The common understanding is that a chipbreaker, when positioned close to the cutting edge (usually 1/16″ away or closer), fractures the wood shaving thus preventing (or lessening) tearout. However, low-angle planes do not have chipbreakers and they do not seem to be any less prone to tearout than bench planes when both have the same effective cutting angle.
I think that chipbreakers were more important in the past, where a 1/8″ thick blade was the norm. The chipbreaker effectively added mass to the blade and also helped transfer the clamping force of the lever cap to the cutting part of the blade, helping to prevent chatter. However, with the 3/16″ or thicker blades seen on today’s planes, I think that the chipbreaker is more tradition than necessity. When I build a wooden plane (45-degree bed), I use a substantial blade and skip the chipbreaker with no adverse effects.
Thoughts?
Chris @ www.flairwoodwork.spaces.live.com
– Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. – Albert Schweitzer
Edited 6/29/2008 5:46 pm by flairwoodworks
Replies
There are two ways to break the chip--a chipbreaker or a high angle bedding angle. It's the type of shaving failure that's the issue.
In practice, the chipbreaker needs to be extremely close to an blade's edge to promote the same failure as a high angle plane. Else the chip does break, but the shaving is already beginning to left. For this reason, a plane with a 45 degree or lower bed also needs a finely set mouth in conjunction with a chipbreaker.
Another issue is the type, or thickness, of shaving. A real thin shaving simply doesn't break even with a high angle plane. Breaking chips is for more substantial shaving thickness as a means of not allowing the shaving to "run ahead" in front of the mouth--lifting the surface with it--before it breaks. Reality is that I have never observed a broken substantial chip. I have observed tear-out (surface lifting) no matter how well fitted "chip breaker" nor how tight I can set the mouth.
And as long as I am responding to threads I usually overlook, I also think so-called chip-breakers are highly over-rated--regardless of the era of development and use. Double irons (so-called chip-breakers) existed for a long time before thin-bladded Stanleys et al planes came to market. Thick, tapered and laminated blades had them as well. I have some. Totally unnecessary. Some of the finest planes I have are single, tapered irons (vintage or new like the C&W).
I'm fairly certain I'll get an email or counter-response. But hey, I had to spend my lunchtime somehow!
Take care, Mike
Well, here's one response Mike. They're not called chipbreakers by other English speakers. They're cap irons, held in place by the lever cap.
There's no indication in the name to suggest they cause the chip to break, or are meant to cause it. I've always rather assumed the cap iron's primary purposes were simply to stiffen the blade, help prevent chatter, that kind of thing. Slainte.Richard Jones Furniture
Yes, the term is American ingenuity at its best. That would be sales ingenuity.
Whether called 'cap irons' or the older term 'double irons', at least they are both properly suggestive and are simply more accurate terms.
However, one point of correction. Both "proper" terms above are used on wedged as well as lever capped planes. And at least in the case of "double irons," pre-existed planes with lever caps. None of the older planes with thick single irons really required double irons as a means to prevent chatter and the like.
Take care, Mikewho really needs to get back to stool making...
Richard,
Yah, cap iron is what I was taught to call 'em too. And, like you, I was told that their purpose was to prevent chatter when taking a heavy cut; pretensioning the tip of the blade so it wouldn't spring further downward, and couldn't whip back up, under the force of the cut.
But even the old timers who taught me, weren't around in the 18th century when planemaking started its decline. Larry's theory is an interesting one. Not being a planemaker myself, I'm not gonna argue the nuances of the technology, for sure.
Ray
I'm kind of like you Ray I guess. I just use planes, and as long as they work I'm happy enough. Obviously I know a bit about about their construction and their various configurations. I know a bit about their history too, but it's not a high priority for me. I'm more than happy to let the toolmakers like Larry, Mike, philip, Clifton, Holtey, Stanley and Lie-Nielsen deal with those elements.
I stick to just buying planes every now and then and using them. I do look at reviews of planes and planemakers, see what seems to be a good option for me and then buy what I would like and can afford. I suspect the bulk of my plane buying days are behind me. I seem to have pretty much all I need in my meagre collection of mostly non-entities, and I'm not much into buying trophy planes that I'd either never use or seldom use. Slainte.Richard Jones Furniture
Richard (is that your name?),
With 3/16" thick blades being the standard these days, do you feel cap irons are still necessary?Chris @ http://www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
Chris,
I have no planes with chipbreakers but all those planes I do have sport thick blades in the style you mention. Chatter is never an issue.
