Thread: Chip breakers ... not cap irons .. and what they really do!

Originally Posted by derekcohen

What a wonderfully detailed and helpful post, H! Many thanks for this follow up report.

Edit: I was just re-reading an article I wrote some years ago about Jim Krenov (Paul posted a link to a video about him on YouTube), and I was replying. I had details of the smoother he built, that I have, and that he used before sending it to me. I recorded that the chip breaker had been set 1/16" back! So it seems that JK also did not use the chip breaker to fine tune the performance of his planes! I wonder how this (common angle) smoother will go on interlocked wood with a finely set chip breaker!!

Regards from Perth

Derek

I think Krenov was more aware than most about the relationship of the chip breaker to the cutting edge. His work with many timbers over a lifetime is a lasting testimony. This is the man who wrote the book on using the plane for final surface treatment.

Originally Posted by Ball Peen

I think Krenov was more aware than most about the relationship of the chip breaker to the cutting edge. His work with many timbers over a lifetime is a lasting testimony. This is the man who wrote the book on using the plane for final surface treatment.

Hi Bill

I would expect so, and I would not generalise from one instance, this being the settings of the chip breaker on the plane I received from Jim. He had used the plane before as well (there were shavings in the mouth it when it arrived).

JK is one of my heros, so my comments are not intended to disparage him (you only have to read the tributes on my website to realise this). I just find it interesting where he set his chip breaker, how he tuned his plane ... The plane makes wonderful shavings with the chip breaker set at 1/16". I use it from time-to-time, but always on softer woods as the bed is 45 degrees. It does good work, but not good enough for some of the interlocked local hardwoods I salvage. Now, however, I wonder if the performance can be upped with a change of chip breaker setting?

In the same light, I looked up plane tuning with a couple of well known woodworking experts. David Charlesworth is known for his books and videos. I have chatted with him via email, and more often he is available on the UK forum. He has been involved with these discussions (there), and posted his experiences of late. It turns out that he has also never considered that the chip breaker could increase the performance of a smoother. He only saw the dangers it presented in degrading performance. In one of his books (I pulled out yesterday) he described filing the leading edge at a low angle, basically getting the chip breaker out of the way.

Another I looked up was Garrett Hack. In the USA he is a god. Garrett has a couple of classic books to his name, perhaps the best being The Handplane Book. This details a vaste range of handplanes, along with their use and heritage. I was interested what he would recommend to tune a Stanley #4. Garrett does not describe any tuning with the chip breaker proximity. Instead it is the mouth size that he describes as the vital ingredient, along with a fine shaving.

At the same time I am now aware of books written over the centuries that document this area (these are coming to light as others go investigating). Mostly they were written a hundred or more years ago. So it appears that we have a period where this information was not only not disseminated, but we have been steered down alternate paths in recent history (these alternate methods do work, which is probably why this chip breaker issue now appears such a surprise).

Regards from Perth

Derek

I think James Krenov would be rolling,laughing in his grave about all of this.
Many people have challenged themselves to make a Krenov inspired piece.


This can only aid to more confusion for the hobbiests out there,with all of the finest furniture that has been made all over the world,how is this so called re-invented wheel going to aid the future of hobbiests or fine woodworkers?

David somed it all up in one sentence, For finer shavings set it closer to the end of the blade.

I read in interest to find out the mythical powers of the chip breaker and how much it will,to a hair splitting degree, improve the quality of ones work.

I loved Bob Lang's reply,

. . . or a new jig (patent pending) that allows the user to calibrate the cap iron to edge distance in thousandths complete with a digital readout and special screwdriver.


This is not personally directed at anyone, it's just my opinion.


Frank.

Derek, Although you did mention that there is a preference for various names for the cap iron/chip breaker but there was post in this thread by Peter McBride of the original patent for the modified cap iron with the bend at the front (of the Bailey-style BD planes fame) which states its purpose and calls it a cap iron. Is there any reference before this point calling it anything else? I would have thought that the role of the cap iron as a 'chip deflector' is merely an interesting (maybe useful?) by-product of the adding of a cap iron to a blade. Was it ever intended in the last 250 yrs as a adjustable component to influence planing effectiveness other than for the support for the blade or is this just an interesting subsequent development? (Disclaimer: sorry but I haven't had time to plough through any other videos/posts before posing this question.)

