Why tapered plane blades?

[Aram]

I've had a bug to build a certain hand plane the traditional way (from solid billet). The latest issue of PWW has an excellent, detailed article on how to build one. The author is specific about using a tapered (wedged) blade. I've built a lot of Krenov-style planes with Ron Hock's blades, which are are parallel. They work beautifully. Why the taper? Is it really necessary?

[hbmcc]

I always thought it was a wedge (additional) factor. Of course, one could call it a marketing gimmick, too.

[Woody Splinters]

I've had a bug to build a certain hand plane the traditional way (from solid billet). The latest issue of PWW has an excellent, detailed article on how to build one. The author is specific about using a tapered (wedged) blade. I've built a lot of Krenov-style planes with Ron Hock's blades, which are are parallel. They work beautifully. Why the taper? Is it really necessary?

The mechanical action of the wedge only serves to not allow the blade to slip backwards/loosen in use.  It is also somewhat of a safety issue and you will benefit from using a tapered iron (available from Red Rose Productions or on Ebay - old stock) as the blade will stay engaged during use.  If the blade loosens there is nothing to keep the blade in the plane and it will fall straight out of the mouth - that's the sharp end.....

All historic wooden body planes used tapered blades.  If it was a gimmick - then for about 150 years the gimmick stuck.  The gimmick discussion still revolves around cap irons or chip breakers or double irons - whatever you want to call them and however you set up their geometry and relation to the actual cutting edge. 

Good luck on the plane - take your time and let us know how it goes.  I've made side escapement planes and need to build a bench plane here soon.

[AHill]

I've had a bug to build a certain hand plane the traditional way (from solid billet). The latest issue of PWW has an excellent, detailed article on how to build one. The author is specific about using a tapered (wedged) blade. I've built a lot of Krenov-style planes with Ron Hock's blades, which are are parallel. They work beautifully. Why the taper? Is it really necessary?

If the blade is tapered, both the blade and the wooden wedge must work against a taper to move.  In other words, there's a taper or wedge on both sides of the blade holding it stationary.  If the blade is parallel (same thickness), then the only thing holding the blade stationary is the wedge's reaction against the plane body, and plain friction against the blade.

This article explains it well:

http://kapeldesigns.blogspot.com/2013/11...s-for.html

[Timberwolf]

The mechanical action of the wedge only serves to not allow the blade to slip backwards/loosen in use.  It is also somewhat of a safety issue and you will benefit from using a tapered iron (available from Red Rose Productions or on Ebay - old stock) as the blade will stay engaged during use.  If the blade loosens there is nothing to keep the blade in the plane and it will fall straight out of the mouth - that's the sharp end.....

All historic wooden body planes used tapered blades.  If it was a gimmick - then for about 150 years the gimmick stuck.  The gimmick discussion still revolves around cap irons or chip breakers or double irons - whatever you want to call them and however you set up their geometry and relation to the actual cutting edge. 

Good luck on the plane - take your time and let us know how it goes.  I've made side escapement planes and need to build a bench plane here soon.

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Tapered irons are said to reduce chattering...and are/were used extensively on many planes without wedges..

" If the blade loosens there is nothing to keep the blade in the plane and it will fall straight out of the mouth - that's the sharp end....."

Blade slipping backward or forward can be greatly reduced or prevented by applying powdered rosin to the frog..Violin bow rosin {available at music stores} can be scraped with a pocketknife on the frog's surface. It creates a strong friction but still allows for adjustment...Old trick I learned many years ago as a machinist apprentice. Friction can be your friend....or enemy...

[SteveVoigt]

I've had a bug to build a certain hand plane the traditional way (from solid billet). The latest issue of PWW has an excellent, detailed article on how to build one. The author is specific about using a tapered (wedged) blade. I've built a lot of Krenov-style planes with Ron Hock's blades, which are are parallel. They work beautifully. Why the taper? Is it really necessary?

Hi Aram,

A tapered iron is nice, it is an improvement, but it is not a deal breaker. If you have a suitable parallel iron, it will work. In the article, I specified a tapered iron because I was talking about finding and using a vintage double iron (cutting iron + chipbreaker), and nearly all old double irons designed for wooden planes have tapered irons. Parallel irons were made, but they are rare.

More important than the taper is that the blade should have some length (around 7" is good), and the chipbreaker should be the old style, with the curved, claw-like bevel at the tip, and a substantial (1/32-1/16) gap just above the curved bevel. See the photo on p.48. The chipbreaker itself supplies about half a degree of taper, so if you have the right kind of chipbreaker, the tapered iron is less important than it would be in a single iron plane.

A few people here have mentioned that a tapered iron resists pullout and slippage, which is true. Another benefit is that a tapered iron seems to adjust more smoothly.

P.S. Glad you enjoyed the article.

[Aram]

Hi Steve,


Thank you for your post! that's why I love this forum. Yes, I did enjoy the article.

Do you mind if I ask you about one thing? What advantage(s) does the long blade offer?  Again, I've been building and using laminated, Krenov-type planes for a long while now. Interested to get the different perspective.

Thanks,

[SteveVoigt]

Hi Steve,


Thank you for your post! that's why I love this forum. Yes, I did enjoy the article.

Do you mind if I ask you about one thing? What advantage(s) does the long blade offer?  Again, I've been building and using laminated, Krenov-type planes for a long while now. Interested to get the different perspective.

Thanks,

Aram,

A traditional plane is nearly square in section, so a smoother with a 2" iron will be around 2-5/8" tall, and the bed will be around 3-1/2" from top to bottom. So, even the longer 4" krenov irons will only stick up about 1/2" from the top of the plane. Once you've used a quarter inch of iron, the plane will be impossible to adjust. If I'm going to pay $60 or whatever for an iron, I'd like to be able to use more then 1/4" of it. On a traditional iron, or a Stanley for that matter, you can use 2 full inches. I've purchased old planes where the slot on the iron was into the bevel, maybe 1/4" from the cutting edge. It's clear that craftsmen of old used every bit of iron they could. 

Aside from economics, a nice vintage double iron looks great to me; far nicer than the modern irons. Of course that's very subjective and YMMV, as they say.

[Aram]

Great answer, Steve, thank you.