Masonry bits. vs. Hammer drill bits

Pete:
I'm sorry to say that the angles at the front of a masonry bit are oriented in entirely the wrong direction to "CUT" into the masonry.
There's no magic here. If a masonry drill bit were intended to "cut" into masonry much the same way a twist drill bit cuts into wood, the masonry drill bit would be designed and shaped very much like a twist drill bit, except perhaps having much harder cutting edges which wouldn't wear down. But, the tip of the bit is not similar to a twist drill bit at all. It's entirely the wrong shape to CUT. It is, however, the right shape to BASH something.
In my view, rotating that forward facing tip against the masonry would only serve to make it duller than it already is.
However, I can easily visualize how having a forward facing tip on the drill bit and hammering that tip against the masonry in front of the bit would pulverize the masonry in front of the tip into dust. And, I also note that the flutes on a masonry bit are designed much the same as those on a twist drill bit, so I expect the purpose of the flutes is undoubtedly to remove the dust created at the front of the bit. It seems to me that the masonry bit is ideally designed to batter a hole in masonry, not cut a hole as you claim.
Perhaps we should just agree to disagree on this one?
--
nestork

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nestork wrote:

Perhaps see if Hilti has a whitepaper or something on their site, they are the experts on this stuff.
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'Pete C.[_3_ Wrote:

So far as I can see, Hilti doesn't have anything on their website about how "masonry drill bits" or "hammer drill bits" work
However, I did find this on Wikipedia under "Drill bits":
'Drill bit - Wikipedia, the free encyclopedia' (http://en.wikipedia.org/wiki/Drill_bit)
The masonry bit shown here is a variation of the twist drill bit. The bulk of the tool is a relatively soft steel, and is machined with a mill rather than ground. An insert of tungsten carbide is brazed into the steel to provide the cutting edges.
Masonry bits typically are used with a hammer drill, which hammers the bit into the material being drilled as it rotates; the hammering breaks up the masonry at the drill bit tip, and the rotating flutes carry away the dust. Rotating the bit also brings the cutting edges onto a fresh portion of the hole bottom with every hammer blow. Hammer drill bits often use special shank shapes such as the SDS type, which allows the bit to slide within the chuck when hammering, without the whole heavy chuck executing the hammering motion.
Masonry bits of the style shown are commonly available in diameters from 5 mm to 40 mm. For larger diameters, core bits are used. Masonry bits up to 1000 mm (39") long can be used with hand-portable power tools, and are very effective for installing wiring and plumbing in existing buildings.
A star drill bit, similar in appearance and function to a hole punch or chisel, is used as a hand powered drill in conjunction with a hammer to drill into stone and masonry. A star drill bit's cutting edge consists of several blades joined at the center to form a star pattern.
That describes what I've been saying except that the author refers to the point on the tungsten carbide tip as being the "cutting edges". While he uses the word "cutting", what he's describing is the pulverizing of the masonry at the front of the bit by the tungsten carbide chip, and the flutes of the bit carrying away the resulting dust. Certainly, however you read the above, a hammering action is essential to the operation of the drill bit. And, nothing there suggests that there are cheap versions of masonry bits that are meant to be used in rotary only drills, which was your premise.

If cheap masonry bits were intended to be used in a rotary only drills, and cut by a different action than hammer drill bits, they would be designed differently and would look different. The carbide tip on the end of a cheap masonry bit and the carbide tip on the end of a high quality hammer drill bit look similar enough to me for me to conclude that they work the same way using exactly the same principles. If they worked differently using different principles, they would be designed differently and would look significantly different.
--
nestork

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On Sun, 22 Jun 2014 17:59:12 +0200, nestork

Masonry bits were widely available at a time when homeowners didn't consider buying hammer drills. This alone tells me that this kind of masonry bit doesn't have to "batter" what's in front of it. I've drilled holes in mortar, brick, even concrete using such bits with a non-hammer drill. It's tedious, but it works.
I would call the action grinding rather than either cutting or battering.
Edward
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