Cap Irons - Taming Tearout
Bailey Style or Old School Heavy Duty, They Both Work Perfectly!
If you’re prepared to experiment with your cap iron, you'll open the door to a new level of versatility, they are a wonderful addition to the bench planes development. They were introduced well before the thin irons of the Bailey pattern planes and therefore have nothing to do with the adjustment of a plane, nor were they initially developed to add more rigidity to the cutting iron. You only have to look at the thickness of a traditional wooden plane’s iron with a cap iron to realise this. They actually added an extra level of cost. The old workers weren’t mugs, if it was a gimmick it would of never caught on.
Unless you had the good fortune to work alongside a mentor who really knew their planes or you actually had the dedication to really experiment you would be forgiven for dismissing it's usefulness. Every book I've read mentions how they work but it's only relatively recently most people have really understood them again.
I think one of the difficulties is that most books, both old and new don't get across the nuance of the workshop environment. It's also difficult to know how much practical knowledge an author had. And I can't help but speculate on the motives that many authors had. We're they making books to direct the trade? Unlikely. Perhaps more likely, they were overviews of varying accuracy, doubtless some are highly accurate. However, nothing beats applying knowledge that you pick up in a book and refining it to suit you, some things you might dismiss some others might open doors.
Cap Irons rarely give problems in a hand plane once they have been set up. Thankfully it's a pretty simple job. The metal is not hardened so it's easy to adjust with a file, abrasive paper on a flat surface or some honing stones. The only flaw I find with cap Irons is with the modern versions found on some quality brands. The front edge on these modern versions is ground to a near cutting edge. I've found success by copying the rounded front edge like Bailey and old Wooden planes, don’t mess with success!
Even the term “Chipbreaker” is odd, a misnomer really. I have no idea who first coined the name but it sounds modern enough phrase that the person who did had no idea what it was for. A plane shouldn't be capable of making chips but shavings, both thick and thin as required.
The first planes certainly had single iron, but just like when video killed the radio star, cap irons finished the single iron plane. Single iron planes are and were cheaper and easier to make and cheaper to buy, but the people at the bench voted with their money because they saw the difference within their work.
Interestingly Japanese planes evolved a cap iron too. I don't use Japanese planes so I don't feel I can comment on how effective or how they are used specifically but I love the way two very separate cultures developed very similar approaches.
There is an interesting study done by a Japanese university which shows how things react when being planed. Sadly it's not an actual hand plane but some kind of machine. Google it, I don't think it's difficult to find.
There are some basics I can share on how I use my cap iron to tame troublesome grain. Forget a tight mouth, a tight mouth is near useless, throw feeler gauges away now! Why did you have them anyway? This is woodworking! Your Bailey style plane can always have it's mouth open to it's maximum, I'll wager that you'll never move it. Then just experiment with getting the cap iron close to the edge and then experiment with the depth of cut too. If you have the cap iron too close to the edge iron the shavings will look like an accordion and it'll be hell to push. Too far away and the shavings will be likely spiral into a tube, the plane easy to push and if you have nasty grain you'll get some tear. Get it right and the shaving is straight, there is resistance to planing, but nothing crazy and a clean surface. I find this approach works on just about anything and have never felt the need to purchase a plane with different frogs for multiple pitches, a handful of irons with back bevels or a bevel up with a crazy steep pitch. You’ll find a bog standard Bailey from a flea market would need minimal work to beat all those more modern approaches.
Should you always have the cap iron set tight? I don't. It's easier working when it's pulled back, with experience you'll be able to decide when a close setting is required. basically when the grain or wood you are working is a bit flighty . There's the rub, this isn't paint by numbers, the reality is making things and building experience.