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JOEL Joel's Blog

Unscrewing a Cap Iron Screw


Unscrewing a Cap Iron Screw 1
I think I have a tendency the unscrew cap irons from their irons more than the average woodworker. I'm always in the middle of one project or another, and in many cases I'm testing and comparing so I'm constantly taking one iron out putting it in another plane and swapping parts around. What you really want for unscrewing a cap iron is a fairly wide screwdriver that is also thin enough to fit in some of the older planes and won't cam itself out of the screw slot because it's wedged. If the screwdriver blade is too narrow, it can ding up the cap iron screw as well. And the screwdriver always needs to be convenient. A bad option is using the lever cap to loosen the cap iron screw. This is a horrible idea - you just crack and mar the lever cap. Don't do it. While many companies sell purpose made cap iron screwdrivers, I've never owned one.

My solution to this problem uses a tool that's always nearby (at least for me), and fits every cap iron screw without dinging it up. And doesn't cost extra.

I don't know when I started doing this. It might have been 30 years ago. But it turns out the back of my closed Swiss army knife blade (which I have had since 1981), and most other normal pocket knives, fit pretty much every cap iron screw out there. When you turn the knife, you get a lot of leverage. The leverage you get from the long knife is really important because you don't need a lot of force that can make you accidentally slip and mangle something. Another benefit is because the knife blade is tapered from the body to the blade, it won't cam out of the slot when turned. The blade is not going anywhere. On most cap iron screws, the blade fits the slot nicely near the front of the blade but because the blade tapers a bit from toe to heel, some cap irons screws fit better at the toe, others at the heel. I mentioned the leverage already. And of course I pretty much always have a pocket knife on me, especially in the shop. One further bonus: a lot of the times when I'm unscrewing a cap iron it is because I'm taking the blade out so I can sharpen it and this reminds me that I should sharpen my pocket knife as well.

Unscrewing a Cap Iron Screw 2

Click here if you happen to need a replacement cap iron for one of your bench planes. Or click here for a replacement iron.
Join the conversation
11/02/2022 Dale Forguson
Gunsmiths often encounter very tight screws that haven't been removed in a long time. Obviously marring the screw head is to be avoided. The topic is addressed in Modern Gunsmithing by Clyde Baker very well. The book is a worthwhile addition to any woodworkers library. Even if you have no interest in guns the metalworking topics covered have other applications.
11/02/2022 Gerry Cox
Great idea! I never would have thought of that application.

You note reminded me that I carry on my key ring aVeritas .pocket screwdriver that is circular with a beveled edge—that should also work.
11/02/2022 Ed Furlong
Appreciate the tip, especially since I almost have a SAK in my pocket and feel incompletely dressed when it isn’t there at hand.
11/02/2022 David Bridgewater
Whats wrong with using the lever cap, which I've been using for the last 62 years.
I've lost count of the lever caps I have seen with a notch in the tip from people doing this. This is especially a problem with newly acquired old tools, when you don't know how tight in the screw is and it might need a lot of force to move. Your cap iron screws are obviously properly maintained and don't need excessive force to move.
11/03/2022 Jesse Griggs
i found a short 1/2" wide flat blade screwdriver. popped it out of its hideous plastic handle. made a new handle. and ground the faces with my bench stones so the faces are parallel and not a wedge. works really well and is pretty nice. though counting the time it took, the cost for a plane screwdriver probably would have been better.
11/04/2022 THOMAS WALTER
A church key can/bottle opener also works.
11/08/2022 G5Flyr
After reading Joel's post I tried this and thought... DUH! 999 days out of 1000 I have my trusty SAK in my pocket.

@David Bridgewater: You are correct. I've seen a lot of well respect woodworkers do the same thing on YouTube, etc. However, I have to echo Joel's response to your comment. Eg: I have a Stanley no. 7 c. late 1920's that you would call a "Perfect 10" were it not for the chip in the lever cap. I bought it because the seller priced it competitively. I have a specialty screw driver. Actually, I have two. One from LN and the other from Veritas. The LN is my favorite because there is no guessing as to the blade's orientation. However, I had to thin the LN's blade down a few thou in order to make it fit all of my chip breaker screws. Umm... my SAK also has a screwdriver. DUH (again).
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