Wednesday, October 21, 2015

About the sharpness levels required on moulding planes

My next posts about using them (building a moulding stick jig and making a Linenfold panel are currently in the holding pattern.  Heather is back at home having completed her first round of palliative care radiations.

She is having all kinds of side effects from it, none pleasant, but it should go
away within weeks to months, no two people being the same.
So for now, I'm playing nurse to her and don't get much shop time...

In the mean time I want to address a conversation I'm having with Ralph regarding how shiny these blades should be...

Like I said earlier, these H&R comes in a varieties of slightly modified forms:
- Various bedding angles (pitch) from Common (45) to Half pitch (50) all the way to York (60)
These various angles are to better address the types of wood you are working with.
The British planes, perhaps because their furniture makers were using more often exotic woods brought back from the "empire" and beyond (Think Mahogany, Rosewood, ebony etc),  made theirs with higher pitches (50 to 60) than the North American makers, who made theirs more often at common pitch (45 ish)
Look at the angles found on a small samples of mines.

Ralph reported that the one he is sharpening is working so so in pine but make beautiful work in cherry, and has some issues in oak (normal since being more stringy).  That would be normal. That one currently with its pitch angle, sharpening level on his blade (he like them shiny), and its bevel angle all are apparently currently tweaked to work better in close grain hardwood (Maple, Birch, Cherry etc).

So what can you do different to make it perform better in say, softer woods like pine or stringy woods like oak??

First understand that some of the criteria's affecting its results are fixed (like the pitch of the blade and the blade being straight or skewed.

That leave us with only two other variables:
- The sharpness level on the blade, and
- its bevel angle.

So back to the original question: Just how sharp should you make it?
Sharper fix a multitudes of sins, but in this case, it cannot overcome the plane limitations (up to a point).
That leave us with the realization that you would need either a different pitch plane, or using a skew iron one.

Doing some research on line, I saw some advocating sharpening their moulding plane's irons to a bazillions grits (talk about shinny, should use sun glasses :-)

In my experiences, it does not make much differences. The higher the pitch, the more of a scraping action than cutting. What is more critical is how durable that edge is. That's why the blades came originally at various bevel angles between 25-30 degrees.  A lower bevel angle, bedded at a lower angle, translate into more of a paring action, I.E. it cuts easier, but the edge is more fragile and can crumble faster if used in harder woods.

Conversely in planes with higher bed pitch (toward York) the scraping action is murder on the edge, hence why the bevel angle is raised higher toward 30 to beef up behind the edge (more resistant).


A higher polished blade is going to stay sharper longer, because the level of shininess indicates less visible scratches, it should crumble slower.

But, the problem with high level of shininess is that it can easily mask a subtly rounded edge...

Understand that sharp is simply two FLAT surfaces mating with ZERO thickness. Of course that is impossible to attain, but when you approach that zero thickness, comes a point when you cannot discern anymore light reflection at the edge, because it is then too narrow to reflect light at you.

You can work for hours raising that edge to a high level of sharpness, and very shiny, just to kill it in one NY minute by poor stropping action, burying the edge in the leather and rounding the end ever so slightly... And you may not detect it, until you attempt to cut wood.

Moulding planes irons profiles poses some challenges sharpening them because of their irregular shapes.  Good news is you only have to touch up that bevel edge rarely after first working on it, you then maintain the edge sharpness by touching only the flat back. Yes occasionally you may have to touch up the bevel to take out chips etc. but not very often if you are careful.

Ever notice that a stock scraper profile is cut almost straight across with a file, then sharpened simply by working the flat faces?  We take a similar approach with our moulding plane's iron.
ALWAYS TAKE CARE NOT TO change the profile of the cutter while sharpening, work on the flat!

When I originally sharpen mine, I start with 220 Grit sand paper, then move on to my diamond paddles (black and red) and give it a quick strop on a leather strop with LV green compound, that's it! Plenty shiny, (look at the last edge pics on Step 2 initial assesment)   When using them, I will then tweak its edge depending on how it react with the wood.

This is very much like what carvers do all the time.  We stop and strop often our edges, changes the bevel angles as required for the wood and the type of work we do etc.  It soon becomes second nature and you go thru the steps quickly without thinking much about it.  We are talking minutes changes, no drastic modifications requiring grinding a new bevel angle, think micro bevels.
Either that OR change tools for the wood.  That's why carvers have so many gouges/tools tweaked for various jobs in various woods.

Similarly, you may find you need more H&R of various design (Skew, higher pitches etc) depending on what kind of woods you uses.


At the initial stage, work on the bevel, ensuring there is no pitting at the edge, go ahead and flatten the back (past pitting at the edge), polish it to whatever degree you like, but since we are often touching up the flat often to keep it sharp, you should keep using the last grit you use or you will kill all that shininess you work so hard to attain initially.
Of course the higher the grit, the more work to maintain the edge (slower).

SOOOOO, we have to find a compromise between blinding shiny and shiny enough to work and easy to maintain.

Truth be know, moulding planes do not required super sharp edges to work correctly, so don't waste you time going nutso on them, make shavings instead and look at the profile left.  Uses that as the ultimate determination of having achieved the right amount of sharpening for this plane bedded at X angle for this type of wood.

Before you go back and sharpen some more, try different woods, see a difference?   If its better, stick to that type of wood...or...get another plane (pitch, skew etc)

And remember stick with clear grain, straight grain woods.
Working on the edge of wood (end grain)? Good luck with that!!!
Some wood may be possible, but they were never designed for that.
Scraping and sanding will fix that surface left on the end grain.

All that to say, understand the tool and its limitations.

Bob, working at his computer "bench"


  1. I found out the hard way that is very easy to round over the edge of the profile. And we both know shiny or not, round will not make a shaving for you.

  2. Amen brother, all too easy...I know.
    Learned that the hard way too :-)