low power drilling

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I've got myself into a situation - I need to drill through 6 2X8 joists which are accessible only from the one side. They are spaced 2 feet on centers. (need to pull cable across to the center of the floor). The joists are sitting directly on concrete, and the decking is 1 1/2" (you read that right) plywood.
What is the lowest power-requiring type of drill to use/ since it needs to be run on a 12 foot long extension-----. I tried a speed-bore type spade bit, but it has a bad habit of "catching" just as it breaks through - putting a severe strain on the connection between the bit and the extension.
Would a forstner type work better? Or an auger?
Still looking for a viable bit extender setup as well - thinking I might need to go to 1/2" steel waterpipe with a 7/16 or 1/2" hex shaft welded into the one end for the chuck to grab. In 3 or 4 foot length with couplers it should be handleable?
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On Thu, 11 Mar 2010 22:46:55 -0500, snipped-for-privacy@snyder.on.ca wrote:

Forgot - the hole needs to be 1 1/2 inch diameter
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On Mar 11, 10:48 pm, snipped-for-privacy@snyder.on.ca wrote:

You would want to use an auger bit, but at that length you will be looking at a custom bit. Not cheap but if you DAGS "custom made auger bit", you will find some that make them. Why does your hole have to be that big?
Allen
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wrote:

You would want to use an auger bit, but at that length you will be looking at a custom bit. Not cheap but if you DAGS "custom made auger bit", you will find some that make them. Why does your hole have to be that big?
A regular auger bit on extensions should do it. It only goes threw one board at a time.
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But 10' of extensions will be the real PITA. If you don't get the set screws tight, you'll be ripping up the floor.
Did 6' like that once. Never again.
Allen
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A spade bit might have a rough punch-through, so go slow and have patience at the end point. Make sure the bit is sharp. I think I would try welding a spade bit onto a 1/2" pipe and make a separate chuck insert (fitted/welded onto a 1/2" sleeve, for the pipe) for fitting into the drill chuck. A spade bit is a lot cheaper than an auger bit for a one-time use (once welded).
If access space, in starting, is limited, also, the 1/2" pipe can be in successive 24" - 36" sections. Any connecting sleeves will pass through the 1-1/2" holes and the chuck insert fitting can be moved back, as each successive pipe section is attached. Save the set-up for future use (???, LOL) and use the pipe sections for pipe clamps.
Sonny
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wrote:

I tried the spade bit first ( on a test piece, out in the open) and the breakthrough was BRUTAL. The forstner is self guiding and worked a real treat.
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On Mar 12, 4:48�pm, snipped-for-privacy@snyder.on.ca wrote:

Glad the pipes/extensions worked. That seemed the logical approach. I didn't think of using a forstner bit and I'll remember the lesson of that big of spade bit. I've never had to use one that big. And you still have the pipes for clamps!
Sonny
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wrote:

Thanks Sonny - you were about the only respondent that even considered my plan might work. Asked the "boss" what the chances were that I might use the setup again in my lifetime (I'm 58) and he just laughed.
If I had to pull the bit back out the holes it might have been a problem, but I was able to reach in the access hole where the electrical boxes will be mounted, 13 feet in, and release the bit with an allen key, tie a twine on the end of the extension, and pull it back out the hole. The twine will pull in the cable on Monday.
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wrote:

I know, I bought a couple of 18" extensions to drill down the wall in my daughter's townhouse to install wiring for bedroom ceiling lights. Paid $18 each for the extensinsa, and stripped one on the first hole. Thanfully the second didn't need as much length.
This time I used 1/2" water pipe, threaded together with pipe couplings.
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wrote:

Have to pull 4 #12 BX cables through it
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On Thu, 11 Mar 2010 22:48:43 -0500, the infamous snipped-for-privacy@snyder.on.ca scrawled the following:

What does the decking have to do with drilling joists? You don't want to pull it?

