Block plane blade

[transatlantic]

I have a block plane (Axminster Rider No. 9 1/2 Standard Block Plane), where the blade is currently at an angle of 25 degrees. The problem is that the bevel of the edge of the blade is a good 7mm. So it takes forever to sharpen. To get around this, I was thinking of grinding the blade down to 20 degrees, so that when I then sharpen again, I won't have so much material to remove.

Is 20 degrees a good angle for this?

 

[MattRoberts]

Why not just have a micro bevel a couple of degrees over the 25? A lot quicker to sharpen. Or re-grind to 20 and have a micro bevel of 22 ish?

 

[Jacob]

Ground at 25º hone at 30º. Standard practice for most planes.
In modern parlance and with a jig "primary bevel 25, secondary micro bevel 30º"
Traditionally; just a rounded bevel with the edge at 30º ish.

 

[transatlantic]

Or re-grind to 20 and have a micro bevel of 22 ish?

Yeah - that was basically what I wanted. Lots of material to remove. Fortunately, I have access to a Sorby pro edge, although I'm probably still going to balls it up!

 

[MattRoberts]

Indeed, but at least you only need to grind the primary bevel once

 

[Jacob]

If it's ground at 25º it takes about 2 seconds to put on a 30º edge. Plane and chisel blades are never so easy to sharpen as when they are brand new and factory fresh.

 

[ED65]

20° should be fine. You really only need one or two degrees of clearance but 5° will allow more honings before you'll want to grind again. But I think you should examine why you're having such a difficult time sharpening the existing single bevel.

Standard honing should not take an age because you do it frequently enough that the amount of steel needing to be removed is minuscule, leading to honing times of 30 seconds to a couple of minutes. And because honing is not like sanding large jumps in grit (huge in fact) are perfectly acceptable, so if need be you can start at 150 to quickly establish a new edge and immediately go to 1000 or even finer.

Lots of material to remove.

Wait till you do this on a 2 3/8" vintage iron

Fortunately, I have access to a Sorby pro edge...

I wouldn't exactly recommend it as normal practice but especially on something the size of a block plane's iron it's perfectly possible to do this manually in a reasonable amount of time (quarter of an hour or so). And because you're abrading steel so slowly it's very easy to catch an error and make any necessary corrections.

 

[ED65]

Or re-grind to 20 and have a micro bevel of 22 ish?

Depending on the steel and the use the plane is put to that could make the edge a touch fragile. If using these angles on a bevel-up plane it might be found necessary to add a small back bevel to make the edge stouter.

 

[MattRoberts]

Or re-grind to 20 and have a micro bevel of 22 ish?

Depending on the steel and the use the plane is put to that could make the edge a touch fragile. If using these angles on a bevel-up plane it might be found necessary to add a small back bevel to make the edge stouter.

Interesting - I would have thought adding a back bevel would further compound the angle and create a more fragile edge?

 

[Jacob]

Some serious over-thinking going on here!
To repeat myself:
Plane and chisel blades are never so easy to sharpen as when they are brand new and factory fresh.
If it's ground at 25º it takes about 2 seconds to put on a 30º edge.
This is normal practice. If it can't be done it's a faulty blade - send it back

 

[ED65]

No bevels on both sides make the edge actually thicker. For example if you have a bevel of the fairly standard 30° the angle at the edge (AKA the included angle) is 30° because the back is flat, i.e. 0°. Add a back bevel and the included angle becomes 30° plus whatever the angle of the back bevel is, and the higher the included angle the thicker and stronger the edge.

One of the standard fixes for softer plane irons is to add a back bevel for this reason. Unfortunately we can't rely on this trick for chisels since nearly always you want the back flat, so you either have to steepen the bevel or reharden the steel.

 

[ED65]

Jacob, yes it's standard to hone at 30° but as this is a bevel-up plane the user might specifically not want to steepen their honing angle. With a low-angle block for example it's particularly useful to keep the bevel as shallow as possible (within reason).

Here, presuming the bedding angle is 19° a change from 25 to 30 means the presentation angle goes from around common pitch to closer to York pitch, which may not be desirable for one reason or another – they commonly work on softwoods, increased resistance in hardwoods or whatever.

 

[Jacob]

Jacob, yes it's standard to hone at 30° but as this is a bevel-up plane the user might specifically not want to steepen their honing angle. With a low-angle block for example it's particularly useful to keep the bevel as shallow as possible (within reason).

