High angle frog vs. back bevel - is one better?

Re: High angle frog vs. back bevel - is one better

Frank D. in Montreal


>Hi Denis,

I'll let the experts answer, but I was just wondering what you meant by "better"? Do you mean more practical, or less tearout? Tearout can be measured, but I think the other "better" depends entirely on the user (goals, budget, planes s/he already has, sharpening techniques, personal preference, etc.). I'm not tot trying to raise a fuss here, maybe just make the question clearer (for me :) ).

One thing to consider....

Jamey Amrine in Ann Arbor


>....is that a back-bevel opens the mouth. Unless moving the frog (assuming no adjustable mouth) allows you to close it up enough, this is going to hurt you since the whole point is to reduce tearout. I would think that a tight mouth does more to prevent tearout than the cutting angle.

Re: High angle frog vs. back bevel - is one better

Denis Ch�nard, Orl�ans, Ont.


>By better, I meant less tearout, as this is the reason why one usually buys a high angle frog plane. Practicality is secondary in my view.

You're right, my question wasn't very clear :)

DC

Re: One thing to consider....

Denis Ch�nard, Orl�ans, Ont.


>Assume that the throat has the same size in both cases.

DC

Re: One thing to consider....

Norman (Ottawa, Ont.)


>Also not an expert, but I imagine you can probably get equivalent performance with a back bevel but you might be comprimising a couple of things.

- The iron is no longer completely bedded on the frog ( thicker irons should be able to handle this I imagine)

- The edge of the iron is possibly weakened with bevels on both the front and back?

Also, this question really only becomes relevant if both bedding angles of 45 and 50 degrees are often necessary. Then it is a matter of swapping irons ( a cheaper and quicker alternative than swapping frogs).

If one is to initially purchase the plane and has the option, then HAF makes more sense than a back bevel.

Norman

Re: One thing to consider....

Norman (Ottawa, Ont.)


>"The iron is no longer completely bedded on the frog ( thicker irons should be able to handle this I imagine"

Sorry, thinking BU planes.

Norman

Re: One thing to consider....

Denis Ch�nard, Orl�ans, Ont.


>See Norm, you can't escape from the world of BU planes. Their attraction is irrestible... ;-)

DC

Re: One thing to consider... chip breaker

Norman (Ottawa, Ont.)


>I was also thinking about the chip breaker and how the contact point at the edge of the iron might be affected by the introduction of a back bevel. If the contact point is very close to the edge and depending on the back bevel itself, you might be introducing a minute angled gap at the contact point unless you redefine the flat part of the chip breaker to accomodate the back bevel.

Again, this is dependant on how pronounced the back bevel field is and if you overlap it.

Norman

Back bevel is much more versatile.

David Charlesworth


>Sorry chaps,

this subject which is dear to my heart is much misunderstood.

Hoadley explains it well. When sufficient effective pitch has been reached to avoid tearout with a fine shaving, mouth width ceases to have any relevance at all.

By sufficient effective pitch, I mean Type 2 chip formation has been achieved, as opposed to Type 1 chip formation which is what happens at around 45 degree pitch and lower. See Hoadley. Hoadley does not use the term EP which is my terminology, he uses the more correct engineers term 'cutting angle').

The precise EP angle required to get type 2 shavings with different timbers may vary. This seems to be the view of Brian Burns, in his excellent pamphlet which Japan woodworker sell. (Used to be about $10).

If you use double bevel sharpening in a conventional bevel down bench plane, you can arrange any EP you want, from 45 degrees to 90, simply by choosing the angle of the minute bevel which you hone on the flat side of the blade.

High angle frogs are set at a particular angle, and if you want a higher EP you have to resort to double bevel sharpening anyway.

I find EPs of around 60 to 75 degrees the most useful for gnarly interlocked dense exotics.

It is counterintuitive but gnarly soft woods seem to respond well to extremely low EPs.

This theory, which works, has been exploited by Lee-Valley with their range of bevel up planes with blades supplied at steeper grind angles. I believe the theory was well known to craftsmen in the past, who might have made wooden planes with steeper pitches as required. Many moulding planes are pitched at 60 deg and have no chipbreakers.

However, it seems to me that a 12 degree bedding angle is rather low to use as a starting point. Karl Holtey's 98 plane with 22.5 deg bed seems better for this function. Philip Marcou seem to be on this track as well.

