Weak Chisel Edge

[edwardlt1]

Is there any benefit by increasing chisel grind angles to 28 degrees rather than 25 degrees?  At 25 degrees my chisel edges are weak (too thin) and a friend suggested increasing the angle to 28 degrees to compensate for the hollow grind the Tormek wheel produces.

[Jeff Farris]

If your edge is weak, it probably doesn't have anything to do with the hollow grind from the TORMEK.  Hold a straight edge across the bevel, from the cutting edge toward the back and look at the space between the center of the ground bevel and the straight edge.  You'll see that on most chisels the hollow is just a few thousandths of an inch -- not enough to introduce a weak edge.  

There could be a couple of issues here. First is how you're using the chisel. If you are chopping mortises or any other work where you are striking the chisel with a hammer or mallet, then the answer is yes, increase your angle -- but don't stop at 28, take it to 30.

The quality of the steel could be the other issue.  If you create a shorter bevel and the edge is still just as brittle, then we have to assume the steel is flawed or has been overheated at some point in its life.

I have one set of chisels that I routinely use for chopping which are ground at 30 degrees. I have another set that are strictly paring tools. They're ground at 20 degrees. I have a bunch of odd ball general purpose chisels that are ground at the general purpose angle of 25 degreees.

[edwardlt1]

After reading your response I went back to the Woodshed, coated the chisel with machinist's dye, went back to my five day old Tormek and discovered I had a few more minutes of grinding to do before the tool had a perfect edge.  What I had before was an incomplete grind and I was cutting on a burr rather than an edge (Newbie).  I think the machinist's dye is superior to felt tips (for newbies) because it flows into the smallest places.  It took a few minutes before all the dye was removed from the leading edge of the chisel.  This chisel now very, very sharp along with the five other chisels I sharpened today.  Thanks for your assistance; Newbie is learning!!