Plane mouth size and pitch (blade angle)

[JohnPW]

To prevent tearout on figured wood and for a single iron plane (no cap iron), does the mouth size relate to the effective pitch of the iron?

If you have a higher pitch, does it mean you can get away with having a wider mouth?

Eg can a 55 degree effective pitch plane have a wider mouth than one with a 45 effective pitch?

 

[D_W]

The short answer is yes, but anything over a mouth of about 4 or 5 thousandths can still experience tearout. A mouth of a hundredth on common pitch will still experience a lot of small tearout in my experience. Enough that you can't quickly scrape it off.

the damage is less at 55. I've found a 50 degree angle to be practically useless.

 

[Derek Cohen (Perth Oz)]

Hi John

As the cutting angle increases about 55 degrees, the mouth size becomes irrelevant. At 60 degrees it matters nought in regard to preventing tearout.

Think of the cutting action as akin to a scraper - one does not need a mouth for a scraper.

But a small mouth is helpful. It makes it easier to set a fine blade projection.

Regards from Perth

Derek

 

[sunnybob]

In a very slight hi jack... Being new to woodworking, and having only just dismantled a bailey plane for the first time, I was amazed to find that the whole blade block is adjustable.
This is obviously the mouth movement mentioned here.
So can I get either a description, or a link, to explain more to me about this adjustment please?

 

[Racers]

Mouth adjustment is negated by the use of a close set cap iron.

That's all you need to know.

:wink:

Pete

 

[Derek Cohen (Perth Oz)]

Hi Pete

That's not correct. Sorry.

When using a closed up chipbreaker, the mouth size must be adjusted (wider) so that shavings can still get through the mouth. So a closed up mouth will be blocked by a closed up chipbreaker.

Regards from Perth

Derek

 

[custard]

IMO a tight mouth is the least effective way of controlling tear out. You're limited to extremely fine cuts or the plane chokes, any time the plane rides over even the slightest hollow it negates the tight mouth benefit, on many planes (not all but many) it's a faff to arrange a really tight mouth, it puts a premium on the precision of every other plane component (i.e. sole flatness, blade alignment, cap iron alignment).

From a practical perspective it's not that a tight mouth delivers zero benefit, but the benefit is small and may not be worth the effort. Interestingly Karl Holtey used to advise his customers against having the ultra fine mouth that they generally requested.

I disagree with DW about a 50 degree pitch. On some timbers that's all you need to prevent tear out, the problem is we're just not working with those timbers to the same extent that we used to. The type of good quality mahogany that's all but disappeared today is a case in point, it's a very mild working timber to begin with, but the occasional bit of ribbon grain can still cause problems which a 50 degree pitch seems to generally tame. Conversely some really awkward timbers might need more than 55 degrees to fully cure tear out. Before I was persuaded to move over to a closely set cap iron I'd sometimes have to go to 65 degrees, which then becomes a real pig to even work the plane.

Most of my wooden moulding planes are at 55 degrees, tear out isn't totally absent but for all practical purposes it's pretty rare, and generally they have really open mouths.

Good luck!

 

[Racers]

Hi Pete

That's not correct. Sorry.

When using a closed up chipbreaker, the mouth size must be adjusted (wider) so that shavings can still get through the mouth. So a closed up mouth will be blocked by a closed up chipbreaker.

Regards from Perth

Derek

True, but with a close set chipbreaker mouth width is unimportant (as long as the shavings can get out)

It is the best way of controlling tear-out apart from my scraper plane.

Pete

 

[Derek Cohen (Perth Oz)]

Yep Pete, I agree with that (which is what I thought you meant to say).

Regards from Perth

Derek

 

[Derek Cohen (Perth Oz)]

IMO a tight mouth is the least effective way of controlling tear out. You're limited to extremely fine cuts or the plane chokes, any time the plane rides over even the slightest hollow it negates the tight mouth benefit, on many planes (not all but many) it's a faff to arrange a really tight mouth, it puts a premium on the precision of every other plane component (i.e. sole flatness, blade alignment, cap iron alignment).

From a practical perspective it's not that a tight mouth delivers zero benefit, but the benefit is small and may not be worth the effort. Interestingly Karl Holtey used to advise his customers against having the ultra fine mouth that they generally requested.

I disagree with DW about a 50 degree pitch. On some timbers that's all you need to prevent tear out, the problem is we're just not working with those timbers to the same extent that we used to. The type of good quality mahogany that's all but disappeared today is a case in point, it's a very mild working timber to begin with, but the occasional bit of ribbon grain can still cause problems which a 50 degree pitch seems to generally tame. Conversely some really awkward timbers might need more than 55 degrees to fully cure tear out. Before I was persuaded to move over to a closely set cap iron I'd sometimes have to go to 65 degrees, which then becomes a real pig to even work the plane.

Most of my wooden moulding planes are at 55 degrees, tear out isn't totally absent but for all practical purposes it's pretty rare, and generally they have really open mouths.

Good luck!

Rule #1: The problem with many planes with high cutting angles is that the high angle increases resistance and makes them harder to push. There are a few exceptions to this "rule".

Rule #2: The wider the blade, the harder it will be to push. And the harder the plane is to push, the more the plane is restricted to thinner shavings.

Rule #3: Lower the centre of effort on a plane, and one lowers the force needed to push it. So a 2" wide BU plane (LV or LN) with a 60 degree cutting angle is easier to push than a BD LN #4 with a 55-degree frog or a Stanley #4 with a 10 degree backbevel.