With the bevel up planes, the ribbons (low cutting angle) or chips (higher cutting angle) exit from the mouth with no problems. I have a bevel down plane with a 5mm thick blade that planes very well and without chatter at both 45 degrees (standard BD blade) and 60 degrees (with a 15 degree back bevel). In the latter case the chips do tend to gather and eventually choke up the throat of the plane. High angle BU blades in my other planes do seem to push the chips out of the mouth better than does that high angle BD blade.
I read in various places that the chipbreaker on traditional bevel down planes is meant to deflect the shavings up and out of the mouth - to prevent that choking my chpbreaker-free BD plane exhibits at the higher planing angle. I can't see how the chipbreaker will help prevent tear out, though, other than as an aid to reducing chatter in a thin or not well-bedded blade.
Is it not a higher cutting angle and a close mouth (as well as chatter-elimination) that prevent tear out? Certainly control of these factors seem to allow me to avoid tear out that otherwise occurs in difficult stuff when the cutting angle is low and/or the mouth is left wide. (A light cut, a well-engineered plane and that thick/stiff blade also contribute).
Lataxe, who is still learning with his planes.
Lataxe,
Tear-out is caused by the blade getting under a piece of wood and lifting up just like when using a bench chisel against the grain. It wants to take a bigger chunk out than you want it to. Effective cutting angle and mouth opening contribute to the amount of tear-out. Chatter doesn't have much effect on tear-out - only chatter marks. In theory, a chipbreaker (or cap iron) steepens the angle at which the chip exits immediately after it is severed and forces it to snap. The result being that it has less force lifting the remainder of the chip up. I hope that makes sense.
If that didn't make sense (and I don't blame you), check out the link lwilliams posted http://planetuning.infillplane.com/html/chipbreaker_study.html.
Chris @ http://www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
Edited 6/30/2008 8:43 pm by flairwoodworks
Edited 6/30/2008 8:46 pm by flairwoodworks
Chris,
When I first started searching out hand planes for my woodworking, in the 70's, every woodworker I talked to seemed to lament Stanley's gutting of their line and moving production to the UK. The lowering of Stanley's production quality in the process was obvious--they didn't seem to take hand planes seriously after that. Everyone was searching out the old Stanley's for their woodworking and no one wanted the new planes.
This wasn't the first time in history that kind of thing happened. Around 1760 double irons were introduced and by 1800 were generally the rule. Double irons were supposed to mimic the traditional bed angles and the steeper pitches were replaced by double irons. Those who claim the double iron were such a great improvement don't understand that they came at the expense of traditional cutting geometry. The British tended to use 47 1/2º as the single bed angle offered in their bench planes and the Americans favored 45º. I haven't seen any old production double iron planes at even York pitch (50º). Even the infills were bedded at 47 1/2º. Thousands of 18th Century molding planes survive but very few bench planes. Like the woodworkers of the 1970's, 18th Century woodworkers turned to the used tool market for their bench planes.
Here are the four traditional pitches in some 18th Century molding planes:
View Image
Look at the famous Seaton Chest from the 1800's. One of the very few plane missing from the chest is a single iron smooth plane. If double iron planes were such a great improvement why didn't the person who took that plane take the good one?
The reality is that for the cap iron to even begin to mimic the performance of the single iron plane at a steeper bed angle, the cap iron needs to be set within .004" of the iron's cutting edge. That's the thickness of the paper a dollar bill is printed on. You can go to Steve Elliot's information to read about this. How practical is it to set the cap iron .004" or closer to the iron's edge?
I view the introduction of the cap iron as the point at which planes began a down-hill slide. It's the first dramatic compromise made by early plane makers as they moved to mass production.
An eighth inch thick iron in a plane isn't a problem. If it's properly bedded, the only difference anyone will notice is the sound of the cut. I view the introduction of thicker irons in molding planes as one of the other compromises plane makers made to mass production. It makes the bedding less critical and working through the mouth much easier and quicker for the plane maker. This is a one-time effort in the life of the plane. It also makes sharpening and maintaining the iron much more difficult for the end user. A molding plane is sharpened a lot of times in its life.
