Gunsmithing Tools You Need: Left Hand Drill Bits

left hand drill bits gunsmith

Tyler Kee for TTAG

I was once stopped by a cop on my way to the ranch because of burnt out tail light. When I made it out to the ranch, I discovered that the head of one of the Phillips screws that holds the lens in place was completely stripped.

If you do any work at all on your guns, you’ve surely run into this problem. It’s some infinitesimally small Allen head screw. You strip it, curse loudly, and then try to figure out how to get it out.

My dad was an automotive mechanic for the better part of three decades and has amassed a large Snap-on toolbox full of various tools. Many of them are specialized to do a single job.

He saw my tail light predicament and headed over to his large chest of tools and returned with a drill bit. He chucked it in a cordless drill and slowly started turning it counter-clockwise. Like magic, the screw backed out.

My dad smiled, returned the bit and drill to his toolbox, and poured himself a cold drink.

A few weeks later, he came to Austin to visit and handed me a Matco 5-piece left hand bit set (there are more affordable options out there). They sat unused in my toolbox until recently. While removing a rail from my AR in favor of a new one I’m testing, I stripped one of the Allen head screws.

I snagged my bit set, selected the proper bit, and — just like my father before me — easily extracted the ruined screw.

The machinists and gunsmiths who frequent TTAG will probably laugh at my ignorance of left hand drill bits (or extractor sets), but I was blown away at how well they worked at screw extraction (Brownells has a handy set).

I’m not necessarily saying you need a set of left hand bits, but if you’re as prone to destruction as I am, it certainly can’t hurt to keep them around. You’ll rarely use them, but when you need them, you’ll be really pleased you have them on hand.

comments

  1. avatar Lexicon says:

    Rounded. You round the heads, and strip the threads….

    1. avatar Joe Miller says:

      It’s cam out on an Allen head. Rounded would be on something like a hex head bolt.

  2. avatar Leslie says:

    Some electronics like LGA computer processors use LH Pitch Screws, and I think the Chinese Military also uses LH Screws…

  3. avatar ROBERT Powell says:

    harbor freight and black&decker both sell a phillips screw extractor that works every time it looks like a counter-sink with reverse cut flutes .it comes as a set for under ten dollars.

  4. avatar Thixotropic says:

    They are called ‘EASE-OUTS’ or simply screw extractors.

    Come with properly sized bits in a range of quality and prices.

    No biggie.

    1. avatar Geoff WWJWD - "What would John Wick do?" PR says:

      “They are called ‘EASE-OUTS’ or simply screw extractors.”

      Similar, but different. Easy-Outs look like the nose of Jules Vern’s ‘Journey to the center of the Earth’ drilling machine. Left-hand bits look *exactly* like a drill bit, but in an inverse pitch…

  5. avatar WI Patriot says:

    Nah…I’ll stick to easy out’s and screw extractors…

    1. avatar Green Mtn. Boy says:

      This as they work.

  6. avatar Timothy Toroian says:

    Lexicon, I just saw an article on Google describing how to remove screws with STRIPPED heads. You round the heads of bolts. And, yes, left-handed drill bits are useful.

    1. avatar Lexicon says:

      That would be either a head that is still rounded out, or a head that has snapped off, in which case you may drill to get some bite with an easy out. Again, threads strip, heads break or round. 2 different words to give an idea as to repair procedure. You will not need to helicoil if you did not strip the threads….

  7. avatar Tom in Oregon says:

    Got a set.
    When you need one, the price you paid disappears replaced with a smile.

    1. avatar VicRattlehead says:

      Yup, I have a number of tools in my box that sit unused for looong periods of time but when the need arises they’re worth anything I paid and more.

    2. avatar Geoff WWJWD - "What would John Wick do?" PR says:

      “When you need one, the price you paid disappears replaced with a smile.”

      Hell, yeah, brother. And the sense of satisfaction is *priceless*.

      (For Tyler’s sake, I hope he’s an only son, so he can inherit that Snap-On box full of tools… 😉 )

  8. avatar tsbhoa.p.jr says:

    these would go nicely with my left handed monkey wrench. i’d give my right arm to be ambidextrous.

    1. avatar Geoff WWJWD - "What would John Wick do?" PR says:

      ” i’d give my right arm to be ambidextrous.”

      You and me both. I’m right-handed, and my little ‘adventure’ last December left me with a right hand that can’t fully close yet, making things like using screwdrivers and wrenches frustrating as hell…

  9. avatar Scratch Penningtyn says:

    (…” the price you paid disappears replaced with a smile.”)