Also, forgive me if what follows is merely restating what you were inferring and what may have been already stated in other locations but it wasn't explicitly outlined in your post....
I would have intuitively thought that what is happening is that if you have the cap-iron (call it what you will) very close to the blade edge then you increase the flexing of the fibres being lifted from the timber and this is most noticeable with longer/straighter fibres, particuarly against the grain because it reduces the 'spitting off' that causes tearout. Maybe fibre length (either apparent length due to grain reversal or real depending on tree species) is the most important factor in this timber specific effect you have detected?
In other words the effect is more noticeable against the grain in Tas Oak cos it is a long-fibred splitty timber and the cap iron prevents long fibres being split off the surface in advance of the blade edge. Maybe not so noticable in Jarrah cos the fibres are shorter? (Either they really are shorter or the reversing grain makes them apparently so)
There may be some scientific literature on fibre length out there. It would be an curious experiment (rather than a practical exercise) to test cap iron adjustment with timbers with varying fibre lengths (difficult to control for other factors such as grain direction, density or hardness however) to see how important fibre length is in determining how useful cap irons are in acting as as 'fibre deflectors'. I tend to concur with Ian in saying it may be possible the xylem fibres may be more tightly crosslinked depending if you are planing along or across the growth rings. I don't know of any scientific evidence to argue either way. Does it require greater force to split/plane timber radially or tangentially? Can anyone offer informed comment on this?

Hi P

Many thanks for the link to that thread, to the Bailey patent, and the discussion that went with the chip breaker. Comments to follow ...

Let's deal with the Bailey patent first. It is dated 1867, and the aim is to use a second iron, the "cap iron" to stiffen the thin blade that Bailey introduced into his planes.

I think that history will show that Bailey's aim was more financial than evolutionary. Thinner blades cost less, and the cap iron served to stabilise it .. as he reasoned.

The thing is that second irons were known at least a 100 years before. Bailey patented his "invention" in the USA, but all this means that he acquired the rights to the design in the USA. The double iron had been described and written about in Europe (France, Holland and Germany) long, long before Leonard was a gleam in Mrs Bailey's eye.

The double iron is described in the 1792 edition of Salivet:



There was a picture of the double iron in Manuel du tourneur.
Manuel du tourneur, Volume 3 (Atlas of Plates)- By Louis-Georges-Isaac Salivet (Second Edition - Revised 1816)

This was taking place all over Europe at the time. I can let you have a number of other references if you wish. Bailey came along later with his adaptation.

It is interesting that Peter, too, emphasises the chip breaker's role as being Bailey's stabilising cap iron. He also wrote of setting it a "fat 1/32" ("That meant a touch more than a 32nd of an inch"). I'll do the conversion. 1/32" is 0.79mm, so a fat 1/32" is approximately 1mm. Since the effective range for a chip breaker is around 0.3mm, this setting would not produce the effect Horaldic and I have reported here.

You wrote, "I would have intuitively thought that what is happening is that if you have the cap-iron (call it what you will) very close to the blade edge then you increase the flexing of the fibres being lifted from the timber and this is most noticeable with longer/straighter fibres, particuarly against the grain because it reduces the 'spitting off' that causes tearout".

There is a simple piece of evidence that negates this view (which is another way of describing the back iron/chip breaker/cap iron as reducing vibration): As one moves the chip breaker to the edge of the blade, the blade will stop cutting. Too much support? No, I think that the too-close proximity prevents the fibres cutting at all as there is too little of the blade entering the wood - can this be?.

Probably a better piece of evidence is the results I get from a LN with a thick blade, one that does not need beefing up. A stable blade is important - no argument - but there is more going on than this.

More later. Many thanks for posting.

Regards from Perth

Derek

Originally Posted by FRB Design

This can only aid to more confusion for the hobbiests out there,with all of the finest furniture that has been made all over the world,how is this so called re-invented wheel going to aid the future of hobbiests or fine woodworkers?

I totally concur Frank. It probably aint gonna do much at all for the average woodworker. But it is a little bit of interesting technological history mixed with the physics of what is actually happening at a micro scale when a blade passes through timber that has created an interesting dicussion...even if it is of limited practical use.

Originally Posted by derekcohen

There is a simple piece of evidence that negates this view (which is another way of describing the back iron/chip breaker/cap iron as reducing vibration): As one moves the chip breaker to the edge of the blade, the blade will stop cutting. Too much support? No, I think that the too-close proximity prevents the fibres cutting at all as there is too little of the blade entering the wood - can this be?

