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

[bridger]

Makes the original invention all that more amazing really.

Just as ideas fail for unexpected reasons so too sometimes ideas work out but not for the reasons the inventor imagined they would.

In this case, it would've almost certainly been for reducing tearout, because the increase in the amount of work done in the 1700s would've been substantial to slot an iron, make a cap iron, thread it and make a cap iron screw. I could be wrong, though, the first planes (I've never studied the issue) may have had two irons almost the same where both were loose. I know we've seen some old french planes recently where they were made that way with a back iron almost as long as the cutting iron.

Isn't that- loose cap iron- how japanese planes are still made?

 

[bridger]

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

Two excellent videos, but neither addresses high angle planes

 

[bridger]

if you look at a proper scraper and a close set cap iron, the cutting edges are the same. It is not too much of a speculation that the inventor of the cap iron in 1700 simply made a logical assumption that he could make a plane iron act like a scraper by making a double iron. The condition of the shavings were not necessarily the starting point for the design.

Mike.

To further useless speculation on this point...

At one point I pursued this line of thought- making a single iron plane blade behave like a burred scraper. My first attempt was to hone a step in the top of the cutting edge. It was impractical. I never got so far as to reinvent the chipbreaker, perhaps because I knew that the chipbreaker was already invented

 

[D_W]

Isn't that- loose cap iron- how japanese planes are still made?

Yes. They're that way, and they're not hard to set in terms of doing it once - especially if you make a mark somewhere on the plane that tells you about where the cap iron needs to go. I just don't think they're quite as easy to set as stanley planes or other western planes that have a well-behaved cap iron (poor behavior being defined as a cap that moves when you tighten it). Certainly viable, anyway - just a little less convenient.

Plus, sometimes you get a japanese plane and the dai was made separate from the iron set, and you find that the cap iron cannot be advanced all the way down to where it needs to be. I had a rash of curiosity about japanese planes for a while, and I still have three, but I used to have a lot more. The ones I kept are inexpensive and I modified the dai wear a little bit so it would be easier to see the set of the cap iron. I looked a lot closer at all of this in 2012 when the cap iron stuff first started. I had delusions that it would make japanese planes very easy to use to get a tearout-free bright finish, but there are some quirks to the planes that I'm not in love with (namely their tendency to ripple a surface in a light cut if you have to take too many passes - one of the reasons that Brian Holcombe takes a LN jointer to the k-zerou events to true the board between passes.

 

[D_W]

I am the cap iron tub thumper.

We know.

You've been banging on about it for damn near two years on this forum.

We get the message. Actually, we got the message some considerable time ago.

Maybe time to drop it and move on to other matters?

[/quote]

I'm not offended if you put me on ignore. Seriously!

 

[iNewbie]

I had delusions that it would make japanese planes very easy to use to get a tearout-free bright finish, but there are some quirks to the planes that I'm not in love with (namely their tendency to ripple a surface in a light cut if you have to take too many passes - one of the reasons that Brian Holcombe takes a LN jointer to the k-zerou events to true the board between passes.

Someone should tell him he doesn't need a LN and get an old plane with a blade that isn't A2/PMV etc. Seriously.

 

[nabs]

why did Bailey bother to design his planes with an adjustable frog?

a historical footnote, Bailey did not design his planes with an adjustable frog (well, unless you count the fact that it is a separate part as meaning it is 'adjustable')

In fact the dubious honour of inventing the feature that allows you to adjust the position of the frog ( and thus the mouth opening) with a set screw belongs to Stanley's Edmund A Schade. He filed his patent in 1895, which meant that for 20 odd years before then Stanley/Bailey planes had no convenient means to adjust the mouth size:

http://www.google.co.uk/patents/us545732

(also his improved solution in 1910, http://www.google.co.uk/patents/US955557)

He also invented the unnecessarily complicated frog adjustment system found in 'bedrock' planes:

http://www.google.co.uk/patents/US955556

Incidentally, the first plane I bought (in the 1990s) was a new Irvin Record #4 and by this time they had abandoned the frog adjustment screw - that's progress for you!

