Wood chisel sharpening

[Prisoner#6]

There I was, merrily grinding/sharpening my grubby old wood chisels whilst reading War and Pease (it takes ages to grind them) when at page 258 I had finished my first one!!!  It has such a shiny edge to it I can see my face. Anyway, I now have the hang of this Tormek machine thingy, so I start to do another one........Page 520 and I've finished it. Looks just like the first. I am ecstatic with pleasure, so much so that I am now hugging the Tormek. So I decide to check the angle of my lovely shiny chisels with the WM-200 angle master. There it is, 25 degrees spot on. I'm jumping for joy now, so I get the third grubby chisel and prepare that one for a new face lift. Before I do though, I thought I would just check the angles again, but this time with my Richard Kell bevel gauge......Oh no, it says somewhere between 27.5 and 28 degrees. Well I thought to myself, who the hell is Richard Kell anyway, so I checked them again with an engineer's protractor and guess what.....27.5 degrees. I then used another protractor and again 27.5 degrees. By now, my excitement has worn off a little. I will try one more time checking the angle with my Veritas honing guide. I set it up to sharpen at 25 degrees and covered up the shiny new edge with a green marker pen. Gave it a few thrusts back and forth and took a look at it. The heel of the now green face was shiny, but the rest was still green.

I suppose, (after writing all this crap above) what I am asking is, has anyone who has sharpened chisels on the Tormek had the same problem as me?
I am using the square edge jig SE-77
Black stone SB-250 and original stone SG-250
The WM-200 angle master (which is the one that tells me my chisels are 25 degrees)
And a copy of War and Peace.

Thanks.

[brettgrant99]

Is the angle master set for the correct stone diameter?  Are you using the notches around the edges?  I have an angle gauge, but I doubt that it is too accurate.  However, I haven't noticed a difference.

Brett

[Jan]

Prisoner, do not worry, everything is OK. 

The Tormek angle master sets edge angle at the tip, while the protractor measures the chord angle which is always larger.

The attached drawing, dimensioned in millimeters, shows that for a 4 mm thick chisel this difference is some 2°.

I guess your chisel is some 5 mm thick. 

Jan

[Prisoner#6]

Thanks Brett and Jan.

If I wasn't confused before, I am now looking at that diagram. 

At the end of the day, if I set the Tormek up to grind a chisel at 25 degrees, surely I should expect to then be able to continue the process of sharpening it on my honing guide at 25 degrees. The Veritas honing guide doesn't have a 27.5 degree setup on it.

I appreciate the input from both of you, but now I'm going to take some paracetamol for my headache this has given me. 

[Elden]

Read this:

https://forum.tormek.com/index.php?topic=1860.msg9619#msg9619

There are other discussions (arguments) as well. Here are a couple:

http://forum.tormek.com/index.php?topic=2413.0

http://forum.tormek.com/index.php?topic=3052.0

[Ken S]

Prisoner,

I am no math expert, however, I have come to realize that Jan is the genuine article.

If you completed sharpening your chisel in only 280 pages of War and Peace, you may not be taking the time to do the job right. 

Incidentally, I have one of Richard Kell's small jigs. It's a very nice piece of kit.

Ken

[Ken S]

PS,

With Jan and Dutchman as our forum mathematicians; Herman as our physicist; and Elden as our research librarian, we have a real dream team!

Ken

[brettgrant99]

Thanks Brett and Jan.

If I wasn't confused before, I am now looking at that diagram. 

At the end of the day, if I set the Tormek up to grind a chisel at 25 degrees, surely I should expect to then be able to continue the process of sharpening it on my honing guide at 25 degrees. The Veritas honing guide doesn't have a 27.5 degree setup on it.

I appreciate the input from both of you, but now I'm going to take some paracetamol for my headache this has given me. 

Jan's diagram just shows what you already know, although I agree it is a little confusing.

If you hone on a stone, the stone should be flat, and the angle along the whole bevel is 25 degrees.  The Tormek has a round wheel, initially it is 250 mm in diameter.  That is where the R125 on the drawing comes from (Radius 125mm).  The actual bevel is hollow ground.  There is a page about this in the manual somewhere.

I personally don't hone to a greater polish than the leather wheel can give, but really my chisels are just used for rough lumber.  I'm not sure how they would do in hardwoods, but I have been happy with the end results.