If you want 75 deg EP, which I frequently do, the blade of a 12 deg bedded plane must be honed at 63 degrees. This does not suit me or my favorite side clamping honing guide. Naturally, Rob Lee's team have designed a honing guide which will achieve this. (I think? It is too late to go to workshop and check!).

It is rather late here, hope this makes some sort of sense.

David Charlesworth

Re: Back bevel is much more versatile.

Norman (Ottawa, Ont.)


>David,

I bow to you and I'm very glad I preceded my opinions with " I am not an expert" :)

The part you mention about versatility makes sense, you can vary the effective angle to anywhere beween 45 and 55-60 by introducing a back bevel as opposed to a fixed angle frog.

Norman

Re: Back bevel is much more versatile.

Andrew F in Australia


>Hi David,

Brian Burns still sells the pamphlet

http://www.lessonsinlutherie.com/homeforlowrez.html - click on the double bevel sharpening link

Trust that all else is well - while my experience concurs with yours, I'll use either a HNT Gordon plane (bedded at 60 degrees) for cranky grain, or a standard Stanley for most tasks.

Best regards,

Andrew

I agree that the double bevel is more versatile

Denis Ch�nard, Orl�ans, Ont.


>But what I had in mind was whether the configuration difference affects performance. Let me try to explain.

Case 1: standard frog, blade with a 5 degree back bevel. On one hand, the chip breaker can not be set as close to the edge of the blade because of the back bevel, therefore providing less support from the CB. On the other hand, the back bevel effectively shortens the length of the main bevel, in theory this should make for a stronger edge because of the reduced lever effect, and could reduce chatter.

Case 2: York pitch frog, no back bevel. Obviously we have the opposite situation here, a longer bevel which could increase chatter, but the chipbreaker can be set right at the edge of the blade, helping support the blade edge.

My question is, will one setup outperform the other in terms of surface quality? Will one be more prone to chatter than the other? Can the back-beveled blade, by virtue of its 5 degree higher edge angle, take as keen an edge as a blade with no back bevel, everything else remaining constant?

Bottom line, can one of the two configurations above tackle gnarly wood better than the other? Or does it make no difference at all?

DC

Re: High angle frog vs. back bevel - is one better

Dan Clermont in Burnaby


>Hi Denis

It is okay to say LN ;)

I don't think one is better then the other. Trying to repeat a Back Bevel or sharpening the back bevel at a common angle all the time requires more care and setup compared to using a HA frog.

You planning a purchase at the Ottawa woodshow? We have our show this weekend and am looking forward to it.

Dan Clermont

Amost no mention of BU planes!! :)

Derek Cohen (in Perth, Australia)


>In theory, putting a five degree back bevel on the blade of a standard pitch plane gives the same angle of attack as switching to a York pitch frog.

In practice, is one approach better than the other?

Hi Denis

In regard to the quality of the planed surface there should be no difference when using a thick LN blade. If you were asking whether there is a difference with a thin Stanley blade then I would be more cautious and want to know about the hardness of the wood.

We are only talking about 5 degrees here, but the higher the cutting angle, the more effort required to push the plane, and the more stress on the bevel edge. A thick blade (1/8" or 3/16") is less likely to flex on hardwood than a 1/16" thick blade. I do not like using a large backbevel on a Stanley blade when planing Australian hardwoods for that reason.

The other area for consideration is the part played by the cap iron (I think I will stop calling it a chipbreaker). The primary role here is to reinforce the bevel end of the blade and improve stability and damp resonances. A thin cap iron is going to do a poorer job of this than a thick one, something we now all are aware of (I demonstrated this when the new LN cap iron came out a several years ago). In other words, a thinner backbevelled blade with a thick cap iron may work where a one with a thinner cap iron may not.

All this disregards whether a backbevel is practical or not. I use backbevels a lot, even with BU planes, but these are of the micro-backbevel type (from DC's Ruler Trick), so are under 1 degree. Their precise angle does not matter for re-honing. However, a precise 5 or 10 or 15 degree backbevel will require special setting up, which is time consuming. I'd much rather have a high angle frog under these circumstances.

Regards from Perth

Derek

Don't know

David Charlesworth


>Denis,

Apologies for not reading your question properly.

