Hammer Drill or Rotary Hammer?
Laser Guidance System
Hammer Drill or Rotary
As the marketing manager for a power tool company, I'm often
asked about the difference between hammer drills and rotary
hammers. Buyers want to know why there's such a price
difference between the two, and which tool is best suited for
I advise users to answer four questions before making the
choice: What material will you usually be drilling? How large
will the holes be? Will you be drilling an occasional hole or
for extended periods? Finally, will you only be drilling, or
would it also be useful to be able to use the tool in chipping,
or hammer-only, mode?
In a hammer
drill, the hammering action is
provided by spinning disks. The toothed disks rotate against
each other, causing the bit to move in and out at more than
40,000 blows per minute.
Although rotary hammersdeliver fewer blows per minute, they
provide about five times the impact force of a hammer drill. A
pneumatic piston powers the striker that transfers impact to
the bit. This design reduces operator fatigue and makes
drilling more efficient. Unlike the more versatile hammer
drill, though, a rotary hammer can't be used for drilling wood
Hammer drills are best thought of as conventional electric
drills with added internal gearing that provides a percussive
action. This rapid in-and-out movement of the bit, combined
with the usual rotation, greatly increases the tool's
efficiency in drilling concrete or other masonry. The hammer
action can be switched off to allow general purpose drilling in
materials like wood or metal.
In addition to allowing the user to choose between
hammer-drill and drill-only modes, most hammer drills feature
two-speed gearing. The higher speed, typically around 2,500
rpm, is best for fast drilling with small-diameter bits; the
lower speed offers better performance with larger bits and
high-torque applications. This flexibility makes the tool a
favorite of mechanical installers and remodelers.
Rotary hammers, on the other hand, are primarily used for
drilling masonry. They typically deliver far fewer blows per
minute (bpm) than hammer drills, but thanks to an internal
pneumatic piston that delivers the impact energy directly to
the bit, each blow is several times as powerful. A hammer drill
is better at making holes in masonry than a conventional drill,
but a rotary hammer is much more efficient than either.
Size of Holes?
Hole size is another important consideration, and this is
reflected in the size and type of chuck provided with each type
of tool. Hammer drills are equipped with standard three-jaw
chucks. As with a conventional drill, the size indicates the
largest shank it will accept. Half-inch hammer drills are most
The nominal size of a rotary hammer, on the other hand, refers
not to the capacity of the chuck, but to the largest hole that
the manufacturer recommends drilling with it. There are three
classes of rotary hammers on the market, each of which uses a
different -- and noninterchangeable -- chuck design.
SDS-plus rotary hammers are
designed for drilling holes from 5/32 inch to 3/4 inch. Because
most masonry drilling falls into that size range, this is the
most popular class of tool. SDS-plus rotary hammers are also
available in cordless versions.
SDS-max hammers are designed
for larger holes, in the 3/8- to 2-inch range.
Spline hammers are similar
to SDS-max hammers in capacity but use a different chuck.
(Because they're similar in function, SDS-max and spline
hammers are often referred to collectively as "combination
In all cases, the recommended maximum hole sizes are for
spiral bits. Going instead to a core bit -- essentially, a hole
saw for concrete -- will let you make a substantially larger
hole, but don't get carried away. Consistently using a rotary
hammer at or near its maximum capacity will shorten its life.
The relatively high failure rates of both SDS-plus rotary
hammers and hammer drills can be traced to the tendency of
users to overwork them.
Size matters.It’s easy to see why an SDS-max
rotary hammer (the red Milwaukee) is the best tool for big
holes and frequent use. The ample size reduces vibration, and
stout motors can turn 2-inch spiral bits. The blue cordless
Makita SDS-plus rotary hammer is handy, but its smaller chuck
and motor are meant only for bits up to 3/4 inch. The 1/2-inch
DeWalt hammer drill is versatile, but drilling in hard concrete
is slow and the conventional chuck isn’t made for heavy
Long- or Short-Term Use?
Choosing the wrong tool can also overwork the user. For a
given bit size and material, it takes more effort and strength
to make a hole with a hammer drill than with a rotary hammer.
This is a matter of weight distribution and leverage: With a
rotary hammer, the heft of the tool itself provides much of the
drilling force; hammer drills are much more dependent on
pressure applied by the operator. This isn't necessarily a
problem for drilling an occasional hole or two, but for heavy
repetitive use, a rotary hammer is the clear winner.
Do You Need Chipping?
Unlike hammer drills, which offer a choice between
rotation-only and hammer-drill modes only, SDS-plus rotary
hammers offer a third option: a hammer-only mode that permits
the use of chisels, pointing tools, and other general purpose
bits. Spline and SDS-max tools drop the rotation-only mode but
allow the user to choose between hammer-drill and hammer-only.
