Member
Pushing from the sole, or using it in the normal way? :-)Originally Posted by Warren Mickley
The results will be quite different, as I'm pretty sure you already know or else you wouldn't have posed the question.
Also you usually don't take 2-mil cuts with a block plane, so that will probably also shift the optimum...
Last edited by Patrick Chase; 06-24-2016 at 12:33 PM.
Contributor
And while you are at it, rig up some method of measuring the exact amount of downforce being applied.
You will need to include a lot more charts and graphs to include every possible kind of wood and grain combination, every possible bedding angle, different amounts of down force and every metal that was ever used to make a plane blade.
After all is said and done, some folks are just not able to see this as a guide or survey of blade wear in a common 45º bedded plane on wood without knots.
So instead of keeping something a simple guide, let us stir the pot and come up with something that would likely be even more confusing.
In the end, it will likely do nothing to convince me to change what has worked best for my needs over the years.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
Contributor
I volunteer to be the control group and keep sharpening at whatever random angle I end up setting the jig to at the time. That at least will give us a nice floor for bad results.
Contributor
Speaking of floors for bad results, just come to my shop and look at all the scraps of mistakes laying on my floor.
Then consider those who make no mistakes seldom make anything else.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
Member
To be clear, my objection isn't that Normand got the wrong answer. It's that there is no right answer.
His claim that "a 17 degree angle is best" (his wording) is at the very least not sufficiently qualified. A 45 deg bedded plane on soft/medium straight-grained wood are only the start of the (many) preconditions that must hold for the results of that experiment to be valid.
I pointed out zero downforce because it's the single biggest deviation from how planes are used in the real world. It is the nature of science that in order for an experimental result to be valid the researcher must show that all of the relevant parameters are representative and properly controlled. A reviewer need only demonstrate one significant exception to invalidate the whole mess. I chose downforce.
As you point out things like downforce and "acceptable resistance" (i.e. how high the cutting forces have to be before we decide the blade is dull) are individual preferences, so even a perfect experiment would only yield a valid result for one person.
Last edited by Patrick Chase; 06-24-2016 at 2:22 PM.
Member
Hehe. There's definitely a (wood-dependent) practical minimum below which the blade won't cut with any reasonable amount of downforce or other "user help". I've seen trouble at 5 deg on relatively soft wood.
There are folks (Sellars for example) who claim good cutting performance at even lower angles, though some of those people (Sellars again) also use continuously-varying convex bevels, so it's not clear to me how they even *know* what angle they're using.
[OP]
Member
Stewie,
There is nothing wrong with O-1 and I've used that steel a lot. 28/30° is very close to what I'm saying.Hi Normand; I am a bit old school so I will stick to what I know best, and that's 01 tool steel. For a 45* bd plane iron; I start with a grinding angle of 25*, and end with a honing angle that comes close to 28/30*. I don't use a honing guide; the results you posted on 01 steel at 28* reaffirms my own understanding.
Luke and Pat
Again, this has been shown by Kato and Kawai.Is it not conceivable that different materials will wear a blade in different manners?
With a raising grain, there is a visible wear on the bevel side. With plunging grain (negative angles) there is very little or no wear on the bevel.
Derek,
It seems that I had not seen that page on Steve website.
In my study I wasn't looking at the best planed surface at all. In fact, the 0.002" depth of cut that I used is ticker than what I would plane to get the best surface finish. For someone working with very hard wood like you, I'm sure that a higher sharpening angle is better.A decision is made to ignore the clearance angle to obtain the best planed surface - rather than better edge holding results
Patrick,
You do not understand yet? Go back and read carefully the study then you can participate in this thread intelligently.
Member
In my experience ad hominem attacks are what people resort to when they have nothing else to say. Address the arguments, please.
Why do you think that pushing from the heel of the plane has any relevance to real-world use?
Contributor
Be what it may, I see it as an interesting starting point for consideration when one is sharpening a blade for what ever reason.As you point out things like downforce and "acceptable resistance" (i.e. how high the cutting forces have to be before we decide the blade is dull) are individual preferences, so even a perfect experiment would only yield a valid result for one person.
Didn't you at one time start a thread claiming to have found the 'perfect' clearance angle?
You stated:
This all reminds me of a radio host who told about an advertising sales representative who said, "nobody listens to AM radio."I'm firmly of the opinion that extra clearance is nothing more than wasted blade life
It started a trend of people calling his program and saying, "high _____, I'm a nobody from _____." Millions of 'nobodys' listened to his program.
I believe it was you who also said, "nobody uses a block plane for a 0.002" shaving."
Well, I am a nobody on that count.
I guess I am also a nobody who pushes a smoother with as little a down force as possible across a surface for final passes.
To me, pushing from the heel of the plane "has real world use."
jtk
Last edited by Jim Koepke; 06-24-2016 at 4:56 PM. Reason: spelling
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
Member
No, I did not.
I said that I'd accidentally used a 5 deg angle and run into severe issues on one wood (Alder) but not another (Maple). I made no claim that my results reflected an "ideal" or applied to any other situation. My exact words in the first post were "so here's one empirical point for the endless clearance debate" and "I'm going to continue to aim for ~10 deg". That's about as far as you can possibly get from claiming to have found a universal answer (as in this thread) or claiming that everybody should aim for that angle on all but the very hardest woods.
