Drilling Perfectly Centered Holes

If you’ve ever been caught in the situation of needing to drill a clean straight hole down the center of a bolt or rod, you’ve probably tried and ended up with a broken bit or tilted hole, and a ton of cursing to boot.

[Vik] let us know about this nifty trick for drilling ‘down the middle’ using a simple hobby drill press and vice. He claims it’s ‘physics guiding the bit’ but in reality its just crafty use of a chuck. Either way the quick trick works, and will hopefully save a lot of hackers some headaches in the future.

Let us know in the comments if you have any simple quick tips that you use when you’re out in the shop.

38 thoughts on “Drilling Perfectly Centered Holes

  1. The process should work fine if the process is reversed, ie clamp the piece to be drilled in the chuck and transfer it to the vice. The drill bit can thus be used in the the standard way.

    1. 5 years late, but oh well. At first glance I thought they were the same, but it’s actually not the same at all. They are in fact exact opposites.

      With the bit rotating, the tip of the drill bit is always central to the rotation, and central to the hole it’s drilling (not the piece the hole is being drilled in, obviously, but the hole itself). This does nothing to center the hole, but it does drill a very nice, perfectly straight hole, which is the point of drill bits.

      With the work rotating and the bit stationary this relationship is flipped, and this causes the cut of the drill bit to always seek the center of the work, rather than the hole it’s cutting. This is the whole point of lathes, and why you can do perfectly symmetrical work on a lathe. Seriously, watch normal lathe work with someone working on the end rather than the side. It doesn’t matter how far away from center he starts, all the guy with the blade has to do is move sort of toward the middle and it automatically works in to dead center. I don’t mean close to center, I mean perfectly centered on the rotation.

      What this means is as long as your bit is reasonably close to center, you will always drill a perfectly centered hole. If it’s NOT reasonably close to center. it will jam up and possibly break the bit and ruin whatever you’re working with, depending on how strong all of your equipment is.

  2. @Phil
    The chuck can hold delicate pieces in a much more stable manner than the vice, and with more contact points.
    Holding a delicate piece (that is being hollowed out by the drill bit) with the vice will inevitably lead to distortion.

  3. @fartface

    Once upon a time, you did not know about this. You probably had someone introduce you to the Advanced Machine Work book too. And for posting such noob things, I thank you. Because now I also know. Or should I have already known about that too?

  4. I have a couple criticism of the article:

    First, hand sharpened drill bits do not drill straight. They chatter. The holes they make will be out of round and off center. Sharpening the flutes symmetrically and with proper angles requires specializes jigs or highly configurable grinders like the beauty recently featured on Hack A Day. I’m not suggesting throwing out your bits, but keep one set of properly sharpened bits for jobs like this.

    Second, even a bit that is sharp and true will tend to wander than starting a hole. Machinists who need accuracy start their holes with either spotting drills or center drills. TFA’s approach might work most of the time, but if you want to get it right every time, put the work piece in the vice and use the correct tools.

    I’ve become something of an evangelist for hobby size machine tools. A table top lathe makes this chore a breeze (tighten stock in 3-jaw chuck, drill), and opens up a world of possibilities. I waited until well into my 40’s to get some really cool tools, and regret not starting out 30 years earlier.

  5. On the physics comment, while true the chuck has its place, it becomes much more center because it is the object instead of the bit in the drill. The centripetal motion forces any objects to it’s center. This phenomena can be broken, but it’s something a craftsman (relative to this case; a person with a lathe or a ceramicist using a wheel) takes into consideration while working.

    Centering the chuck can be done wrong as well, but its more obvious then if the position of the bit lodged between the clamp was off.

  6. Spinning the work instead of the tool is a great technique for a lot of projects. It’s how people drill gun barrels, for instance, since the drill is self-centering when used this way so it’ll run right down the middle of the stock. It is also a good technique if you need to put a centered point on the end of a rod: chuck it in the drill and spin it against a bench grinder. You’ll get a nice sharp well-centered point. Ditto putting a centered cup on a nailset, if you have a small-diameter grinding wheel on your Dremel.
    This is the reason lathes are the most versatile tool.

    1. You don’t use normal drill bits on gun barrels, they don’t drill straight.

      You use D-bits, which look like they shouldn’t work but they do.

      A lot of ‘drilling a hole is obvious’ stuff isn’t. Spinning the work gives a different result to spinning the bit (although ‘common sense’ says “what’s the difference?”).

  7. By the way, in case anyone reading this needs to drill deep holes, by which I mean more than 10x as deep as they are wide, here are a couple of suggestions. Rotate the work, not the drill, as we’ve already said. Amazon.com will sell you really long thin drills, like 1/8″ drills 12 inches long, but I’ve found they don’t really work well because the flutes make the drill squirm and cut poorly. Use aircraft drills, that have long unfluted shanks with only a short fluted section at the very end. Peck: drill in maybe twice the diameter of the drill, then pull it all the way out to empty the chips. And if you can manage it, double-drill using one drill about 1/8″ or so smaller than the final size, and the second drill the final size, drilling an inch in with the smaller drill then following up with the larger, alternating as you drill through. (Similar to cutting a long thin rod on a lathe.)

  8. I work for a company that makes office screens http://www.ecomfg.com/
    And have spent some time working in all the departments of the factory (including metalwork). The way I’ve always done centred drill holes is to take the piece of metal (in my case it was with flat bar 25mm/2mm) and measure halfway across the flat bar (12.5mm) and ‘centre punch’ (I don’t know if that’s the real name but that’s what we called it in the factory) and punch a start dent on the metal then we would use a premade jig and clamp it all together in a vice. Once in the vice we place under a pillar drill and drill the hole! It sounds quite long winded but it worked every time!

  9. Jesus what’s with those twats who go “Oh everybody that has years of experience or read one specific book knows this, this is boring”
    Guess what’s REALLY boring? You idiots and your pratty comments, you types have been ‘helping’ for thousands of years too, and it’s enough already thanks.
    And they forbid parents smacking kids…

  10. I second that a lathe would be the best way to do something like this, but when you’re short on time, a lathe, or both, this would be the way to go. As someone who isn’t a machinist by trade or any standard for that matter, this is a hack.

  11. if you use the right feeds and speeds you dont need these little “tricks” you can drill a 3/16 inch hole through 12 inches of steel with the right feeds and speeds.

    what do you do when you have a bigger, or irregular work piece?

    Use a center drill first, then drill your hole. works every time.

  12. Also note, this trick only works if the piece being drilled is smaller than the feed depth the drill press is capable of, otherwise, you have to move the drill but/vise to get the work in the chuck and it will not return to the same location.

    But it is a good alternative if you do not have a small lathe available. Even when using this method, I’d think about starting off with a center drill bit. They are cheap and very handy.

  13. Can a laser distance meter fixed on top of the bolt which would constantly measure the distance from the bolt to the laser light while the bolt is being rotated on the chuck be used for this ? then i guess it could help to increase the accuracy of finding the center

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