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Posted by Bob Engelhardt on May 2, 2008, 12:25 pm
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http://home.comcast.net/~bobengelhardt/drill1.jpg (37kB)
http://home.comcast.net/~bobengelhardt/drill2.jpg (43kB)
I found this bit at the dump. It has a tapered shank & is marked "star
- hammer - twist". It has a chisel point, not a cutting lip, so it
clearly does impact cutting & hence (?) is for masonry. But it is not
carbide tipped! It has some rust, so it can't be solid carbide, can it?
So, I guess the question is: is there some steel alloy that is used for
masonry impact drilling?
Thanks,
Bob
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Posted by Lloyd E. Sponenburgh on May 2, 2008, 12:35 pm
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> http://home.comcast.net/~bobengelhardt/drill2.jpg
Bob, I have four "star drills" in various sizes, none of which are fluted
for twisting like yours, but none of which have carbide tips, either.
The star drill has been the standard for decades for penetrating block
walls precisely and easily without a lot of spalling on the downwind
side. Just a gentle "tap-tap-tap-turn, tap-tap-tap-turn" and the hole
virtually makes itself.
The twist version allows you to clean out a blind hole, which a common
star drill cannot do.
LLoyd
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Posted by Pete C. on May 2, 2008, 12:35 pm
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Bob Engelhardt wrote:
>
> http://home.comcast.net/~bobengelhardt/drill1.jpg (37kB)
> http://home.comcast.net/~bobengelhardt/drill2.jpg (43kB)
>
> I found this bit at the dump. It has a tapered shank & is marked "star
> - hammer - twist". It has a chisel point, not a cutting lip, so it
> clearly does impact cutting & hence (?) is for masonry. But it is not
> carbide tipped! It has some rust, so it can't be solid carbide, can it?
>
> So, I guess the question is: is there some steel alloy that is used for
> masonry impact drilling?
Answer: Certainly, people were drilling masonry and rock long before
high tech materials like carbide were available.
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Posted by RAM³ on May 2, 2008, 12:45 pm
Please log in for more thread options > http://home.comcast.net/~bobengelhardt/drill1.jpg (37kB)
> http://home.comcast.net/~bobengelhardt/drill2.jpg (43kB)
>
> I found this bit at the dump. It has a tapered shank & is marked "star -
> hammer - twist". It has a chisel point, not a cutting lip, so it clearly
> does impact cutting & hence (?) is for masonry. But it is not carbide
> tipped! It has some rust, so it can't be solid carbide, can it?
>
Most unlikely to be carbide - most likely a hardened high-carbon steel.
> So, I guess the question is: is there some steel alloy that is used for
> masonry impact drilling?
>
Hardened High-Carbon steel has been used for a very long time for masonry
drills - long before the invention of the power hammer-drill which this bit
would appear to be designed for use with - that were (and still are) used
with a hand-powered hammer. <grin>
BTW, are you _sure_ that you didn't mis-type the subject? A "gloat" would
also be appropriate for this bit. <GRIN>
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Posted by Robert Swinney on May 2, 2008, 3:25 pm
Please log in for more thread options The early oil and gas wells were drilled with "star pointed" drills. In
pixtures of cable tool rigs
where you see the guy giving a twist to the drill stem on every "up" motion, he
was rotating the
star drill. Oil derricks for cable tool rigs weren't as substantial modern
ones. All they had to
do was support the drill pipes (stem) as the tool pecked up and down. In
contrast, modern drilling
rigs have to be able to resist torque from the rotary tool. Most derricks you
see over wells now
are put in place after the well is drilled. They are there for maintenance
urposes - they only have
to support the weight of drill pipe as it is pulled up for service, etc.
Bob Swinney
http://home.comcast.net/~bobengelhardt/drill1.jpg (37kB)
http://home.comcast.net/~bobengelhardt/drill2.jpg (43kB)
I found this bit at the dump. It has a tapered shank & is marked "star
- hammer - twist". It has a chisel point, not a cutting lip, so it
clearly does impact cutting & hence (?) is for masonry. But it is not
carbide tipped! It has some rust, so it can't be solid carbide, can it?
So, I guess the question is: is there some steel alloy that is used for
masonry impact drilling?
Thanks,
Bob
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