    The money disappears true, but a smile is just a frown turnd upside down.
    I’m left handed and these dern things dint seem to help in my cause.

  10. avatar Dyspeptic Gunsmith says:

    I don’t have any left-hand drill bits. I have some extractors in my mechanics’ tool box (have have three monstrous roll-arounds in my shop, and a dozen smaller tool boxes for various tooling, and one roll-around is devoted to mechanics’ tools). I have metric and US drill bit indexes – but no left hand bits. For a job like this, I might use a small end mill, plunge cut a cylindrical hole in the screw head, then I’ll glue/solder/weld in a machined piece that I can really get hold of, then back out the screw. It’s the same technique I use on all screw heads, be they slotted, phillips, hex or torx.

    Now you understand why gunsmiths don’t like allen-head screws, and why we hate phillips-head screws with the flaming passion of a hundred suns. If you have a properly made standard-slotted screw head, and you have a screwdriver that fits, this happens very infrequently.

    The big issue, of course, is that there are lots of people who don’t want to spend the money on screwdrivers that fit gun screws properly. They bugger up the slot in the screw head, and then I’m having to deal with that before I can pull the screw.

    Of all the fastener head driving ideas, Phillips head screws are the worst.

    1. avatar Squiggy81 says:

      A proper set of screwdrivers is a must. I buggered up a screw on one of my rifles while refinishing the stock a couple years ago. Bought a new set of screws for it and a nice gunsmith screwdriver set also. Haven’t had that problem since. A decent set can be had for about 20 bucks and it saves a lot of frustration.

    2. avatar Wood says:

      I buy the gun model-specific driver & but kits from Brownells. My first experience with screws I could turn with standard utility screwdrivers was an Auto-5. That kit works beautifully!

    3. avatar Dani in WA says:

      “…the flaming passion of a hundred suns.”
      I could only fit one sun in my avatar.
      But yes, I have found my extractors useful.

    4. avatar Jeff says:

      “For a job like this, I might use a small end mill, plunge cut a cylindrical hole in the screw head, then I’ll glue/solder/weld in a machined piece that I can really get hold of, then back out the screw.”

      Assuming the original example, what if your car doesn’t fit in your end mill?

      1. avatar Eric in Oregon says:

        Letting DG correct me here, but I believe what mechanical people call “end mill” is what we lay people would call a “bit”.

      2. avatar Dyspeptic Gunsmith says:

        An end mill is this:

        http://www.micro-machine-shop.com/end_mills_3.jpg

        You can get them in small sizes, up to about 2″ cutting diameter (above that, inserted end mills take over), in HSS or carbide, coated or plain.

        The benefit of an end mill is that they tend to walk less, cut a square bottom to the hole, and a more accurate hole size.

  11. avatar Imayeti says:

    Some EASY OUTS sets come with left hand drills which is usually all you need. Let your neighbor borrow the EASY OUTS, sans drills, so if they don’t come home, meh.

  12. avatar BobS says:

    Neither hex socket (Allen) nor cross (Phillips) drive screws can stand repeated use, especially if they’re frozen with corrosion or thread locker or just differential contraction when they cooled.

    I replace them with star (Torx) at every opportunity.

    1. avatar Geoff WWJWD - "What would John Wick do?" PR says:

      “Neither hex socket (Allen) nor cross (Phillips) drive screws can stand repeated use,..”

      The story I have heard is that Phillips heads were designed to be installed *only*, never removed, while assembling cars in Detroit in the 1950s. They were designed to ‘cam-out’ when a set level of torque was applied to the head. The ‘buzzing’ sensation all too familiar with us when ruining the head was the signal for the installer that the fastener was set. All in the interest of speed, speed, speed, move those cars down the line…

      1. avatar dph says:

        I have an AR with the Magpul enhanced trigger guard and the little Allen screw in the front is only 2/3’s of the way in because that 1/16″ Allen stripped out. Now won’t go in and it won’t come out out. I am a huge fan of Torx, Allen not so much.

      2. avatar Jim Bullock says:

        I read something similar, about the screw head design.

        Philips head was designed to counter over-tightening n snapping screws on install, and to be self-centering.

    2. avatar Geoff WWJWD - "What would John Wick do?" PR says:

      There’s another unpleasant surprise out there in ‘fastener land’.

      ‘Spline’ heads. At first glance, they look just like hex heads, but if you put a hex wrench on one, it won’t quite fit, and round out the head, ruining it as well.

      My unhappy introduction came from the knobs of an old Hallicrafters tube shortwave radio…

  13. avatar Jonathan-Houston says:

    That’s a solid pro tip. Not everyone is a mechanical engineer, machinist, gunsmith, or even an avid DIY gunner. Lots of guys and gals out there, with absolutely no reason whatsoever to feel guilty or embarrassed for not already knowing about these tools and techniques, can benefit from this information.

