon steel, resist the
bend of an errant hammer blow. But at
a certain point, stiffness becomes a bad
thing. Nails that are too stiff are brittle.
They break instead of bending. The best
I’ve found are from Maze, an American
manufacturer that makes its nails out
of a tough, but not brittle, form of high-
carbon steel. Maze even has a fitting
slogan: “Put an end to the bend.”
Send your home and yard questions to:
[email protected]
@askroypm
I painted some pine,
and something that
looks like rust is
showing through
the paint. Why?
Rod C., Mamaroneck, New York
It sounds like extractive bleeding. Extractives are nat-
urally occurring chemicals that are locked in the wood
grain until a solvent extracts them. The solvent may be
as simple as water or it may be more complex, like a lco-
hol or a petroleum-based chemical. The solvent washes
the extractive out of the wood and it floats to the sur-
face, where it is redeposited after the solvent evaporates.
You’re going to want to use a stain-blocking primer.
These paints do one of two things: They loosen and
dissolve the extractive and then trap it inside the paint
film, or they seal over the existing extractive stain.
If the paint you applied is slightly glossy, sand it
lightly. Remove the sanding dust, apply the stain-
blocking primer, and then add a top coat with your
desired paint.Is a thin concrete
overlay a durable
way to finish
your driveway?
Chris R., Easton, Maryland
There’s no reason that an overlay
would be any less durable than ordi-
nary concrete. But here’s the thing:
The material has to be applied over
structurally sound concrete. Apply-
ing a concrete topping to a ruined
slab is like painting over rot ted wood. It won’t ta ke long
for either surface to look lousy. If the original concrete
is badly cracked or has areas that have deeply settled,
you’re better off tearing it out and starting over.
Also, your surface preparation has to be meticu-
lous. The entire surface needs to be pressure- washed
with a minimum of 3,000 psi to remove dirt, mildew,
algae, dust, masonry stain, and paint. Grease spots left
from parked cars, tire marks, and all flaking and dusty
concrete has to be removed, too. This may also involve
chemical cleaning with masonry acids and degreasers,
and wire brushing, either by hand or with power tools.
Anything that will prevent the overlay from bonding
has to be removed.