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

Very sharp fellas. Hope you can back it up with some steely mettle..... (or is it metal?)

NB

You just have to take the rough with the smooth
Cheers,
Jim

I'll never be able to cap that! (I think I will cap my offerings here with that post! Everyone will be relieved)

Regards from Perth

Derek

Originally Posted by derekcohen

I'll never be able to cap that! (I think I will cap my offerings here with that post! Everyone will be relieved)

Regards from Perth

Derek

Thats it
AR 3RU

We have all followed the evolution of a great sharp and well capped story but I guess thats it. AR 3RU

Originally Posted by derekcohen

Hi Ian

The Japanese research used a wood that looked very similar to the quarter sawn Tassie Oak in this experiment (I included a photo in the experiment of the gran direction). In their experiments they planed into the grain. The aim was to see if the chip breaker could counter the expected tear out.

Tassie Oak was planed here in the same manner (into the grain). Consequently I do not see this as back sawn versus quater sawn, only how reversing grain is controlled by the chip breaker.

Do you see it differently? Do you see an issue that might contaminate the results?

Regards from Perth

Derek

Hi Derek
In a way I do, see it differently. I had eye surgery yesterday and am very definitely one eyed today.

Please indulge me and let me try and write a proper response in the morning.

Hi Ian

Sorry to hear about your eye. I hope all is well now.

Post away! I am keen to read what you have.

Regards from Perth

Derek

OK ... should probably keep my nose out of it ... but I won't ...

Chippy objected to this that Derek wrote:

It is interesting that the use of a chip breaker, as discussed here, has been recorded for 250 years. It is not new. Nevertheless, the prevailing view in recent decades has been that the chip breaker served only to stiffen thin irons. Blame it on Stanley? No, I think not. There are many cabinetmakers who were taught correctly. But carpenters probably were not And the literature in recent times generally neglected, or ignored, this procedure.

and I wasn't really thinking about it ... but came across this re a question I wanted to put into another thread ...

(from here: Furniture without Glue - The Woodworkers Institute)

Chair stripped bare
The maker of this mid 18th-century chair has been sparing with his selection of material. The back and rail of a chair can tell us a great deal about its age and who might have made it and in spite of its simplicity this example is actually very revealing.
The choice of material is rather lean which suggests it was not intended to be a luxury item. However, the baluster back panel indicates that it had every intention of appearing attractive albeit from a distance.
The hard flat seat was not made for comfort and it is likely the user was never intended to sit for long. A carpenter or similar tradesman and not a furniture maker would probably have made items of this nature.

And it occurred to me that many times I've read something along the lines that carpenters might do or use XYZ whereas cabinet-makers were EFG - often when reading about the history of tools or woodwork etc.

It is probably a lesson to all of us not to generalise too quickly ... I think it is sort of 'in the atmosphere' that carpenters do one kind of work, to one level of precision, and a joiner or a cabinet-maker does this other kind of work, to this other level of precision.
But obviously there will have been carpenters that also built furniture, and cabbies that might have built a house or two ... something that obviously still applies today.

Paul.

actually Paul i just happened to be pondering how i could help Ian with his question

I'm ready to be convinced that there is more to cap-irons than dampening, when hit over the head with irrefutable evidence, but I want to see some of the possible alternative explantions eliminated, 'cos I'm such a sceptical old carmgeon.......

but i am wondering why alternative explanations have to be explained away (i may not quite understand the question maybe), or eliminated, for it to be true that the cap iron is used to bend or break the shavings, as i said the high school texts by Walton lists the cap iron purpose as ". . . to break the shavings, thus preventing the fibres breaking from tearing up, enabling a smooth surface to be produced..." also secondly it provides tension to the cutting edge. a more modern woodwook text used by the department of ED in SA says the same thing, doesnt go into fine detail but it also says that on a jack plane to set it back about 2mm and on a smother to set it as close as possible...as things happen, i happened to be at a high school on business and talked to the woodwork/tech teacher there and he said (without me prompting him one way or the other) that they taught that the cap iron is for chip breaking, as well, of course on bailey type planes it also serves to tension the blade, but i dont think anyone has argued that it doesnt do (or assist) that...i am not sure what other proof would satisfy anyone, its not just the multi thousands or perhaps millions of carpenters and other trades around the world that understand about the cap iron i assume, (at least all that i know do), its still taught in high school...i thought i gave a description of how it pushed the fibres down, but perhaps i am not explaining it well enough, or people simply dont believe me, what evidence would be acceptable (maybe if i know i can provide it)? i was once offered a job at TAFE, if i had of told them this i guess i would have spreading all sorts of bunkum haha

nah, Paul i am sure any carpenter worth his salt understands about cap irons, hard for me to imagine otherwise anyway

cheers
chippy

Here's an old saw, " It's easier for a carpenter to built a violin than it is for the violin maker to build a house."

