low power drilling

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.

Reply to
clare
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Absolutely no way.

And I did it today. Started with the first hole just clear of the decking - ended up abot 3 inches down from the decking at the other end.. And I had something like 15 inches of joist to play with.

Reply to
clare

Ended up using 3 lengths of 1/2 inch pipe @ $7.50 each, 2 of 1/2 inch pipe couplings @ $1.24 each, 2 of 1/2 to 3/8 reducers @ $1.35 each, and 2 of 1/2 to 3/8 NPT bushings @ $0.89 each, plus a $16? 12 inch extension bit (7/16" hex both ends).

Half an hour of labour welding two halves of the extension int the pipe bushings and the extension was done.

Total cost less than $50.

Rented a 450 RPM drill and a 1 1/2" forstner bit for $14 for a half day - so total outlay still under $65. Half an hour to set up and drill the first set of holes and cut an access hole in the floor where the cables will come out, and just over

10 minutes to drill the second set of holes.

Labour included still under a hundred to get the job done. The boss is happy.

Reply to
clare

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)

Reply to
clare

So you posted here for what reason? You were obviously finished the job before most people had a chance to reply.

And now you decide to come back and insult the people you were asking for advice...

Nice way to meet a bunch of kill-files, Clare.

Reply to
Dave Balderstone

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.

Reply to
J. Clarke

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

Reply to
Sonny

Your Original Post:

[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.]

See anything about plywood Glued to Joists there? See anything about $50/yd Carpet there?

Reply to
LDosser

You said NOTHING about carpet in your original post.

Plonk.

Reply to
Dave Balderstone

And if that doesn't work, Python it.

Reply to
LDosser

That's a half-asp addertude.

Reply to
Morris Dovey

You're all going about it from the wrong end. This is a job for trained termites.

Reply to
J. Clarke

No, but just the 1 1/2 inch plywood alone makes it an expensive proposition, even without carpet.

Reply to
clare

I also didn't ( i think) mention that the 2X8 joists were stacked, giving 15 inches, more or less, of height.

No, but did you see anything that indicated I was entertaining ANY OTHER solution, other than drilling? I just asked WHICH KIND IF BIT would do the job with the least resistance /power usage since I was pretty well committed to drilling with a 12 foot extention of some sort. (I also didn't ( i think) mention that the 2X8 joists were stacked, giving 15 inches, more or less, of height.)

Anything that jammed up would make it difficult and retrieving a damaged bit or extension would not be an easy chore.

NOBODY addressed that question. 1 1/2" auger bits are not common. They also tend to drill faster, requiring more driving torque. Spade bits I found to be problematic in break-through as they are not self guiding. The forstner IS self guiding and self clearing and it ends up, also requires the lowest drive torque as it shaves the wood off in thin layers, and does not bind - even if the hole comes out tight against, or impinging on the joist or plywood decking.

Reply to
clare

"the original" ten foot drill? Ran across that one as I was looking for a solution.

Reply to
clare

I was hoping for some input last night. By noon today I had to get moving. I decided on my own that the forstner was the way to go, and it appears I was right..

No one even addressed the question I asked - everyone (well, just about everyone) intimated I was crazy to try and I was better to dismantle the raised floor to do the job. Was NOT going to happen.

Reply to
clare

Yeah, right ...

Reply to
LDosser

aaargh .,..

Reply to
LDosser

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.

Reply to
clare

Methinks some of these joke don't adder up. OH, krait, I'm contributing to the problem.

Reply to
Robert Bonomi

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