Question about wooden plane mouth size...

[Kelly Jons]

Hi guys - If this has been discussed before, please direct me to the appropriate thread... I searched, but couldn't find what I want to know, which basically is:

Really, how important is it to have a tight mouth on a wooden plane? Every metal block plane and bevel up plane (like the Lie-Nielsen and Veritas Lee Valley ones) seems to have a sliding mouthpiece to tighten up the opening, but bevel down wooden planes don't have that, and they seem to plane just fine until the opening wears pretty wide and you have to put in a patch. I've never used a Krenov-style wooden plane but he certainly got good results with his home-made planes. My antique wooden planes have loose openings in front of the blades for the most part and they seem to work OK.

Is the sliding mouthpiece critical to the best use of bevel up planes and bevel down planes don't really need a way to adjust the mouth opening? Or is it more a function of the type of wood being planed? (Bevel up planes, at least traditionally, were used for different tasks than bevel down planes?)

I am planning to make a few wooden planes with Hock blades and want to know what to expect...

Thanks for the info.

Kelly

[Mike Henderson]

Depends on what the plane is going to be used for. For a smoother, a tight mouth is important.

Mike

[Ian Wormsbecker]

Every metal block plane and bevel up plane (like the Lie-Nielsen and Veritas Lee Valley ones) seems to have a sliding mouthpiece to tighten up the opening, but bevel down wooden planes don't have that, and they seem to plane just fine until the opening wears pretty wide and you have to put in a patch.

On bevel down planes, in order to make the mouth smaller, you move the frog forward which moves the blade closer to the front of the mouth. So you can do this on a bevel down plane It isn't so much the mouth size, but the proximity of the cutting edge to the edge of the mouth that is important.


Ian

[Richard Magbanua]

As mike said, it depends on what you're doing with it. Generally the opening should be just a bit bigger than the shavings you intend on passing through it. this helps prevent tearout ahead of the blade. When you make a wooden plane you can make the mouth very tight to the blade when the blade is set for a cut. The, since the inside of the plane is a "v" shape, you joint the sole of the plane until the mouth opens up to where you want it. If you are making a smoother, stop when the mouth is tight and you can make thin shavings. If you're making a jack, go until you can make thicker shavings without stopping up the mouth. If you have a woody that has a mouth that is too big, you can re-sole it and start over or inlay a new strip in the mouth. Or just make a new plane. I hope this helps.

[Pam Niedermayer]

OTOH, had a piece of bocote a couple of years ago that none, and I mean NONE, of my planes could handle with any grace; so I grabbed an old, very old, coffin smoother with a mouth gape like you wouldn't believe, hadn't had a chance to "fix" it. It planed thin shavings from that bocote like crazy, very smooth; so I set the plane aside and decided not to "fix" it.

Pam

[Robert Rozaieski]

Mouth size isn't really important except on a smoother. However, with that said, I've had better experience improving the smoothing ability of a plane by using a higher bedding angle rather than a tighter mouth.

Back when wooden planes were the only planes, smooth planes came in varying pitches from 45 degrees to 60 degrees and maybe even higher (in the case of toothing planes). The higher angles were for tougher to plane timbers. Today, it's extremely rare to find a wooden coffin smoother at any angle other than 45 degrees as the multiple pitches seemed to disappear when mass production and factories took over.

Custom planemakers like C&W or Philly will still make you a York or higher pitch but finding an old one with a bed angle higher than 45 degrees is rare. For this reason, when I made my home made smoother, I made it with a higher angle (York pitch) bed. I knew I could easily find an older common pitch smoother so I made the higher angle one. I have yet to work a board that the 50 degree pitch couldn't handle easily, however, I don't work with exotics, only typical domestic furniture woods.

If you are going to make your own, I'd recommend making one or two higher angle smoothers (maybe 50 and/or 55 degree bedding angles) to handle the tougher to plane boards. For jack/fore or try/jointer planes, I wouldn't worry about the mouth opening or bedding angle. These planes aren't in the business of leaving finish ready surfaces so the mouth opening isn't a big deal in my opinion.

[Kelly Jons]

Thanks for the input, fellas... looks like David Finck also answered my question in his _Making and Mastering Wood Planes_, second ed., page 83: "... should your efforts produce a plane with a wider opening (mouth), it will still function perfectly well with all but the most demanding woods."

My concern was with solid wooden planes with no frog... there's no way to adjust the mouth opening at all (well, I guess you could always shim the blade forward).

Everyone seems to make so much of tight plane mouths (especially the manufacturers of bevel up planes with sliding front adjusters)... I guess it's not that important except, as noted above, when smoothing.

Kelly

[Michael Faurot]

Is the sliding mouthpiece critical to the best use of bevel up planes and bevel down planes don't really need a way to adjust the mouth opening? Or is it more a function of the type of wood being planed?

In the October, 2008 (#171) issue of Popular Woodworking Christopher Schwarz has an article entitled Taming Handplane Tearout. In answer to the question: Do you need a fine mouth for high-tolerance work? Christopher wrote:

I think the answer is: It depends. I think tightening up the mouth aperture of your plane is just one of the weapons you have in your battle against tear-out. But I don't think it's the doomsday weapon.

This goes along with what Mike Hendersen said about, "Depends on what the plane is going to be used for." So for a smoother, this can be helpful, but a tight mouth isn't necessarily as important as a sharp blade or having the blade at the right angle.

[David Keller NC]

And an even more radical opinion - a tight mouth on a plane doesn't matter at all, even for a smoother, if you're planing well-behaved cabinet woods in the right direction. If you're going against the grain or planing highly curly maple, not even the tightest mouth (I've a plane with a 0.003" mouth) will totally prevent tearout, nor will a closely-set chipbreaker.

In such cases, only a very high planing angle (60 degrees) or a near vertical pitch toothed blade followed by a scraper will produce a glass-smooth surface.

[Steve knight]

wooden planes tend to less tearout then metal planes and they don't seem to require as tight of a mouth overall.

[Richard Dooling]

Actually the ECE Primus Reform Smoothing planes are an interesting alternative and an unusual blend of mechanical, metal parts and a wooden body with an adjustable mouth. There is no reason that a woodie can't have an adjustable mouth.

Having said that I agree that this is just one element in among a number of important factors. I was having trouble with some basswood the other day and tried a couple of different things including a higher (50*) angle frog. What solved the problem was my favorite old Stanley #4 with - the sharpest blade in the shop and an average mouth opening. Smooth and sweet.

Sometimes I just have to play around 'till I find something that works. Like many of us here experience, posts here and other reading materials are my teachers.

.

[Joel Goodman]

Here's a link to a design of adjustable mouth wooden plane. The mouth is fairly similar to the ECE adjustable mouth except that the ECE uses a threaded insert in the adjustable section of the sole that closes the mouth. A machine screw is tightened on top of the plane to lock the mouth setting. Perhaps some who has built this design will join in.

http://linuxplane.awardspace.com/index.html

[Phillip Pattee]

The jointer I built awhile back is based on the linux plane. I did not glue on a sole, but other than that, I followed the tutorial closely. Here are some pics that aren't as blurry as the last ones I posted. You can adjust the mouth pretty easily.

Terry Gordon, of HNT Gordon, recommends about a 0.3 mm mouth opening for his smooth planes. If I recall correctly 0.5 mm is acceptable. He discusses this in his FAQ. http://www.hntgordon.com.au/faqs1.htm
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What do you think is the optimum mouth spacing should be to reduce tearout?