Here, presuming the bedding angle is 19° a change from 25 to 30 means the presentation angle goes from around common pitch to closer to York pitch, which may not be desirable for one reason or another – they commonly work on softwoods, increased resistance in hardwoods or whatever.

30º gives an effective cutting angle of about 50º which will do for almost everything.
People often miss the point of the block plane - it's not about the cutting angle it's about having a compact small plane which can be held in one hand. The BU design helps makes this possible but it won't cut as well as a BD iron with a cap.

 

[custard]

Fortunately, I have access to a Sorby pro edge, although I'm probably still going to balls it up!

Transatlantic, here's what happens in my workshop.

1. Get yourself a thick black indelible felt pen and disassemble your block plane.

2. Colour in the bevel with the felt pen.

3. Place the iron on the platten of the Sorby Pro Edge (ignore the red tape...I'm sure you always do anyway!). Almost everything gets ground at 25 degrees in my workshop, but low angle planes are one of the very few exceptions, these are ground at 20 degrees. I use A2 and PMV-11 irons and I regularly work some of the hardest timbers there are, but I still haven't had chipping problems. You may find the shape of your iron means it won't register against the vertical fence on the Pro Edge, as long as it's on the platten then it's no big deal to work free hand. Just use a light touch until you've got your eye in and you'll be fine.

4. Grind until there's a mill or less of felt pen remaining. But don't remove the felt pen entirely. That way you won't have any overheating problems and on bench planes you preserve your camber. After a while you won't need felt pen, but until you've done it a good few times it's a very useful guide.

5. Hone in your usual fashion at anywhere from 22-25 degrees. If you want to use a honing guide that's okay, sometimes I do sometimes I don't, but it's your workshop so you make the rules. Don't get over enamoured with honing, you want the minimum number of strokes to complete the task. Any additional stroke beyond that is just making more work for you next time when you have to remove the blunt edge. I see beginners making loads of polishing strokes like it'll magically improve the edge, it won't.

6. The two critical things are to get a wire edge right along the cutting edge (to validate that you've removed the previous blunt edge), and then to get a polished surface right along the cutting edge. In fact I don't believe it's actually necessary to go down to polishing grits for most practical woodworking purposes, but the polish is clearly visible and therefore an easy way to validate that you've worked the entire edge and haven't missed a bit. The absolute essence of honing is these two elements. Never move on to polishing grits until you've raised a wire edge. And then check you've polished the entire edge. If I were to add a third rule it would be to re-grind frequently, if you've got a power grinder use it to remove the sharpening donkey work, if you're using ultra thick modern irons a power grinder is pretty much essential. As soon as I find a tool takes more than eight or ten strokes to hone then I regrind.

7. Back off the iron to remove the wire edge. I will use back bevels and the ruler trick, but only very rarely and to achieve specific objectives. The problem once you start messing around with that stuff is that you can get yourself in a right mess, did you use the ruler trick on this iron last time or not? Does this tool have a back bevel or not, and if so what angle was it? Personally if I find a tool is pitted or warped and needs the ruler trick then I'll chuck it out and keep my workshop running efficiently.

8. Re load the iron and set the lateral adjustment (it really helps to do this against a light background), then it's job done so get back to work!

Good luck!

 

[MattRoberts]

No bevels on both sides make the edge actually thicker. For example if you have a bevel of the fairly standard 30° the angle at the edge (AKA the included angle) is 30° because the back is flat, i.e. 0°. Add a back bevel and the included angle becomes 30° plus whatever the angle of the back bevel is, and the higher the included angle the thicker and stronger the edge.

One of the standard fixes for softer plane irons is to add a back bevel for this reason. Unfortunately we can't rely on this trick for chisels since nearly always you want the back flat, so you either have to steepen the bevel or reharden the steel.

Of course - I don't think my brain was working this morning, thanks!

 

[transatlantic]

Thanks custard. That's pretty much what I was going to do. So glad you confirmed it

 

[Jacob]

Fortunately, I have access to a Sorby pro edge, although I'm probably still going to balls it up!

Transatlantic, here's what happens in my workshop.

