newbie chisel sharpening question

[TomP]

hi,

I've just been given some older chisels, I'm attempting to sharpen them however I'm a tad confused with what angle to aim for with a honing guide. Some say 30 degrees some say 25, is it a case of both or one or the other. Im not sure anything super technical will benefit me at my current skill level just looking for simple way to sharpen chisels. I already have a honing guide and a old sharpening stone in front of me ready to go.

Thanks in advance

 

[Fitzroy]

You don't know what you've done!

You often see a primary grind at say 25 then a secondary at a greater angle, say 30. This way when you resharpen the edge you have a lot less material to remove. Paul sellers would say the precise angle is not all that important, so long as you are in the 25-30 region.

F.

 

[TomP]

Thanks for that, Take it i have opened a can of worms then

 

[undergroundhunter]

Thanks for that, Take it i have opened a can of worms then

Not necessarily a can of worms but everyone has their way of sharpening and their angles they use. The most referred to angles are primary bevel of 25 and secondary of 30 but this will vary on the type of edge being sharpened, for example a pig sticker mortice chisel would be more like 30 degrees and a paring chisel more like 20 degrees.

Matt

 

[RobinBHM]

hi,

I've just been given some older chisels, I'm attempting to sharpen them however I'm a tad confused with what angle to aim for with a honing guide. Some say 30 degrees some say 25, is it a case of both or one or the other. Im not sure anything super technical will benefit me at my current skill level just looking for simple way to sharpen chisels. I already have a honing guide and a old sharpening stone in front of me ready to go.

Thanks in advance

Oh dear Oh dear!

 

[thetyreman]

to start with I used a honing guide set to 30 degrees, it works just for getting you going, then you can learn how to freehand sharpen in time, it took me a while to get good a freehand sharpening and a lot of patience and practice.

 

[Jacob]

Hone at 30º. They may be in good nick and this is all they need - you'll soon see.

 

[sploo]

If you have old chisels (possibly damaged, probably questionable bevels) then the first thing I'd do is use a guide to grind a new main bevel at 25 degrees. That might take a lot of work by hand, so a grinder or similar tool might help. 80 grit sandpaper on a sheet of float glass or granite slab works, but obviously takes elbow grease.

After that, the back needs flattening - not much; you only really need a few mm at the tip.

Personally I'd then sharpen freehand, likely rounding to a single curved bevel (going to about 30 degrees at the tip); though putting a 30 degree microbevel on the very leading tip of a 25 degree main bevel using a honing guide is absolutely fine too.

As for the correct angle - it really depends on the material; different bevels are better on different types of wood, but with my (relatively lacking) skill level I do tend to just keep them with a 30 to 25 degree single bevel.

This may be helpful: https://www.youtube.com/watch?v=Ki8tt-VjwqI

The thing to remember with sharpening: ask 10 people for advise and you'll get 11 different answers

 

[David C]

The age old recipe is grind at 25 degrees and hone at 30.

David

 

[Phil Pascoe]

Sploo - I get your point, but actually, if you ask 10 people probably eight out of ten would probably say as David just said - grind at 25, hone at thirty - because most of the time it's correct, and many people don't use the types of chisels than really benefit from anything being done differently.

 

[Jacob]

I'd say hone a touch at 30º, whatever condition it seems to be in, it will reveal see immediately what shape the bevel is in.
If the honing doesn't reach the edge then it's been rounded over or ground too steep and may need grinding at less than 30º. On the other hand it might be all it needs and a quick de-burring on the face is all that is now required. Depends on what condition it was left in.

 

[sploo]

Sploo - I get your point, but actually, if you ask 10 people probably eight out of ten would probably say as David just said - grind at 25, hone at thirty - because most of the time it's correct, and many people don't use the types of chisels than really benefit from anything being done differently.

I was being a bit tongue in cheek

Though mostly I was referring to technique and equipment rather than specific bevel angles.

 

[matthewwh]

I'd worry about the other side first, if that's not right then the bevel angle is the least of your worries.

 

[RossJarvis]

Jacob's given some good advice. All you need to do is get the cutting edge "sharp" this only needs to be a fraction of the metal well "honed" or "ground" and a degree or two either side of 30 degrees is neither here nor there.

The reason that chisels are ground to 25 degrees and then the cutting edge to 30 degrees is so that you don't need to grind too much metal away to maintain a sharp edge and can do this frequently, until you need to spend a while re-grinding the whole bevel. Different angles can be beneficial for different types of working but the 30 degree angle seems to be the best compromise for general purposes.

