# HAND PLANE THROAT OPENING



## stefang (Apr 9, 2009)

Most of my modest knowledge about hand planes comes from the net. The one thing I really don't get is the correct mouth opening. The experts say that the mouth opening should be set to about the desired thickness of the shaving. I don't dispute this, but it just doesn't work for me.

For example, I've been smoothing some maple today, starting with a small mouth opening of about 1/32", a really sharp iron with a very slight camber also about 1/32". Didn't get much bite with the plane set with the small opening, so I enlarged the throat opening to a little under 1/8" and got the shavings I wanted. My planes are all high quality and well tuned. I also have an inexpensive Stanley/Bailey which is about 3 years old, but which is also well tuned and performs beautifully (miraculously). My experience with the mouth openings has been the same for all of my planes.

It probably doesn't really matter as long as the planing results are good, but it it's irritating that my own experience doesn't coincide with standard practice. Any idea why that might be?


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## pintodeluxe (Sep 12, 2010)

My experience has been the same as yours. Fairly narrow throat opening, but not equal to the shaving. I still don't trust a hand plane on quartersawn oak. The first three swipes I see smooth, delicate shavings and the fourth pass I get tearout. For this reason I trust sanders and card scrapers on figured wood.


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## dbray45 (Oct 19, 2010)

Hard maple can be interesting on any day. All my planes have an opening of less than 1/32" except for the scrub and that one is 1/4". I use a scraper plane or #12 for hard maple, curly maple I take to someone that has a planer or jointer with a spiral or helical blade set - or drum sander.


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## stefang (Apr 9, 2009)

Thanks Willie, I feel better already! I bought a #80 scraper plane from Kunz which I often take a few strokes with after smoothing. It really leaves a beautiful surface. I rarely get any quarter cut or pure straight grained wood here.

My only experience with planing oak has been white oak and I machine jointed and planed quite a bit of it a couple of years ago with great results. I thought it would quickly dull my plane blades, but didn't. I was surprised at the nice shiny surface I got.


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## Dal300 (Aug 4, 2011)

My understanding and experience (albeit not much), leads me to believe you have the iron extended too far.
I don't know if it's just me, but setting the iron seems to be an almost esoteric art.
I have 8 planes, nothing fancy, just the standard Stanley/Bailey's, 409 Sargent, 414 Sargent, #7 Stanley, 60 1/2 Stanley, and a small record block plane or two.
Each one I need to work at setting the blade depth correctly.
My Stanley #5 takes a whole different setup than my Sargent 414. My Stanley #4 is completely different from my Sargent 409.
I have a wood 24" shipwrights plane that I have still never figured out how to set up. Certified built in 1754, a nice lady at TX. A&M I know did some tests on it and is 95% sure the seller was honest.


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## stefang (Apr 9, 2009)

*David* To be honest I doubt this is hard maple, compared to rock maple for example, but it is pretty hard. All I could find out from my supplier is that it is European maple and that's it.

*Dallas*I have the iron out about 1/32" from the chip breaker. I was thinking about that myself, but it doesn't seem excessive to me. However I'll take your advice and try an even shorter extension just to see if it helps. Everything is working fine for me as is, but I don't have any basis for comparison, so I guess just have to experiment a little.


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## shipwright (Sep 27, 2010)

Is that maple for the chevalet Mike?


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## stefang (Apr 9, 2009)

Yes Paul. I had a little spare time today so I wanted to see how well it would hand plane. I had already machine jointed and planed it so I just wanted to correct a very slight belly in one of the boards. I could probably glue it up with the belly which might even be an advantage as it would keep the ends very tight. I am just trying to get some more experience with my new planes.


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## Brit (Aug 14, 2010)

*Mike* - Read and inwardly digest this article. It helped me.


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## a1Jim (Aug 9, 2008)

Hi Mike
I'm sure just about everyone knows more about planes than I do ,I just adjust them until they do what I want.
I did find this on line from Roy Underhill who's planes always seem to glide through wood like a hot knife in butter on TV. Some of it is pretty basic but further down the post he gets into mouth openings among other details.

http://books.google.com/books?id=8Y2uAAH3YqoC&pg=PA79&lpg=PA79&dq=roy+underhill+plane+mouth+opening&source=bl&ots=VHrysHWYjX&sig=-KWf1mLkBrB750fJNZUQw7dQFbc&hl=en&sa=X&ei=ekuvUoajE4b5oASHuoCoCw&ved=0CHgQ6AEwDA#v=onepage&q=roy%20underhill%20plane%20mouth%20opening&f=false


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## stefang (Apr 9, 2009)

*Andy* I read it and here is an excerpt *"You won't need the mouth to be set tight if the cap iron is working properly"* That seems to be my experience here. Although my cap iron is not set 'super close' it is pretty close.


