Since ranting about using the cap iron for dealing with tear out, the question ‘why do you only use it when smoothing?’ comes up a lot.
This question is best answered by me asking you to go and do something.
Go and set your hand plane up to take a shaving with the cap iron nice and close to the edge as we discussed, so it’s actually doing something.
Take a shaving with the grain on a fuss free piece of timber. Begin the cut as normal, but once started take your hand off the front of the plane, only push from behind and give no downwards pressure.
Now a comparison shaving.
Use the same plane but this time with the cap iron right back out of the way (1/8″ or more). Aim for the same depth of cut and of course both times ensure a sharp iron.
Repeat the shaving and once again take off the front hand so the plane is only being pushed forward and not down.
Did you notice the difference? Try it a few times more if you didn’t.
Here’s what you should find:
Planing with the cap iron set is hard work.
Normally a plane will pull itself down in to a board as we take a shaving, which means we only need to push forwards. Close cap irons remove a lot of this benefit and without applying downwards pressure it will probably skip (something I see people suffering with a lot). This need to add downwards pressure together with the cap iron’s effect on the shaving, adds friction, so all in all it becomes a bloody hard job. This is magnified on thicker shavings.
Like four wheel drive, the cap iron is tremendously useful in the right situation, but turning it on for anything else it’s inefficient. With four wheel drive this will hurt your pocket, while inefficient planing affects you.
To do a good job we have to learn to be efficient. Tear out isn’t the only battle that we have when planing and a bigger one will likely be fatigue. Getting knackered makes us sloppy and that’s a big cause for a rough job.
Don’t confuse that with meaning that it should never be used in anything other than smoothing, but those scenarios are niche and wouldn’t be general run of the mill stuff.