flattening the back of a chisel

[Corneel]

Actually I think about selling it. So I can leave it to the new owner or put in the extra work and raise a little bit extra money.

 

[Jacob]

Actually I think about selling it. So I can leave it to the new owner or put in the extra work and raise a little bit extra money.

Yes it's had it really. Looks like over enthusiastic buffing by the previous owner.

 

[G S Haydon]

Ok corneel, this is most likely a stupid idea so forgive me in advance but could you hollow out the back with a powered grinding medium so when you to try to create a flat back it focuses your work behind the edge? Like I said probably silly.

 

[RossJarvis]

Ok corneel, this is most likely a stupid idea so forgive me in advance but could you hollow out the back with a powered grinding medium so when you to try to create a flat back it focuses your work behind the edge? Like I said probably silly.

Not really a silly idea, as this is what Japanese Chisels have. Having given it a half hearted attempt myself, I think a reasonable amount of skill/experience is needed though. An engineers scraper may do the job, but it all comes back to time. My Bahco chisels (mainly designed for site use I think) all had convex backs so flattening these would be a bit of a nightmare, I've spent many a happy hour trying to get these right and I think I've just succeeded with the 36mm one, shame they're not particularly good as chisels

 

[Corneel]

I've done that in the past too. Using the round part of the bandsander where it goes over the roller, and making sure the edge never touches the sanding band. It is hard to control though.

 

[Jason]

But there is no "flattening" involved...

In my experience, Marples chisels are almost always "flat" out the box.

 

[MMUK]

FWIW in my experience, albeit limited compared to others here, I have found that as long as the back is smooth and not obviously banana shaped then it works fine. I've not come across a chisel yet that has an obviously concave or convex back when looked at end on.

 

[Jacob]

Same here. Though on that green one above you could see the concavity. Not a problem.
The biggest prob is getting one like Corneel's above, which has had the edges rounded by an over enthusiastic polisher. Basically unusable - straight back on ebay with it!
Or reduce the width I suppose. Easier than flattening and might remove less metal?

 

[Corneel]

Jacob, it's also possible these kinds of chisels were produced on a hollow oilstone. If he would have sold his stone with this chisel, I might not have the same problem. Trouble is the convexness in combination with a bit of rust damage.

Personally I prefer flat(tish) stones.

 

[Richard T]

That's right Corneel, the tell - tale sign of the burr being taken off many times on a dished stone. It is (one of) the curses of buying old, used edge tools and the reason I splashed out big money on a extra coarse, dead flat diamond plate. Still a lot of work to get a straight line even just between the corners though ... something for the long, winter evenings.

As you say, further work on a hollowed stone would get into the corners but (personally) I would not be satisfied with walking such an edge along a nice, straight scribed line for instance. Picky, maybe, but I like to start with the best tool I can.

 

[Graham Orm]

I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?

 

[bugbear]

I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?

If you're talking about the Japanese model, it's "complicated". The hollow is shallow, and as the chisel wears, the hollow is actually FILLED IN (!!!!) by gentle, careful, accurate hammering on the upper side. This is only possible because the chisel is a thin hard layer laminated over a malleable support layer. But it's easy to get the hammering wrong.

So the hollowing, the hammering and the lamination are all part of an integrated process. You can't just pick one element (the hollowing) out and use it in isolation.

BugBear

 

[Graham Orm]

I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?

If you're talking about the Japanese model, it's "complicated". The hollow is shallow, and as the chisel wears, the hollow is actually FILLED IN (!!!!) by gentle, careful, accurate hammering on the upper side. This is only possible because the chisel is a thin hard layer laminated over a malleable support layer. But it's easy to get the hammering wrong.

So the hollowing, the hammering and the lamination are all part of an integrated process. You can't just pick one element (the hollowing) out and use it in isolation.

BugBear

You have to hammer the chisel into a new shape????? That couldn't possibly be done accurately or without heating.

 

[bugbear]

You have to hammer the chisel into a new shape????? That couldn't possibly be done accurately or without heating.

Yes it can!

http://kskdesign.com.au/blog/files/tapp ... dashi.html

BugBear

 

[Jacob]

I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?

Every time you turn the face to take off the burr you flatten it slightly so the flat rim of the hollow gets moved back a touch as the hollow gets shallower.
So you'd expect the end of this chisel to look much the same even years later when it's lost an inch or so in length

 

[Graham Orm]

I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?

Every time you turn the face to take off the burr you flatten it slightly so the flat rim of the hollow gets moved back a touch as the hollow gets shallower.
So you'd expect the end of this chisel to look much the same even years later when it's lost an inch or so in length

I'm struggling to get my head round it Jacob. Surely if it's concave when you grind back that 5mm or whatever there's a dip in the edge to conform with the hollow?

 

[Graham Orm]

You have to hammer the chisel into a new shape????? That couldn't possibly be done accurately or without heating.

Yes it can!

http://kskdesign.com.au/blog/files/tapp ... dashi.html

BugBear

I will take your word for it BB, sounds odd and not something I've ever seen or heard of. :wink:

 

[Phil Pascoe]

I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?

Every time you turn the face to take off the burr you flatten it slightly so the flat rim of the hollow gets moved back a touch as the hollow gets shallower.
So you'd expect the end of this chisel to look much the same even years later when it's lost an inch or so in length

I'm struggling to get my head round it Jacob. Surely if it's concave when you grind back that 5mm or whatever there's a dip in the edge to conform with the hollow?

No, because the back gets flattened further back as you sharpen - just like Japanese ones.

 

[Corneel]

Tapping only for Japanese planeblades! Not chisels! You risc breaking your Japanese chisel. Just polish the back after each sharpening and the hollow will move back a bit each time.

 

[bugbear]

You have to hammer the chisel into a new shape????? That couldn't possibly be done accurately or without heating.

Yes it can!

http://kskdesign.com.au/blog/files/tapp ... dashi.html

BugBear

I will take your word for it BB, sounds odd and not something I've ever seen or heard of. :wink:

That's the joy of other people, and the internet. You can learn new stuff! (did you follow the link?)

Corneel is right about it being plane blades only though.

BugBear