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## stefang (Apr 9, 2009)

*Jim* Thanks. I had a look at it.


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## Smitty_Cabinetshop (Mar 26, 2011)

"It probably doesn't really matter as long as the planing results are good…"

Mike, I think that nails it.

Mouth setting (either adjustable or tightened by moving the frog forward) is done to reduce tearout, as is setting the chipbreaker closer to the cutting edge of the iron. Without tearout, no need to tighten the mouth in my world.

I'd not heard "the mouth opening should be set to about the desired thickness of the shaving" before. I mean, it makes some amount of sense because jack planes are set more open than smoothers (for example) and the finest smoothers are even tighter. But if there were a 1:1 intended, it's news to me.

Very interesting post, thanks for putting it out there. This is something I'll pay closer attention to now.


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## superdav721 (Aug 16, 2010)

Mike I have a small coffin with a bit of wear on the sole. When I get the iron at a razors edge and set the chip breaker to where I just see a glint of light shining off of the iron it will take wonderful shaving off of figured maple and other hardwoods with no tear-out. The shavings are under a thou.
That is a wood bodied plane. I am still learning metal bodies. I don't have enough experience to give a good opinion.
To me proper set up and tuning is the key.
Keep in mind everything I own is 75 to 200 years old.
A mouth that is to tight just hinders the egress of the shaving leaving the plane.
IMHO


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## kiefer (Feb 5, 2011)

Hand planes , a art and sciences .
Enjoy learning your planes and the good results you get .


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## JohnChung (Sep 20, 2012)

The mouth is suppose to minimize tearout if the plane was push down hard on the surface. If the grain is too bad then it does not matter if the mouth is super close.

If the tearout is occurring I will adjust the blade height first then the chipbreaker. The mouth would be the last. I generally have the mouth midway unless it is heavy stock removal which I need the mouth all the way open.

In all, I still am learning about the mouth opening. It does help if I push down the plane hard with small opening on bad grain but not much. On against grain it does help well to close the mouth gap.


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## 12strings (Nov 15, 2011)

Mouth opening is only ONE factor in taming tear out…a sharp iron, set shallow, in a plane so it doesn't rattle or chatter are vital…

...that said, it seems to me that by definition, your mouth opening MUST be at least slightly bigger than the shaving passing through it, NOT the same size, right?


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## JohnChung (Sep 20, 2012)

@12Strings - I believe you are right. If it was that close I generally don't get shavings….... I actually get tearouts. That happens on the LN apron plane…....


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## stefang (Apr 9, 2009)

Great comments guys, thanks for taking part in this discussion. Every one had something useful to offer. Some of it is a little contradictory, but that is to be expected due to the difference in wood types and grains which all behave differently under planing. It's great to get more insight into this from your actual experience.

The link in *Brit's* comment above says that the edge beyond the chip breaker should be just visible as *Dave* mentions above, but that is for difficult grains, and it also says that more forward pressure (not downward pressure) is required to push through a stroke. Otherwise a normal setting and mouth opening is ok for normal grain.

The maple I was planing was pretty much normal. What I didn't check too closely was the distance between the front of the mouth and the apex of the camber, which I later found out is the proper measurement point. That means that the throat in my planes are probably more closed than I first thought. I'll have a look at that today.

I haven't experienced any chatter whatsoever regardless of the setting I used, but thats a tuning thing. I plan to try the super thin chip breaker setting as described by Dave in his comment just for fun. I also agree with *Smitty* and *12strings* that the mouth should be slightly more open than the shaving thickness desired. That's where the word 'about' comes in.


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## stefang (Apr 9, 2009)

A little update: I just tried *decreasing* the gap between my chip breaker and the iron down to just a light sliver, and with a mouth opening of 1/32". I then tried planing on a cutoff with figured maple. It went beautifully with no tear out. About half of the short piece was straight grained on one side and it worked good on that too, but even better on the figured part.

Fun to learn this stuff and get some handy new skills.


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## rhett (May 11, 2008)

Mouth openings are irrelevant with a properly set chipbreaker. The proof is the Kato video, where fluffly shavings and no tearout were achieved with an iron and breaker, rigidly attached to an armature, without a plane body.