 

[ac445ab]

why did Bailey bother to design his planes with an adjustable frog?

a historical footnote, Bailey did not design his planes with an adjustable frog (well, unless you count the fact that it is a separate part as meaning it is 'adjustable')

In fact the dubious honour of inventing the feature that allows you to adjust the position of the frog ( and thus the mouth opening) with a set screw belongs to Stanley's Edmund A Schade. He filed his patent in 1895, which meant that for 20 odd years before then Stanley/Bailey planes had no convenient means to adjust the mouth size:

http://www.google.co.uk/patents/us545732

(also his improved solution in 1910, http://www.google.co.uk/patents/US955557)

He also invented the unnecessarily complicated frog adjustment system found in 'bedrock' planes:

http://www.google.co.uk/patents/US955556

Incidentally, the first plane I bought (in the 1990s) was a new Irvin Record #4 and by this time they had abandoned the frog adjustment screw - that's progress for you!

Ciao,
You are right regarding the frog adjusting screw, however elonged holes for frog screws, allowing to change the frog position and mouth opening by hand, were already present on Stanley Bailey planes before Edmund A Schade's patent.

 

[memzey]

Yes - I have a number of pre-1895 Stanley Baileys and the frogs are adjustable but require the user to dismantle the plane in order to do so.

 

[David C]

D_W wrote "I don't have a holtey plane (I would take an A13 donation from Karl, though!), but I can't imagine his planes have anything like a large mouth in them".

I have one of the first 98 planes that Karl made. I know quite a lot about it because Karl used to ring me up and discuss some of his ideas at considerable length. I wrote a review for him in F & C.

The plane is bevel up with a bed of about 22 degrees.

The mouth is about 1 mm wide.

Karl did this because he was firmly of the opinion that an EP of perhaps 57 degrees, was quite steep enough to produce a type 2 shaving, which would not need a narrow mouth.

I say EP 57 degrees because A2 is probably best sharpened at 35 degrees.

Best wishes,
David Charlesworth

 

[Corneel]

Bugbear, why do you ask this question when I just left for a long weekend on the camping without internet access? (hammer) :lol:

I have some clues, not a definite answer. I researched this quite a bit some years ago. First I tried to find which high pitch corresponded to what chipbreaker setting in tear out reduction, in order to be able to compare them. I found that a 60 degree pitch nicely matched a 0.1 mm setting of a chipbreaker with a 45 degree front bevel. http://planetuning.infillplane.com/html/cap_iron_study_by_kees_van_der.html

Then I set up a planing machine with force transducers on our metal working lathe. http://planetuning.infillplane.com/html/mechanics_of_chipbreakers.html I could meassure force in two directions, horizontal, the force you feel when you push a plane from behind, and vertical. The horizontal was an easy one, higher pitched planes are harder to push then double iron planes with a comparable chipbreaker setting.

The vertical force is more interesting. This force is a result of the shaving pushing down on the plane iron, and the reaction force is the plane iron pushing the shaving upwards and trying to pry it out of the wood: tearout. Here I found something interesting.

With increasing pitch the vertical force dissapeared quickly until it was about 0 in a 60 degree plane (always under assumption of this type of wood with this grain direction and this shaving thickness). This means that with increasing pitch, the shaving is being pushed upwards less and less, it only receives a forward push. In other words, the shaving collapes forward, and isn't pried up out of the wood, result: no tear out.

In a double iron plane this vertical force is also reduced but not nearly as much as in the high pitch plane. It went from -0.5kg in a 45 degree plane without chipbreaker to -0.4kg in a 45 degree plane with the capiron set at 0.1 mm from the edge. In other words, this is not nearly enough to reduce tearout in the same way as it does in the 60 degree plane. There has to be another mechanism.

My theory, and it is of course just a theorie, I can't really prove it. The shaving after being cut at 45 degrees flows up the face side of the iron and is nicely being pried upwards, probably wanting to be torn out in a major way. But then it suddenly meets a wall. The vertical face of the chipbreaker bevel! The upwards flow is hampered, the shaving meets resistance. Thus the upwards travel of the shaving is hindered, you could say that a force is pressing the shaving backwards, backwards into the wood. I think that this is the main reason why a chipbreaker is effective against tearout.

