Sharpening Auger Bits

Note: The content of this post has been moved to my new blog.  You can find the new post here:

http://brfinewoodworking.com/sharpening-auger-bits/

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12 thoughts on “Sharpening Auger Bits

  1. Thanks Bob! Your list of DO NOT’s is pretty much my list of things I’ve done to try and sharpen one of my bits.

    Have you got any advice on size or sources for auger files?

    Somewhat unrelated, but is there something out there that’s appropriate for boring into end grain? I tried that with one of my auger bits and it was a miserable failure – I have a hunch that’s what ruined one of my bits (the lead screws don’t really work anymore).

    • I think The Best Things still has some auger bit files left. You might try them out. I heard a rumor that Nicholson was not making them anymore, so I’m not sure if they will be available in the future. A small needle file can be used too, I’d just grind the teeth off one edge to make it a safe edge. It’s not necessary, but nice to have.

      Boring into end grain doesn’t really go well with any kind of bit. Forstner is probably the best bet, but even that doesn’t work real well. It shouldn’t ruin the lead screw though. It probably just clogged all up with chips and dust. Pick the wood out of the threads with an awl, needle, or whatever you can. Then look at the threads. If they are munged up, hit the with a triangular saw file. If they are just a little rusty, but not burred, then do what Josh says below to polish the threads. I did this in Part 4 of the sharpening podcasts with loose SiC grit. It works great to polish the threads and help prevent them from clogging. If the threads have a lot of bent metal and burrs though, you need to file that off first. The SiC grit or valve lapping compound will only polish what is there. It won’t fix damage.

  2. The tip that had been handed to me – and I’ve seen it on Sawmillcreek as well – was to touch up the lead screw by drilling the brace just enough to bury the lead screw, back it out, and then drop a bit of valve grinding compound in the hole, and screwing in and out. This helps sharpen the leadscrew. Sometimes it takes a couple of holes worth to get it good.

    A lot of times, especially with bits you find used, the problem with the leadscrew is not that it’s not sharp enough, but that it’s gummed up with pitch and woodbits. A little care to clean up the leadscrew really helps.

    • Yep, this works great to polish the threads and help keep them from clogging, as long as the threads aren’t damaged. It won’t repair damaged threads. If the threads are damaged, you need to file them first to remove the damage, then polish them with the valve lapping compound.

  3. Bob,

    Lie Nielsen has found an alternate supplier in India and sells auger bit files at a good price.

    Question: The bits I find are for softwood. If you use them in hardwood with enough torque, will they function?

    • Look for Russell Jennings no 100 bits. The thread pitch of the set I have works well in hard and soft woods. If you are using Irwin bits, I’ve found their screws pitched too coarse for hard woods. They require more torque but even then the screw seems to strip the guide hole out more often because the coarse screw makes them more aggressive.

  4. I can’t get the correct bevel on mine. I am still doing something wrong. I can get it to start but can’t drill deeply. Is picture one have the correct bevel? I guess that’s my problem.

    • The bit pictured has the correct geometry. The bevel on the top of the bit (picture 4)really doesn’t matter all that much. The geometry of the bottom of the bit (picture 5) however is extremely important for proper function of the bit. Make sure that the bottom of the cutting lip (picture 5) has no secondary bevel at all. It should simply be one continuous surface starting at the cutting edge and spiraling all the way up the bit. If there is any hint of a secondary bevel on the bottom of the cutting lip, it will need to be filed away so that the surface is uniform without any secondary bevel.

      However, if your bit starts to cut and then stops part of the way into the cut, I suspect the cutting lip is not the problem. More than likely, either the spurs are not sharp enough to score the outer edge of the hole well, or the lead screw is clogging up.

      What kind of bit are you using (Irwin, Jennings, etc>)? What kind of wood are you boring? Are you boring through the grain (face or edge) or into the grain (end grain)? If you can, email me a picture of the cutting end of the bit so I can see what you are working with.

      • They are Jennings bits. This weekend I will give them a look over, especially the screw and cutting lip. I was just trying the bits in the face side of pine. Thanks for the help. Obviously I don’t know what I’m doing! Your blog has been helpful. How many people can I ask help on sharpening auger bits!

  5. Hi Bob,
    Thanks for the tips on sharpening auger bits, they’re a great help.
    I have a couple that need tuning for use.
    I prefer using auger bits with a brace, to driving flat bits using an electric drill.
    Using an electric drill is always a lot slower noisier and most often overheats the bit ruining the temper (bluing it) and not holding its edge.
    The old ways still work best.
    Maurice.

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