Use a 12ga extension. HF has 25' x 12ga for $10 which are nice. I use mine all the time for their 12" SCMS. YOu don't mean 12' metal extension, do you?!?

Augers self-feed and don't break out as hard. There are short auger sets available if you like 'em.

Oh, you do mean physical, not electrical. Why don't you just unscrew the decking and have a friend help lift it? Or did some jerk just nail it in? <grrr> Ooh, flooring might be glued, too, huh? Skilsaw, cut a long slot, lift it, replace and reglue with caulk as an adhesive. Cost: 1 sheet of flooring. Time saved: a day. Frustration saved: Humongous amounts.

I'd hold my light sabre down there for a couple quick punches through, one from each side. No extension necessary. ;)
-- There is no such thing as limits to growth, because there are no limits to the human capacity for intelligence, imagination, and wonder. --Ronald Reagan
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I'm with you on this one, C-less.
He gets through 4 of the 6 joists, and whatever rig he's using snaps somewhere between #3 and #4, with the bit embedded in #5 becuase he's hit a knot... Start again.
How many times, and at what cost?
Clare... Don't be stupid. take the easy way.
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On Fri, 12 Mar 2010 15:10:36 -0600, Dave Balderstone

I did take the easy way. The dang carpet is worth something like $50 a yard. The plywood is glued and screwed to the joists. Cannot remove it without doing significant damage. And remember i it is ONE AND A HALF INCHES THICK.
I made the tool to do the job and got the job done. Including my time the cost was just around the hundred bucks (they pay me $35 an hour)
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On 3/12/2010 6:05 PM, snipped-for-privacy@snyder.on.ca wrote:

That's not bad at all--there's a guy who makes 10 foot extensions and gets something like 100 bucks a shot for them.
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On Fri, 12 Mar 2010 20:10:08 -0500, "J. Clarke"

"the original" ten foot drill? Ran across that one as I was looking for a solution.
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You said NOTHING about carpet in your original post.
Plonk.
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On Thu, 11 Mar 2010 21:15:07 -0800, Larry Jaques

It is gled and screwed to the joists so it can not be removed without destroying both.

Yes TWE:LVE FEET.
I did it this afternoon. bought a 12 inch 7/15 AF extension and cut it in half. Banged the cut end of each peice into a 1.4 to 3/8 NPT bushing and mig welded it in. Put that bushing into a 1/2 to 3/8NPT reducer and threaded it onto each end of a 4 ft piece of 1/2" galvanized water pipe. Chucked a 1 1/2" forstner bit into the hex bit holder end, and chucked the other end into a 450RPM half inch drill. When I got in 4 feet, I took off the drive end with s pipe wrench and using a pipe couipling, added another 4 feet, and so on untill I was in all the way.

Did you read ONE AND A HALF INCH THICK PLYWOOD????
Doing it with the water pipe took almost half an hour for the first hole, and 10 minutes for the second one. Making the tool took 1/2 hour at the "borg" getting parts, and half an hour at the fabricating shop cutting and welding.

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On Fri, 12 Mar 2010 17:31:41 -0500, the infamous snipped-for-privacy@snyder.on.ca scrawled the following:

Nah, just cut a foot wide strip, cut it out between joists, break off most of the top, and route or chisel it flat. No joist damage.

Oh, so you had access from the side? I don't believe you mentioned that. You just say you -didn't- have it from the bottom.

I love those four words together, in that pattern. <domg>

Yeah, it's called "flooring", clare. Some is screwed, some nailed, some nailed and glued, some screwed and glued. Here's the key point I was making: IT'S JUST WOOD. You can handle cutting wood, yes? ;)

Alright, so you're done. Good for you. How did you like the way the forstner worked?
-- There is no such thing as limits to growth, because there are no limits to the human capacity for intelligence, imagination, and wonder. --Ronald Reagan
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On Fri, 12 Mar 2010 21:00:58 -0800, Larry Jaques

It worked very well, thank you. Would have worked better if it was sharp (it was a borrowed well-used bit)
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