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Many folks I talk to don’t know what a flex-shaft bit is, but when it’s called by one of its other many names, like fishing bit or piranha bit, inklings of recognition glimmer here and there. Basically it’s an aggressive demo bit on the end of a flexible shaft that has a hole in the bit and another on the end of the rod to run cable with — and they’re lifesavers.

You can make them yourself out of flex steel or carbon fiber rod (my dad and I always used carbon arrow stock with a metal insert in the drill end) and it’ll work just as well. The idea is to drill into one end and pass the bit through whatever obstacles are in the way and come out the other side exactly where you intended with only one shot.

The bit in the picture let me run an old-fashioned satellite co-ax cable through the attic, down a closet and out two walls, drilling only twice. The whole run thing was done inside 20 minutes, and that counts ten minutes installing the box into the wall. It seems like a fairly obvious timesaver to me but even though it’s been offered to others many times, thus far, no takers.

A six-foot length on the shat will run you about $20, so really it’s a matter of what is more hassle — paying the cable installer guy $75 to get full of fiberglass, or saving $50 and doing it yourself.

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8 Responses to Flex-Shaft Bits: The DIYer’s Friend

  1. Mike says:

    We call these bits Jesus bits. As in, drill through a wall and pray to Jesus that it comes out where you want it.

  2. fred says:

    Nice find – these seem to be a less expensive alternative to their Greenlee, Klein and Ideal Cousins. Greenlee is now marketing a kit that includes flexible shafts with a 1/4 hex quick mount at one end and a 1/4 hex socket at the other. They come in 12, 18, 24 and 36 inch lengths and presumabley can be snapped together to give you different lengths.


    There are also placement tools or guide bars made to help you direct the drilling – and I think Greenlee or one of the others makes a non-rotating sleeve to cover the shaft to help avoid tangles with fiberglass insulation

  3. rob says:

    I have the greenlee one with the hex and I have a 5 foot greenly 9/16

    the nice thing about the hex one is the 3/4″ auger on the end of it only cost a few bucks to replace and makes a great tight space bit too and I have put a magnetic
    driver bit into the 18″ extension and drove screws with my impact gun into a couple of places that would other wise not be reachable or need a ladder

    but totally agree with the Jesus bit reference you never know what you will hit and aiming can be a bit of a trick

  4. Phil says:

    I have 3- and 5-foot Greenlee versions, and they come in extremely handy for electrical reno and retrofit. It takes a good bit of feeling around with the bit placer to get the center of the sill or top plate, since getting a Milwaukee M-Spector that has gotten a tad easier.

  5. Brau says:

    I spent 12 years of my life using these bits to retrofit security systems into homes. When I quit, I kept a couple sets (2′, 4′, 6′) for my own home use as they are bloody indispensable.

  6. Frank Townend says:

    When drilling into a windowsill to run alarm wires to the basement be careful not to hold the drill too close to your forehead when holding the drill over your head. You may pull the better part of the hair off of the front of your head.

    Don’t ask me how I know.

  7. Bob says:


    I did that while standing on the top (not a) step of a ladder. Had to reverse the drill blind since it was up against the side of my head really tight. Didn’t fall or loose my hair.

  8. Stony Silence says:

    Ouch! Frank and Bob that is really brave and nice of you to warn people of that danger. I never would have thought of something like that happening, and I’m just the person who would be holding it that way. I’m sure it’s not your proudest moment, so I appreciate the warning!

    Besides that, I was going to comment on the flex shaft bit. Just yesterday I finally had a new dishwasher installed. The installer said we need a new air gap and wanted to charge $70 to put one in. I asked how much the part was if I wanted to do it myself. He shrugged and said “Maybe ten bucks?” After he left, I decided it probably just needed to be cleared because it had sat unused for so many months. I searched the garage looking for some kind of snake type weapon. I wonder if a Flex Shaft Bit, set on a very low speed would have been overkill?

    Eventually, I took some scissors to a dryer vent cleaner to make it more narrow, and that did the trick.

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