I do not know which setup will perform "best", as I have used double bevel technique for years, rather than having several different pitched planes. Double bevel sharpening should be no more difficult than regular sharpening, tho it involves one extra operation. (In my system, two stones for the normal bevel and two stones for the back bevel).

Double bevel certainly works better with modern thick blades than it did with thin standard stanley blades. Bevel up planes also work better with thick blades.

My feeling about high angle frogs is that they are set at a fixed angle. The increase in EP is small and will not be sufficient to deal with the nastiest cranky exotics. It is significant that Terry Gordon uses 60 deg EP on his excellent wooden planes, this is combined with very narrow mouth. If I use 70 or 75 degree EP for African Blackwood, Lignum Vitae,Cocobolo or Tasmanian Blackwood, mouth width ceases to matter, as Type 2 chip is formed.

I think it would take a lot of work and experiment to establish which system performed best, as they will certainly both produce the desired result, i.e. zero tearout.

David Charlesworth

Thanks all

Denis Ch�nard, Orl�ans, Ont.


>I guess we can safely say then that it boils down to an issue of cost vs. convenience...

Thanks again,

DC (the other one)

Re: High angle frog vs. back bevel - is one better

Denis Ch�nard, Orl�ans, Ont.


>I'm not planning on a purchase, but there's at least one member of our local association who's thinking about it... My question on this board stems from a discussion we had locally...

Mind you, I wouldn't mind a #8 or a skew rabbet block plane, but I've bought so many tools this year that SWMBO's goodwill must be wearing thin... She called me at work this morning to tell me that I received a shipment from Japan Woodworker... Better not push my luck, or find a project for her that requires a new tool... ;-)

DC

Re: High angle frog vs. back bevel - is one better

Dan Clermont in Burnaby


>I dunno is the HA frog leaves a better surface then a comparable Back Bevel but do think it is easier to set up IF you are only going to plane at 50 degrees.

My York pitch 5.5 planes all the woods I work with very little problems so I can't say I have had a need to test this. I do own a BU Jack and have a low angle blade and another blade set up at around 70 degrees which I have never used (got this plane before the 5.5)

I do use the Charlesworth trick for sharpening but would hardly call that a significant Back Bevel.

Can't say I have spent much on tools over the past year but our woodshow is this weekend and I have ordered a LN Bronze 4.5.

Think I am gonna stick to looking for some one - of - a - kind woods this year at the woodshow and maybe a small crosscut saw.

Cheers

Dan Clermont

Re: High angle frog vs. back bevel -no difference

Lyn J. Mangiameli


>I've played with this in almost every possible configuration, including comparing L-N 4.5s with a back bevel against the L-N HA frog (though frankly a difference of only 5 degrees is pretty subtle in most cases). I've done it with infills and woodies. I've done it with angles up to 70 degrees.

When comparing within essentially the same plane design (say a L-N or Shepherd Infill where I had the choice of using different bedding angles or back bevels to acheive the same effective cutting angle) I found absolutely no difference when the criteria was surface finish. This is really not surprising when you consider that the surface of the wood is seeing the same effective cutting angle either way, and that the back bevel need be little more than the depth of extension into the wood (thus making issues of cap irons and the sort moot).

If you have a plane with a bedding angle below 60 degrees, you are apt to find it worthwhile to at least experiment with obtaining a higher effective cutting angle via a back bevel. As David has noted, angles as high as 70 and 75 degrees can be helpful at times on the more "exotic" woods, though personally, I rarely find a reason to go above 65.

One other thing I would note is that some planes don't consistently perform as well above 60 degrees as they do at lower angles. I found this with most bedrock styles and the Shepherd infills where quality of surface finish sometimes deteriorated slightly at the highest angles. I see this as a plane issue, rather than an effective cutting angle issue, as other planes managed to achieve increasing better performance on the same woods as the effective cutting angles climbed above 60 degrees. In general, the BU Iron and BD Woodies more consistently managed to maintain or increase their performance as the effective cutting angle increased. I think this has to do with bedding and damping issues, but at this point I can only report the empirical findings.

Re: One thing to consider....

Greg Sloop, Portland Oregon


>DC addressed this well, but I thought I'd chime in and add a "I agree" to his assertion that mouth opening is almost immaterial to the tear-out situation.

