Quote:
Originally Posted by Pete C.[_3_]
nestork wrote:
'Pete C.[_3_ Wrote:
;3250882']
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
first hole.
Pete:
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
brick mortar.
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.
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Pete:
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.
Mickey:
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.