On Oct 6, 8:28 pm, willshak wrote:
on 10/6/2007 10:55 PM Steve Barker LT said the following:

You need to rent or purchase a good hammer drill. You also may be
encountering rebar.

No rebar. I'm drilling 3/4" diameter holes 2" deep in a poured concrete
sidewalk around my pool. The holes are to attach a mesh winter cover on
my inground pool. The holes are to hold the cover's 40 spring loaded
straps. Previously, I had been using the solid winter cover with water
bags. I just got tired of cleaning the water and debris that accumulated
on top of the cover when I went to open the pool in summer. I looked
enviously at my neighbor's mesh cover all winter and it was clean except
for a couple of twigs laying on top. Then I looked at mine and there was
a foot of dirty, leafy water after the rain and melting snow had pushed
the cover deeper into the clean pool water.

When I first start the drill, I can see the crushed concrete powder
coming out and forming a ridge around the hole. All of a sudden the
powder stops building and I can hear the drill bit kinda bouncing over
something. The bit never stops turning, it just stops cutting.
I wash out the hole and look in. The aggregate filler in this concrete
is small roundish pebbles, about the size of a green pea up to a lima
bean size with colors of yellow, orange, grey, or whitish. I may see
parts of one, or two, or maybe three pebbles intruding in the hole, the
tops of which look sanded from the drill rather than cut. At this time I
take the small sledge and a 12" long steel tapered flat nosed punch with
a 1/4" wide tip and try to crack the pebbles into smaller pieces that
the drill bit can handle. I think that the 3/4" hand tool star drill can
do a better job of cracking the pebbles with fewer blows since the star
drill will completely fill the hole and may crack two or more pebbles
with one blow.







s

"willshak" wrote in message
...

X-posted to other relevant group.

Before there were concrete drill bits, or electric drills for that matter,
small round holes in concrete or rock were made by a round chisel type
tool that was pounded into the stone with a small sledge hammer while
turning the tool. It might have been 8" or 10" long. The face of this
chisel had a star-like pattern, only with 4 points, like a plus sign " +
". I believe it was called a star drill.
A Google search brings up a lot of sports drills (training regimen).
Anyone know if they still make them, or if so, where to get one on-line?
I'm trying to drill some 40 - 3/4" holes in concrete and my 1/2" corded
electric drill with a concrete bit stalls on the stone aggregate in the
concrete requiring me to stop and try to crack the aggregate with a large
punch. I figured a star drill would work better.

--

Bill
In Hamptonburgh, NY
To email, remove the double zeroes after @

--

Bill
In Hamptonburgh, NY
To email, remove the double zeroes after @- Hide quoted text -

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For a couple of holes, your method is workable. For 40 holes, bite
the bullet and rent a real rotary hammer. The cost is miniscule
comapared to the time, effort and frustration you save. My nearest
rental is 20 miles away and I have made the trip to do as few as 4
holes. Believe me, it is worth it.

Harry K