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.
Obviously you have never used a star drill.
Forget it. You will use the electric drill only, after
about 15 min of pounding on the star drill. Maybe you
are pushing it too hard. I usually drilled a 1/4" hole
and then drilled it out bigger with the 1/2" or
I'm 100% sure they are available, but I really don't think many 1/2"
corded drills will do much for you.
These are impact, so you need an impact tool.
I use an IR tool that uses star bits, works nicely (but is air
powered!) I know you can rent electric ones (or buy, but they are
But using a star drill in a standard drill won't do you any good,
you'll never really make a hole--you have to have impact. BTW, with my
IR tool, I provide the rotating force, the tool only provides the
impact. And if I don't provide rotational force, things get very
strange after a short while! (I usualy do a continous 90 degree
rotation back and forth as I'm drilling...)
And, yes, the star drill will work better. I punch 3/4" holes about
three inches deep in about a minute or so per hole.
Try a tool rental place. Tell them what you need, they will have
something to do it.
I have the small sledge hammer. I just want the hand tool star drill.
I'm not going to try to put it in the electric drill. When the electric
drill with the concrete bit just spins on a bit of aggregate I can use
the star drill to break up the aggregate.
We pretty much stopped using them in the early 70' but I would expect an
electrical supply to have them. For 40 holes, you'd be better off using a
rental hammer drill. Without the hammer, that blue stone aggregate just
burns up bits
on 10/6/2007 10:55 PM Steve Barker LT said the following:
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.
The hammer drill (or better yet, rotary hammer) is one of the more
indispensable tools - there's nothing that works even remotely as
well. Your question is vaguely akin to someone asking which is the
best brand of screwdriver to use as a chisel, 'cepting a screwdriver
is a lot closer to a chisel substitute. Yes, I know they used star
drills for ages, and yes I know you could do it that way, but I'd
borrow or rent one, or buy/sell on eBay to get the proper tool for the
job. You'll find all sorts of projects for it.
Hence the 'vaguely akin'. I was going to go with the 'asking for help
selecting a horse drawn buggy' analogy, but I thought I'd stick to
Not sure why your Google search turned up dead ends. When I Googled
"star drill" it came up with a bunch of hits - Ace Hardware has them
and eBay as well.
You'll be spending $10 or $20 on something you'll probably never use
again and it's going to take you far more time to do the drilling.
Your time, your money.
harbor freight sells a hammer drill for 60 bucks bits a little more. a
great price for a occasional need tool.
star drills work but can take hours, hammer drill can do the same job
better in 5 minutes...
plus you have the tool for the next time you need a hole, or have
other jobs. the chisel bit is wonderful, used it once to hrak up a big
rock in my yard when planting some stuff.
Go a step further and get a rotohammer. I bought a good Makita the other
day for $25 at a yard sale. It has a SDS bit system, and has both the demo
hammer and rotohammer mode.
A hammer drill will get it done. A rotohammer will get it done in less than
half the time. They can be had at pawn shops, in the local Quick Quarter
rags, and at yard sales for prices that make it so that if you don't use it
much, you don't lose a lot of money.
The other day, we were ripping out caliche from where we want to put a
walkway. I needed a trench about three feet long and a foot deep and wide
for a French drain. I got out the Makita, and was done in a couple of
Get the rotohammer. You'll be glad you did.
People are just trying to point out that you are really choosing to make
a lot of work for yourself by insisting on using a star drill which no
one uses anymore for obvious reasons.
You could rent a rotary hammer for not much more than the cost of a star
drill and drill all of the holes in no time with considerably less effort.
Eggsactly ! and you can rent one from HD (Bosch Hammer drill or rotary
hammer) for the 4 hr minimum for about 25 bucks and get the job done in less
than an hour..or "tinker" around with ancient technology and spend all day
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.
I know "rent a hammer drill" is not the answer you're looking for.
Still, it is the best advice for your situation. With a hammer drill,
you will NEVER have to stop to bust up the aggregate. A hammer drill
will bust right through on its own.
The amount of time and money you spend running around looking for a
star bit will more than offset a 4-hour rental on a hammer drill.
Drill 20 holes with your regular drill, using the star bit every time
you run into a pebble. Then drill the other 20 with a hammer drill.
You'll wonder why you even bothered with the star bit.
As an aside, and in the vein of this thread ..........
I have used star drills when I hit a hard piece of aggregate when drilling
with a hammer drill. It fractures the piece of aggregate and gets the drill
One of the best was a 3/16" rod that came as a tensioner for a wrought iron
gate. I believe it was cold rolled, or whatever makes it not bend. I would
grind the end to a screwdriver point, and just put that in the hole and hit
it with a hammer a few times, turning it as one would do with a star drill.
Actually, the handmade tool was better than the factory job.
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