Masonry bits. vs. Hammer drill bits
I had assumed they were the same. Maybe not?
Hammer drill bits seem very expensive. The cheapest was $4.50 and I
think that one was small. A lot are 40 dollars or more. That's more
than the drill was.
They are the same thing.
Twist drill bits CUT a hole in the material being drilled, like
aluminum, steel or wood. Masonry bits or hammer drill bits BATTER a
hole in the material being drilled. That's why a "dull" masonry bit
works nearly as well as a brand new one. A dull twist drill bit no
longer cuts well, but a dull masonry bit bashes masonry into dust just
as well when it's dull as it does when it's new.
Cost is not always indicitive of quality. The tungsten carbide at the
front of the bit comes in different hardnesses and you pay more for
harder tungsten carbide. You'll find that retail stores tend to charge
more because each and everything they sell is vaccuum sealed onto a
card, and you're paying mostly for the packaging. Phone around to see
who sells these bits "in bulk", where you buy the bits loose with no
individual packaging and you should get a much better price on each one.
There are similarities but the rotary hammer drill bits have a different
base, generally the standard SDS pattern in the smaller drills, rather than
just a plain 'drill' shaft found on your typical masonry bit. An SDS bit
could be used as a simple rotary bit although I can't imagine why anyone
would while a regular masonry bit won't fit any sort of hammer drill I've
ever seen. I've never seen an SDS bit that was as flimsy as your typical
hardware-store masonry bit and I've never had a SDS dull or fail in any way
which inhibited their operation while I've had regular masonry bits grab
and fail catastrophically.
Yes, you _could_ chuck up an SDS bit in a regular drill. The shaft size is
10mm so virtually any drill would accommodate one although you'd want a
keyed chuck since a keyless might not tighten enough to hold. Why anyone
would want to do this is beyond me though.
You can't use an ordinary masonary bit in a rotary hammer. Well, you
can, but the chuck you put the masonary bit in will be shaken apart.
Those Jacobs chucks are press fit together, and normally that's enough
to keep them in one piece for decades. But, if you mount it in a rotary
hammer, you'll shake it apart.
Years ago I bought a Hilti TE-10 rotary hammer. It had both "rotation
only" and rotary hammer modes on it. For use with the Rotation Only
mode, it came with a keyless Jacobs chuck mounted on an SDS shank so
that I could use twist drill bits up to 1/2 inch diameter in it.
However, the owners manual for the tool warned never to use ordinary
masonry bits in this Jacobs chuck for drilling masonry because the
pounding action would shake the press fit Jacobs chuck apart, thereby
wrecking a $75 or $80 accessory. The SDS system (patented by Bosch)
allows for the forward and backward movement of the drill bit while it's
turning, and is designed to stand up to that shaking.
No, SDS drill bits have special machining at the base of the shank.
But, because the SDS chuck is a standard size, for drill bits smaller
than 10 mm, the shank is larger in diameter than the drill bit itself.
Other than that, they're ordinary masonry drill bits and I expect you
could probably fit one into a 3/8 or 1/2 inch Jacobs chuck if you
weren't too concerned about how well they fit. Certainly, you could
slip some 10 mm plastic tubing over the SDS end, and then put that into
a Jacobs chuck.
'The SDS Carbide Tipped Drill Bit ~ Concrete Fastening Systems'
The machined slots is where the torque is applied to the bit. The
shallow ovals is where a ball bearing rides on each side of the bit.
When you turn the collar on the SDS chuck, those ball bearings tighten
up in their slots and hold the bit steady as well as prevent the bit
from falling out of the SDS chuck if you hold the drill in a downward
orientation. The SDS bit can still move back and forth in the chuck
even when the chuck is rotated to lock the bit in place.
I'm thinking that you'd have better luck putting the SDS bit in a 1/2
inch chuck so that it would go in deeper and the chuck jaws would grab
around the round portion of the drill bit shank in front of the machined
Masonry bits are intended for rotary drilling only and use cheap carbide
and other cheap materials. Hammer drill bits look similar, but use
higher grade materials to withstand the percussive forces of a hammer
drill or rotary hammer. If you put a cheap $5 masonry bit in a hammer
drill or rotary hammer it will be destroyed before it even finishes the
Any drill bit with a tungsten carbide point on it is meant to bash a
hole in the masonary in front of it. There's no such thing as a masonry
bit meant to cut a hole the same way a twist drill bit does. Putting a
masonry bit in a drill that only rotates is just going to grind a hole
in the masonry, and that will only work for very soft materials like
A friend of a friend borrowed my hammer drill. They didn't ask for bits
and I wouldn't have had any anyhow. It came back with a little white
dust in the chuck and the message that it didn't work for what they were
doing. Maybe because they didn't have the right bits.
This means if I need the hammer part, I'll probably have to plan a bit
further in advance.
The drill came from Harbor Frieght. Has a Jacobs chuck which I don't
think is designed for SMS bits, and since the chuck is barely longer
than any other chuck DOESN'T THAT MEAN THAT AN sms BIT WON'T WORK IN IT?
In fact it's not even labeled a hammer drill. It's called an Impact
Drill. (Maybe I shouldn't have bought it, even for $15) **
The drill cost only about 15 dollars, varialbe speed, reversible, and
switchable to a regular rotary drill, but isn't one of the ones they
sell now. It's all blue with black trim, no metal part to the case (not
counting the chuck) . The brand is "Drill Master. "
And I used it Friday to remove two screws from a lawn mower that would
come out with torx or flat. I wanted the drill to go SLOWLY, BUT IT
WOULDN'T, no matter how careful I was. It would go at different speeds,
but none were slow. My Sears variable speed reversible that's 40 years
old will go slowly but I think its max speed is lower than one.
