Sharpening

[marcros]

I have been looking through the sharpening posts and have a couple of (beginners) questions...

Scary sharp- would the glass out of a double glazed panel be flat enough to use for this system?

It seems the more grits the better, but what are the essential grit steps for limited space?

What is a hollow ground chisel- I see numersous mentions to it, but Google has me baffled on this one?

I have seen on a couple of threads mentions of chisels being reground to have "minimum lands". What does this mean, and what is the advantage to it? Again, Google has not been my friend on this!

TIA
Mark

 

[Alf]

Scary sharp- would the glass out of a double glazed panel be flat enough to use for this system?
Yep, reckon so. Make sure it's supported on something flat though, 'cos it'll flex.

What is a hollow ground chisel- I see numersous mentions to it, but Google has me baffled on this one?
It's a bevel ground on a vertical wheel - thus leaving a bevel with a concave surface, the degree of concavity depending on the size of the wheel.

I have seen on a couple of threads mentions of chisels being reground to have "minimum lands". What does this mean, and what is the advantage to it? Again, Google has not been my friend on this!
The area where the bevel bit of a bevel-edged chisel meets the back can vary. Some have virtually no straight side remaining, making them ideal for getting into restricted corners such as fine dovetails. Others have such a token "bevel" that they still have a noticeably straight side and some folks will take the time to grind them down to a finer edge.

 

[custard]

Mark, couple of comments

1. the glass you need is thick (at least 1/4" thick but thicker is better to minimise flexing) float glass. I doubt double glazed panes would fit the bill, but you can get something appropriate fairly cheaply from any glass merchants. Also avoid safety glass as I understand part of the process can result in small ripples in the surface. Another (and even better) option is an offcut of flat granite worktop from a kitchen supplier. With glass you need to be sure the bench is reasonably flat, with granite it's less of an issue.

2. Hollow ground means there's a minute hollow in the back to make flattening easier.

3. The land of a chisel is the very small flat section on the side, the issue is that without it the edge might crumble and you'd probably cut yourself, but having it makes it hard to get into the corners of a dovetail. Look at the sides of bevel edge chisels, they don't actually come to a knife edge, there's a tiny flat which is called the land, problem is on some bevel edge chisels the land is pretty thick! Ashley Illes bevel edged chisels are terrific in this respect, no land but a tiny radius to prevent crumbling and accident problems.

 

[Racers]

Hi, Mark

Double Glasing tends to be pulled inwards in the middle, have a look next time you walk down the road at the reflections.
You can also use a granite choping board most I have seen are flat, even the £10 ones from sainsburys.

Pete

 

[Alf]

Dammit, I wish I could go back the necessary number of years and tell myself that the bog standard bit of glass on a bit of MDF that I was using wasn't actually sharpening anything like I thought it was... Ah well, ignorance was obviously bliss. :roll: Chaps, really. Do you have to complicate everything (and add expense) immediately?

Dammit, I've broken out the rolling eye smilie. I swore I could get involved in a sharpening thread without wanting to do that, and I've failed. Already.

Someone cast a deciding vote on hollow ground, would you? Because I was perfectly confident with that one, and now I'm thinking I must have missed a whole load of chit chat about chisels and new thinking (which, in fairness, is not unlikely).

 

[Jacob]

.....
Scary sharp- would the glass out of a double glazed panel be flat enough to use for this system?

Anything flattish will do - this is woodwork not surgery :roll: . A bit of mdf or other board. Glass, granite etc all a bit OTT

It seems the more grits the better,

t'other way round. 2 grits is the most you need and it's quicker. Coarse for fast backing off, fine for honing. Absolutely no point in anything in between

What is a hollow ground chisel-

ground on the edge of a wheel hence concave. Quick n easy and also the flat edge bevel is quick n easy to hone, but not good as it leads to a weaker edge. Particularly undesirable with thin plane blades.

 

[Pete W]

Dammit, I've broken out the rolling eye smilie. I swore I could get involved in a sharpening thread without wanting to do that, and I've failed. Already.

I admire your good intentions. I've now decided to contribute* to no sharpening threads. Too much like religion and politics

*Originally wrote "participate in" then realised I was participating, but not contributing!

 

[Richard T]

I think Hollow Ground can mean both; the bevel ground on a wheel thus leaving it concave and also the back (flat) having been finished on a (much larger) wheel leaving it slightly concave so that when you take off the sharpening burr you only work on that very small outer area.
The later is very common, if not obligatory, to Japanese chisels and irons but the only example I have is a draw knife by Gilpin which is a dream to sharpen because of it.

 

[woodbloke]

The later is very common, if not obligatory, to Japanese chisels and irons

Called the 'ura' on Japanese tools and it does make them easier to hone as there's less material to remove. That said, the steel on Japanese chisels etc is usually a lot harder than Western tools so it's probably just as well that it's there - Rob

 

[jimi43]

Most double glazing is deceivingly thin...I know...I broke a pane.

