Tuning the cap iron (chip breaker)

Shop Timetestedtool's tool Store ......... And The Etsy Shop

For the whole restoration guide, click here

For the bench plane tuning guide, click here

As I was riding through the foothills of Vermont and collecting a nice #3 and #7, I had bid on another #7 on Ebay. My bid, I thought, was low enough that I just wanted it to show up in my bidding list. When I got home, toting a #7 in my saddlebags, didn’t I have an email telling me I had won the bid? With the price I paid, I was happy enough. I went from no #7s to two #7’s in a single day. As I started to clean this one up, the one issue with this plane was the very end of the iron and the cap iron was rusted and pitted pretty bad. With the iron, I simply “sharpened” it down about an 1/8”. That got it past the bad spot. I always polish up the cap iron (also known as the chip breakers) for a much smoother operation. This blog will show you how I get the cap iron job done.

Depending on the severity of the work needed, I may just wire brush the top side and polish with the deburring wheel , but in some cases its more severe than that. I will sand this out starting with a grit appropriate for the rust, (this one started with 120, it was pretty bad) and gradually increase grit size up to 600, then polish on the wheel.

Fixing the cap iron

Tuning the cap iron (chip breaker), its only important to get from the tip to the top of the crown. After that’s its just cosmetic and i don’t get as fussy. I will clean this one up a little better, but it will not shine all the way to the top.




Tuning the cap iron (chip breaker), you also want to make sure there is a tight fit between the cap iron and the iron itself. If there is not a tight fit, wood chips will clog up between the two and just ruin your day.

First grind the tip so its sharp. It doesn’t have to be sharp like your iron, but smooth and straight so a good seal is formed when you screw the two together. I usually do this on my horizontal wet stone, by simply holding the top end lower than the tip.


It usually doesn’t take much. If you don’t have such a grinder, a whetstone will work, as before, hold the top lower than the tip.


Next lets ensure there is some spring in the cap to force it against the iron when the two are attached. Using a straight edge, make sure there is a gap when the straight edge is set tip to tip.


When Tuning the cap iron (chip breaker), If there is not a gap, clamp the cap iron in a vice and gently push it to create it. Try to keep the pressure low so the movement comes at the bend in the iron. You can also clamp from the other end and tap it with a hammer. Use a block of wood as wide or wider than the iron so the whole width gets bent evenly.


After the iron has been sharpened, here is the results.


I hope it helps                

________________ As an Amazon associate, we earn income from qualifying purchases when you click on a link. Your link clicks help us fund our website. ________________