I'll add a couple of things however.

A small mouth appears to limit how much flex impact the cut - a small mouth will prevent (my opinion) flex from causing a deeper cut. If the cut angle isn't sufficiently high, and tear-out is likely, then a VERY shallow cut will help. If the plane body flexes and takes a deeper cut, tear-out is going to sprout everywhere. In this case, IMO, the very small mouth helps control very carefully the cut depth and thus "appears" to help in controlling tear-out.

(Perhaps it's not flex, but some other factor, but I think it's flex. Perhaps someone else has another more reasonable explaination.)

A small mouth _might_ also help hold down the fibers of the wood so the iron will cut them. I, however, discount this theory, because in most woods where I see it help, the wood has lots of reversing grain and it simply doesn't run up the surface of the board, but often nearly straight down at the point of tear-out. (Again, complete speculation based on a fair bit of observation.)

The real point in all this is simply this:

IMO, mouth opening is a *very* small factor in controlling tear-out. A much larger influence is cut angle. If you're trying to solve a tear out problem by adjusting mouth size, it's not going to be very effective. It will be like trying to decrease your back-pack weight by cutting off the handle of your toothbrush instead of removing the case of beer. (Remember the objective was decreasing pack weight, not enjoying the beer...)

A better solution is to adjust cut angle. (Unless you can't, obviously.)

Anyway. Just my thoughts.

-Greg

Thanks Lyn, glad to see you back!

Denis Ch�nard, Orl�ans, Ont.

Re: One thing to consider....

Dan Clermont in Burnaby


>Sorry Greg,

I disagree.

IF a sole pushes down on the wood fibres directly in front of the cutter (tight mouoth) the fibres cannot tearout or tearout will be very minute poroviding the thickness of shaving is very close to the size of the mouth opening.

I do agree with you on DC that mouth opening makes no difference when you get into high bevel angles like 70 degrees and up but it should be noted the thickness of shaving should also be very thin cause if you gouge the wood with a blade set to deep you will get tearout.

Dan Clermont

Re: One thing to consider....

Greg Sloop, Portland Oregon


>In reversing grain, just tell me. Is the grain running up toward the front of the plane? (My answer: Almost never - certainly not where I see tear-out.)

Second: The blade never reaches the mouth. It moves along behind it. If the wood is splitting, it's going to simply split as you move the plane forward.

I'd love to see someone study this, but I still stand by my assertions.

A small mouth helps control depth of cut - nothing more. In controling depth of cut, it helps control tear-out. (Around as much as cutting off the handle of the tooth-brush vs. the case of beer controls pack weight.) Since very light cuts can help in tear-out situations, this may help.

IMO, when the cut angle is too low, then mouth size doesn't prevent tear out. It prevents too deep a cut which helps minimize tear-out.

Finally, in either case - regardless of what action the mouth has, if one wants to tilt at windmills by claiming cutting the toothbrush handle is a help, be my guest.

(The take away lesson to me is this: If you're attempting to solve a tear-out problem, ignore the mouth unless there is absolutely nothing else you can do, or the problem is exceedingly minor.)

Cheers,

Greg

Re: One thing to consider....

Dan Clermont in Burnaby


>Hi Greg

You are right. The grain is runnning in an upward direction toward the cutter in a reversed grain situation. That is why good quality infill makers make infills with tight mouths and why LV, LN, Clifton, Bailey, Bedrock.... etc all give you the option to close the mouth down.

I spent last week making beveled panels for drawer fronts and a door using Western Curly maple and some of the boards had reversing direction. When I was done smoothing them they were soft like a babies bottom despite the grain reversal. I also beveled the panels with a york pitch plane and never paid ANY attention to grain direction cause I find it easier to bevel off the side of my bench.

I included a pic of the cabinet. The large door panel was cut from a piece between two knots and same goes for some of the panels.

I used a tight mouth with good downward pressure to ensure the fires were pushed down before the cutter. The blade was sharp.

If you want. Come on up to the CLoverdale Woodshow near Vancouver BC, Canada. It starts tomorrow. We can take your questionable board and try it at the LV booth with their planes and then maybe see if Rob Cosman at the LN booth can palne it without tearout. I'll even buy you a burger or hot dog, might even pay for your gate entrance. Lemme know.