It just looks the job because it is fat but float glass is best.

Since I wanted to contribute to this thread I tested the theory and phoned a double glazing factory in the next village and asked for some float glass.

He is saving me a piece for nothing...10mm thick about...for nufink!

Job done...try it...it works.

A cutting part of a chisel comprises the bevel and the edge which is honed.

Make the bevel using any grinding surface...eg...great big sandstone wheel, Tormek type thing with water....fast or slow grinding wheel with care and lots of dipping in water...belt or disc sander...and shape it to whatever angle suits the job...about 30 degrees or whatever Jacob says... :wink: This is the GRINDING of the bevel.

I found that whatever you do...keep it cool to preserve the hardness....and keep going until a burr forms...you can feel this as a sharp edge on the flat side of the chisel...just turning over the edge.

I then take this off by flattening the surface of this "back" edge....the shinier you can get this the better

Then I create a honed "microbevel" with a few swipes on a fine abrasive surface...this is the HONING of the edge.

Don't confuse the two.

I use a Tormek for a slightly concave main bevel...it's easy and cool but you can use anything that grinds it flat or concave as long as it ends in a point...

The flattening and polishing the back along with the honing of a microbevel leads to the goal which is two perfectly flat surfaces meeting at a perfect point...

Now...over to Jacob to rattle on about making ice cream scoops and wiping it with diesel and avoiding overheating by dropping it in your garden pond...... :mrgreen:

Mr Grimsdale?

Jim

 

[Jacob]

......
It just looks the job because it is fat but float glass is best.

Since I wanted to contribute to this thread I tested the theory and phoned a double glazing factory in the next village and asked for some float glass.

He is saving me a piece for nothing...10mm thick about...for nufink!.....

I think all normal flat glass is float glass nowadays including thin DG panes. The exceptions usually being obvious - cheap agricultural glass (aka "Dutch lights", still "drawn" I think) and other specialities.

 

[jimi43]

......
It just looks the job because it is fat but float glass is best.

Since I wanted to contribute to this thread I tested the theory and phoned a double glazing factory in the next village and asked for some float glass.

He is saving me a piece for nothing...10mm thick about...for nufink!.....

I think all normal flat glass is float glass nowadays including thin DG panes. The exceptions usually being obvious - cheap agricultural glass (aka "Dutch lights", still "drawn" I think) and other specialities.

I spoke to him about this...he said most is rolled and toughened...not good for "flat" surface.

J

 

[Jacob]

......
It just looks the job because it is fat but float glass is best.

Since I wanted to contribute to this thread I tested the theory and phoned a double glazing factory in the next village and asked for some float glass.

He is saving me a piece for nothing...10mm thick about...for nufink!.....

I think all normal flat glass is float glass nowadays including thin DG panes. The exceptions usually being obvious - cheap agricultural glass (aka "Dutch lights", still "drawn" I think) and other specialities.

I spoke to him about this...he said most is rolled and toughened...not good for "flat" surface.

J

Toughened glass starts as float but loses it's flatness (it's heated in a kiln). Not usually used for windows except where required by building regs (e.g. below 800mm above floor level, or for doors, or something along those lines). Very little glass is rolled nowadays except for special purposes.
You can always tell float - you get a perfect reflection, though this might be gently (but perfectly) curved if it is bent e.g. if you hold up a large sheet by its edge. Or look at the reflection in a DG unit on a day when air pressure is higher or lower than the day on which the unit was made.

 

[jimi43]

Since he's saving me some thick float glass....I'm not that bothered....I will make sure I correct him though... :wink:

Jim

 

[matthewwh]

10mm or thicker float is the thing to go for if you are buying it, if you can rustle up a freebie all the better. Our customers have had various reactions from glaziers, from 'no problem we will put an offcut aside for you' to quotes of up to £40. - I know who I'd be going back to when it comes time to get the house re-glazed!

Grades wise I have settled on 40, 30 and 5 micron for general sharpening, the next most common is 30, 15, 5 and 1 set out lengthwise on the glass, I believe this is the option favoured by the Barnsley Workshops but scary sharp is a very flexible system so you can have a play and then adapt it for your own needs. I'm the first to admit that 0.3 micron is overkill but it does remove metal and will squeeze the last ounce of performance out of a blade, if you have a really critical cut to make then it's nice to have a sheet or two on hand.

For grinding I use 100 micron stuck to MDF; plenty flat enough for grinding and you can bin it when you are finished, the 100 micron sheets are not available in PSA so I stick them down with PVA or a smear of epoxy. The 100 micron removes material rapidly but in a controlled way, it will produce a beard of iron filings on the blade and get it hot enough that you can't hold it in about a minute, which is a useful safety valve for not overheating the steel. If you are just dressing the primary bevel you will probably be done long before that happens anyway.