Hammer-only mode is great for tasks like removing tile,
cleaning up concrete forms, and removing brick or stucco. Even
though the rotary hammer won't replace a demolition hammer,
this mode is handy for light demo and greatly increases the
is the marketing manager of industrial
accounts for Bosch Power Tools.
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Laser Guidance Systemby Jeremy Hess
Manufacturers have installed lasers on miter saws for years
now with little professional acceptance. Even carpenters who
are comfortable with technology tend to see lasers only as cool
gadgets; others see them as fragile and gimmicky. I've seen
laser guide systems that promise more than they deliver, but I
also see the potential benefit. Despite previous
less-than-positive experience with laser saw guides, when I saw
an ad for the BladePoint laser (BladePoint, 617/770-4575,
www.bladepoint.com), I decided to give the
technology another chance.
The first aftermarket laser I ever saw was mounted to the
safety guard of a miter saw. It was easy to install and fairly
inexpensive, but also pretty unreliable. Once the blade started
spinning, vibration created a lot of line movement. The laser
also required frequent adjustment because the mounting location
was prone to impact. Even ordinary handling threw it out of
adjustment. Another version, mounted to the back of the saw
table, made lining up the blade on anything other than flat
stock nearly impossible; any profile proud of the surface
obstructed the beam. The BladePoint Laser Guide claims to
eliminate many of these problems.
The 3/8-inch-thick round stainless-steel disk takes the place
of the outer blade washer. Unlike other lasers, this guide can
be used on nearly all 12-inch or smaller circular, miter,
sliding miter, or radial arm saws with a 5/8-inch arbor and a
blade arbor hole smaller than 1 inch. Installation takes less
than a minute. No adjustments are needed because the lens is
recessed into the housing, protecting it from scratches,
breakage, and misalignment.
Installing a BladePoint laser takes
about a minute. The3/
8-inch stainless disk replaces the
blade washer and is held in position by the blade
Once the guide has been installed, the manufacturer recommends
making at least 50 test cuts into various sizes of wood at
different angles. This is necessary because the laser reference
line doesn't exactly coincide with the cut line. The small
fraction of an inch between the laser line and the actual cut
will vary with the saw blade and with whether you're cutting to
the left or right of the pencil mark. Even though eyeballing
the difference between the laser line and the pencil mark
sounds dubious, I found that after about 25 cuts, I had a
pretty good feel for how the laser needed to be lined up with
my pencil marks.
The BladePoint's red line is easy to see
indoors, but visibility outside is a problem. The laser line
falls a fraction of an inch away from the cut line, so it takes
about 25 practice cuts to get a feel for placing the stock on
The BladePoint has no effect on saw operation. The only
difference is that the user can now see a reference line where
the blade is going to pass through the stock. A centrifugal
switch turns the laser on at about 700 rpm, creating a
continuous line across the work piece. The line extends wide
enough to reach across the entire table. The beam makes it easy
for the user to see where the blade will enter, eliminating the
need for "nibble" cuts.
Three watch cells provide power, and the manufacturer claims 8
to 10 hours of operation before battery replacement is
necessary. To prolong battery life, the laser is activated only
when the blade is turning.
Three watch batteries power the
The BladePoint laser's biggest limitation is its poor outdoor
visibility. It's hard to see even in partial shade, and in
direct sunlight it's practically invisible. I didn't have a
problem indoors, but if you do a lot of cutting outside, keep
this in mind. Even so, and despite the $150 price tag, I'm
quite happy with the BladePoint. Now that I've had it on my saw
for a few weeks, I wouldn't want to be without it, especially
for interior trim work.
is a carpenter with D.E.R. Construction
in Bainbridge, Pa.
Snapped in Ink
Snapping chalk lines in wet or damp weather is typically an
exercise in frustration. Chalk sticks to the line without
leaving a mark, and the wet string inevitably tangles inside
the case. Another problem with chalk is fat, fuzzy lines that
smudge easily or simply wash away. Promising better performance
in wet weather and crisp, distinct lines, Tajima's new
Ink-Rite, an ink-based snap line, uses a waterproof,
quick-drying ink to produce permanent, smudge-free lines that
won't wash away. Although it sounds messy, the manufacturer
claims otherwise and says that after a couple of trials, users
will be pleased with its performance. The 65-foot line
automatically retracts when extended up to 25 feet, and a
flush-mounted reel brings it back when it's extended farther.
Normal quick-drying inks are available in red, white, blue, and
black. The wet-weather formulation is available in white, blue,
and black. The Ink-Rite has a list price of $22.
Site Office in a Box
Finding a secure space for tool storage and a convenient place
to review plans is the unfulfilled dream of most builders. With
an angled desk and 9 cubic feet of storage underneath, the 119
Portable Field Station from Knaack provides both in a 16-gauge
steel cabinet, proving dreams can come true. Featuring a 17- by
12-inch pegboard for hanging accessories, a hard-hat bracket,
and a 19-inch full-width shelf for small tools, the Knaack 119
lists for $1,543.