I have20/20 vision but still need a magnifying glass to get a chipbreaker as close as needed, to negate the mouth opening.


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## stefang (Apr 9, 2009)

That is real interesting rhett, thanks for letting me know. I will try to find that video so I can see it in action. It also somewhat reflects my real life experience, although I did close up the mouth a bit on this last test.


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## dbray45 (Oct 19, 2010)

rhett - Cannot argue with you on that. The problem is that I have a few planes where the chip breaker does not extend far enough to be effective. I compensate by closing the gap.


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## stefang (Apr 9, 2009)

Ok, I saw the Kato video *rhett*,here thanks. And it seems (in simple speak) that a chipbreaker with an 80' bevel and set with a very small blade extension will make a smoother cut without regard to the mouth opening. Music to my ears! One problem could be that with a cambered blade the chipbreaker will cover the outside edges of the blade.

I will try not to get too excited though before I try this myself. First with the finest opening I can attain and maybe again with a chipbreaker ground to 80'. I'm not sure I dare take the risk of ruining a good chipbreaker, but I have an older Stanley Jack plane with broken side that I might consider using for such an experiment. It's just that the plane still performs well in spite of the breakage, so I'm not overly enthusiastic about it.

I think we need to keep in mind that a machine moving a blade at constant downward and forward pressure is not necessarily the same as what is going on when done by a human. Granted some folks will be better at it than others, but it's still not a machine working on a bolted down piece of wood, and only magnolia was tried in this instance. However, interesting enough to try it on a practical level.


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## stefang (Apr 9, 2009)

Ok, I just went out and tried a teeny blade/chipbreaker gap, then opened the mouth to about 1/16". It worked great with the grain, but a little tear-out against the grain, but not very deep.

I can still close up the blade a teensy bit, but then the camber comes into play. I think my next move is to reduce to the camber to about 1/64" or less and a further reduction of blade exposure to see how that works. I more than pleased with the result so far. I can now only wonder what miracles that 80' chip breaker could perform.

Wooden planes with chip breakers can perform just as well without a chip breaker, which leads me to believe that the popular word 'chipbreaker' is actually incorrect unless it has a very steep bevel, and it should probably be called by it's more proper name 'cap iron' as it is really there to reinforce the blade/iron and make it stiffer in an inexpensive way. the wedge would do this reinforcing in a wooden plane.

My little experiments seem to verify the results from the Kato video and the comments above so far even though I haven't taken them to the nth degree yet, i.e.; the 80' iron cap. It's fun to learn about this stuff. Thanks again everyone for your input!


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## TheWoodenOyster (Feb 6, 2013)

Brit, very interesting video^. It was really informative to see shavings being made on the microscopic level. It reminds us that there is always a mechanical reason behind what is happening when it comes to the interaction of our tools and wood. There is no ghost of stanleys past or anything, there is a reason for tearout.

My only qualm with the video is that it does seem theoretical to some extent. From what I can tell there is no body of the plane nor is there a frog. Ideally a frog will be perfectly steady and wobble-free, even to the point of being comparable to a milling machine. But, I think we all know that antique planes often are not perfect. Also, using a milling machine with what seems to be infinite and steady force doesn't seem to duplicate a human. The setup makes any sort of vibration or chatter veritably impossible.

That all being said, it is a lab experiment and variables (such as frog wobble and unsteady,human-like pressure) must be removed in order to get results that can verify anything. If anything, I think this video reinforces not only proper blade and cap-iron setup, but also the importance of a rock solid frog and good body mechanics when planing.

Great article and video Brit! Incredibly informative and helpful.


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## mafe (Dec 10, 2009)

Interesting blog here Mike,
I love the video, I have a soft spot for this micro universe…

My own experience is also that the chip breaker are not working well when to low angel, in my own un scientific tries. So I also honed then more steep.

When I get a new plane I usually spend a good time making a good fit between the iron and the chip breaker.
1. making sure the iron is flat.
2. making sure the irons cutting edge is 90 degrees to the side.
3. making sure the chip breaker is flat and I hold it a little lover than the sharpening stone when doing so, in this way I secure there are no gap.
4. making sure the chip breaker is 90 degrees to the side, so the breaker and iron can meet.
5. Flattening the front of the chip breaker, in this way I make sure I have a little thickness where the two meet.
Now I know my no 5 also helps to make the chip breaker more effective, thank you.