Many years ago I purchased a LN #4 1/2 Anniversary plane (that the heavy, limited edition bronze version). It came with a 50 degree frog. This was the days before I understood about the chipbreaker being used to control tearout. Well, the 50 degree cutting angle was not enough to control tearout on West Australian timbers, and a closed mouth added little. I swapped the frog for a 55 degree one ... but all this did was make the plane even harder to push. And so the plane sat on a shelf for years. A year ago I decided to get a common angle frog for it (45 degrees). Now this, plus a closed chipbreaker (and open mouth) works wonderfully. It is easier to push, although I do prefer a narrower plane in this regard.

BU planes and low-centre-of-effort BD planes (such as the HNT Gordon range), all with high cutting angles, can perform magic on interlocked grain. However they are still rather limited to thinner shavings because of the high cutting angle. High cutting angles = less penetration than low cutting angles.

(my remodelled Veritas BUS)

One of my best smoothers is a Veritas Custom #4 with a 42 degree frog. Used with the chipbreaker, this plane has tamed everything I've thrown at it.

Regards from Perth

Derek

 

[Racers]

This is my lion tamer.



Pete

 

[swagman]

Hi John

As the cutting angle increases about 55 degrees, the mouth size becomes irrelevant. At 60 degrees it matters nought in regard to preventing tearout.

Think of the cutting action as akin to a scraper - one does not need a mouth for a scraper.

But a small mouth is helpful. It makes it easier to set a fine blade projection.

Regards from Perth

Derek

Derek; thank you for a fair and reasonable response to a single iron approach..

regards Stewie;

 

[MIGNAL]

What is the point of that comment and what purpose does it serve?

 

[ED65]

This is obviously the mouth movement mentioned here.
So can I get either a description, or a link, to explain more to me about this adjustment please?

I'd recommend you save yourself the considerable time it will take reading the (many and varied) opinions on this and just set your frog nearly fully back so the iron is fully supported along its whole length and then fully tighten the frog screws, intending never to touch them again.

I'm literally planing on epoxying the frog in place on one of my smoothers, that's how much use I think the adjustable frog is once you learn to use the cap iron properly.

 

[sunnybob]

I'm doing m best NOT to learn to use a plane ( I have far too much machinery to justify), but I have an enquiring mind.

I've just about worked out the cap iron position, I'm very happy to leave well alone (g)

 

[ED65]

I've just about worked out the cap iron position, I'm very happy to leave well alone (g)

Just in case it's needed: the cap iron position isn't a set-and-forget thing. You will want to vary it as needed for the wood you're dealing with for best results.

Back off a bit when the going is easy (1.5mm or so, a bit more than this if hogging off) and much closer to the edge if you're getting tearout you don't want. Take it down to less than half a mil if the tearout is persistent, or switch to scraping or sanding.

 

[D_W]

I disagree with DW about a 50 degree pitch. On some timbers that's all you need to prevent tear out, the problem is we're just not working with those timbers to the same extent that we used to. The type of good quality mahogany that's all but disappeared today is a case in point, it's a very mild working timber to begin with, but the occasional bit of ribbon grain can still cause problems which a 50 degree pitch seems to generally tame. Conversely some really awkward timbers might need more than 55 degrees to fully cure tear out. Before I was persuaded to move over to a closely set cap iron I'd sometimes have to go to 65 degrees, which then becomes a real pig to even work the plane.

That's certainly fair (regarding the mahogany, etc). There's not a lot of that vintage good quality good-working wood here. Cherry is the closest thing we have to it for a reasonable price.

I agree with the comments about angles above 55, one of my original no-tearout favorites was a chinese plane bedded at about 65 degrees. It's OK as long as the surface is level and you only need to take a little bit off smoothing. Anything else, it's too hard to push, and there's one thing certainly true about it - it leaves a hairy surface on a lot of woods.

I had made, after that, an infill at 55 degrees with a mouth somewhere between a 64th and a hundredth, and then another at 55 degrees with a mouth between 3 and 4 thousandths. Then, I made an infill panel kit bedded at 45 degrees and figured that a hundredth would be a good mouth on it, and allowed tearout all over the place. I need to file it open a little bit, because it will work with a cap iron set closely, but it would be better if the mouth was a 32nd or so now with the cap iron.

I figure the original poster didn't want to hear about double irons given the subject matter, but I'll never use a bench plane without a cap iron again. The single iron model is so inferior to it that it's ridiculous for anyone who wants to be serious about planing.

 

[swagman]

I figure the original poster didn't want to hear about double irons given the subject matter, but I'll never use a bench plane without a cap iron again. The single iron model is so inferior to it that it's ridiculous for anyone who wants to be serious about planing.

Understandably I will avoid making comment. :mrgreen:

Stewie;

 

[D_W]

I figure the original poster didn't want to hear about double irons given the subject matter, but I'll never use a bench plane without a cap iron again. The single iron model is so inferior to it that it's ridiculous for anyone who wants to be serious about planing.

Understandably I will avoid making comment. :mrgreen:

Stewie;

I should probably condition that statement, by serious, I mean really serious - like what custard showed flattening a figured slab. If someone wants to just use a shooting board or plane off planer chatter, it really doesn't matter what type of plane is chosen. Once you get beyond that, then the separation becomes apparent.