hand sharpening chisels...I've been crowned..

As is probably not uncommon, something I should have taught myself early on has come later. After really coming to the understanding of what truly sharp hand tools can do compared to the ones you think "are probably sharp enough", I have begun trying to clean up most of the edges on my chisels and planes and get them at least to a state where a quick touch up will keep them good and sharp.

I am using the old marples blue handles, which have been good chisels for the money. In the case of my 1" chisel, I began trying to restore its edge the other night(it has seen significant use, and was very dull). I was using my new Norton 4000/8000 combination stone, my veritas Mark II honing guide set to 25 degrees, and my old, off brand home depot stone that I would imagine is close to 220 grit. I used this stone to remove a lot of material and then proceeded to the 4000/8000. After discovering that the edge was slightly out of square, either from the box or as a result of some horrendous and misguided previous attempt at sharpening, I reshaped it with a file, then proceeded to hone away at the now completely dull(but square) edge. The long and the short of it is that after quite a bit of rocking back and forth over the workbench, it is now as sharp as a razor...and crowned. I am in the process of cutting a lot of dovetails right now, and noticed as I set it in the first back line that it has a fine, but noticeable crown.
What improper technique did I likely employ to create this? How do I avoid replicating it in the future? Thanks in advance, you guys always have constructive and thoughtful advice....

Mac,

Is it crowned from one side to the other, or from the bottom of the bezel to the top?

I had the same "aha" moment with sharpening a couple years ago - it really is a gateway skill. I also use blue-chip Marples as my only set of chisels. Plan to upgrade eventually, but am in no great hurry. They're good chisels, if a bit topheavy when dovetailing.

Mark

IF it's crowned side to side it sounds like you may have worn a grove in your stone.Do you mean the outsides are further back than the center of the cutting edge?If so make sure your stones are flat then go back at it.When correcting this you should see the sharpened bevel be wider at the center than the outside,as this is the only spot that the bevel will be touching.Keep at it until you get a straight bevel across the edge.Hope this helps.Steve

If you can file the chisel,it is too soft, and may not hold an edge well,especially on hard woods.

To determine the problem, more information is needed.

The possibility of a stone having a trough may be the case if you are pushing the chisel onto the stone lengthwise. This is one reason some suggest flattening the back of the chisel going across the stone. If one is lapping the back of the chisel by holding it sideways on the stone and running it back and forth over the length of the stone, then it is likely a rocking motion that is the cause of the crowning.

Of course, these are only valid if the crowning is occurring on the back of the chisel and from side to side.

I also agree with George, if the edge can be easily filed, then the metal may be a bit on the soft side. I am not sure if there could also be a problem with uneven hardness across the metal. That could be another cause of crowning.

If the cutting edge is crowned, this could be an unflat stone or could be technique. The blade should be stropped with the edge held perpendicular to the direction of the honing. If the blade is skewed, the edge will also end up skewed. If the blade is held a little to the right on the push and a little to the left on the pull, then you will have a cambered edge.

Sharpening is a learning process. It is a labor, a skill, an art or a ritual, take your pick, but one needs to learn sharpening if one wants to make use of hand tools for working wood.

jim

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Originally Posted by Mac Houtz

sorry to take a long time responding...for once I was busy in the shop all weekend.(christmas must be coming).

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Great part of the season is as long as you are making things for others, others will not mind you going to the shop and they will not come bother you every five minutes.

Mac, your profile does not show your location. You may have another Creeker in your area who would be willing to spend some time with you to help with this chisel.

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Originally Posted by Mac Houtz

The edge was crowned from side to side. It was not extreme, but it was noticeable.

I have flattened my cheapo stone with a diamond plate, so I know it doesnt have a groove, and honestly the norton is brand new, so unless it came with a trough out of the box then it should be good, I will check it.

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I have read many comments here about diamond plates not being flat. I flatten my stones using abrasive paper on a granite tile. Most of the time I do not bother to flatten my stones as much as most others and even with a stone that I know has waves a good edge can be achieved.

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Originally Posted by Mac Houtz

With regards to the comments about the fact that I should not be able to square the edge of a chisel with a file, I don't know what to make of that. I will leave the metallurgical aspects to the experts, but I can tell you that these are old blue handled marples chisels that are approx. five or six years old.

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My father taught me about using a file to gauge how hard a metal is many years ago. If you have a hardened chain or a lock shackle, run a file across the surface and you will usually find the file will not cut the metal, it will just "roll" over the surface. Different hardness material will respond differently. This is just a "guess test" of something's hardness. Getting an actual hardness number will require further testing.

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Originally Posted by Mac Houtz

I checked the edge, found it to be slightly out of square, and used a mill file to square it. It really didn't take a lot of sweat and time either. Does this mean that this chisel was not right from the factory, or is there something I could have done to it along the way to change its hardness?

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This leads me to believe your problem may be with the chisel not being hardened evenly. If it is harder in the center than at the edges, this could cause a crowning. I am not sure this is possible, but in the world I live in, I have come to accept that anything is possible.

It may also be possible to use a steeper "micro" bevel on the edge. With a slight crown in the center, the micro bevel would remove the most metal from the crown and when the edge was squared by the micro bevel, you are done.

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Originally Posted by Mac Houtz

It seems to hold an edge ok.(I just finished chopping 36 pins for a sugar chest in black walnut, and its still good.) I just want to avoid crowning it in future sharpening sessions.

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This may not be possible with this chisel. That it works well for you is good. In the past, others have mentioned that the "Blue" Marpels are not as hard as other chisels they have.

If it happens to a lot of chisels or blades, then it is either the stones or the technique. If it only occurs with one blade, it is likely the blade.

One thought comes to mind from many years ago when someone was explaining how to trouble shoot a car engine. His way was to break it down into the three things the engine needed, fuel, ignition and compression. Pick one and check it. If it was OK, move to the next until the problem is found.

So, for sharpening a blade, it is either the stones, the method or the blade that is at fault.

jim

sorry to take a long time responding...for once I was busy in the shop all weekend.(christmas must be coming).

The edge was crowned from side to side. It was not extreme, but it was noticeable.

I have flattened my cheapo stone with a diamond plate, so I know it doesnt have a groove, and honestly the norton is brand new, so unless it came with a trough out of the box then it should be good, I will check it.

With regards to the comments about the fact that I should not be able to square the edge of a chisel with a file, I don't know what to make of that. I will leave the metallurgical aspects to the experts, but I can tell you that these are old blue handled marples chisels that are approx. five or six years old.
I checked the edge, found it to be slightly out of square, and used a mill file to square it. It really didn't take a lot of sweat and time either. Does this mean that this chisel was not right from the factory, or is there something I could have done to it along the way to change its hardness?

It seems to hold an edge ok.(I just finished chopping 36 pins for a sugar chest in black walnut, and its still good.) I just want to avoid crowning it in future sharpening sessions.

thanks for taking the time to respond, and yes, when it comes to Christmas builds, your logic is spot on.....you get to make things for your loved ones, and your loved ones thus grant unlimited(almost) shop time.....it is a very symbiotic relationship....

The MK II should keep you on track. I'm +1 for a stone that needs flattening. I used plate glass and micro-abrasive film with good success.