Straightening a chisel’s cutting edge
DanielBottari
| Posted in New To Woodworking on
Hi guys,
A couple of the new chisels I have received have slightly squint edges.
To straighten them, would I just push the ‘shortest’ point of the cutting edge against the protrusion stop to set the angle for my honing guide?
That way the ‘excess’ edge (the part of the cutting edge that protrudes past this shortest point ) would be ground off, and a straight edge would be produced?
Replies
Squint - do you mean that the two corners of the chisel edge are not 90 degrees, edge to side (at the chisel back)? If so, using a honing guide (or a grinding guide) can ensure that those corners go to a right angle if the back of the chisel and what the chisel is sharpened on are held in such a way (there's a geometry term I can't think of) to achieve those square corners.
But .... do you need to keep the corners square? A skewed chisel is useful for many cuts, which is why many manufacturers make them with various skew angles. A slightly skewed "straight" chisel may be of no consequence when you come to use it. You can just skew the handle slightly to compensate.
But if you sharpen all your chisels in the same way and only one is so-skewed, that may indicate something awry with the geometry of the blade that matters - a twist or some other unevenness of the blade that'll make the control or use of the chisel less than ideal. Using the chisel will tell you if the skew is indicative of a bigger problem.
'do you mean that the two corners of the chisel edge are not 90 degrees, edge to side (at the chisel back)?'
Yes, so that the one side of the cutting edge is slightly lower than the other, creating a slight slope.
Grand. I'll use the honing guide to sort it - I would like a straight edge on this occasion! Cheers
You will need to first translate what a squint edge is for those of us on the western side of the Atlantic, either that or wait for lat_axe to chime in.
If it's, as I suspect an edge out of square to the sides, it's not uncommon. You have two solutions the simple and easiest solution is what I believe you suggested simple, simply set up to hone your secondary bevel(typically 30°) on your jig and hone until your cutting edge is defined across the full width of the blade. This will leave a slightly irregular appearing bevel when viewed from above but will in no way hinder the performance of the chisel. If on the other hand you are possessed by any degree of OCD tendencies, you will need to regrinding your primary bevel (typically 25°) before honing your secondary bevel. This will make your chisel more photogenic but will not perform any better.
Yes, an edge that is out of square to the sides :)
Yeah, that was my plan - grind and hone the secondary bevel (30 degrees) then the secondary.
That's useful information to remember about how this method will leave a slightly irregular seeming bevel. I do have slight OCD/perfectionist tendencies (!) but may try the simpler of the two methods for this stage in my experience if perfermance is unaffected.
Cheers
Just as a clarification. Your chisels are already ground to what is probably a 25° primary bevel. All you need to do is hone the secondary bevel which is typically 30° this process should not take more than 5-10 minutes on new chisels start with the equivalent of 1000 grit and quickly work through your progression. Only lap the back after honing on your finest film just 3-4 strokes to remove the wire edge.
Wider chisels are easier to get the edge at 90 degrees. Narrow chisels are easy to get off a bit. Most of the time, being a little bit "squinty" doesn't matter at all.
I have in the past ground mine to 90 deg on the grinder then sharpened. It's a waste of time. As John said, it really makes very little difference.
If the squint is enough to stop the chisel from registering properly in a scribe line that's another matter but beyond that, who cares?
In any case, if you are using a honing guide then you may find it takes a little longer the first sharpen as the leading corner will have to be ground down until the trailing corner is sharp, but after that it will sort itself out over time.
+1 esch
I’d learn to sharpen from an expert.
I generally sharpen free hand but will use a honing guide to resquare an edge. More pressure on the long side eventually does it.
Truthfully it's not usually a big issue. I doubt any of my chisels are perfectly square.
Not so for plane irons!!