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Effects of cap iron on planing...

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Paul Chapman

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Very interesting - thanks for posting.

It seems to me that the set up with the cap iron shaped to 80 degrees and set a little way back, approaches the sort of set up that you have with a scraper plane. With the scraper plane the blade is angled forwards (similar to the front edge of the cap iron shaped to 80 degrees) and breaks the shaving in a very similar way, thereby avoiding tearout.

Cheers :wink:

Paul
 

Jacob

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Interesting. Seems to confirm what we already know. Have I got this right? I might have to watch it again:
Finely set very sharp blade copes best and cap iron has no effect. NB We know this already or we wouldn't find BU planes so useful.
Deeper cut then the cap iron does have a useful effect, but there's an optimum position above or below which it has less value, and an optimum angle. The nearer it resembles a scraper the more it behaves like a scraper. No surprises there then.
Hmm.
Quite how you translate that into day to day plane usage is another question!
 

Corneel

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Re your first conclusion, wish it was always true. There are plenty of pieces of wood that give you trouble also with very thin shavings. And then there is the speed of working. It would be nice if you could take thicker shavings.

Re the second conclusion, maybe but it doesn't leave a scraped surface! This is very important for the japanese who work often with unfinished wooden surfaces.
 

Philly

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I wish they would do the same tests but with the iron at higher angles than 40 degrees - be interesting to see how that alters the equation?
Cheers
Philly
 

Cheshirechappie

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That is interesting.

Another test that might be of value is to investigate the effects of the plane's mouth - does a very tight mouth setting affect the shaving by preventing splitting ahead of the blade edge? The old infill planes suggest that - be interesting to see if there's substance to the theory. They might even work without a cap-iron fitted.

The tests done also suggest that a plane with a widish mouth setting might be persuaded to reduce or eliminate tearout by the use of close-set or tight-angle cap-iron, and it seems that David C has already tried a few experiments 'in the field' with some promising results - see Bugbear's thread. So tight mouths may not be always necessary - and wouldn't work anyway with the 80 degree cap-iron, because the shaving escape would be blocked.
 

Corneel

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You do all allready know this is an old study? The machine probably doesn't exist anymore.
 

Derek Cohen (Perth Oz)

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We had a long discussion on WoodCentral. This was my take ..

1. A better term (in the context of this research) for cap iron (although this was used in the subtitles) is "chip breaker" since the research is all about how the second iron breaks the shaving and how it may improve the surface left behind.

2. The aim is to use the lowest possible bevel angle. This point was raised by Warren (a longstanding member of WoodCentral and confirmed "neanderthal", professional furniture maker) since a lower bevel angle will produce a better surface finish than a higher bevel angle (all other conditions held constant, including the use of medium difficulty woods). Consequently, the use of a high angle plane in this context is counter to the ideals of the study.

The conclusion of this research may be summarised as: on a 40 degree bed (= cutting angle), using a 30 degree bevel angle, the least tearout occurred when the chip breaker was 0.2mm from the edge of the blade, and the leading edge of the chip breaker was ground at 80 degrees.

Observations and questions:

1. The setting of a chip breaker at this distance is not easy. There appears to be a small margin for error. The performance was slightly worse 0.1mm further back but still good.

2. The ideal chip breaker type is to be identified. Warren and others have been happy with the standard Stanley. I am not sure what angle Warren has his ground, or whether he simply relies on the distance to the edge of the blade. Warren?

It does strike me that there are several aftermarket chip breakers that lend themselves better than Stanley to being ground to the ideal angle at their leading edge.

3. If experimenting with Bailey-type planes, such as LN, or woodies with double irons, where the frog may be 50 degrees (which is not much different from 45 degrees), what is the ideal angle for the chip breaker. My logic says it should be 75 degrees (5 degrees lower than the 80 degrees on a 45 degree frog).

4. Keep in mind that this is about finding a way of improving smoothers only. The research includes using a very fine shaving. This would not be practical in other types of planes and woodworking demands where thicker shavings are more appropriate (such as jointing or using a jack).

5. There is no implication here that higher angled planes are irrelevant. Both BD and BU planes are still as valid as ever, However, there is the possibility that (a) the performance of a lower cutting angle may be capable of being used for more complex situations, and (b) some will enjoy the benefits of fewer smoothers (OK, I was just kidding ..).

6. The area needs to replicated on different woods. The Japanese White Bark Magnolia is a medium hard wood (Janka around 1000, as I can make out), and does not look as though the grain wanders around much (noting, however, that the tests were done into the grain). Harder woods and more complex grain may vary the outcome. As far as I know this area has not been addressed.

Regards from Perth

Derek
 

Derek Cohen (Perth Oz)

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The tests done also suggest that a plane with a widish mouth setting might be persuaded to reduce or eliminate tearout by the use of close-set or tight-angle cap-iron, and it seems that David C has already tried a few experiments 'in the field' with some promising results - see Bugbear's thread. So tight mouths may not be always necessary - and wouldn't work anyway with the 80 degree cap-iron, because the shaving escape would be blocked.
There is sufficient evidence from studies (some of it mine) and anecdotal reports that the size of the mouth is no longer of any importance at about 55-60 degrees.

