Why can't I flatten the back of my mortice chisel?

[Phil Pascoe]

Yebbut one system suits all, i.e. full sheets of wet n dry on a big enough plate. This for remedial work only not for routine sharpening.

But they do wear out, as oil stones don't, which typically can last for life, as long as you don't spend hours pointlessly flattening them.

Waste of time. I never flatten sharpening stones - if you spread the work they stay flat enough for life. A bit of a dip length-ways is no problem and a hollow across is OK as most plane blades need a camber anyway.
I occasionally freshen one up with a 3m diapad to remove clogged up surface, embedded wire edges etc.
I had one 2nd hand Norton "0" combination stone with a deep hollow lengthways on the coarse side which must have been done with regular axe sharpening or similar, and in fact I found perfect for axe sharpening! The fine side was rounded over very slightly which made a change from hollowed out. Didn't realise this at first until it started showing up on plane blades. No prob, just have to change the technique slightly to get a camber instead.
My basic opinion of modern sharpening is that it is grossly over thought and is much easier done almost head-down-brain-off, with no fancy gear

Funny, that - I got déja vu all over again.

 

[Blackswanwood]

My basic opinion of modern sharpening is that it is grossly over thought and is much easier done almost head-down-brain-off, with no fancy gear

You’ve never mentioned that before

 

[imageel]

Wet n dry paper is really cheap and available everywhere.

It's not a new idea - it's how DIY engineers did things in the old days like flattening cylinder heads for new gaskets on their Ford Prefects etc etc and is designed for the job.
Sparks totally improbable! It's all wet surfaces to start with and you could do it with water if you are really anxious!

@donturner - Glad you got it sorted!
Wot Jacob said, I remember as a kid my dad having a 12in x 3in ply board that had emery cloth stretched across it and held in place by some similar ply offcuts and he used that to sharpen chisels knife blades etc.
Fast forward I use cheap rolls of 80 and 160 grit alu-oxide paper spray glued either side to a cheapo length of float glass 'shelf' bought at one of the sheds. I only use the 80 side if I need to put a new bevel on but for merely touching up tools the 160 is fine followed by full sheets of 320 silicon carbide then 1200 to finish.
In this way it takes no time to sharpen up an edge and get back to work with whatever task I'm using it for.
I tend to use them dry however using water for sure helps hold down the full sheets and allows very fast waste removal.
Appreciate we all have different sharpening techniques however this works for me and is fast!

 

[Jacob]

You’ve never mentioned that before

Yebbut I try to say it differently every time!

 

[Phil Pascoe]

unsuccessfully.

 

[Jacob]

......
My basic opinion of modern sharpening is that it is grossly over thought and is much easier done almost head-down-brain-off, with no fancy gear

Or to put it another way; normal sharpening is about keeping the thing sharp but modern sharpening is about letting them go blunt and then fiddling about for an hour or so.
Similar with kitchen knives - a few regular swipes with a steel is all they need for life, unless you are a modern sharpening enthusiast!

 

[donturner]

Currently your mortice chisel edge resembles a saw.

This made me laugh. Behold my beautiful hand mirror! Honed on 1500, 2000 then 8000 grit lapping paper stuck to polycarbonate plates (the scary sharp system).

Go get mortising - what’re you making?

Bench for our hallway. Oak top, oak slats and a pine frame which will be painted white to match the staircase.

 

[HOJ]

You'll certainly need sharp tools, to make the bench to the decimal place tolerances you have shown on the drawing.

 

[Fred48]

This made me laugh. Behold my beautiful hand mirror! Honed on 1500, 2000 then 8000 grit lapping paper stuck to polycarbonate plates (the scary sharp system).

View attachment 177136




Bench for our hallway. Oak top, oak slats and a pine frame which will be painted white to match the staircase.

View attachment 177140

I'm glad you took the advice of @Adam W. to work on the back.
I also have a mirror finish using 8000 grit water stone for the back, and a micro bevel on the 8000 grit stone.
I believe it's worth the effort
Fred

 

[donturner]

You'll certainly need sharp tools, to make the bench to the decimal place tolerances you have shown on the drawing.