Reversible run CCW with a left-handed drill bit will sometimes unscrew a
screw while it is drilling off the head, but that didnt' happen to
either of these. But it did do enough that I got the cover of the lawn
**This is the closest to what I have that they are selling now
No reference to a minimum speed. No reference to SDS either, but it
is called a hammer drill, not just an impact drill. 3 of the 11 hammer
drills are labeled SDS. Not only are two $80 and one #120, but they
don't have the same shape as mine, which is shaped like a rotary-only
drill. Here they are: Even the url says SDS.
Both are variable speed, even though only one has it in the URL.
I would never have spent $80, or even what they charge if it goes on
sale, so at least I have a spare drill for not much money. With this
extra information, maybe I can find out why my drill didn't work right.
Used cheap masonry bits that broke?
BTW, reading wikipedia on SDS, it seems SDS allows only the bit to be
propelled at the target, not the whole chuck. Hence the smooth shank
and the way it's clamped in. And this is supposed to work faster.
Wouldn't it work better with the weight of the whole chuck behind the
bit?. Like the difference between one guy trying to break in a door
and a guy with a steel battering ram?
Hmmmm. One of the advantages of my 15 dollar drill is its 1/2 inch
chuck** And it's pretty deep. I've never seen an SDS bit, maybe I
could get it into this chuck after all.
**I've replaced the chuck on one or two other drills with 1/2" instead
of 3/8" but this came that way.
Sure they are. You go buy a pack of plastic masonry anchors that include
a 1/4" masonry bit, chuck it up in a hammer drill or rotary hammer and
see how long it lasts. Then buy a proper quality hammer drill bit in the
same size and try that. The quick ID is if it's got an all over silver
dip it's a cheap masonry bit suitable for rotary drills only, while bits
that have other finishes are likely hammer drill bits, even though
superficially they look to have the same style carbide tip.
You seem to be saying that the cheap masonry bits that come with a
package of plastic anchors are meant to be used in a drill that only
turns, but doesn't provide a hammering action. Sorry, this simply isn't
the case. No matter how cheap the drill bit is, if it has a tungsten
carbide tip, it's meant to BATTER a hole, not cut a hole like a twist
drill bit does.
And, even the cheap masonry bits that come with a package of plastic
anchors will last longer if used in a hammer drill. Using them in a
drill that rotates without any hammering action simply erodes the
tungsten carbide tip so that it dulls quickly.
There are two kinds of hammer drill:
There are "percussion type hammer drills" that generate a hammering
action by having two plates, each formed so that there are bumps on it,
press against each other while the bit is turning. This "percussion
type" hammer drill will give you up to 50,000 BPM (blows per minute) but
each blow will have a tiny stroke of maybe only 1/100th of an inch.
Also, as those plates wear down, the hammering action gets worse, and on
an old drill it doesn't do much except shake the drill.
There are also "rotary hammers" that generate a hammering action by
having a piston in cylinder arrangement whereby the piston or cylinder
moves forward causing air pressure to push the cylinder or piston which
is attached to the drill bit forward. Rotary hammers have a much
smaller number of blows (300 to 600 per minute), but each blow has a
stroke of about 1/8 inch. Since it's that battering action that
pulverizes the masonry in front of the drill bit, rotary hammers work
much better than percussion type hammer drills because of their superior
hammering action. Rotary hammers come in all shapes and sizes, and the
smaller ones generally use SDS chucks to accomodate SDS drill bits. The
bigger rotary hammers use drill bits with a splined shank.
But, the bottom line is that there are only two efficient ways for a
drill bit to make a hole in something, and that's by cutting a hole or
battering a hole. If the drill bit you have has a tungsten carbide
tooth at the front, it's meant to batter a hole, and that means you need
a hammer drill of some sort. Putting that kind of a bit in a normal
"rotate only" drill is just going to dull the bit as you grind your way
through the masonry.
There is absolutely no need to start insulting me, Pete.
If you believe that there are tungsten carbide tipped drill bits that
CUT into masonry just like a twist drill bit cuts into wood, then can
you explain why a masonry drill bit doesn't have a sharp edge on it like
a twist drill bit does?
That is, how would this drill bit:
be optimally designed to _CUT_ into masonry when there are not sharp
edges to it? Don't you agree that the only edge that can be argued to
be "sharp" might be the one facing directly forward, in which case it's
not designed to CUT masonary as it rotates.
On the other hand, it's easy to explain why the shape of that tip is
designed to bash the masonry in front of it into dust.
If you look at the front of that bit you can clearly see that the two
faces of the carbide tip are ground with relief angles giving the
cutting edge. It's not a fine edge like you will find on a twist drill,
but it is indeed a cutting edge. Look at some carbide milling / turning
inserts and you will also find profiles that are less visibly sharp than
you might expect. Carbide is hard but brittle and thin "sharp" edges
will fail quickly.
I have and have used multiple hammer drills and rotary hammers from
Makita, Hilti and others, and percussion rated masonry bits are indeed a
different species from regular hardware store rotary masonry bits. I've
also used carbide core bits which also are not intended for percussion
use (neither are the diamond ones).
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