Chisel edge

[francis]

I have a knife with a chisel edge blade. What do you suppose is the most ideal angle to sharpen this ?

[Herman Trivilino]

First. measure the existing angle.  Usually the recommendation is to just match it.  You could also color the existing bevel with a marker and then check to see if you've got the jig adjusted to the correct angle by setting it against a stationary grindstone and rotating it a bit by hand.  Then you can see where on the bevel the grindstone is hitting, and adjust accordingly.

Does that knife edge have a single or double bevel.  Wood chisels have a single bevel and I usually grind them at around 30^o if I'm going to be hammering on the chisel, or 20^o if not.  Usually I'll go somewhere in between depending on how well the existing angle has held up.

Here's what I mean.  And this applies to your knife, too.  If the edge has gotten pretty beat up, then I'd grind it at a more blunt angle so it'll hold up better in the future.  If instead I want better control for gentle use of the tool I'll go with a more narrow angle.
 

[francis]

Does that knife edge have a single or double bevel. 

It only has a single edge bevel....However I have some other knives that doesn't have an existing angle yet. I'm just about to sharpen them and  I just want to have an idea on what the best angle to have on the edge...

[Herman Trivilino]

For a knife (with a bevel on each side) I usually do between 10^o and 20^o on each side.  As a rule of thumb, for me anyway, the smaller the knife the smaller the angle.  So I might do a paring knife at 10^o and a butcher knife at 20^o.

If I find that a knife doesn't stay sharp very long, the next time I sharpen it I'll make the angle a little bigger.  Some types of steel hold their edge better and so I can get away with a smaller angle if desired, but some won't so I have to make the angle larger.

The nice thing about the Tormek is it allows you to experiment with different angles and find what works best for you.  It depends on what you're using it for, how you use it, and how well the steel holds an edge.

In Ron Hock's book he says that when it comes to different types of steel you can have two of these three: ease of sharpening, ability to hold an edge, and ability to resist rust.  As far as I'm concerned the Tormek allows us to sacrifice the first so we can have the other two.  In other words, the Tormek makes it easier to sharpen steels that would otherwise be difficult to sharpen.  It just takes more care and experience. 

These are just my opinions based on my experiences.  The others will chime in with their opinions and we learn a lot form each other.

What I mean by "hard to sharpen" with a Tormek is a steel that doesn't form a burr that I can see or feel.  Typically we know it's time to stop grinding when a burr forms.  In cases where no obvious burr forms I have to examine the bevel closely with a magnifier and good light to see if I've reached the cutting edge.  In these cases though, the effort is well worth it if the steel then rewards us by holding its edge well and remaining rust free.

[Ken S]

Welcome to the forum, Francis.

The bevel angle would depend largely on the use of the knife. This includes the material being cut.  Chisels are a good example.  A chisel used for delicate paring would have a longer bevel (lower cutting angle) than a chisel struck with a mallet (ex for cutting dovetails).  A chisel used for chopping mortises would be of beefier construction still and have a more obtuse bevel angle.

I am partial to single bevel knives. Having one face flat allows the knife to more precisely follow a cut mark.

I would suggest beginning with a broader angle, say thirty degrees for single bevel knives.  (more for rough work) Experiment with that angle for a bit and adjust accordingly.  If the edge breaks down quickly, resharpen with a higher degree bevel.  If you think the work would benefit from a narrower angle, try that also.

Over the years, I have often recommended the sharpening books by Leonard Lee and Ron Hock. Both should be a working part of a serious sharpener's library.  More recently, I have also added and like Thomas Lie-Nielsen's sharpening book.

Good luck and keep us posted.

Ken

[Herman Trivilino]

I am partial to single bevel knives. Having one face flat allows the knife to more precisely follow a cut mark.

For cutting dry wall and the like?  Where would I find one?

I saw on a TV show a recommendation for a single bevel knife.  They said it made slicing easier because the slices were less likely to stick to the knife.

[Rob]

I've always scored my drywall (Plasterboard here) with a sharp Stanley knife and then snap along the line.  I honestly dont think how the bevels are formed makes a lot of difference in such a rough cut material.  Once I've snapped the board in 2, that's when the sharp blade really comes in handy to just slice through the cardboard outer surface.  Once your knife starts blunting the cardboard has a tendency to ruche.  With Stanley's I just have a 10 pack of replaceable blades and "Bob's yer Uncle"  :-)

[Ken S]

Herman, I have a similar situation with my mat cutter. The straight cutting blade is the garden variety utility knife blade. The bevel cutting blade is single edge.  It makes very clean cuts.

Where the double bevel blade has the advantage is when the blade dulls.  The blade is reversed then and presents a new clean edge.  The single bevel blade is not reversible. I have a number of used single edge blades with half the blade quite sharp.

As a telephone man, I used (and often abused) a "blue knife", the name derived from the blue handle.  It was double beveled, although I have wanted to regrind one as single bevel. It might work very well for drywall.  They are available at the big box stores with telephone or electrical tools, although the handles may be orange.  A knife reground like that should please your inner scientist, even if your inner handyman is a bit puzzled and might prefer a utility knife and a hundred blades.

Ken