Thread: Low angle vs. High angle Planing

What happens under the Terry Gordon (or Australian) definition of cutting angle when you hold a card scraper such that the upper edge is in front of the lower edge? Does this result in a negative cutting angle?

Hmm, it almost seems as though it would make sense if it did...

There are so many variables in all this that Derek's comment in his original post is probably the most commonsense approach

Originally Posted by derekcohen

There is no one plane, or one cutting angle, that is "best". It really comes down to the piece of timber that you are planing. Even within species, there is such variation of grain that it will respond differently to different planes. This is why it is a good idea to have several smoothing planes at the ready ( or so I tell Lynndy ).

Derek

And, of course, it provides a perfect justification for buying more tools!

Col

I think all the confusion stems from the North Americans!

Quote from the back page of the LV&V catalogue:

“The low bed angle of 15° combined with the 25° blade bevel results in a cutting angle of 40° for exceptional end-grain cutting performance”

Quote from page 6 of the LV&V catalogue:

“the 20° bed angle plus the 25° bevel angle on the bevel-up blade result in an effective cutting angle of 45°, the same as found in most bench planes”

Quote from page 5 of the spring 2002 LN catalogue:

“being fond of low angle planes, we’ve lowered the cutting angle to 12°.

And from Hack’s hand tools book:

“The lower the cutting angle, the easier it will work and the smoother the surface will be. Hone a bevel close to 20°, and find a plane with a 12° bed angle for the lowest overall cutting angle”

I think us Australasians might be a bit smarter!

Hell, if it works, use it.

... the LN 164. As I understand it, it is in fact a bevel-up plane, and I think that is what Derek meant to say

Just to correct myself, Rocker is accurate. In mitigation all I can say that I wrote the post at 1.00 am Perth time. At least you all knew what I meant to say!

The question that remains unanswered is why we don't just use low angle set ups if they are potentially capable of cutting so much better? The answer is that, for the most part, our indigenous timbers don't seem to follow the same rules as those in the USA and UK. Our Oz timbers are tougher, more unruly, usually oppositional, and clearly anti-authority! The grains of timbers such as Jarrah and Karri can strike out independently in all directions. Cutting soft woods with straight, predictable grains is just so different, hardly a challenge at all.

SilentC wrote:

What happens under the Terry Gordon (or Australian) definition of cutting angle when you hold a card scraper such that the upper edge is in front of the lower edge? Does this result in a negative cutting angle?

Card scrapers are just another variation of high-angle blades. The high degree of friction caused by the scraping action is experienced in a build up of heat. Who hasn't burnt their fingers in a vigorous session of scraping? I would not call it a "negative cutting angle" (I think I know what you mean). Don't forget that a card scraper blade has a burnished hook, and this probably cuts around the 80 degree mark.

Regards from Perth

Derek

Thinking about it, I suppose that a negative cutting angle wouldn't cut much at all. I guess if the angle was past perpendicular, it would just drag along and not cut anything.

The point is that I hear what you are saying regarding the difficulty of applying Northern Hemisphere technology to our Southern Hemisphere timbers. Nevertheless I saw with my own eyes what that Lie-Nielsen plane (sharpened properly and in the hands of an expert) could do to a piece of the wildest looking grain I've seen. I suppose I'll just have to save up and buy one

Three pages, one headache and I'm still none the wiser.

Next year, why not go and watch Terry Gordon use one of his planes "sharpened properly and in the hands of an expert"? Then you'll probably be doubly confused

Craig, I sympathise. My head is full of information but I don't know nuffin.

Hi -

It's not about the planes - it's about the wood, and how the wood fails.

A plane is a carrier for a blade used to induce controlled wood failure.

Much of the confusion over which plane is best, or which angle is best really comes down to which wood are you using... tougher, more "failure resistant" woods can be well worked with a low angle plane....

Y'all have have a bunch of tough, failure resistent woods down there - which may run contrary to the experiences N Americans and Europeans have with their common domestics.

Wood failure generally falls into two types - Type 1 and Type 2 chip formation (creative naming, eh?). Type 1 is typical at lower bevel angles (angle between the bevel and the wood), and involves having the wood "splinter" ahead of the blade...usually evidenced by tear-out... For a really tough wood - this may not happen!

Type 2 chip formation is where the wood fails right at the cutting edge - essentially, the wood fibres are severed by the blade before they fracture. Type II chip formation (or behavior) is what we strive for, for a clean surface..

Now, there will be some exception woods to all of this...

Really soft/fragile woods can be difficult to get Type 2 failure .... so now we have to discuss Type 3. This is where the blade actually pushes the wood fibres ahead of the blade, inducing a compression failure - often leaving a fuzzy or furry surface. It looks a lot like the way a snow plow pushing sticky snow does....you can picture that, eh? (couldn't resist!)

This is why softer pines don't scrape well.... there's compression failure....

So - now we come to plane geometry...

Standard angle planes have a 45 degrees effective cutting angle, and are generally bevel down - a generic "best" angle for NA and European domestic woods...Keep in mind too, that planes were developed a century ago, when the quality of wood used was far better (more plentiful, old growth woods, and lots of mahogany) - today we work generally more "demanding" woods....