Back on topic ... I went back to Derek's first post to check out some of the background to this discussion.

First there is the now subtitled Japanese study on chipbreaker function - which I found much more insightful. For instance I hadn't twigged that the point was to study planing against the grain of the wood.

The study is here (again): giant Cypress: Japanese woodworking tool punk • This is the full version of the video created by...

And a technical summary is here: Review of Cap Iron Study
although it seems to refer to a larger study than just shown in the video, or something slightly different.

and BTW Jeff Gorman has done some similar work:
Planes in Motion
Shavigs Close-up

- - - - - - -

Here is my non-technical summary:
(1mm=40 thou, so 0.1mm=4 thou, 0.3mm=12 thou, and 0.05mm=2 thou)

The blade is honed with a single bevel at 30o, with a 40o 'bed', leaving a 10o relief angle.

First 3 clips deal with no cap-iron.
- with the grain, depth of cut = 0.1mm = 4 thou --> OK
- against the grain, depth of cut = 0.1mm = 4 thou --> BAD
- against the grain, depth of cut = 0.05mm = 2 thou --> OK

I think this relates to the Ron Breze picture ... given a sharp, thick, solidly bedded iron and a thin shaving then a fine surface can be made against the grain with no cap-iron.

The next three clips introduce a 0.3mm = 12 thou tall chip-breaker, inclined at an angle +50o to the blade. All against the grain at a 4 thou cutting depth. Only variation was the chip-breaker offset.
- 0.3mm --> somewhat acceptable surface
- 0.2mm --> better
- 0.1mm --> good

The next three clips introduce a 0.3mm = 12 thou tall chip-breaker, inclined at an angle +80o to the blade. All against the grain at a 4 thou cutting depth. Only variation was the chip-breaker offset.
- 0.3mm --> good (or not bad?)
- 0.2mm --> good
- 0.1mm --> too close

- - - - - - -

I also read quit a bit from woodcentral.com that Derek linkd too. (Some curmudgeons there too I dare say, Ian )

I came away with lots of good info off on tangents, but re this thread ...

- I think lapping is defined as fitting on surface precisely to another. Derek to you see any call to lap a cap-iron directly on the blade - say with diamond powder or suchlike?

- The Japanese were able to precisely control cap-iron offset AND depth of cut. Maybe that is an important variable factor in your explorations?
If you felt the need I suppose you could put the plane on a flat surface, hold the heel to the surface and use feeler gauges at the front - then sit down to some calculations. The metalwork guys would know what to do ... dial indicator? some sort of height gauge?

- I read you put a microbevel on the cap-iron. What angle do you think it made to the blade, and how high do you think it was?

Thanks,
Paul.

Originally Posted by Ball Peen

Here's an old saw, " It's easier for a carpenter to built a violin than it is for the violin maker to build a house."

I'm not so sure it's not potentially equal.
What about a *good* house and a *good* violin?

Paul.

Hi Paul

I am very pleased that you had a look at the links I supplied. They flesh out a great deal I wrote, and provide a context for the relevance of this study.

However, I thought it was clear that the planing on the Tassie Oak I did was into the grain. The whole point of this study was about improving performance on reversing grain. But even more than this, it was to do so with a low cutting angle since it has been argued that a high cutting angle will not leave as smooth a surface.

In the conditions I think that it is fair to say that it s looking like different woods wil demand different set ups.

You ask about chip breaker preparation. It is very important that you lap them to fit seemlessly. The closer the leading edge gets to the edge of the blade, the more vulnerable it will be to shavings squeezing into any gap - and these can be extraordinary small - and clogging up the mouth.

The leading edge of the chip breaker (on the #604) was given a 70-80 degree microbevel. The idea is that this guides the shaving ... bends it ... vertically, thereby minimising the amount of tearing in the chip. A 50 degree bevel at the leading edge in the video set up did not work as well for them as did the 80 degree edge, so I used 80 degrees as well. Is this vital? Well, I used the standard LN chip breaker in the LN. This has a leading edge of 50 degrees (if I recall). However the cutting angle of this plane was 55 degrees, not the 45 degrees of the #604.

On the basis of the improved performance of the LN #3 with the chip breaker at 0.3mm, I estimated that the improvement is similar to adding 10-15 degrees to the cutting angle (with the benefits of the lower bevel angle).

Regards from Perth

Derek

Originally Posted by derekcohen

However, I thought it was clear that the planing on the Tassie Oak I did was into the grain. The whole point of this study was about improving performance on reversing grain.

Hi Derek,
I meant - the first time I saw the Japanese video - without subtitles - I thought that it was very interesting, and I took in the numbers (dimensions) ... but missed the point of planing into the grain.

Cheers,
Paul.