Angles on tools.....

[LENPAM]

I read the post about the gentlemen who called setting prcise angles "bunkum" and to some degree I agree with his assumption. The whole sharpening book of wisdom has so many ways to accomplish a pretty simple task that it's taken on a life of it's own and I think many new or wanta be woodworkers are scared away or see sharpening as such a technical drugery that they shrink away from woodworking entirely.

I've never understood why manufacturers of tools would make chisels at one angle and tell woodworkers to change the angel for best results or why secondary bevels are so popular to increase cutting angles. I've been cooling around collecting long enough to know from what I see that most oldtimers sharpened by hand with little regard to what angle they might be at exactly. I have infill planes that have so many angles honed on the iron as to make it darned near impossible to pick just one.This kind of sharpening must have been pretty efficient and time saving since so many appeared to adopt it and I don't recall reading many books or treatises from the past saying how difficult it was to get and maintain a sharp edge on thier tools for woodworking.

I think it's done nowadays because the technology allows us to be more exact and repetition is easily attained by the means of jigs or Tormeks or electric grinders with good ways to set angles or other gizmos for sharpening.The question is does it make us better woodworkers or does it just make the job easier through the technology we have at our fingertips.I learned from an older guy who always sharpened his tools by hand using the existing angles of the tools as a guide to redo or freshen up dull tools and I don't recall him ever saying anything about the 30 degree angle or whatever the tool was. His only goal was to reestablish a good working edge that lasted.

I have to say I'm kinda the same way and I change an angle on a tool when it doesn't work well cutting and not because conventional wisdom says a parring chisel should have a 22 degree bevel. I believe some of the current wisdom because I know it works like a steeper angle cuts better in really hard wood or squirrley grained wood,but I don't do it because it's supposed to be 60 degrees,just do it because ot works better. Len

 

[dunbarhamlin]

Heresy! We'll have none of that rational talk here

 

[Fromey]

So by this logic we should also go back to hide glue heated up in a pot because that's what used to be done. No need for Titebond or equivalents.

Honestly, some things done in the past were best and so-called innovations have actually been retrograde, but that doesn't logically follow that everything done in the past was the best, simple for being done in the past. If that were the case, there would be no word "progress".

 

[Modernist]

squirrley grained wood. Len

Love it

 

[Tom K]

Of course there was a time when apprenticed boys slept under the bemch so there was no where to store all these new fangled angles.
How about this for a fairy tale. Once upon a time one chap who could read and write looked among his fellows and said "who's chisel cuts best in this old oak" He took the tool and checked the angle and then he doth jot the angle of the dangle on his pad. Now when others struggle he shares the information saying "if you copy that angle we will know if it's the tool or the dolt standing behind it. Thus was borne the heresy of repeat angles.

 

[Corneel]

It's a communication thing. When a beginner asks on an internet forum how to sharpen his iron, it's not helpfull to give a vague comment. Just give him or her a number or a range of numbers. Everybody all over the world understands degrees. Of course the number should be put in perspective. Best to explain what the angles are about, but I am under the impresion that most reponses about this are quite good about this.

Explaining things on an internet forum is a completely different world from the classical aprentice and master relation.

About just following what you find on an iron, that's not always helpfull. I've found plane irons sharpened so steeply that there was almost no clearance angle left.

 

[Jacob]

..... ..... I don't recall him ever saying anything about the 30 degree angle or whatever the tool was.

Well he wouldn't necessarily. 30º is a "natural" sort of angle, being 1/3 of a right angle, half an equilateral triangle angle, gradient of 1/2 (sine not tan), is easy to hit and luckily is good for most woodworking sharpening purposes. So he'd hit it naturally without thinking about it. Then he could do angles "a bit bigger" or "a bit smaller" and he'd cover the whole range.

 

[woodpig]

Well he wouldn't necessarily. 30º is a "natural" sort of angle, being 1/3 of a right angle, half an equilateral triangle angle, gradient of 1/2 (sine not tan), is easy to hit and luckily is good for most woodworking sharpening purposes. So he'd hit it naturally without thinking about it. Then he could do angles "a bit bigger" or "a bit smaller" and he'd cover the whole range.

Quite right, 30º is a good starting point.