The mouth…
Honestly I never really got the feel.
I also just set it as tight as possible when doing finish and when using a plane for roughing I don't really care…
I can see against the grain it seems to help sometimes, I have had the thought that it was holding down the wood and therefore not made the tears as long.

Usually I can get around it by skewing the plane, before I did that I had much bigger troubles planning.

Hmmmm.
That was my thoughts.


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## stefang (Apr 9, 2009)

Good thoughts Mads. I am no longer very concerned about the mouth opening on my smoother, as it seems that it isn't so important as I have been led to believe. That said, I will still be trying new setting combinations just for the practical learning experience.


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## Timbo (Aug 21, 2008)

Interesting thread Mike, not much to add unfortunately but good info. I have my Stanley smoother set around 1/16" (maybe a little less) with a really close chip breaker like you describe, works for me. My contribution to the recent hand plane swap had a mouth that was all but closed and thin shavings passed through with out issue, I wonder if a wood body planes react different somehow?

Also +1 to Mads comment on a good fit between the chip breaker and the iron.


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## donwilwol (May 16, 2011)

See if any of this helps, http://lumberjocks.com/donwilwol/blog/30376


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## bandit571 (Jan 20, 2011)

Lets see. I have a Wood River #4 V3 with barely any gap showing, and, a FrankenBailey #5 ( made from just a collection of parts) with a Buck Brothers iron and a smallish gap.

Both will give the same shavings in QSWO, everytime. The #5 will even do end grain work.

On cambered irons I have, I stop the chip breaker just short of the corners. I don't even check the center of the iron.

Seems to be more about the sharpness of the iron first, the do the fettle so the iron is stable as it works. Start heavy at the knob, switch to the tote as you go along towards the end.

Wild grain? i recently made a cutting board out of Cherry and Black Walnut. The walnut had a few LARGE knots in it. No tear out with either of the the planes above.









Both irons have zero camber to them.


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## stefang (Apr 9, 2009)

Thanks for those enlightening/confirming comments *Tim, Don and Bandit*

So lets sum up what has been established for smoothers/jointers using the Kato video and the actual experience/testing of you guys:

1. A super small gap between the cap iron is the best setting.
2. An 80' bevel on the cap iron is best.
3. *Don* had great success with the mouth opening being about the same as the iron extension. I still have some small doubts about this, but I can't deny that *Don* has done some good practical tests on this point.

This pretty much confirms my own tests done yesterday except for the mouth opening. I could't find any advantage to a very small mouth opening, but I won't make any claims with my limited experience and tests so far, and *Don* has forgotten more about planes than I will probably ever know.

The camber issue still bothers me. Ideally it would be great to not get dig-in with the corners, but that has consistently been the case for me when using an iron without it. However, it seems that *Bandit* isn't having a problem with that. So the question is; have you rounded the corners of your iron?

I haven't tried a straight edged iron with no camber or rounded corners yet, so that is probably my next test. I'm hoping the very small iron extension will negate the need for camber. It would make sharpening a bit more straight forward. Maybe I'm just dreaming?


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## JohnChung (Sep 20, 2012)

I rounded my corners to eliminate the track marks made from smoothing. It is highly recommended. You can create a slight chamber but I generally associate that with making scallops on the surface. A scrub plane has a chambered blade. If you are leveling stock a chamber blade is acceptable. I generally don't bother using chamber unless it is the scrub plane.

Rounding corners for a smoother is a resounding yes


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## stefang (Apr 9, 2009)

Thanks John. I plan to try that today. I agree that a cambered blade will leave a slight scallop, but that is not really a problem unless you are going for a surface ready for finishing. I usually do a final pass with my #80 scraper plane. It leaves a wonderful smooth surface. I do think it can be an advantage without any camber and maybe I can eliminate the scraper work at the same time, although in practice the scraping goes very fast and easy, even on a large surface.


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## donwilwol (May 16, 2011)

I round the corner on all my smoothers.

Back to the mouth issue. You'll find its more of an art than a science, but if you think about it logically there is science behind it. You will get different results from different planes and different woods. With a straight grain soft wood the mouth can be 5' wide, it doesn't matter. A maple with difficult grain may require tightening.

