Plane Iron Grind Angle for BDs

[Harbo]

I realise this has probably been covered before but I got fed up "searching".
I received this week, my long awaited, replacement plane iron from Jim Reed which arrived with a 32.5 degree bevel. Much steeper than what I am used to so I had a look at others I have and found them to vary from 12 degrees to 30.
I then looked at my text books:
David Finck recommends 25 for thin irons (less than 1/8") with a secondary 30 bevel. For thicker ones 30 degrees only.
Leonard Lee states 30 to 35 - anything lower than 30 will encourage blade chatter.
DavidC advises a primary grind of 22 followed by a 30 or 35 secondary - does this introduce blade chatter?
Opinions gratefully received.

Rod
:?

 

[JesseM]

I usually establish my primary at 30 and a couple of degrees for the secondary. From my understanding the higher the angle the longer the edge is retained. For the scrub, mortise chisels, and cutters for the combis I usually go up to 35 for the primary. I think edge retention for the combis is important since you don't want to keep pulling the blade out to sharpen it once its set up.

Also, I think A2's edge is more brittle at lower than 30 degree angles though I have nothing to base this on since mine are all at 30.

My personal opinion is that the edge you have sounds fine, as long as it is lower than the bed angle. One other point is the wood you'll be using it on. Higher angles (30+) are better are for hard woods, and lower (25) for soft woods.

 

[bugbear]

Much steeper than what I am used to so I had a look at others I have and found them to vary from 12 degrees to 30.

What on earth do you have with a 12 degree primary?!?!

BugBear

 

[Anonymous]

All of my bevel down planes are hollow ground at 25 degrees on a bench grinder and then honed at 30 degrees which works fine for me

All the blades are LN A2 steel if that makes any difference

 

[bugbear]

All of my bevel down planes are hollow ground at 25 degrees

On a geometrical note, how so you define "angle" for a hollow grind?

BugBear

 

[Harbo]

Bugbear - the 12 degree was on a S/H iron I bought - I reground it with a 25 secondary.

I think Tony means the hollow you get using a wheel - but I am sure he will answer that himself?

Rod

 

[Jake]

On a geometrical note, how so you define "angle" for a hollow grind?

By reference to the chord, surely.

 

[Anonymous]

All of my bevel down planes are hollow ground at 25 degrees

On a geometrical note, how so you define "angle" for a hollow grind?

BugBear

Simple. I set the support the blade sits on at 25 degrees to the stone where it meets, and then grind the blade. The curvature on the blade gives a hollow grind that is on average 25 degrees - absolute is unimportant as the cutting bevel is honed 5 degrees steeper

 

[bugbear]

On a geometrical note, how so you define "angle" for a hollow grind?

By reference to the chord, surely.

That could get interesting; here's 25 degrees...

BugBear

 

[Jake]

You are obviously a step ahead of me, so do carry on...

 

[bugbear]

You are obviously a step ahead of me, so do carry on...

My example is (of course) utterly worst case, where the chord is 25 degrees, but the bevel angle measured at the edge is zero - so is the blade thickness.

This (extreme!) case illustrates why I asked the question about defining bevel angles under hollow grind.

BugBear

 

[Jake]

But that's immaterial, providing (like any sharpening nut apart from the straight-from-the-Tormek-delusionals) one immediately puts a secondary bevel on.

 

[Anonymous]

(like any sharpening nut apart from the straight-from-the-Tormek-delusionals) .

:lol: :lol: :lol:

BB, your image does not match the grind I get on my plane blades, possibly because the grind stone I use has 150mm diameter and the rest is positioned level with centre.

I'll photograph the resulting bevel and post - I use a Tormek angle setting guage picked up from Yandles show to set the angle on the blade support

 

[lucky9cat]

I'm sorry but I just gotta ask; why are straight-from-the-Tormek people delusional? My Tormek gets edges really sharp and it doesn't feel like a delusion.

Ted

 

[Chris Knight]

Ted,
Your edges may feel sharp to you but they will not be as sharp as edges created on a benchstone etc etc. The Tormek is a very useful bit of kit but it just doesn't produces edges as sharp as other methods. The coarseness of the stone being the primary reason.

 

[Jake]

My Tormek gets edges really sharp and it doesn't feel like a delusion.

Delusions never do!

Seriously, Chris said it.

 

[lucky9cat]

LOL . Sorry to highjack this thread, but if one wanted to hone an edge produced on the Tormek, which type and grade of benchstone would be best? I've started to dispense with the secondary bevel and go straight for the final angle in one go. Doing it this way, I find re-honing an edge on the hollow grind very easy to do freehand. I may do a search on "Tormek" and see what's been said about it before.

Ted

 

[Harbo]

The Tormek will grind at 250 or 1000 grade and can then be honed on the leather wheel with the polishing paste.

If your are using bench stones then the generally recommended path is 800, 1200 then a 6000 or 8000 or 10000 grade followed by a final polish with (say diamond) paste on a leather strop or piece of treated and flattened MDF.

But other people's method of choice is limitless as a search on the Forum will reveal?
Wet, dry, wheels, plates, glass, stones, ceramic, diamond, papers etc. etc

Rod

 

[bugbear]

(like any sharpening nut apart from the straight-from-the-Tormek-delusionals) .

:lol: :lol: :lol:

BB, your image does not match the grind I get on my plane blades, possibly because the grind stone I use has 150mm diameter and the rest is positioned level with centre.

Of course not - my diagram is exaggerated to try and make the principle clear. The chord I drew is at 25 degrees, and the amout of hollowing would vary with wheel diameter; an infinite (or very large...) wheel would give a bevel the same as the chord, the smallest possible wheel (which is what I drew) generates an edge bevel which is at zero degrees (tangential). In theory at least, there's nothing to even put a secondary bevel on!

BugBear

 

[Jake]

In theory at least, there's nothing to even put a secondary bevel on!

Until the first stroke on a stone, even angels can't dance on it.