1. Get yourself a thick black indelible felt pen and disassemble your block plane.


2. Colour in the bevel with the felt pen.


3. Place the iron on the platten of the Sorby Pro Edge (ignore the red tape...I'm sure you always do anyway!). Almost everything gets ground at 25 degrees in my workshop, but low angle planes are one of the very few exceptions, these are ground at 20 degrees. I use A2 and PMV-11 irons and I regularly work some of the hardest timbers there are, but I still haven't had chipping problems. You may find the shape of your iron means it won't register against the vertical fence on the Pro Edge, as long as it's on the platten then it's no big deal to work free hand. Just use a light touch until you've got your eye in and you'll be fine.


4. Grind until there's a mill or less of felt pen remaining. But don't remove the felt pen entirely. That way you won't have any overheating problems and on bench planes you preserve your camber. After a while you won't need felt pen, but until you've done it a good few times it's a very useful guide.


5. Hone in your usual fashion at anywhere from 22-25 degrees. If you want to use a honing guide that's okay, sometimes I do sometimes I don't, but it's your workshop so you make the rules. Don't get over enamoured with honing, you want the minimum number of strokes to complete the task. Any additional stroke beyond that is just making more work for you next time when you have to remove the blunt edge. I see beginners making loads of polishing strokes like it'll magically improve the edge, it won't.



6. The two critical things are to get a wire edge right along the cutting edge (to validate that you've removed the previous blunt edge), and then to get a polished surface right along the cutting edge. In fact I don't believe it's actually necessary to go down to polishing grits for most practical woodworking purposes, but the polish is clearly visible and therefore an easy way to validate that you've worked the entire edge and haven't missed a bit. The absolute essence of honing is these two elements. Never move on to polishing grits until you've raised a wire edge. And then check you've polished the entire edge. If I were to add a third rule it would be to re-grind frequently, if you've got a power grinder use it to remove the sharpening donkey work, if you're using ultra thick modern irons a power grinder is pretty much essential. As soon as I find a tool takes more than eight or ten strokes to hone then I regrind.


7. Back off the iron to remove the wire edge. I will use back bevels and the ruler trick, but only very rarely and to achieve specific objectives. The problem once you start messing around with that stuff is that you can get yourself in a right mess, did you use the ruler trick on this iron last time or not? Does this tool have a back bevel or not, and if so what angle was it? Personally if I find a tool is pitted or warped and needs the ruler trick then I'll chuck it out and keep my workshop running efficiently.


8. Re load the iron and set the lateral adjustment (it really helps to do this against a light background), then it's job done so get back to work!


Good luck!

Phew!
What happens in my workshop (with a new blade ground at 25º):
I pick up the blade and hold it at about 30º (i.e. just a bit more than the 25) and rub it up and down a fine oil stone for a few seconds, until I can feel a burr - (yes across the whole width). Then remove the burr by putting it face down and moving it about a bit. say 30 seconds max.
The ruler trick is for desperate cases and incidentally is much easier to do without a ruler. I call it the "without a ruler" trick :lol:

 

[ED65]

I call it the "without a ruler" trick :lol:

I call it the "concentrate effort at the tip" trick

Seriously though, it is capable of salvaging an utter disaster of an iron like this one so except for the very worst cases, in the hardest of steels, I don't see the point myself.

 

[Bodgers]

If you have a bench grinder with a decent wheel and a holding jig the hollow grind is worth giving a try too. Garret Hack does a good guide on this. I have tried it on a few blades and it cuts down on honing and produces decent results for me.



Sent from my MI 3W using Tapatalk

 

[Jacob]

I call it the "without a ruler" trick :lol:

I call it the "concentrate effort at the tip" trick

Seriously though, it is capable of salvaging an utter disaster of an iron like this one so except for the very worst cases, in the hardest of steels, I don't see the point myself.

Agree.
Actually that very rusty blade is about the only situation where a sharpening jig is useful - before you do anything else you put the blade in a jig at 30º and give it a quick hone (just a few seconds). It works like a tell-tale and the position of the shiny bits show what shape the bevel is in.
Not sufficient reason for buying a jig but if you have one lying about unused this is one way to use it, no need to bin it!

I'd avoid machine grinding on a block plane blade - they are thin and narrow, easy to do by hand, easy to overheat on a grinder.
Unless you've made the mistake of buying one of those expensive fashionable retro-style thick blades made of magic steel! In which case it'd take far too long by hand.