I would recommend not sweating it or overly thinking about it, as long as the tool does what you want.

Brett

[cbwx34]

Thanks Brett and Jan.

If I wasn't confused before, I am now looking at that diagram. 

At the end of the day, if I set the Tormek up to grind a chisel at 25 degrees, surely I should expect to then be able to continue the process of sharpening it on my honing guide at 25 degrees. The Veritas honing guide doesn't have a 27.5 degree setup on it.

I appreciate the input from both of you, but now I'm going to take some paracetamol for my headache this has given me. 

I have two general suggestions...

If you're switching between sharpening devices, sometimes it's easier to just try and see what works, and adjust accordingly, instead of trying to "match the numbers"... if that makes sense.

You might consider doing all the work on the Tormek, and not switch to the Veritas?  Tormek can be an "all in one" solution.

Just a couple of thoughts... disregard if it doesn't apply.   

[Jan]

I am attaching another drawing which shows the hollow ground edge of a 6.35 mm (1/4") thick chisel.

In geometry we say that the edge angle, which is set by the angle master, defines the tangent to the stone.

The heel angle, which is measured by protractor, is defined by a chord line which connects the tip and the heel of the bevel.

The difference between the heel angle and the edge angle increases with chisel thickness.

For a heavy duty mortising chisel (16 mm thick) the angular difference is almost 7 degrees! 

Jan

[Ken S]

Sharpening woodworking tools is usually different than sharpening kitchen knives.Whereas a knife sharpener often sharpens for other people, a woodworker generally sharpens his own tools. As such, he is free to experiment and modify his technique if he desires. There is nothing sacred about using twenty five degree bevels with chisels and planes. The angle may be decreased for more delicate paring or increased for heavier work. With bench stones, a more obtuse angle is generally obtained by adding a secondary or micro bevel. It should be noted that this is primarily a labor saving strategy.

With the Tormek, adjusting the microadjust is all that is needed to change the bevel angle. The Tormek, with the SG grindstone graded coarse, does the work.

With chisels and, to a lesser extent, with planes, it is common to have multiples of the same tool ground differently. In generations past, a craftsman might have different tools of the same size. In a common width, like half inch, he might have long bladed straight and/or crank neck paring chisels; bevelled bench chisels for dovetails; firmer chisels in different patterns without bevels for heavier work; and very heavy mortise chisels. He might vary the bevel angles for different widths or purposes.

Today, bevel edge bench chisels and power tools are used for most of these functions. The old guidelines for bevel bench chisels may or may not be ideal for the intended purpose. The opportunity to fine tune a tool benefits the more sophisticated sharpener. Don,t feel locked into one traditional standard degree setting.

Ken

[RickKrung]

Very interesting.  Jan's second diagram really helped.  Thanks Jan. 

Maybe I wasn't aware about the 25 deg.  I just matched the existing angles using black marker.  One turned out about 32 deg., the other 35 deg.  They are both about 4mm thick.

Rick

[RickKrung]

There is nothing sacred about using twenty five degree bevels with chisels and planes. The angle may be decreased for more delicate paring or increased for heavier work. With bench stones, a more obtuse angle is generally obtained by adding a secondary or micro bevel. It should be noted that this is primarily a labor saving strategy.

With chisels and, to a lesser extent, with planes, it is common to have multiples of the same tool ground differently. In generations past, a craftsman might have different tools of the same size. In a common width, like half inch, he might have long bladed straight and/or crank neck paring chisels; bevelled bench chisels for dovetails; firmer chisels in different patterns without bevels for heavier work; and very heavy mortise chisels. He might vary the bevel angles for different widths or purposes.

Today, bevel edge bench chisels and power tools are used for most of these functions. The old guidelines for bevel bench chisels may or may not be ideal for the intended purpose. The opportunity to fine tune a tool benefits the more sophisticated sharpener. Don,t feel locked into one traditional standard degree setting.

Ken

That is all good to know.  Thanks, Ken.  I have the two chisels and don't do much woodworking that requires more.  As you pointed out, power tools do most of the work, at least in my shop. 

Rick

[Jan]

Rick, you are welcome!

Jan

[Ken S]

Rick,

Once you have your chisels ground to one angle, if you need to change the angle for another application, we won't tell.   

Whatever works!

Ken