Regards from Perth

Derek
 

custard

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What are the implications of a 0.2mm cap iron setting in terms of,

1. Cambered iron?
2. Back bevel/ruler trick?
 

Corneel

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1. Yes that doesn't work. But for smoother type cambers it'll still fit.
2. A ruler trick sized backbevel doesn't matter. Bigger ones could be problametic. But the bigger ones are used to reduce tearout, which isn't neccessary anymore with a well fited capiron.
 

custard

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Maybe the new ruler trick is the "camber trick"! You position the cap iron by aligning it to the limits of the camber, each defines the other!
 

Derek Cohen (Perth Oz)

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custard":2n89jc0v said:
What are the implications of a 0.2mm cap iron setting in terms of,

1. Cambered iron?
2. Back bevel/ruler trick?
With regards the cambered iron, the camber on a smoother is very small. Nevertheless it seems to me that it would still be too large to allow the chip breaker to get to the desired distance from the edge, and even if it did, it would be uneven. If serious about this technique, one should also file the chip breaker to match the camber.

I cannot see the ruler trick having any impact on the effect reported. It is simply a method for ensuring a clean blade back/sharp blade.

A high back bevel is in the same category as a high cutting angle - not desired in the context of this technique as the aim is to use a common cutting angle.

Regards from Perth

Derek
 

Paul Chapman

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Far less trouble to just use a scraper plane, IMHO. Very easy to set up and, in my experience, works successfully every time in dealing with tearout.

Cheers :wink:

Paul
 

David C

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Paul,

Can you take 4 thou" shavings with your scraper plane? And I wonder which set up is going to keep working for the longest time?

best wishes,
David
 

woodbrains

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Hello,

The ruler trick will definitely affect this setup as I doubt you could make the back bevel produced this way significantly less than .2mm. setting the cap iron.2mm back from the intersection would mean the minimum distance from the point the shaving is raised to the leading edge of the cap iron is not likely to be less than .4mm. However, the slight increase in effective pitch might just about negate the losses and a finely set mouth, exerting some downward pressure at the point the shaving is raised will definitely more than compensate. Also, a 0.1mm thick shaving is quite thick if you know you are taming difficult timber, a sensible person would reduce that significantly. The tester has to keep parity in all things to make the results meaningful; Keeping test simulated criteria in real world situations is inappropriate.

A fine mouth does give significantly reduce tear out. I have used a Steve Knight single iron smoother with a mouth setting of about 1thou (sorry for mixing my measurement systems, but the plane is American!) Admittedly it was a thick York Pitched iron, but no cap iron and a 30 deg honed bevel. Obviously the shaving was super fine with a mouth opening like that, BUT it out preformed LN and Veritas planes of all descriptions, wood smoothers and everything else with double irons, but slightly wider mouths and/or thinner irons. The only other planes that worked were Veritas and LN scraper planes, though the surface was not as smooth.

The upshot is, a slightly wider mouthed plane is achieveable with a double iron which allows faster workrates (thicker shavings) in almost all woods, to a comparable finish to a fine mouthed smoother. The latter will surpass double ironed planes in the most difficult woods, but it may not be possible to use a cap iron due to the shavings choking. That said, it is unlikely the cap iron in this instance will actually give any benefit. Balancing the size of the mouth and the cap iron setting is the thing which experience helps us with and some knowledge we find alone the way from tests such as these.

Incidentally, I have always set my cap irons very close, though I have never bothered to measure exactly how close. Logic told me a long time ago, that the shaving should be broken as soon as possible after the cut, so I did and found it worked better than the 'usual' setting prescribed in textbooks. Sometimes trial and error is all we can go on, when we do not have electron microscopes to hand.

Mike.
 

David C

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Mike,

That was most interesting.

I don't understand your reservations about the ruler trick which was used on the blades for my experiment. Ruler trick polish may be anything from 0.5 mm to 1.5 mm wide. The angle is approx 0.6 of one degree. I form the underside edge of my chipbreakers with at least one degree of clearance angle, so they fit the blade perfectly whatever setting is used.

I am fairly sure that the finish from 0.1mm shavings, taken with ultra close set chipbreaker will be independant of mouth width, (there is no mouth shown in the research film), so choking will not be an issue.

Best wishes,
David
 

woodbrains

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Hello David,

I actually like the ruler trick and use it occasionally. It got me out of trouble when I had to prep up 2 dozen block planes for a school tec dept. Obviously no cap iron there, it just got the very poor irons usable without flattening the backs.

I think I may have misunderstood your method, though. The time I used the ruler trick on a BD plane, I kept the bevel very short as if it was a 'real' back bevel and then positioned the cap iron as you would in that instance. it works well and can be changed back without too much effort. Obviously you are seeming to ignore the 'back bevel' and place the cap iron onto it, with a releif angle on the cap iron, to maintain a good contact. I stand corrected. I think one or two contributors here might also be misunderstanding.

Mike.
 

Corneel

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Yes Mike, you are absolutely right. There is more to it then just the capiron. It's not a magic stick, just a very usefull tool.

As David explained, there is no problem with setting the capiron on top of your backbevel, as long as it's not too steep, and as long as your capiron has a relief angle behind its edge.
 
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