    You might even add a short video demonstrating the extraction. I’m sure something similar is already on YT somewhere, but why drive traffic to their site?

  14. avatar jram01 says:

    Geoff WWJWD – “What would John Wick do?” PR says:
    August 1, 2019 at 13:53
    ” i’d give my right arm to be ambidextrous.”
    You and me both. I’m right-handed, and my little ‘adventure’ last December left me with a right hand that can’t fully close yet, making things like using screwdrivers and wrenches frustrating as hell…

    NO BIG DEAL. Just break your right arm, use your left arm for 6 weeks, take off the cast and there you go. PROBLEM SOLVED. 🙂

    1. avatar Geoff WWJWD - "What would John Wick do?" PR says:

      It ended up I got a pleasant payday from the hand crush injury. Breaking the right arm will be an expense I don’t want or need at this time…

  15. avatar A. C. says:

    Also, get a brace – yes, as in “brace and bit” for your home tool kit. I own four, different sized, different torqued, drill motors. Each can do a different job, and there’s no complete overlap between any two of them. But there are still some times that I want to apply torque in a more controlled manner than a power drill can and a brace allows me to do that. Like when I’m extracting a screw with a stripped out head.

    1. avatar Wood says:

      Agreed on the drill brace! The original cordless drill!!

      A bench top drill press works well for this too. Chuck up the LH bit or ez out, feed down with pressure, and grab the chuck by hand to apply the break-out torque. This is not a powered operation of course.

      1. avatar Geoff WWJWD - "What would John Wick do?" PR says:

        Squirting a bit of ‘Liquid Wrench’ (or similar) penetrating oil and lightly shocking it by tapping on the ruined head and waiting for awhile can also be helpful.

        (John Wick would just take the gun into his ‘Sommelier’ to request repair and drop a gold coin in his hand, of course…)

        1. avatar Wood says:

          It’s the waiting that’s so hard, but it sure can be effective. We use Kroil. Great stuff.

  16. avatar RapidTransit says:

    I have to mention for allen keyed heads there are a type of extractor that get tapped in with a hammer that work wonders but they get pricey because they are specific to the type of fastener, socket head, button head, set screw etc. It also pays to buy quality tools from brands like PB Swiss, Wiha, etc. I cammed out a phillips head once using a cheap screw driver from El Cheapo Depot, grabbed a Wiha and was shocked it actually was able to remove it.

  17. avatar John A Gavin says:

    OK I HAVE A 1/64- 1/2″ SET OF THEMAS SO HAVE 2-4 SET OF SCREW EXTRACTORS. THE LEFTHAND BITS WILL OFTEN START WHEN RIGHT WALK ALL OVER W/OR WITH OUT C PUNCH

    1. avatar Someone says:

      WHAT???

  18. avatar Doc says:

    Do yourself a favor and buy a set of Wiha drivers and you will not mess up small screws. They are worth their weight in gold if you are a smith. http://www.Wihatools.com

    1. avatar Bob in IN says:

      Use the right sized tool and dont round the screw in the first place.

  19. avatar DCChristian says:

    A lot of times, tool tips will wear down first. Allen wrenches and small screwdrivers are commonly not hardened well. An old trick my dad taught me is to harden the tips by heating the tip to red, then plunging it in table sugar. Carbon from the sugar infuses the metal, making it a higher carbon steel, thus much harder.
    Also, I’ve found that a small drill bit (left or right) works well for extracting a broken-off headphone plug from the jack of an iPad or other device.

    1. avatar Wood says:

      Great tip! When the points on an Allen wrench get rounded or worn down, I touch up the tool on a grinder or sander.

  20. avatar Jeff says:

    You should be using some sort of extractor, not a drill bit, to remove buggered-up screws. The problem is that drill bits are not made for that, are brittle and you may well break them. The purpose of a left-hand bit is, in this case, to drill a hole through the screw (without further tightening it), so that you can either insert an extractor, or to allow the screw to collapse and release its grip on the part so you can remove it in pieces. If the screw is loose enough to come out during the drilling process, that’s great. But that probably just means you misjudged your problem and picked the wrong tool. None of us ever do that, right?

  21. avatar Samuel T Coon says:

    Star bits work too. Go with the one that is just slightly oversized and they work really well on allen bolts. Tap it in as best you can, get a ratchet and socket and be gentle. It’s worked everytime I’ve done it in 20+ years of maintenance.

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