In later posts in the thread I also acknowledged that the cutting forces at the angles I use are slightly greater than at higher clearance angles (I think Kees' ~20% number from that thread is about right for typical hardwoods), and others might have different preferences as a result.
I do in fact think that excess clearance is simply wasted blade life. Acute angles wear faster than obtuse ones, so If you allow more clearance than you actually need (based on the woods you work, your technique, etc) then you're wasting time honing and throwing away perfectly good tool steel. Note however that I carefully acknowledged and left room for the fact that the threshold for "excess" is subjective.
It's called "nuance".
EDIT: Since you brought up [in]consistency, let's all remind ourselves of these results: http://www.sawmillcreek.org/showthre...25#post2567525.
If the same person can come up with data that differ by more than a factor of 100 for nominally the exact same thing, then that should tell you something very significant about the difficulty and validity of such experiments.
Last edited by Patrick Chase; 06-24-2016 at 10:40 PM.
Member
After re-rereading the study I think I understand this part.
Normand, in your study your only criterion for stopping was whether the plane would self-initiate a full-width shaving, correct?
It appears that you didn't consider things like surface quality, so that means that your chosen metric is insensitive to non-abrasion failure modes like chipping (at least not until it gets bad enough to prevent a full-width shaving). That may in turn would explain why you found the same optimum for steels with wildly different "balances" of hardness/toughness/abrasion-resistance. If your chosen metric only tests one attribute then its relation to the others is no longer a factor.
At the risk of reopening the "end grain sub-debate" this is exactly why Derek pares some end grain in pine every N strokes in his studies, to make sure that the blade is still cutting cleanly as opposed to just cutting. I think that would be a worthwhile process improvement here.
On a separate note, I'd suggest honing on diamond (film or paste) for experiments like this in the future. It can be spendy, but it cuts basically all tool steels well and therefore controls for stone<->steel incompatibility issues like the one you saw with PM-V11 on oilstones (or like what happened to Derek when he evaluated a CPM-10V chisel after honing on Shapton Pros).
Last edited by Patrick Chase; 06-25-2016 at 12:04 AM.
Member
Patrick; I have a terrific idea; since your never shy of offering advise to others; why don't you run your own independent tests and forward the results to the forum; with your expertise in mechanical engineering and computer skills, you would make the ideal candidate; you could call it "Cutting to the Chase".
regards Stewie;
Last edited by Stewie Simpson; 06-25-2016 at 9:19 AM.
Member
Why on Earth would I waste my time like that?
My principal and consistent argument in this thread is that the optimum is driven by subjective preferences, both in terms of how to drive the plane (downforce etc) and in terms of what we consider "good" performance. That being the case, the results of my testing would only be valid for me.
Case in point: While I think that the "zero downforce" test condition is unrepresentative of all real-world use (unless somebody here actually does plane by pushing from the sole?) there would be no way to agree on how much downforce to use for a more representative test. It would instantaneously degenerate into a religious debate about bench height and/or tote angle, and we all know there is no single right answer to those.
Anticipating a likely reply: Even if you try to push directly forward on the tote of a plane alone (no knob), you are applying downforce. This is so because the tote is above the sole, so pushing on it always creates a forward/down moment. That moment must be cancelled by a normal force on the sole/blade, a.k.a. "downforce".
Last edited by Patrick Chase; 06-25-2016 at 12:14 PM.
Member
A very interesting and stimulating debate indeed.
On the other hand, it is worthy of note that the debate is about the conclusions to be drawn from the data and not about the data itself. I think that distinction is of some import. Viewed as a set of data, measuring what is (at least close to) a single variable test, it's meaning is contradictory to other testing that other folks have done (at least as I understand the history here and elsewhere).
As with any testing regime with multiple variables, only a relatively large number of tests varying multiple permutations of variables can provide an adequate dataset for the application of multivariate calculus to derive any truly solidly grounded results. Multivariable systems often produce unexpected conclusions when proper mathematical analysis is applied. In advance of such an undertaking, it is not possible to know with any fundamental certainty what hypotheses about the exiting data are correct or even reliable across a useful spectrum of usage.
In that context, "follow historic precedent" is one decent stop gap choice, "it works for me" is another, and so on. Interesting as these debates may be, no one should "bet the farm" on a single proposition hypothesized from these data or in light of others. The most we can realistically say is that exemplars that demonstrate failure may help us discern the boundaries of effectiveness. They do not lead us to optima.
I suggest that we need not "... rage, rage against the light ...." in debating this isolated dataset.
Fair winds and following seas,
Jim Waldron
[OP]
Member
Hi James,
My son, who is a data scientist, would tell me that I do not have enough data!
Many people here argue about the results of this study. May I suggest that you, or anybody interested, sharpen a blade at 28° and then test it. Then resharpen at 35° - or any other angle that you would be interested - and test it again. Doesn't take long - maybe faster than writing here.
I just found this website http://homepages.sover.net/~nichael/...ters/caop.html where the clearance angle role is very well explained
"The clearance angle is the angle between the bevel on the back of the blade and the wood surface. It is the angle by which the blade clears the freshly cut surface (Fig.A-l:2). This clearance is required, for the following reason. The thrust as the blade moves forward distorts the wood a small amount, until the wood yields to the cutting action. Part of this distortion is a downward compression. As the blade moves on, the freshly cut wood springs back and would tend to lift the plane blade if it had no clearance. Greater downward pressure would be required for a smooth cut, and friction would increase."
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