Set the guide to do 30 degrees. If you get a nice clean edge across the sharp end then you're ready to go. If you end up grinding away somewhere else on the bevel then you could grind away the whole bevel to 25 degrees, but you could do it at 26, 27, or 28 or 29. Then a quick touch on a fine stone at 30 degrees so that you get a sharp edge all across the width of the chisel. Alternatively you could set the guide to be slightly over 30 degrees and if this gives you a sharp edge across the chisel then you're ready to go and saves a lot of effort.

As some have mentioned, the other side of the chisel can influence performance. If the "flat" side is rough, Eg due to rust or rough grinding, it can help to grind this side too. Generally a grind of a degree or two on the flat side, so that the full width at the sharp end is shiny may help. If you are really bored you could "flatten" this side so that the whole side is shiny and polished, but generally this is more effort than needed.

 

[Jacob]

I'd worry about the other side first, if that's not right then the bevel angle is the least of your worries.

Personally I wouldn't worry about the face at all. Flattening and /or polishing the face of chisels and plane blades (or "back" as they call it) is a bit of fetish amongst modern sharpening enthusiasts - along with the daft mantra: "a sharp edge is the intersection of two flat planes" as often repeated, with variations. :roll:
When you get your 30º bevel to reach the edge (with honing and grinding if required) AND showing a burr on the face side (you should be able to feel it even if you can't see it) you need to take off the burr with a bit of gentle flat honing near the edge - not all the way back. If it's a rusty old chisel you will see where it is or isn't coming into contact with the stone. If necessary you might need to lift the handle a touch (as little as necessary) to remove the burr. Thats it - nothing else needed. Rust - rub it off with wire wool or just ignore it (it'll leave skid marks at first). Pits - ignore them until they make sharpening an edge difficult - then just hone/grind past them, though for most purposes a little nick in the edge won't matter.
Over time the very slight face bevel you've put on will reduce every time you flatten to remove the burr, but in the meantime it won't have the slightest effect on your chisel use - carvers have very sharp chisels with double bevels - in use it's just a different technique.

PS newbies need to warned - fashionable modern sharpening practices are best avoided; fussy, over precise, difficult, involve buying all sorts of kit, largely pointless; no more effective than the old freehand simple methods used almost universally since the stone age :lol:

 

[swagman]

Jacob; I suggest you need to do some research on early practices regarding the need to work the flat of the chisel. Its not a newbie phenomenon. I am also a little surprised at the suggestion by Ross Jarvis Generally a grind of a degree or two on the flat side, so that the full width at the sharp end is shiny may help. The topic is chisels, not plane irons.

 

[Jacob]

Jacob; I suggest you need to do some research on early practices regarding the need to work the flat of the chisel. Its not a newbie phenomenon. I am also a little surprised at the suggestion by Ross Jarvis Generally a grind of a degree or two on the flat side, so that the full width at the sharp end is shiny may help. The topic is chisels, not plane irons.

Works for chisels too. Hence the endless complaints about old chisels being slightly convex (or "bellied" :shock: ). They were like that because that's what happens if you hone off the burr on the face a few hundred times, and it doesn't matter.
If a new chisel is not flat enough for use immediately (after a minute of honing) then it should be sent back to the shop you bought it from.

swagman where did you read this stuff about "early practices regarding the need to work the flat of the chisel" ? I'd be interested to see it.

 

[ED65]

@TopP, this old article by Tom Caspar might be of interest as it covers many aspects of sharpening, 16 Tips for Sharpening.

 

[ED65]

...along with the daft mantra: "a sharp edge is the intersection of two flat planes" as often repeated, with variations. :roll:

How is this daft? That's exactly what a sharp edge is. If it's not then pray tell what is it?

...no more effective than the old freehand simple methods

While I'm a big supporter of freehand sharpening I'm not blind to how good it can be. You shouldn't be either.

Jigged sharpening, powered or by hand, can routinely create edges superior to those that the great majority of freehand sharpeners are capable of. That's a proven fact. The key point is however that freehand sharpening only done a reasonable standard is good enough for most people, for most jobs. But good enough is not the same as equally good.

 

[AndyT]

@TopP, this old article by Tom Caspar might be of interest as it covers many aspects of sharpening, 16 Tips for Sharpening.

That looks like a useful article for any newbie, or as a reminder to anyone else.

(Of course it's possible to say more about sharpening - but sometimes the most helpful thing is to say a little, then stop.)