 

[Tom K]

Hmm I'm an uncouth apprentice how shall I find this fabled 30? I checked Mr Jacobs tools and they are all curved

 

[Jacob]

Hmm I'm an uncouth apprentice how shall I find this fabled 30? I...

Start by switching your brain on and stop being infantile.

 

[Tom K]

Why so grumpy you old troll? Ask a youngster to show you 30 deg without a reference. Most have no clue. I'll put the grumpiness down to that cantankerous gene kicking in :lol:

 

[woodpig]

Can't get much easier than Jacob's third of a right angle!

 

[Jacob]

...Ask a youngster to show you 30 deg without a reference. Most have no clue. ...

Why without a reference? You'd show them how to do it. Give them a 30/60 plastic school protractor or something similar for reference. They'd soon get the idea and be able to do it accurately enough unaided. Much easier than learning to tie shoelaces and other similar infantile problems.
Do you have a problem with tying shoelaces?

 

[GazPal]

Why so grumpy you old troll? Ask a youngster to show you 30 deg without a reference. Most have no clue. I'll put the grumpiness down to that cantankerous gene kicking in :lol:

Most use the pre-set 25 degree grinding guide found on many cap irons and work from there, but adequate guidance from a mentor generally works extremely well. Hand to eye co-ordination comes comparitively quickly with practise. :wink:

Any youngster with half an ounce of common sense will realise they can use a 60:30 drawing square as a rough guide. Very basic maths and an eye for geometry is something that's needed when woodworking.

 

[xy mosian]

Length of bevel at 25 degrees is roughly twice the blade thickness.

xy

p.s. see next post please.

 

[xy mosian]

Just done some Sketchup stuff.

Grinding angle From sketchup

25 degrees length of bevel is 2.36 times thickness of blade, at heel of bevel
when length of bevel is 2.5 times blade thickness angle is near enough 24 degrees

bevel length 3 times blade thickness gives angle of about 20 degrees, a bit bit thin but will work

xy

 

[Jacob]

Length of bevel at 25 degrees is roughly twice the blade thickness.

xy

p.s. see next post please.

So tis, (nearly)!
tan25º=0.47
tan30º=0.58 which isn't convenient, but sin30º=1/2 which makes 30º really easy i.e. translates as; the length up the slope is twice the rise.

 

[matthewwh]

What a splendid exercise in how to over fernangle an otherwise straightforward issue.

The optimum angle is the lowest that you can get away with.

Start with a known angle (these are prescribed by centuries of experience as 30 deg for general work, 25 for paring and 35 for morticing) if the edge holds (i.e. wears rather than chipping or deforming) go a little lower til it doesn't, if it doesn't go a little higher till it does.

Once you have found the point at which that particular iron / chisel is only just holding an edge on the timber that you are working with, you have the optimum honing angle.

Some choose to do it by feel, others by measurement. Either way that's the process of tuning a given tool to the circumstances it will be expected to work under and will give the maximum performance it is capable of.

Honing angles - done!

 

[Steve Elliott]

The optimum angle is the lowest that you can get away with.

Matthew's statement would be a good place for discussions of honing angle to begin and end. The angle right at the cutting edge does matter and lower angles give a longer-lasting edge provided they are able to resist chipping and deformation.

In the case of bevel-up planes where a higher cutting angle is achieved by increasing the blade's bevel angle I believe there's a small loss of useful edge life due to the larger bevel angle and resulting loss of clearance behind the edge as the blade wears.

 

[Jacob]

........

Once you have found the point at which that particular iron / chisel is only just holding an edge on the timber that you are working with, you have the optimum honing angle........

In theory there could be such a point but I think it's much more likely to be a progression with no obvious optimum.
In practice you use a tool and just sharpen it at intervals in a routine sort of way, or when you vaguely think that it's not as sharp as it should be.
What the fernangling is about is simple ways to visualise an angle, for those who want to make the daring and almost impossible move towards freehand sharpening.
90, 45, 30º all easy to hit. Add angles "a bit more/less" then you have enough for all purposes.

....lower angles give a longer-lasting edge provided they are able to resist chipping and deformation.......

:lol:
Very true.
What you are saying is that a lower angle gives a longer lasting edge if it doesn't go blunt. You could say the same of a higher angle edge.