run cable in interior wall/drill fireblock

I need to drill a 5/8" or 3/4" hole in a fireblock in an interior 2x4 finished wall in order to run a cable. I have reasonably good access from above the wall in the attic. I could have access from below the fireblock but I don't want to cut the holein the sheetrock for the box until I'm sure I can get the cable run. I am considering either long flexible bits (like Greenlee D'Versibit auger bits) or using 18" extensions for auger bits to reach the fireblock. I am concerned about flexible bits being able to punch completely through the fireblock. The fireblock is centered about 42" from the ceiling or 48" from the floor. I'm interested in any experience by others on the group who may have done this task before and their suggestions on the best way to approach this.
Also, the fireblock seems to be at least 3" thick as measured by the stud sensor. Is it common for fireblock to be a doubled 2x4?
John Keith snipped-for-privacy@juno.com
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The diversabit will work fine. I bet your stud finder is lying. There is a hole in the spade of the bit to clip a pull string on if you can reach it through the hole after drilling.Paper clip. It makes fishing easier.
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On Sat, 05 Jul 2008 14:01:14 -0400, snipped-for-privacy@aol.com wrote:

OK, I was worried about getting just to the end of the hole and srew tip not having anything to pul lit through to complete the hole. That is why I considering just using non-flexible extensions.

Hmmm, well it seems to be correct for the vertical studs.

Yes, I've seen that feature. And I think I will be able to reach the bit but I think threading the needle will be somewhat of a blind operation.
Thanks for your (quick) feedback.
John Keith snipped-for-privacy@juno.com
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Is this for an electrical box or data box?
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wrote:

Neither. Video cable.
John Keith snipped-for-privacy@juno.com
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Only electrical boxes are required to be in the wall.
Data boxes can be drilled thru the floor.
Guess that doesn't help you though. :)
Video cables don't have to be in the wall either, but putting them in the wall is the professional way to do it.
They do make stick strip wire mold that does a pretty good job of hiding the cables, but fishing the wall is best.
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wrote:

I'll invest the effort to put the cable in the wall and use a nice wall plate. I'm not impressed with the surface solutions.
John Keith snipped-for-privacy@juno.com
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The D'Versibit is a beautiful thing, however I try to avoid using mine whenever possible due to the fact that you're drilling blindly into a wall cavity. You have no idea what else is in the wall and the drill bit will easily go through other wires, plastic pipe and maybe nick a copper pipe without you knowing it. Before drilling, look and see what is on the other side of this wall. Check below in the basement as well as in the attic.
The indication that the fireblock is at least 3" thick indicates to me that there possibly is another obstacle in the wall. Drill a hole from the attic down into the wall cavity and push a fishtape down to feel around. Then cut your hole in the wall and push a fishtape up into the wall cavity to feel around. If you sense that the only thing that you are hitting with the fishtape is wood, then proceed to drill with the D'Versibit. Use a D'Versibit with the screw point on the end as that will help pull the bit through the wood. The D'Versibit does not get along well with nails. If you feel it start to get jammed up, reverse the drill immediately and move the bit to another location. Otherwise the bit will break and you will be left with a very nice rod (Been there, done that).
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On Sat, 5 Jul 2008 17:09:00 -0400, "John Grabowski"

You drill 2 holes in the top plate so you can look in and aligh the bit before pulling the trigger (a LED flashlight with the extended tip is perfect for this)
As for threading the needle, use a paper clip and hook it in there with the string tied to the clip.
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wrote:

*Yes you can see the top side by doing this, but you you have no idea what is on the bottom side of the fire block unless you also look upwards from below. I have a mirror on a wand that I stick in the outlet opening to get a glimpse. If there is insulation in the wall visibility is very limited.

*The fiberglass rods are good for getting through holes inside of the wall with some accuracy.
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On Sat, 5 Jul 2008 18:50:15 -0400, "John Grabowski"

I understand the desire to look up but I'm a little reluctant to make the hole for the box before I have the hole drilled in the fire block.

This is an interior wall and I am pretty sure there is no insulation.

I looked at the glow in the dark rods today. Slick but pricey.
John Keith snipped-for-privacy@juno.com
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On Sat, 05 Jul 2008 18:19:01 -0400, snipped-for-privacy@aol.com wrote:

Good idea.
John Keith snipped-for-privacy@juno.com
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On Sat, 5 Jul 2008 17:09:00 -0400, "John Grabowski"

The wall has no plumbing. There is 115 VAC but it is on the other side of the cavity so I think I can avoid it. There is no access from the basement.
Thanks for the tips.
John Keith snipped-for-privacy@juno.com
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