Another thing about this vertical force, I firmly believe that this is the more important factor in how we determine if a plane iron is still sharp. When the edge wears, a wear bevel forms, a rounded bulge under the edge. This bulge presses against the wood and pushes the iron upwards, counter acting the downwards pressure of the shaving. If this balance gets too much out of control, you have to press down on the plane harder and harder to keep it cutting. Thereby also increasing the friction under the plane making it harder to push forwards. This also explains why a jackplane can keep on going much longer then a smoothing plane: a thick shaving presses down on the iron much harder.

Hope this was kind of illuminating. Feel free to answer questions.

 

[Derek Cohen (Perth Oz)]

Hi Kees

I agree with this reasoning. It follows Newton's third law: "For every action, there is an equal and opposite reaction".

I learned this in shrink school.

Regards from Perth

Derek

 

[D_W]

D_W wrote "I don't have a holtey plane (I would take an A13 donation from Karl, though!), but I can't imagine his planes have anything like a large mouth in them".

I have one of the first 98 planes that Karl made. I know quite a lot about it because Karl used to ring me up and discuss some of his ideas at considerable length. I wrote a review for him in F & C.

The plane is bevel up with a bed of about 22 degrees.

The mouth is about 1 mm wide.

Karl did this because he was firmly of the opinion that an EP of perhaps 57 degrees, was quite steep enough to produce a type 2 shaving, which would not need a narrow mouth.

I say EP 57 degrees because A2 is probably best sharpened at 35 degrees.

Best wishes,
David Charlesworth

I guess I'm not surprised with a millimeter if the expected angle to be used is 57 degrees. It would be a pretty tough plane to use for anything but the thinnest shavings if it was honed to 25 degrees, though.

A lot of the infill makers have gone to making very technical designs, and I can understand that, but it is the revisions of the older designs that I like the best. Though I know Karl is tortured by the idea that wood moves over time. An A13 version of Karl's would be just dandy, and they come up used once in a great while here in the states, but usually for about 5 grand. Just too much for me.

 

[bugbear]

At one point I pursued this line of thought- making a single iron plane blade behave like a burred scraper. My first attempt was to hone a step in the top of the cutting edge.

Some metal work lathe tooling is made like this.

BugBear

 

[bugbear]

With increasing pitch the vertical force dissapeared quickly until it was about 0 in a 60 degree plane (always under assumption of this type of wood with this grain direction and this shaving thickness). This means that with increasing pitch, the shaving is being pushed upwards less and less, it only receives a forward push. In other words, the shaving collapes forward, and isn't pried up out of the wood, result: no tear out.

In a double iron plane this vertical force is also reduced but not nearly as much as in the high pitch plane. It went from -0.5kg in a 45 degree plane without chipbreaker to -0.4kg in a 45 degree plane with the capiron set at 0.1 mm from the edge. In other words, this is not nearly enough to reduce tearout in the same way as it does in the 60 degree plane. There has to be another mechanism.

And that, ladies and gentlemen, answers my question.

Another question might well be - what IS the mechanism in both cases, but that wasn't my question.

Thank you, Corneel.

BugBear

 

[D_W]

One holds a chip down with an additional device and cuts it separately from where it's being pushed down. The other holds the chip down and cuts it at the same point. What more is there to talk about in terms of mechanism?

 

[bridger]

At one point I pursued this line of thought- making a single iron plane blade behave like a burred scraper. My first attempt was to hone a step in the top of the cutting edge.

Some metal work lathe tooling is made like this.

BugBear

Yes, but......

I think that the shapes involved are different. Machine bit chipbreakers are sort of a scoop shape, where the chip is ejected an eighth of an inch or so back from the cut, where a plane chipbreaker works in the .005 to .020 range or so.

In any case, I wasn't able to get my regular honing gear to make a chipbreaker.