Shape and Angle for Cap Irons

[Glen Johnson]

I just bought several Stanley replacement cap irons. They looked rounded at the end where the cap iron met the blade and pushed captured shavings between the cap iron and the blade. I used sharpening stones to put a flat bevel of about 80 degrees and they now work much better. I would be interested to hear what other creekers do to the front bevel of the chip breaker. What angle do you use? Do you use a flat bevel or try to have it curved?

[Phil Mueller]

Do you mean the top of the cap iron, or the edge of the cap iron where it actually meets the iron? If the top, vintage tends to have a rounded top and new tends to have a flat bevel. Both angle down to the iron in the neighborhood of 30-35 degrees.

The important thing is that the leading edge that meets the iron is flat and makes complete contact with the iron across the entire width. A number of videos are online that show how to put a slight back bevel on the cap iron edge to ensure the leading edge makes full contact.

When you put the cap iron and iron together you should not be able to see any light coming through between the cap iron and iron. I've never messed with the actual angle of the curved top or changed the bevel on new....

If you're getting shavings under the cap iron, it means either the back of the iron isn't flat, or the cap iron leading edge isn't flat, or both.

[Glen Johnson]

Thanks. The new cap irons sits well on the iron and come with some back bevel. My question is what angle and shape should the leading edge of the cap iron be relative to the blade. I remember the japanese video on cap irons had a pretty steep angle. I was wondering if someone had explored the advantages and disadvantages of different angles.

[Tom Trees]

You obviously have been watching the Kato and Kawai video ..influence of the cap iron
David Weaver, (David W) has gone to much effort to make it widely known, that the cap iron can be used to eliminate tearout.
He has done a write up on wood central about this.
Basically anywhere above 50 degrees but less than 80, as it gets harder to push.
He prefers a rounded edge on the cap iron.
There is some correlation between close setting of the cap iron and the leading angle f it.
From what I understand, the less steep the angle the closer the cap needs to be.
I chose to do a bevel of 51 degrees and got good results.

This setup is to be used without having a tight mouth !
Look up Davids or Brian Holcombe's youtube channel on this.
Have fun
Tom

[Kees Heiden]

Original Stanleys are about 45 degrees and rounded. Those old woodie irons look like they are very flat but the round nose often ends around 45 too.

So I keep to 45 nowadays and make them rounded. Much steeper and it seems to become more binary, either not much effect or suddenly too much and pushing resistance increases a lot.

You can even make 30 degrees working correctly to avoid tearout but you'll have to set it even closer to the edege.

[Jim Koepke]

My Stanley chip breakers are usually polished a bit on my stones, stropped and then lightly waxed to improve chip flow.

He prefers a rounded edge on the cap iron.

+1 on that.

jtk

[Derek Cohen]

I purchased an extra chipbreaker for my LN #3. One has a flat 50 degree secondary bevel on the leading edge, and the second has a rounded 50 degree leading edge.

There is no difference between them when set at the same distance (around 0.3 - 0.4mm).

Regards from Perth

Derek

[Glen Johnson]

I greatly appreciate your replies. I have also found that opening up the mouth of the plane a bit helps when the cap iron is set tight. I think I will lower the angle from its current 80 degrees to something closer 60 and see how it goes.

[Robert Engel]

My question is what angle and shape should the leading edge of the cap iron be relative to the blade.

Its never been an issue IME, but so long as the cap iron makes continous, tight contact with the iron when levered down it will perform, even a rounded edge.

Because the Stanley cap irons flex so much, you should probably put a bit steeper angle on like you did.

The angle is irrelevant just hone it till its flat against the iron.

[Warren Mickley]

smith's key.jpg

Here is Smith's illustration of a double iron. Nicholson says: The basil of the cover must be rounded and not flat, as that of the iron is.

I agree with Nicholson. I have used a rounded bevel that meets the iron at a steep angle for over 40 years.

[David Bird]

Nicholson says: The basil of the cover must be rounded and not flat, as that of the iron is.

(a simple typo made the quote hard to understand)