Hollow grinding simply means a surface that is intentionally made concave. In chisels you can have hollow ground bevels, as Alf describes above, which are often preferred by freehand honers as it gives them two lines to register against the surface of the stone (that is if they are not using the rounded bevel method as advocated by Jacob although I'm guessing you could combine the two quite happily if you got a really bad ding in the edge).

Hollow ground backs are split into two distinct types but the principle is the same, the arrangement is self-jigging and greatly reduce the amount of effort required to produce an accurate surface:

First there is the Japanese Ura where a shallow oval is ground into the centre of the blade. This gradually recedes ahead of the cutting edge each time you polish off the burr so it will become circular and then oval the other way as the chisel wears but never actually break through the edge.

Second is the English hollow ground chisel (i.e. Ashley Iles) where the non bevelled side is concave in its length by a couple of thou, this is not enough to make the chisel dive in the cut by any amount that is significant in even exhibition quality work, but it is just enough that the underside of the bevel can be polished in isolation from the rest of the blade. Barry Iles and Tony the foreman spent about 18 months perfecting the hand grinding technique for achieving this reliably and ended up achieving half the tolerance that I had asked them for.

It makes them very fast to hone and because you are working such a small area you can eliminate the scratch pattern from the previous grade easily and completely, you can typically get even a wide blade from box to bench in under 3 minutes. If the shiny bit starts to get too big, working the middle of the blade at an angle across the edge of a sheet of 100 micron or across the width of a coarse stone (David C's method) will reinstate the very fine curvature.

The only other chisels I have found with a consistent hollow in are Narex, I believe this is caused by shrinkage during heat treatment - if you've ever cast lead in the frog of a brick you will see how the billet shrinks back in the centre. This is usually just a fraction deeper than the AI's and in an oval shape like the Japanese chisels, it is not engineered to be there, just a happy by-product of their accurate grinding and austempering hardening process.

 

[Jacob]

.....
The only other chisels I have found with a consistent hollow in are Narex, I believe this is caused by shrinkage during heat treatment - if you've ever cast lead in the frog of a brick you will see how the billet shrinks back in the centre. This is usually just a fraction deeper than the AI's and in an oval shape like the Japanese chisels, it is not engineered to be there, just a happy by-product of their accurate grinding and austempering hardening process.

I bought some Axminster cheapies a bit back and was surprised to find that their faces were just slightly hollow in the preferred way. Could be chance or by design?
I guess any chisel face which isn't perfectly flat has a 50/50 chance of being concave, so maybe not so rare.

PS Just checked and they aren't so cheap anymore. http://www.axminster.co.uk/axminster-ax ... prod31355/
Just noticed it says "bevel edge" in the heading but "firmer" on the packet. In fact they are in between, neither one thing nor the other. Steel is OK though.

 

[Jeff Gorman]

Marcros wrote: Scary sharp- would the glass out of a double glazed panel be flat enough to use for this system?

The question suggests that Marcros wants to get a dead straight edge when he hones, but excepting for use on a shooting board, it is better to have a slightly cambered profile.

This page might explain why: http://tinyurl.com/27lwtxn

Jeff
http://www.amgron.clara.net

 

[Jacob]

Agree.
Even on a shooting board a bit of camber is no prob if you can tilt the blade enough to get it how you want.
Flatness has become a bit of a pointless holy grail.
It's more to do with jigs IMHO as most of them they don't work so well if things aren't dead flat and edges dead straight.
Cart before the horse!
In view of recent tedious thread - apologies to all those who find opinions like this offensive but I'm not trying to be deliberately provocative here - it's actually what I think and how I do woodwork, believe it or not!
Hmm I might add that phrase as a signature to all my posts!

 

[marcros]

Marcros wrote: Scary sharp- would the glass out of a double glazed panel be flat enough to use for this system?

The question suggests that Marcros wants to get a dead straight edge when he hones, but excepting for use on a shooting board, it is better to have a slightly cambered profile.

This page might explain why: http://tinyurl.com/27lwtxn

Jeff
http://www.amgron.clara.net

Jeff, to be honest Marcros doesn't know quite what he wants and is reading the thread with great interest!

 

[Corneel]

Agree.
In view of recent tedious thread - apologies to all those who find opinions like this offensive but I'm not trying to be deliberately provocative here - it's actually what I think and how I do woodwork, believe it or not!

No Jacob, it's not your opinions that are offensive. Far from that. Sometimes I agree, sometimes not. But it seems that you are not always able to accept a different opinon and the tone is then somewhat offensive at times.

Anyway I really like to read your opinions, and I learn quite a bit in the mean time. For example, free hand sharpening of my chisels is a coming along now, and it's not too difficult. I'm still a bit leary to try it with the plane irons yet.