Tear out - are cap-iron, high EP equivalent?

[bugbear]

Both a close-enough cap-iron and the high enough effective pitch
will reduced tearout. Are the mechanisms (in fact) the same,
or do they work in different ways to achieve the same result?

On the face of things, it seems "quite reasonable" that adding a cap iron with a 20 degree
bevel to a plane iron at 45 might behave very similarly to a single iron bedded at 65 degree.

I am aware that most of the "cap iron conversation" took place on US and AUS
forums, so the answer to this might be well known, so any links
to previous discussions would be just as good as laboriously typed out answers,

BugBear

 

[swagman]

Your an evil man BB; :lol:

Single Iron vs Double Iron debate. :shock:

Batten down the hatches, save your children, this discussion is heading for the sin bin. (hammer)

 

[bugbear]

Gutsy move BB; :lol:

A Single Iron vs Double Iron debate. :shock:

The Moderators may need to step in and stop this discussion. #-o

I don't care which is "best", "cheapest", "easiest", "oldest", etc.

I just want to know how they work - if anyone knows, that is.

BugBear

 

[G S Haydon]

The best way to get your head around it is to watch the Japanese video https://www.youtube.com/watch?v=ygcRgQUUrnk . When I watch it I see the cap iron compressing the shavings as it is formed, preventing it from splitting away from the wood in front of the cut. When I watch it I see a shaving being cleanly cut and supported. When the wood is easy to work you can move the cap iron back and take advantage of the standard 45 cutting action.

I would describe a higher pitch as approaching a scraping cut. The higher the pitch the less it becomes a true cutting action. Although effective there is more stress put on the cutting edge, you have to have more planes or different irons to then work with less resistance on easy working wood or on non show surfaces.

However, this knowledge is not essential to designing and making great projects from wood.

 

[swagman]

Forget the Japanese video. It was aligned with research into Supersurfacer Machines. https://www.youtube.com/watch?v=_L0SaSMfvkA

The following video imo has more relevance to the OPs discussion on single iron and double iron bench planes. https://www.youtube.com/watch?v=c0N5pV8 ... u.be&t=373

 

[G S Haydon]

Thanks, some good footage! I think I'd describe what I'm seeing in the same way as I did in the Japanese video.

 

[D_W]

Cap iron should leave a better surface and be less difficult to push for the same amount of wood removal and tearout prevention. It should also last a lot longer between sharpenings.

The reason for the better surface is that it is still cutting at a lower pitch, and should only have a negative effect on the surface if it's set too closely.

 

[bugbear]

Cap iron should leave a better surface and be less difficult to push for the same amount of wood removal and tearout prevention. It should also last a lot longer between sharpenings.

The reason for the better surface is that it is still cutting at a lower pitch, and should only have a negative effect on the surface if it's set too closely.

Thank you for that. Most interesting.

While you're about, would you mind reading and answering my question? I mean,
you don't have to, but I'd appreciate it.

BugBear

 

[Derek Cohen (Perth Oz)]

I have pointed previously that the (straightened) shaving from a closed up chipbreaker/cap iron (LN #4 1/2) ...

.. is the same as from a plane with a high cutting angle (HNT Gordon smoother) ...

.. and Veritas BUS with 62 degree cutting angle ....

My apology for the poor photos - all I could find as Photobucket, with all my photos, appears to be down at this time.

The point is that the bending of a chip by the chipbreaker, and its downforce when this occurs, appears to be doing something similar to the high cutting angle. Their shavings are straight. The shavings from a non-chipbreakered plane is curly.

The other factor of a high cutting angle being less capable of a shiny cut compared to a common angle may be true. However this is less apparent on hardwoods. Here is a surface off the BUS (reflections of a window on planed Jarrah) ...

Regards from Perth

Derek

 

[Trafalgar]

I've found a close cap iron plane harder to push, similar to the slight increase you might notice with a higher pitched plane. Of course this doesn't mean the physics at the chip level are the same, but still....

 

[ED65]

Are the mechanisms (in fact) the same...?

I would say no, not exactly. At least not all the time. Sorry to sound like I'm hedging, I'm not, but because of the additional variables to high AoA and cap-iron setting I don't think there is a definitive yes or no here.

Using planes of each type can you get nigh-on identical shavings from the same wood – the same piece, not another piece of the same species – at the same time? If so does that point to the mechanism being the same? It would be suggestive, but only if the surface left behind were also indistinguishable. This is the key pointer IMO.

Low-angle porn shots of planed wood notwithstanding the fact that it's so difficult to get equivalent results (to the point of being impossible for some) I think tells us that most of the time the mechanism isn't the same, otherwise this wouldn't be the case.

 

[bugbear]

Of course, if the mechanism in either case is unknown (or at least open to doubt or debate) my question is unanswerable.

BugBear

 

[swagman]

BB; attached is a post where the single iron's approach angle was increased from York Pitch (50*) to Cabinet Pitch (60*) to address tear out.
refurbished-french-smoothing-plane-t104850.html

 

[DoctorWibble]

One breaks the fibres at the cut, the other breaks them a little higher.

 

[ED65]

One breaks the fibres at the cut, the other breaks them a little higher.

Given our knowledge of what tearout is does that not suggest that the first would leave a better surface? However the opposite appears to be the case, more often than not. The plot thickens!

 

[Derek Cohen (Perth Oz)]

BB, the closed chipbreaker works by creating a Type II chip ("the wood is cut right at the sharp edge of the blade and is then forced to bend sharply"). The high angle blade creates a Type III chip ("Because of the high angle of the blade, significant forces are created that can deform the wood below the cutting line"). Quotes are from Steve Elliott - http://planetuning.infillplane.com/html ... ation.html

In other words, two different mechanisms that end up with the same result.

Regards from Perth

Derek

 

[G S Haydon]

I think that's what I tried to say but did less well doing so.

 

[D_W]

I've found a close cap iron plane harder to push, similar to the slight increase you might notice with a higher pitched plane. Of course this doesn't mean the physics at the chip level are the same, but still....

And there is that thing that if you're making stuff for a customer, they're not going to care at all. I can't debate that.

If wood is absolutely horrid, you can get stuck setting the cap close enough to get the same resistance you'd get from a high angle plane - that's certainly true.

 

[D_W]

Forget the Japanese video. It was aligned with research into Supersurfacer Machines. https://www.youtube.com/watch?v=_L0SaSMfvkA

It is a suitable video to understand (visually) what's going on with the cap iron, but not for taking strict numbers and applying them to hand planes or suggesting that what's best for machine is the same for the hand plane.

 

[Trafalgar]

Makes the original invention all that more amazing really.