Is your plane as sharp as these?

[sneggysteve]

Start at 2 min 10 secs

https://www.youtube.com/watch?v=zs9X-XzFGHI

 

[ED65]

I presume the link is to a video of a planing competition in Japan?

Few planes elsewhere in the world are as sharp as that! But the good news is they don't need to be.

 

[Tasky]

Seeing that big ol' spear plane just reminded me of Western spill planes...
Would be nice to have my own squad of Taiko drummers to accompany me in the workshop, though!!

 

[Doug71]

Very impressive, do you think they sharpen freehand or use a honing guide..........

 

[novocaine]

how many shavings between sharpening?

 

[ED65]

how many shavings between sharpening?

Good question.

The very amiable easy-planing wood chosen for these contests coupled with the very hard steel most Japanese plane irons have at their cutting edge might lead one to think it could be quite a few. But taking shavings like this must require an amazing edge and it's well known that peak sharpness diminishes steeply once steel meets wood, so it could be far fewer than you'd imagine.

I presume there's loads to read on this in Japanese, less in English. I found this page on Brian Holcome's site, the main body of which is interesting (five or six shavings!) but some of the best nuggets relating to sharpening are in the comments.

 

[Claud1]

Thanks for posting very interesting

 

[custard]

how many shavings between sharpening?

It's an interesting question.

If it was possible to objectively measure "sharpness", and then graph how sharpness declines with use, I'm pretty sure you'd see a curve something like this,

In other words sharpness declines very quickly when you first use a tool after sharpening, but then the decline in sharpness progressively slows down as you keep using the tool. Eventually you get to a situation where the tool is "moderately blunt" and you can keep postponing sharpening without noticing much further reduction in sharpness.

I don't know any of this for a fact (for one thing I've no idea how, outside of a laboratory, you'd objectively measure sharpness?), but it seems to make sense, based on both personal experience and the logical view that as the cutting edge becomes ever more rounded then the blunting forces are being distributed around a progressively larger surface.

If true, and I'm guessing it is, then it explains a lot about sharpening in the context of practical workshop operations. Take these statements for example, which would all rationally flow from this view,

-The more frequently you sharpen the easier and faster each honing is, assuming of course you either use a power grinder to intermittently refresh the primary bevel, or if you maintain tools with just a single bevel.

-It's usually pointless honing to very fine grits unless you plan on sharpening very frequently.

-It makes sense to sharpen immediately before a critical cut, so for example when chopping out a pin board for a dovetail there's a rational argument to chop out all the waste apart from the final few cuts, sharpen the chisel, and then make those final cuts.

-It makes sense to establish a fixed routine for sharpening or replacing planer knives, even if that routine is actually pretty arbitrary.

-It may explain why HSS router bits, which can be easily re-touched in the workshop, still have a role compared to TC router bits.

I'd also argue that it explains why more experienced woodworkers tend to organise their workshops differently to newbies. The experienced woodworker will tend to prioritise a dedicated sharpening station, the newbie is more likely to stuff their sharpening kit in an inconvenient drawer and use the space for something else.

 

[JonnyW]

Thanks for posting the link; really enjoyed watching that.