And why different planes react different? I haven't fully found the answers, but I'm sure it has to do with all of the follow, and some I'm not thinking of. The angle of the chip breaker, the depth of the chip breaker, the angle of the front of the mouth, with wood, the grain, the depth of cut, and even the humidity would play some role in how the wood reacts. How dry the wood is? Feed rates, hand pressure. Think of all of the variables that will affect how the wood will chip and cut. The dryer the wood, the better it chips but the harder it cuts. Blade sharpness, blade angle. Amount of skew.

A complete list? Probably not.


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## superdav721 (Aug 16, 2010)

Has anyone thought of compression.
You go over the piece 2 or 3 times and it just wont bite. This has then compressed the piece. You adjust a little deeper and it bites the compressed wood to much then "tear out".
I have been known to get my joiner out and relieve the work surface and then try again with the smoother. With fair results.
This is one reason IMHO that a wood body plane has an advantage over the metal. You can feel the work piece better.
The western style planes rely on a lot of downward force. Where as the eastern rely on the pulling force. Remember we push ours they pull them.
Mike this has been a wonderful read.


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## dbray45 (Oct 19, 2010)

Don - blade thickness, hardness and frog style and size have a lot to do with the throat opening in relationship to the sole thickness (leaves an unsupported gap). As the blade grabs the wood, the blade deflects. Having the throat opening limited reduces the amount of defection at the beginning of when the blade grabs. This will change as you sharpen the blade, whether you put a secondary bevel, angle of the frog, hardness of the wood, moisture content, direction of the grain, knot locations (hidden or otherwise), even the angle of the tote in relation to the blade combined with the workbench height and height of the woodworker.

There is a little science that goes on in these tools but to think that much of it was done - because it feels right, is kind of interesting.


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## stefang (Apr 9, 2009)

*Don* I have to agree with you on all the possible variables. There can never be one truth. That's where experience comes into play. I don't have that experience so getting acquainted with some of the theory and then trying out different approaches (and different wood if I ever get any) gives me a reasonable learning curve. I am having fun learning this stuff and it is important to me as I really like hand planing and it is a very handy skill to have. Most of the hand planing I've done is over the past 2 or 3 years, but in a fairly headless fashion, but now I want to get good at it.

*Dave* I don't have much experience with wooden planes, but I have made a couple of them. One with a rounded sole and blade for doing bucket staves and another flat jack plane that I'm too ashamed to show. The round one works pretty well, probably because of the rounded blade. The other not so good. I'll be burning that one! I do love the lightness of the rounded one and you might have a good point there about being more sensitive to the wood, as you can easily feel the vibrations through the plane as the cut is being made.

*David* I think what you are saying seems to pretty much be in agreement with what Don said. I plan to focus a little more on the mouth opening issue with my next test. Of course, I will be using mainly maple for my tests, but it is pretty hard and maybe a good hardwood representative. I also have white oak which I might try. I'm not doing any pine tests because it is pretty easy to get good results with a lot of different settings. I had planned to do more today, but I got selected as driver of the day by my boss to do some shopping. Tomorrow I have to visit my MIL at the old folks home and also go to the dentist, the perfect day! I am hoping to make another attempt on Friday.


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## dbray45 (Oct 19, 2010)

The most important thing is what works for you.


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## stefang (Apr 9, 2009)

Amen to that!


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## Timbo (Aug 21, 2008)

Another viewpoint from Tom Fidgen

http://www.theunpluggedwoodshop.com/cambered-iron-or-a-broken-corner.html


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## Brit (Aug 14, 2010)

Regarding rounded corners on an iron, I once had a conversation with Deneb Puchalski of Lie Nielsen tools and he said that he didn't round his corners because he didn't see the point. He said that instead of getting plane tracks with square corners, you get plane tracks with rounded corners. Either way, you still get plane tracks. He did add a slight camber though I believe. Just thought I'd put it out there.


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## stefang (Apr 9, 2009)

*Tim* I Read what Tom had to say and it looked to me that his 'rounded edges' resulted in a camber very much at the about the same amount that I have done mine. (about 1/32). I plan to reduce mine to 1/64".

*Andy* I have to agree with that as I have rounded the corners on my damaged jackplane and I do get tracks with it. All my other planes have a little camber.


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## mafe (Dec 10, 2009)

http://virginiatoolworks.wordpress.com/2012/07/28/open-vs-closed-mouth-the-adjustable-plane-facts/






Hmmmmmm


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## stefang (Apr 9, 2009)

Thanks Mads. The iron did look like the corners were relieved quite a bit and otherwise a very straight edge. Having seen these in action before it seems to work extremely well without any camber.


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