Yes I think it most certainly can be. In effect you have created a blade with a tiny little bevel (a bit like a scraper) which cannot lift fibres away from timber very effectively as it doesn't penetrate far enough. As you retract the edge of the cap iron away from the edge of the blade, fibres start riding up the front of the blade due to better penetration and probably splitting off the timber further ahead because they are bent back toward the toe of the plane to a lesser extent. Then there is a sweet spot where the fibres are just bent back enough by the extra curve going over the toe of the cap iron to slice them cleanly off the underlying timber. Move it back too far and, ignoring blade stiffness for a minute, then splitting possibly occurs further ahead of the blade itself as fibres are lifted but not turned over. The reason I was suggesting it is so timber specific is that maybe this effect only works for some fibre lengths and maybe fibre angles (or in hindsite maybe a lesser degree of cross-linking to other xylem vessels maybe more important). Maybe the fibres of really hard timbers (also short angled fibres in variable grain) are just too brittle for it to work the same way. This is kind of thinking out loud...not really a well formulated theory.

This all refers to planing against the grain mind you. Dunno how it applies to planing with the grain.

This can only aid to more confusion for the hobbiests out there,with all of the finest furniture that has been made all over the world,how is this so called re-invented wheel going to aid the future of hobbiests or fine woodworkers?

Hi Frank

Indeed we are re-inventing the wheel. We are re-discovering how to tune a double iron plane. Confusion only exists when you do not understand the motive and the method. I would suggest that both are abundantly clear here.

David somed it all up in one sentence, For finer shavings set it closer to the end of the blade.

No. That is what promotes confusion - inexact recommendations. What exactly is "closer"? I have already demonstrated (as others have also found), 0.1 - 0.2 mm is too close. 0.3 - 0.4 was sweet spot for me. 0.5mm had lost it again. 1mm is way out of the game. Tell me again, what does "closer" mean?

Regards from Perth

Derek

Originally Posted by derekcohen

Hi Frank

Indeed we are re-inventing the wheel. We are re-discovering how to tune a double iron plane. Confusion only exists when you do not understand the motive and the method. I would suggest that both are abundantly clear here.

I understand the motive and method very clearly, but with out taking into account all of the different planes on the market,that all have slightly different designs,thickness and size of blades and chip breaker,come cap irons,not to mention the shape and design at the business end of the chipbreaker.


No. That is what promotes confusion - inexact recommendations. What exactly is "closer"? I have already demonstrated (as others have also found), 0.1 - 0.2 mm is too close. 0.3 - 0.4 was sweet spot for me. 0.5mm had lost it again. 1mm is way out of the game. Tell me again, what does "closer" mean?

In actual fact this is how confusion can set in with the exact measurement you state,and also not taking into account blades that have been radiused, closer is not an exact science, but the human eye can finely set it to the blade.
While planning I am not thinking, god I better stop and move the chipbreaker back 0.1 - 0.2 of a mm ,it just doesn't happen. With an exact measurement set wouldn't your sweet spot change on different species, kiln or air dried, interlocking grain, curly grain ,and hardness. If you could tell the difference of the surface texture ,by eye or by feel after moving it 0.1- 0.2 of a mm then may I suggest someone take a patent out on Bobs idea.


Edit : One other thing to ponder is how a card scraper can produce the finest whispiest shavings with a feint facing hook,zero clearance and with the scraper itself pushing or rolling the shavings forward as it cuts?
Frank.

Actually Frank, once you have done it a few times, it is quite easy to determine 0.3mm from the edge of the blade.

I think that you take this too literally, and this obscures the message from this thread. My description was to illustrate that one can dial in the chip breaker to improve smoothing performance. Indeed, you can improve the performance of other planes as well. This is not beyond the average amateur (or hobbiest as you call us). It is not complicated. It just requires an open mind.

Regards from Perth

Derek

Originally Posted by FRB Design

Edit : One other thing to ponder is how a card scraper can produce the finest whispiest shavings with a feint facing hook,zero clearance and with the scraper itself pushing or rolling the shavings forward as it cuts?
Frank.

It is an interesting comparison, given that the card scraper is the 'weapon of last resort' I understand in dealing with difficult grain.

I am wondering what size the burr on a scraper might be ... 1 thou???

1mm ~= 40 thou, so 0.3mm ~= 12 thou.

Also - Derek - could you photograph a cap-iron (I still prefer that term (to describe the object, not the function)) with 0.3 and 1.0mm offsets? Or point me to it if you already have that elsewhere?

Lastly ...
I would expect that surely the 'departure profile' of the cap-iron is going to have an effect on results, and might even trade-off with the offset distance?

Two extreme examples would be:
(1) using a square-faced 2mm thick cap that comes down and forms a 90o 'wall' near the edge, and
(2) a cap that ends in a curve sweeping down and forward.

(see attached for laughable attempt at illustration - the third example attempts to approximate a 'normal' cap-iron)

Thoughts? ... other than comments on the 'art'

Paul.

