From Lowly Can Opener to Mortise Clean-out Tool

Wednesday 15th February 2017

I know, I should have just made one or two of these years ago. I knew exactly what I wanted but was too lazy to just make one. Fast forward and I decided to do something about it so here it is. What to call it?? Waste extractor? Chip remover? You help me decide. Right now, from the package, it’s just a little ol’ paint can/bottle opener. Why do I so need one? To stop those uninitiated around me using 1/4″ chisels as paint can openers. No, not really, they learned that long ago. What I need something to excavate with. For years now I have chopped all of my mortises by hand and it looks as though I will be doing it for another decade (hopefully). Inside the mortises we accumulate chips that build up and get wedged between the walls until we lever them out either with the same mortising chisel or a slightly narrower one because it’s easier. Generally we avoid levering the chisel on the ends of the mortise holes because these are often seen. Any bruising then looks ugly and sullies the view people have us. On shallow mortise holes and non-through mortises it’s not such a problem to remove the waste wood, but as we deepen the mortise in deeper mortises, such as in door stiles and table legs, the chips can often be hard to remove because of the angle of leverage in relation to the length of the mortise. My new device takes all of this into account. I have looked at many possible options for the past couple of weeks having made my mind up and finally I found the paint can lever with the curved tip. I refined it just a little to remove the blunt or square end. So that in the mortise it will slide into and under the chips more readily. It’s not at all meant to cut. The tool dislodges chips and the hook end is large enough to lift out the waste. I made one full width, which is 7/16” wide, ideal for 1/2” mortise holes. The second one I filed down, to ¼” bare so around 7/32” or 6 mm. Perfect for 1/4 “ – 3/8” holes. Like many things, I should have done this before now and had the benefit of it in daily use. One day I will learn, but at least i have it now.


  1. Great idea Paul.
    I cut a couple of 10mm mortises yesterday and used a 6mm chisel to remove the waste chippings but still ended up having to unclamp my work and invert it to get the tricky bits out.
    I will pick one of these can openers up and give it a go.

    1. Not too useful for smaller holes but great for cutting deeper in door mortises. Also cost and size, they don’t do what the can levers do, but thanks for the suggestion.

  2. Crown make these two little chisel scrapers that are off set to the opposite sides one left and one right and they are “L” shaped so you can lever off the bottom of the mortise holes. I got mine from Woodcraft maybe 8 years ago . I just hone the ends and draw a burr and they work great. There only about 5″s long with short fat handles so there easy to hold but will scrape the bottom of a mortise hole nice and flat. Plus you can modify them any way you want. Just a thought. Of course yours have very little overhead compared to mine. Call them bottom scrapers.

  3. The Japanese use a similar chisel called sokosarai-nomi to cleanup the bottom of mortises. I was always interested in that tool, one of those “do only one thing and do it well” tools. But using a paint can opener is clever, I am going to make a few of them. Thanks for the tips as usual

  4. A few months ago I bought some paint at Home Depot and they gave me of these and never would have thought of using it for this. Brilliant!

  5. now you need to turn a cool handle for it. I hope you warned the hardware store to be ready for a run on paint can openers.

    1. No no no… don’t forget, as it is it’s still just as useful as a bottle opener as it always was 😉

  6. I do what my Dad did and blow down a short bit of 1/4″ tube ! He also taught me to close my eyes when I did it!!

  7. Couldn’t help but notice that the walls of the mortise are very thin. I thought the rule of thirds applied to tenon and mortise width. Is this just a demonstration piece or does it have real purpose? If so, what use calls for such thin mortise walls?

    Great idea! I must have near a dozen of these things accumulated over a lifetime of buying paint. I shall definitely make a couple of them!

    As always, thank you for teaching us, Mr. Sellers!

    1. This is a demonstration mortise — he didn’t make any layout lines and the walls are unequal in thickness, also. Clearly it was created just for teaching. The right edge is bruised to show you what could happen.

  8. Wonderful idea, Paul! Like a naturalist finding food in a forest where others see none, your experience and inquisitiveness benefit us all. Thanks.

  9. Methinks eBay sellers are going to leave them outside to rust, then sell them as “collectable, vintage”.

  10. You might call it a frass removal tool. Roy Underhill has referred (S33 Ep13: Big Ash Mallet!) to the material being chiseled out of a mortise as frass. Wikipedia gives a definition (Frass) as ” . . . the term also may refer to excavated wood shavings that carpenter ants, carpenter bees and other insects with similar wood-boring habits kick out of their galleries during the tunneling process”. ” . . . insects that tunnel to construct such nests do not eat the wood, so the material that they discard as they tunnel has not passed through their gut”. So is not referring to droppings.

Comments are closed.

Privacy Notice

You must enter certain information to submit the form on this page. We take the handling of personal information seriously and appreciate your trust in us. Our Privacy Policy sets out important information about us and how we use and protect your personal data and it also explains your legal rights in respect of it. Please click here to read it before you provide any information on this form.