Low angle planes are generally below 45 degrees, and are typically bevel up...

High angle planes are generally 45 degrees plus, and bevel down...

So why bevel up/bevel down? Well - there are engineering constraints imposed by each method of construction... If you want an adjustable mouth - then there's a limit to how small an included bed angle you can have. Using a frog – it’s larger. Using an adjustable sliding plate ahead the blade – it’s smaller. With a low bed angle – a bevel up configuration gives a cut angle of “bed angle + bevel angle” – with modern blade steels – this can effectively be as low as 12+20 , or as high as 12+ 78… (a 58 degree range)

A higher bed angle – with a bevel down blade – is fixed at 45 degrees (or whatever the bed angle is). In order to increase the effective cut angle – we have to introduce the concept of a “back-bevel”…. Using back-bevels – the effective cutting angles can range from “ bed angle” to 90 degrees … (a 45 degree range for standard planes). Additionally – using a back bevel has the advantage of strengthening the edge on the blade – as the included angle on the blade tip is greater.

So for bed angles – there are also performance differences. Lower bed angles make the plane sole more susceptible to distortion – as tightening the lever cap can exert enough force to cause sole deflection. This is commonly observed in LA shoulder, rabbet (rebate) block planes etc., and is a technique often used purposefully to “adjust” blade projection.

Low bed angles do have the advantage that the blade is held in an orientation more in-line with the force applied – with should resist chatter more effectively than a higher bed angle plane made to the same tolerances.


A list of “truisms” (not really rules) I’d put forth would be:

1 - A back bevel works at least as well as a change in bed angle - and possibly better if the blade is not perfectly bedded, as a blade more in-line with the applied force can resist chatter better. (note - an adjustable mouth is usually necessary if using back bevels)

2 - A bevel up plane will work at least as well as a bevel down plane with the same effective cut angle - same reason as above...

3 – a low bed angle (bevel up) plane gives you the widest range of cut angle choices (rapidly changeable, if you have extra blades!)

4 – A narrow mouth with a light blade feed may allow a plane to “emulate” type 2 chip formation by reducing the possibility of the wood tearing-out (the sole ahead of the blade reduces the magnitude of, or stops the type 1 chip)

5 – how the wood you’re using fails is really the most important factor in determining which cut angle is best…

All of these factors (and there are more - like skewing a plane to reduce the effective cut angle) can make for a real witches brew when it comes down to interpreting why one configuration works, and another doesn't...but it's really about the wood...

Cheers -

Rob

It looks a lot like the way a snow plow pushing sticky snow does....you can picture that, eh?

Rob, this is Australia!!! Snow??? (well Melbourne doesn't count)

Anyway, thanks for the thoughtful comments. It is always great to hear from you.

Regards from Perth

Derek

Originally Posted by silentC

Thinking about it, I suppose that a negative cutting angle wouldn't cut much at all. I guess if the angle was past perpendicular, it would just drag along and not cut anything.

A negative cutting angle probably wouldn't work too well on a hand plane but you can buy circular saw blades with negative rake (same as cutting angle) eg CMT dado sets and blades for cutting non-ferrous metals.

Rob,

Thanks for the comprehensive reply. It pretty much echoes Derek's earlier post and it's good to hear some of the science behind it. It's all about the wood.

I'm also glad to hear that I wasn't totally off-beam regarding the relative position of the blade. The lower the bed angle, the less likely you are to get chatter. I guess this allows you to have a thinner blade in a low angle plane whilst a thicker blade in a high angle plane would help to counter the chatter.

Your truism number 3 is where I was headed but wasn't quite game to make the statement yet.

Craig is right, I should have spent more time at the HNT Gordon stand. I know I would have been equally impressed. I'm also aware that Lee Valley has some excellent planes but unfortunately I didn't come across anyone demonstrating them at the show.

Cheers.

Craig is right, I should have spent more time at the HNT Gordon stand. I know I would have been equally impressed. I'm also aware that Lee Valley has some excellent planes but unfortunately I didn't come across anyone demonstrating them at the show.

I spent a fair amount of time a the stand, whilst I had heard good things about the planes, I was a bit scared of adjusting a plane by whacking it. Terry has given me the confidence to at least have a go. To see these planes in action, on the timber he was using, is a sight to behold.

The other realistic option for me is a Veritas plane with adjustable mouth, there is little doubt that being able to adjust this without pulling everything apart is a BIG bonus. Especially for a mug like me. The other great thing about them is the price/quality factor. You can't get bench planes of this quality at this price from any other manufacturer that I am aware.

Please note I hvae no affiliation with Veritas, or HNT Gordon, but they know where to send any graft they feel appropriate.

Hi -

No worries - HNT Gordon makes fine planes...

There're lots of choices out there - and one may feel better to you, or suit your method of work best...

The important thing is to be armed with the information to choose which one will work for you... No manufacturer/retailer can tell you which one you'll like best!

Cheers -

Rob

Originally Posted by Rob Lee

Hi -

No worries - HNT Gordon makes fine planes...

Rob

Geez Rob - you're even picking up the lingo - youve been oat and aboat on this BB too much!
avagooday,