Idiot ... I drew the blade Bvl Up instead of Bvl Down

Coming across these Ron Brese pictures:




I was looking at the lever-cap photo and my first thought was about its shape and how it related to the above post ... until I realised that the lever-cap will sit far above the edge - duh!

So a consistent theory/understanding of planing action needs to stretch from the card-scraper to the blade & cap to these uncapped, thick-iron planes.

Bloody hell.

Paul.

Originally Posted by derekcohen

Actually Frank, once you have done it a few times, it is quite easy to determine 0.3mm from the edge of the blade.

I think that you take this too literally, and this obscures the message from this thread. My description was to illustrate that one can dial in the chip breaker to improve smoothing performance. Indeed, you can improve the performance of other planes as well. This is not beyond the average amateur (or hobbiest as you call us). It is not complicated. It just requires an open mind.

Regards from Perth

Derek

I really didn't want to get drawn too far into this but the idea of it requiring an open mind is making me see red at the moment.
For decades, probably eight or nine with the conventional BD metal planes, it has been received wisdom that you adjusted the chipbreaker to suit the wood and the type of planing you are doing. Then along came the studies that argue that chipbreakers don't really do anything and that we've been wrong all these years. Now the argument is that we've been right all along as experience has shown generations of woodworkers.
So who exactly is introducing confusion and complication and requesting an open mind?
The exact measurement is exactly (intended) what Bob Lang was talking about in his editorial. It creates if not confusion then at least an industry to make that measurement. Woodworking is practical and no two pieces of wood are the same, not even the same piece has exactly the same characteristics in the morning as in the evening. A bit more or a bit less is really all the measurement you need. Practice does the rest.
Cheers,
Jim

Well, this thread has ceratinly drawn some strong opinions from the crowd, and gone off at a few tangents, so perhaps a bit of summing-up is called for? As I see it, the original post shows that that simply moving a cap iron over some pretty small distances, all else being equal, can make a significant difference to both the appearance of the shavings, and the surface quality. As a (former?)believer in the cap-iron-as-stiffener-only theory, I find that an interesting result, at odds with my own views and experiences, and it begs some sort of explanation, whatever it may be (I certainbly don't have one at this stage).

I will have to trawl through the links to see if there are any plausible suggestions as to exactly what the cap-iron is doing at its 'sweet spot', but so far no-one has offered what I could accept as a full explantion in this thread, unles I missed it.

To me, it was demonstrated clearly that you can set too close (this is definitely my own experience, too, & obviously that of others), which to my reasoning, doesn't sem to fit with the chip-bending theory. Someone worked out (can't remember where I read it) that the average beam-strength of a shaving is so small, that the bend would have to be starting right at the cutting edge to have any effect, not 0.3 of a mm back from it, which is about 10-12 times the thickness of a fine shaving. So if bending of the fibres to break them at the blade contaact point is the explantion, either their calculations were wrong, or wood fibres have a much higher stiffness in micro sections than they have in thicker sections (which is quite possible, as many materials are 'stronger' in ultra-thin sections than thicker section strengths indicate).

As some other posters do, I rely on experience and guess-work when setting cap irons. I was taught as a lad to set at a 'fat 32nd', which is around 1mm, for general work, and a 'fine 32nd', which is perhaps .6-.7mm, for fine work. This seems to work for me for the majority of situations. I have never had much luck setting finer than about 0.5mm, and then only for very fine shavings. If I dial for a coarser cut, I am soon getting crinkly shavings that jam the thoat and work under the cap iron, which defeats the exercise utterly. Having highly polished cap-irons helps, but doesn't eliminate the problem, for me. I expend a good deal of effort in getting my cap-irons & blade backs mating as perfectly as I can, but admit they may not be absloute, so there is one area that could be improved.

I think the message from the 'experienced' set is that cap-iron settingss are important, but just one factor in a complex equation. Blade sharpness, cap-iron fit, general seaworthiness of the plane itself, and of course the wood being atacked, all make a big contribution to results. Not only that, but we all have different ideas of what will do "off-plane", based on our personal skill, equipment, and need to get the job done in a time that will pay the rent. Some strive to get a polishable surface with planes only, while others are happy to knock the rough off, and finish with scrapers, abrasives, or whatever is their weapon of choice. (And please don't get into the argument about which leaves the perfect surface in this thread - start another! )

If I were instructing a beginner in hand-plane use, I think I would still advise sticking with the settings I was given, as a good starting point, until the person became proficient with sharpening & general plane use. Once you are happy with your general abilities with the tool, if you are the inquisitive kind, start playing about with specific settings for specific purposes. Which is of course, where Derek is at........

Cheers,