Thread: I done made me a plane!

Originally Posted by Tools4Me

Ooh, I think you've opened a can of worms there...

Nope - the answer is easy - there are LOTS of optimum bed angles. Just depends what you want your plane for, & which way up you like your blades.

T/T - not sure which bit of the maths you don't get (it's geometry, actually )?

I guess we should establish whether we are talking about 'bevel up' or 'bevel down' blades for starters. Let's go with bevel-down, which I assume T4M has used on his plane.

We will also assume a pretty standard sharpening routine of a 25 degree primary bevel and about 30 degrees honing angle. There is no magic in these numbers, they have been arrived at by trial & error as about the best compromise between a keen edge, & one that will hold up in use. While that varies a bit betwen the different steels used, it's close enough for most purposes. This establishes that the bed angle of the plane must be something greater than 30 degrees, otherwise the secondary bevel is going to ride on the wood, & that won't help its cutting ability at all! To see what I mean, try putting the blade in a standard block plane (~25 degree bed), bevel-down, as I did when I got my first block plane at age 12.

The angle that the FRONT of the blade makes with the wood is called the cutting angle. On a bevel-down plane, with parallel blade, that angle is the same as the bed angle. For SOME purposes, it's considered desirable to have as low a cutting angle as possible, so how to achieve that?

The minimum practical cutting angle for a bevel down plane is just about exactly what T4M put on his plane, i.e. 30 degrees PLUS some clearance, which in his case is 7 degrees. I wouldn't try any less clearance than that, because you will get some 'riding' of the back of the bevel if you take heavier cuts in softer (= compressible) woods.

Now bevel-down planes are different, insofar as the the cutting angle is determined initially by the bed angle, but this is added to by the sharpening bevel angle - adding the two gives the cutting angle. So where has that got us? The lowest practical bed angle on a METAL (not wooden!) plane is about 12 degrees. Add the typical honing angle of 30 degrees, and we have a cutting angle of 42 degrees, just 3 degrees lower than your bog-standard Barnum&Bailey. In other words, the minimum cutting angles for both BU and BD planes aren't a lot different.

So why does anyone bother with BU planes at all? They are more fussy to make, & harder to get nicely bedded compared with the higher angle (= shorter) beds of BD planes. Well, the answer is they DO perform better at some tasks. Just how many things, and why, is the subject of a raging eternal debate, which I would prefer tro keep out of, at least partly because I don't think any of us, (protagonists or onlookers) are in possession of a full set of indisputable facts...

Cheers,

I been thinking about this. I tend to over think this sort of thing and complicate the science. I was thinking that there was a perfect mathematical angle for a plane blade but i guess there is no such thing. But it occurs to me that Tools4me has used his nous to find the most suitable angle. The definition of a perfect angle is what suits the person who made it.

TT
3 scotches in

Originally Posted by Twisted Tenon

...... The definition of a perfect angle is what suits the person [for that particular job] .........

I liked your definition, TT, & edited it a bit to cover all the bases...

But it never hurts to think about thes things (unless your better half is telling you something serious & you are supposed to be giving it your full attention ), & analyse what others have to say, then come up with your own ideas & put them to test. That's the fun of it all, & the way to really learn.

I reckon there is as much subjectivity as science in a lot of what is said about planes (& saws & chisels, etc.) & I'm far from innocent myself. As I've said elsewhere, if you like the idea, or the feel, or the look of a tool, there's a very good chance it will perform well in your hands. I have a choice of high & low & medium angle planes in my kit, but the ones which get the most use by far are my Record # 7 and Stanley #5 & Clifton #4 - all 45 degree bed planes. The others come out for special jobs, which they usually do very well, and I am pleased to have them, but for years I got by in happy ignorance with just a couple of Bailey type planes & my very basic 110 block. If the Baileys wouldn't get the material to a satisfactory stage, there were other ways. For too many years the only other way was sandpaper (which I loathe!), but the discovery of card scrapers (thanks to Tage Frid & an early FWW article) was a landmark in my woodworkng life. At the moment, I'm having a love-in with the little Ironwood smoother I made a couple of weeks ago. I seem to have hit the jackpot with this one, and it outperformed the Clifton on some (unknown) fiddlebacked wood I am using for a small cabinet, atm, but it is a bit of a fiddle to set up just so, and because of the high bed angle (57.5) will need more frequent sharpening to stay at its best. So I'm not about to part with the Clifton!

If I was sent to a desert island, & allowed only one plane, it would be my trusty old #5, which can do most things well, given a chance. Those who'd take a BU plane with a couple of differently-ground blades would be smarter, perhaps (but cheating?). However I reckon I would be happier with my old general-purpose workhorse. Besides, since I'd be doing everything by hand, I would be selecting my wood very carefully!

OK, enough philosophy - let's just make some shavings......
Cheers,