I know right

The drawing was done in Fusion 360 and the dimensions with 2 decimal places are calculated from other dimensions. They're there to give me a reasonable idea of what that dimension should be when building it, rather than being exact.

 

[okeydokey]

Sorry but I have to ask - other than the mirror finish looking really good does it make the tools easier/better to use or is it a beauty in the eye of the beholder type of thing?

 

[Jacob]

Sorry but I have to ask - other than the mirror finish looking really good does it make the tools easier/better to use or is it a beauty in the eye of the beholder type of thing?

It's a modern sharpening fashion.
In normal use the face of the blade gets polished up a little when you turn it to take off the burr. But a bit of extra polishing with a strop just a few mm behind the edge and also on the bevel can improve the cut - less resistance as its forced into the wood.

 

[Adam W.]

It makes a big difference, as it gets the edge fully sharpened across its width.

Polishing the whole of the back is a personal decision that should be respected if it keeps the user happily chopping away.

 

[Jacob]

...

Polishing the whole of the back is a personal decision that should be respected if it keeps the user happily chopping away.

Except it's a mistake to do it with a newish chisel as they generally are ground slightly hollow on the face, which makes them very easy to sharpen, the hollow staying untouched but gradually flattened from the edge back with subsequent sharpenings.
A chisel is never so easy to sharpen as when it is brand new, and is the work of seconds. Flattening it is a lot of work and removes this advantage - in fact unless you do it with every sharpening the face will become slightly convex as material is removed from the area behind the edge - what DaveC used to refer to as "bellied"

 

[--Tom--]

Much less likely to be ground hollow - much more likely to move after grinding due to release of internal tensions created during hardening. Hollow grinding on a surface grinder would take a fair bit of effort with the set up.

@okeydoke- always worth thinking of an edge as two planes intersecting - a 1000grit side meeting a 60grit side won’t be as fine an edge as a 1000grit side meeting a 1000grit side. When sharpening consider how to handle both sides of the edge

 

[Jacob]

Much less likely to be ground hollow - much more likely to move after grinding due to release of internal tensions created during hardening. Hollow grinding on a surface grinder would take a fair bit of effort with the set up.

.....

Amounts to the same thing. I often wondered how it came about, I guess not deliberately, as you say.
All the new chisels I've ever bought (not that many!) have had this feature.
A lot of older chisels tend to have a more polished face and also may be slightly convex due to sharpening efforts being applied more at the sharp end.

 

[Terry - Somerset]

@okeydoke- always worth thinking of an edge as two planes intersecting - a 1000grit side meeting a 60grit side won’t be as fine an edge as a 1000grit side meeting a 1000grit side. When sharpening consider how to handle both sides of the edge

I find this the most convincing argument I have seen for sharpening both sides of the edge to a similar high level of fineness.

 

[Jacob]

I find this the most convincing argument I have seen for sharpening both sides of the edge to a similar high level of fineness.

But it is impractical. You hone 2 or 3 mm on the bevel but the face may be 100mm or more. Instead the traditional process is to hone the bevel until a burr is raised on the face side, and then hone the face just enough to take off the burr.

 

[okeydokey]

I find this the most convincing argument I have seen for sharpening both sides of the edge to a similar high level of fineness.

Thanks Terry thats good reasoning!

back to my comment I can easily see now that maybe 5mm or 10mm can be beneficial but the rest of the entire back is for cosmetic reasons?

 

[Jacob]

Thanks Terry thats good reasoning!

back to my comment I can easily see now that maybe 5mm or 10mm can be beneficial but the rest of the entire back is for cosmetic reasons?

Yep. It's a modern sharpening fashion and leads to thousands of beginner woodworkers spending many hours doing something quite useless, spending money on kit they don't need and even spoiling their tools in the process.
If your new chisels need flattening they are faulty and you should send them back