"Those who claim the double iron were such a great improvement don't understand that they came at the expense of traditional cutting geometry. The British tended to use 47 1/2º as the single bed angle offered in their bench planes and the Americans favored 45º..."
Just as a point of clarification, with a 47 1/2º bedded plane utilizing a tapered iron, the effective cuting angle is lower. Often enough nearly 3 degrees, largely by about two degrees. This makes the cutting angle, despite the bedding angle, roughly equal to a plane with a parallel iron and a 45 degree bed.
I agree about the efficacy (or lack thereof) concerning a cap/double iron.
*Edit to add...nice planes Larry. Love them wide chamfers.
Take care, Mike
Edited 6/29/2008 11:00 pm by mwenz
I'm not sure about that, Mike. It's been a while since I figured the angle of the taper on our irons and my memory is that it is 3/4º. It's been awhile since I checked that and the bits and bites in my old head don't function like they used to. It does seem that 3º is pretty radical to get any length in an iron. The infills also used 47 1/2º and they didn't use tapered irons.
Hi Larry,
I am pretty sure my C&W smoother has a pretty low effect on reducing the effective angle. I was more referring to my vintage ones and ones I and others have measured. There was a thread on Roger's site where some of us got to measuring after the issue was raised.
It was something I had never really considered until then. So I got protractor happy and measured a bunch of mine. Not talking molding planes as they have a fairly thin iron in comparison to the larger planes. Of course, I'm memory challenged and so I might be off on the numbers. Guess I'll have to revisit the issue.
The greatest change was the plows. The English plow was close enough to 45 degrees iirc. The German plow which has thick, massively tapered irons came in at about 42/43 degrees e.p.
In practical terms, I used two smoothers today (yes, a bit of real woodworking!). One a double iron, one a single iron. The one with a 45 degree bedding angle has a double iron. Cap iron set extremely close. The other the C&W (cannot recall but I think it is a 50 deg. bedding angle). Curly Imbuia. I'll let everyone guess which handled the curly grain better.
Take care, Mike
Edited 6/30/2008 12:21 am by mwenz
Larry,
Thank you very much for the Steve Elliot link-very interesting indeed.
I doubt if anyone will think it practical to set a top iron at .004" or so, unless he has some sort of super plane. Would there be anyone out there who has made such a plane? Should I be thinking of making such a plane?
What is the reason for having a tapered iron, and how do you make yours thus, assuming you are not using a surface grinder?
Philip Marcou
Philip,The reason for a tapered iron is to have opposing angles between the iron and wedge on a wedge set plane. There's no reason to try to put a tapered iron in a plane that uses a lever cap or screw cap to secure the iron. The tapered iron makes it much easier to use light wedge pressure to secure the iron. Applying too much pressure to a wedge is probably the biggest single issue in problems people have in adjusting wedge set planes.I don't see why you would want to develop a plane with a cap iron that can be set to within .004" of the edge of an iron. I don't see any advantages but I see a lot of draw-backs. The cap iron was an advancement, alright. It wasn't an improvement in the function of bench planes, it made planes fit better into the evolving modern retail system. Rather than offering the end user a choice of four different versions of each plane, the end user had only one choice. In return; the retailer, wholesaler and plane maker had to make, package, ship, store, and display only 25% of the inventory when adding cap irons to bench planes. Packaging, shipping, warehousing and display space are all real costs involved with modern retail. What business wouldn't reduce many of their major costs by 75% if they could? I think the claimed performance benefits of cap irons might be the most successful marketing hoax of all time.Philip, you and I deal directly with the end user much like early 18th Century plane makers did. We aren't faced with all the logistics of modern retail and can offer the end user exactly what will fit their needs. I don't know why you'd make a plane like you mentioned. It might be interesting to experiment with this but I think it'd be going up a blind alley. That .004" is only to start to get close to the performance of traditional cutting geometries. To match them, I suspect you'd have to set the cap iron right at the cutting edge and then you add the issue of pushing a very obtuse edge through the wood.
Edited 6/30/2008 10:40 am by lwilliams
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