I'm experimenting a bit now- but have to comment that this was a
winner of an inspiration. I have some good blu-mole and other
My plumbing collection ran out at needing a 1/4" nipple/pipe to
chuck-- Went to Lowe's and they didn't have any either. Bought a
1/2" bolt that I figured I could grind some flats on so it wouldn't
slip in the chuck.
Then I cam home and read this! One of my hole-saw arbors screws into
the 3/8 pipe fitting on my connection 1.0.
I also note that the EMT I have is 3/4", not 1" as I thought. And
a 5/8 hole saw fits [loosely] inside. Connection 2.0, if needed,
will probably be a split conduit, clamped tight over that 5/8 hole
saw. [or, if I pass by an 11/16"/17mm hole saw before I get there, I
won't even split the conduit.
[first 5 minutes of trial, I busted the connection between the conduit
and the garden tool-- I either need a less aggressive digger or a
better connection there-- Otherwise I might be on the right track]
I'm a bit late to the thread but I think you're on the right
I've water jetted and I've hand dug under sidewalks (etc).
Water jetting is messy & unless you've got a place for the water to
drain away, the used water accumulates.
Hand digging undermines the side walk or driveway strips & you run the
risk of concrete failure later on.
It's hard to get a good number for the tourque output for electric
drills... the mfrs either fail to state or give bogus numbers.
hp = rpm x torque
so at normal operating speed you get the drills honest torque rating.
The problem is..... a the drill apporaches stall, the torque goes WAY
up, hence the tendency for a powerful drill (like a Milwaukee Hole
Hawg) to twist your wrists & arms.
My best suggestion for a cheap adapter would be:
a piece 1/2" black pipe (we need as small an OD as possible) x ~6"
long threaded both ends
1/2" x 3/8" reducing bushing
~2" to 3" piece of 3/8" pipe (ideally sch 80)
the one sticking point is....
nominal ID of 3/4" EMT is ~.824
nomimal OD of 1/2" black pipe is ~.840
so we have a theoretical interference of about .008" per side.
I'm hoping that the pipe mfr is shorting us on material cheating down
on the OD a bit.
You might be able to pound the adapter assembly into the 3/4" EMT.
Whether this scheme works is dependent on the connection from the 1/2"
pipe to the 3/4" EMT.
My calcs say we'll need about 14 #10 self-drilling / tapping screws
through the EMT into the pipe.
I'd use three rows with 5 screws per row..staggered spacing.
Getting the pipe into the EMT will be the hard part unless you can
machine the OD down to give you a slip fit.
Removing .016" with a lath is snap... by hand, not so much. :(
The torques & forces are substantial and I doubt any kind of clamping
arrangement will work.
My apologies.... I did not view the link in your OP.
So my post about the connection to EMT is probably useless.
Driving a device such as that garden claw doesn't require all that
much torque as long as one can control the "bite" into the soil.
Driving it by hand is safe & easy..... adding 1/2" drill to the mix,
not so much.
Even a 1/2" drill like a Milwaukee Hole Hawg on low speed runs at ~300
A typical post hole auger runs at ~150 rpm.
As in my previous post.... hp= torque x rpm
Any kind of bite by that claw is going to require some decent
torque...multiple that torque by 300 rpm (typical low speed drill
range) and you're going to need some serious horsepower, way more than
a typical 1/2" drill.
Consider renting a soil auger bit that is made to interface correctly
with a 1/2" drill.
I once saw a resoanbly priced horizontal soil drilling auger system
but I cannot locate it online. :(
check these out
The torque issue what I was talking about earlier. I imagine that it's
going to be hard to control in the manner intended. I also brought up run
out. Putting together a rig tat is going to be perfectly straight is going
to be pretty tough. Any offset at the junction is going to be multiplied 6’
Controlling a wobbly garden claw installed in a 1/2 drill is going to be
I would use a garden hose with a nozzle on the end, tape the hose to
the side of your conduit and use water pressure to cut into the clay
and flush out what it cuts. WIth your weasel, how are you going to
remove the clay as the cutter moves forward? That do you need as the
final diameter of the tube/hole?
When I ran into that problem (I needed a 12 foot long roughly 2 inch
diameter drill) I bought a hex drive bitextender and cut it in half,
welding each half into a 1/2" to 3/8" pepe reducer, then used 3 4 foot
long chunks of galvanized pipe and couplings to make a 4 foot then 8
foot, and finally 12 foot long drill -(I had a forstner bit on the
Not much welding required - I was able to do it myself, but it should
not be hard for you to find someone with the equipment and capability
to do it for you for cheap, or even free.
Instead of trying to drill/cut one large diameter horizontal hole, couldn't
you first drill a much smaller diameter hole (maybe an inch or so), and then
widen that hole by pulling out more dirt/clay with a pole with some type of
small hook or bent piece on the end?
Or, rent or buy a hand-held post hole digger and just use it horizontally
instead of vertically?
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