Full Chisel Blog

June 11, 2008

Sharpening Drill Bits

Filed under: Drilling,Uncategorized — Stephen Shepherd @ 6:56 pm

Now these don’t work well unless they are sharp.  Well a burn auger works if it is red hot, sharpness is not that much of an issue.  On all other bits it requires that the bits are sharp to easily remove the wood occupying the space in which you want to make a hole.


The Center Bit on the left is easily sharpened with a flat file, auger file or triangular file.  The Gimblet bit on the right needs a round file and a flat, auger or triangular file to sharpen.  The numbers indicate the order in which the bit should be sharpened.

When sharpening center bits it is important that it is symmetrical and that 5 the center pivot is in the center.  The spur is for scoring the wood so it should be sharpened like a knife edge, sharp on the bottom and leading edge.  The excavation cutter on the opposite side is sharpened like a chisel or plane blade, with the bottom flat and the bevel dressed to a sharp edge.

The Gimblet bit needs to be sharp on its edges and this requires a small round file.  Needle files work well to bring the inside pod edge up to meet the outside edge to provide a sharp cutting edge.  The edges of the tip need to be sharp as they act as a screw to pull the bit into the wood.  This bit produces a smooth exit hole as it enlarges the hole and pulls the dreck back through the hole.

Here is the method of sharpening twist auger bits.

Sharpening Augers

Auger bits can be sharpened with a flat file, a triangular file or much easier an auger file, a special file with safe edges and safe faces to allow for proper sharpening.  The numbers indicate the order in which the edges are addressed.  When sharpening it is just like sharpening a knife, chisel or plane iron in that you get the flat surfaces flat then work on the bevels.  The last part #5 is to freshen the threads of the screw, this is generally done with a triangular file.  If the threads are sharp, then no attention is needed, but most need to be freshened a bit.

Reciprocating bits are sharpened flat and square as they cut in both directions, spoon bits on their end, nose augers on their nose.  It helps if the bits are bright, for one thing that helps prevent rust and for another it facilitates chip removal, rough, rusted or pitted surfaces tend to clog up.  Some bits remove their chips as you work, others require that the bit be periodically removed to remove the dross from the hole.

I sharpen bits like I sharpen saws after I have joined off the teeth.  I remove the metal until the shine on the top is gone.  Same for sharpening knives look at the edge and when the shine is gone, it is sharp.  Hand drills are not that hard to sharpen, with the exception of flat countersink bits intended for metal, they are quite a bit harder and require honing on a stone.

Equip yourself with round needle files, round files, triangular files (in all their iterations), flat files and most importantly the auger file.  Joel at Tools for Working Wood sells auger files, order one you will need one.  Avoid filing on the outside of any bit as much as possible as it will eventually reduce the diameter of the bit and can cause binding, etc.

When drilling through boards it is always a good idea to have a backer of scrap wood to prevent split out on the off side.  A square or bevel can help get the hole at the proper angle, a bit extension can help with angles and the wedding ring can be used to drill horizontal holes.

I sometimes dip my bit into the grease cup to help with difficult woods, such as green or wood with a lot of pitch.  When drilling green wood, make sure to wipe off the bits immediately to prevent rust.

Choose the proper bit for the proper job.  Wait a minute what kind of stupid advice is that?  You are adults you know what you are doing. 

Any Questions?



  1. Stephen,

    I just bought an auger file last night so that I can restore a bunch of auger bits I inheirited. I was just about to do some research on how to sharpen them when I came across your blog. Great timing and thanks for the information!

    Comment by Shannon — June 12, 2008 @ 6:35 pm

  2. Shannon,

    Glad you found the site, if you have any questions feel free to ask.


    Comment by Stephen Shepherd — June 12, 2008 @ 11:06 pm

  3. Stephen, Shannon

    To clean up or otherwise restore rusty threads on the screw tips of bits, try this easy tip.

    Smear some LV green compound on a piece of scrap wood and drill just deep enough in it to bury the screw tip back and forth. The abrasive action of the stuff will clean the screw threads. Repeat as needed. Safe and efficient, without fear of buggering up the threads as often seen with a file.


    Comment by Robert Demers — June 14, 2008 @ 2:33 pm

  4. Bob,

    That is a good tip on cleaning those threads. The threads like other parts of the auger need to be bright to work properly. A file should only be used if you are confident enough to fresh out the threads without buggering them up.


    Comment by Stephen Shepherd — June 14, 2008 @ 7:14 pm

  5. Thanks guys. One stupid question though, what is LV compound? Also how important do you think it is to remove the rust on the rest of the bit. I have seen some posts on evaporust out there and I am wondering if I should put this to work on the bits I posted about on my blog. http://rogersfinewoodworking.com/blog/2008/06/13/the-magic-toolbox/

    Comment by Shannon — June 23, 2008 @ 3:46 pm

  6. Shannon,

    The compound is a buffing compound, LV is the Company Lee Valley and they sell the stuff. I clean the entire bits of rust as it helps the chips work out of the hole better. I don’t know about evaporust, never tried the stuff. I use electrolysis and and ultrasonic cleaner (Yeah how historical is that?) to clean my old tools. I appologize to the purists for that comment.


    Comment by Stephen Shepherd — June 23, 2008 @ 7:13 pm

  7. […] First though, I wanted to catch up on the blogosphere. After logging into Google Reader, I see that Stephen Shepherd has put up a few new posts. Low and behold there is a post on sharpening drill bits and about […]

    Pingback by The Magic Toolbox… | The Renaissance Woodworker — January 15, 2013 @ 3:22 pm

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