mortise chisel back flattening - fun!

photostu

New User
Stuart

spent about 5m to get it the point you see in the picture on a 1000g diamond stone. Was thinking, oh, this will be easy to finish...
20m later, still haven't fully removed that cove at the tip. Hopefully the flattening on the 8K and 12K stones will go 'smoother' ;-)
 

Mike Davis

Mike
Corporate Member
I would start at 325 to get it flat then work up to polish it.

Sometimes I start with 80 grit on a belt grinder. Whatever it takes.
 

Chris C

Chris
Senior User
I keep 80 grit paper around for just that purpose..... It'll save time and a little wear on the coarse DMT stone.
 

Graywolf

Board of Directors, President
Richard
Staff member
Corporate Member
Yep, I'd go courser it removes material faster and gets you back to work faster.
 

photostu

New User
Stuart
Yes, in hindsight, this would have been the wiser choice. I was going with the Rob Cosman method of setting up a new chisel. He starts with 1000 on the back, hence my selection. The other chisels I'll start with the 300 side for flattening ;-)
 

Jeff

New User
Jeff
Why are you fretting over a cove on the back face of a mortising chisel? That's overkill overdone and will have little effect on a mortise.

The other chisels I'll start with the 300 side for flattening
That's a better idea. Here's a video by Paul Sellers. Lord knows where Rob Cosman came up with the 1000 g for initial flattening. BTW, it's not flattening but polishing.

 

Jeremy Scuteri

Moderator
Jeremy
.....20m later, still haven't fully removed that cove at the tip

Why are you fretting over a cove on the back face of a mortising chisel? That's overkill overdone and will have little effect on a mortise.

Jeff,
I believe he is saying that the "cove" is at the very end of the chisel. That is the one place where it DOES matter if you want a sharp edge. The back is just as important as the bevel where the two surfaces meet at the tip/edge.
 

Jeff

New User
Jeff
That is the one place where it DOES matter if you want a sharp edge. The back is just as important as the bevel where the two surfaces meet at the tip/edge.
Yes, I understand that. However, I'm not so sure that it's necessary for a mortise chisel, but it's needed for bench chisels in order to get that really sharp edge.
 

Jeremy Scuteri

Moderator
Jeremy
You are effectively saying that it isn't necessary for a mortising chisel to be sharp. I guess everyone can decide whether mortising chisels need to be sharp for themselves, I won't debate that point.

If one doesn't care if the tool is sharp (which is what you will get if the back is not smooth/polished), then there is no reason to waste time working on the bevel either. The importance of the bevel is exactly equal to the importance of the back.

Note that the very video you posted ensures that the back is flat at the very tip of the chisel which is contradictory to what you are now saying. Are you posting a video that shows techniques that aren't applicable to the original posters question? Why would you do that?
 

Gofor

Mark
Corporate Member
Is the back tipped up in that corner, or was the chisel not truly square on the stone? The honing marks would tell me I needed more pressure on that corner to get an even edge. Is the rest of the sharp edge square with the sides?
 

Jeff

New User
Jeff
Mea culpa for suggesting an alternative slightly out of the ordinary accepted practice for discussion.
 

photostu

New User
Stuart
Since I'm still pretty new to this world, I'm trying to do things the best way possible. Most of what I have read suggests the back of any chisel needs to be dead flat, so I'm going to put in the time to make sure that is the case. Back flattening is certainly not the sexy part of this hobby :D
 

Jeremy Scuteri

Moderator
Jeremy
Mea culpa for suggesting an alternative slightly out of the ordinary accepted practice for discussion.

You are so full of it.
"Why are you fretting over a cove on the back face of a mortising chisel? That's overkill overdone..." is not just a suggestion. It is a strong statement that is belittling to the person asking a very reasonable question.

The idea that you are being called out for suggesting a slightly out of the ordinary practice is ridiculous. Go ahead and tell yourself that if it makes you feel better.
 

Jeff

New User
Jeff
Since I'm still pretty new to this world, I'm trying to do things the best way possible. Most of what I have read suggests the back of any chisel needs to be dead flat, so I'm going to put in the time to make sure that is the case. Back flattening is certainly not the sexy part of this hobby :D

That's fine and welcome to the wonderful world of woodworking. I agree that bench chisels need to be dead flat on the back but was suggesting that maybe a mortising chisel doesn't need that extra effort to make a good mortise. I don't know and it's just a suggestion for discussion. Try chopping a mortise with your less than perfect chisel and see for yourself. I'm not advocating bad habits but there may be alternatives.
 

Mike Davis

Mike
Corporate Member
I have seen mortise chisels where it looks like the "ruler trick" was used to save time in flattening the back effectively making a secondary bevel on the back. It is usually very shallow and one may say inconsequential. It all depends on the quality of cut you expect, the time you want to spend, how consistent you want all of your chisels to work/feel, how much extra effort you want to put into being sure your mortice ends are square, etc. I like all my chisels to be the same, I never use a back bevel. I want my mortise chisels to cut straight down and for that the best practice is to have a flat back.
 

Roy G

Roy
Senior User
Stuart, it looks like you are flattening the whole back of the chisel. I have always just tried to get the last inch closest to the edge flat.

Roy G
 

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