The Twisted Truth

Need a hole?  Many of our plans require drilled holes, so here are some Tips about drilling in metal, like steel, as well as in wood, and other materials.

Two-Handed Power Drill
Use a two-handed grip for a steadier, smoother drill.

There is a ton of information on the web about drilling, so I won’t go into a lot of detail, but I will point out a few tricks for the DIY builder — because we don’t always have the perfect tool for the job.

Background

  • A drill is tremendously efficient at removing material.  Some manufacturing folks claim it’s the most efficient — meaning you remove more per watt of power.
  • Drilling metal is arguably the most common form of machining.  Almost every home has a drill, and most DIY’ers have a few.  If you think of drilling as machining, it changes the way you approach it.
  • The process of Drilling involves one moving (spinning) part that cuts another stationary part (the workpiece).  If the cutting part (the drill bit) is drastically harder and stronger than the workpiece (like wood, for instance), then drilling is simple and usually without problems.  If, on the other hand, the materials are similar (steel drilling steel), there are some things to pay attention to.  Oh, and if the drill is softer than the workpiece, you’ll likely fail.  Make sure you know what your drill bit is rated for so you won’t damage your tools – or the project.

Drilling Metal

Let’s look at drilling metal.  The tips are the same for all metals, but you can get away with more if the workpiece is softer (like aluminum).

First:
Tools for Marking for Drilling
Make sure the hole you drill is the hole you want.

Make sure the location of the hole-to-be is well marked.  If the project is less constrained, like using a hand drill, then the drill will “wander” if the location is not well defined.  We recommend a carbide tipped scribe to mark the location, then a center punch to create a small divot for the drill to locate on.

A guided hole like in this tip about Matching Bolt Holes takes the measuring and center punch out of the equation.  It’s an easy way for drilling matching holes in metal.

Second:

Use a drill designed for metal.  The cutting angles and features are important.  If you’re not really familiar with drill bit angles for materials, you may want to start here for a basic explanation, and a list of point angles for metal and others depending on basic work materials.

Make the drill work for you.

Third:

Combination Center DrillStart with a small drill (or a center drill) to initiate the hole.  A small drill will wander less, stay in your punch divot easier, and take less force to get started.

Side Note:  A larger drill will follow a previous, smaller drilled hole.  Once you start a hole, it’s really hard to move it a little, so be sure you get it right the first time.

Fourth:

Increase drill sizes going larger and larger until you reach the desired size.  The amount to increase depends on power available, and the steadiness of the drill.  With a hand drill, for instance, smaller steps up in drill size help a lot.  Bigger steps with a big drill press.

Side Note:  Maybe more of a common sense note.  Don’t try to drill big holes with a small drill.  You’ll end up hurting your tools or yourself.

Fifth:

The most common causes of drill failure are:  Over Speeding & Under Feeding.  In wood it isn’t a big deal, but in steel it’s important.  The bigger the drill diameter, the slower it must turn, and more force is required to “feed” it.  So, Bigger = Slower + Push Harder.  That also means more power required.

Another common drill failure comes with cutting on just one side of the bit, or trying to drill an interrupted hole.  This drilling technique (see the article) is a great way to align holes, but will likely take a toll on the cutting edges of the drill bit.

Sixth:

Use lubrication.  That may seem counterintuitive, but they make cutting fluids for a reason.  Cutting fluids do a few things:

  • Help cool the cutting edges.
  • Lubricate the non-cutting areas (sides) of the drill that are spinning in the hole.
  • Helps chips move away from the cutting edges, and helps make a clean cut .
  • Cutting fluid helps the bit stay sharp.

You don’t need something specific for drilling.  Tap fluids like Tap Magic, for instance, are great for drilling metal.  I personally prefer something with a little more body and apply it with a small brush, but any like these with a squirt top work fine too.

Drilling and Cutting Fluids

Side Note: You don’t have to use special cutting fluid.  It’s preferred, of course, but in a pinch, use motor oil or some other lubricant.  It stinks when it burns and often smokes as you drill, but it works.  It’s much better than drilling dry.

Seventh:

When drilling in metal, go in increments.  If the material is thick, drill some, then pull the drill out, clean off the chips, add some cutting fluid, then resume drilling.

Eighth:

Be careful punching through.  One of the most common times for a drill bit to break is when it punches through the back of the workpiece.  If force down (feed pressure) stays the same, the drill bit takes larger and larger bites of the material as it finishes the hole.  If the bite is too big, it will jam.  That can be dangerous for you if the bit breaks, or if it flips the workpiece — or worse, flips the drill out of your hand.  To avoid these unpleasantries, lighten up on the feed pressure as the drill comes through.  If you’re using a hand drill, you can usually feel the moment it starts to give way.

Ninth:

Drilling Chamfer ToolAfter drilling, clean up the holes.  A round file, chamfer tool, or whirly-gig are all great to remove sharp edges.  This helps bolts enter easy, keeps fingers from getting cut, and generally makes it professional looking.  A small burr left on the hole can also compromise a bolted joint by not allowing the bolted pieces to mate fully. Just take the time and do it.

Drilling Wrap Up

Wow, this post is a lot longer than I intended.  Hopefully you get some good info from it.  We’ll look at techniques for drilling big holes in metal with small hand drills in another post.

Drills Note:  If you need some specific drills or sizes, like to build one of our DIY Projects, you can get nice single bits at Drills and Cutters.  Browse around a little and you can find reduced shank drills with 3 flats on the spindle — which are excellent for drilling medium sized holes with a hand drill — like those needed for our Gantry Cranes. You can choose Made in USA or Imported.  I have found they are better quality than Home Depot or Lowes or Ace, and the price is usually better.

Storage Note:  For easy access to drills near a drill press, here’s a Solutions! post worth reading.

Drill Bit Chuck Flats

For more info in fabricating, read the 7 Ways To Cut Steel article.

Good Luck With Your Projects !!

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