Thread: Tips, Techniques and Theory

Originally Posted by Simplicity

........But I don’t understand why there would be any differences.
If you put a piece of timber in your vice at a angle of 20 degrees or something.
Then started planing it,
Would the Lever Cap know any difference? .......

Matt, I doubt the lever cap knows much about what angle blade it's clamping up, but there IS a difference in how the cutting force is distributed into high & low-angle blades. I made this quick sketch to try & illustrate it: Blade vector forces.jpg

This shows a high and low angle blade experiencing the same cutting force at their edges (F). Each blade is clamped near the cutting edge by the same clamping force (C)

Without resorting to a vector analysis (which I can't remember how to do!), I think you can see intuitively that the proportion of (F) that is transferred into the direction of the blade bed (f) is greater for the low-angle blade than for the higher angle. Imagine if the blade were lying flat, ALL of the cutting force would be trying to push the blade back. At he opposite extreme, if the blade was vertical, there woud be virtually no force trying to make the blade slide up the bed.

There should be (& undoubtedly is) a greater tendency for the low-angle blade to be pushed backwards under cutting pressure, reducing its set. What I'm saying is that in practice, it doesn't seem to be a major issue, as long as your blade bed is flat, and the clamping pressure from wedge or lever cap is even & adequate. In neither case does it take as much pressure as I used to think when I started out. I always compare with the pressure you would apply with a Bailey type cam-locked LC, it isn't huge, or it would make adjustment difficult.

As I said above, I have had problems with blades not wanting to keep their set. One was my very first infill, which has a bed angle of 55 deg. and one was a low-angle job with a bed at 15 deg. In both cases I traced the problem to an uneven, slightly convex blade bed. B*gg#r of a job fixing an uneven bed once it's pinned in the plane body, let me tell you! Setting in the rear infill is a job I do very carefully after those experiences!

Cheers,

Ok that makes sense,

Cheers Matt.

Originally Posted by IanW

I made this quick sketch to try & illustrate it: Blade vector forces.jpg

Cheers,

Hi Ian,

The thing that jumped out at me with the sketch is that with the single pin point C you get different rotational forces being applied in the anticlockwise direction by F, the high angle plane should have a higher rotational force that would result in the blade not sitting as tight and potentially more likely to move.

It surprised me researching the Kanna planes just how tight and acurrately adjustable a plane blade could be held in nothing but wood when using a blade only.

Cheers
Phil

Originally Posted by Aussiephil

Hi Ian,

It surprised me researching the Kanna planes just how tight and accurately adjustable a plane blade could be held in nothing but wood when using a blade only.

Cheers
Phil

I hope your research is correct Phil because that is what I am planning on doing - A single plane blade and a wooden wedge.

Cheers
Bob

Originally Posted by Oldgreybeard

I hope your research is correct Phil because that is what I am planning on doing - A single plane blade and a wooden wedge.

Cheers
Bob

Well my research was about the Japanese Kanna planes essentially pre ww2 that used a wooden body and a metal blade, no wedge, no chipbreaker just 2 parts. The blade on those however is itself the wedge and is tuned exactly to the body it goes in.

The concepts though are similar to wooden plane using a wedge, accurate fitment is key, the rest should take care of itself .... and who says a plane with only two or three parts will be simple ....

EDIT PS: i do wonder if the concave surface on the Kanna Plane blades could offer some inspiration for the tradition wooden plane blade anchoring.

Originally Posted by Aussiephil

...The thing that jumped out at me with the sketch is that with the single pin point C you get different rotational forces being applied in the anticlockwise direction by F, the high angle plane should have a higher rotational force that would result in the blade not sitting as tight and potentially more likely to move....

Phil, indeed the rotational force on the cutting tip will be greater with the higher angle blade, independent of the blade retention mechanism.

If you are using a lever-cap, which bears on the blade across a single line behind the cutting edge (or should do), and the blade is not well-bedded at the sole end such that there is a slight gap between the back of the blade & bed near its end, the blade could flex slightly under load. That would ease the pressure at the bottom end, but should increase it under the thumbscrew, although that depends on where along its bed the blade is 'pivoting'. I'm pretty sure an un-flat bed was the source of my trouble with #1. I inked the back of the (lapped) bade & rubbed it over the bed, which showed up several dips & highs in both the wood of the infill & the metal part of the bed. After spending a lot of time (very carefully) filing & re-testing, I eventually had full contact of the blade along the lower half of the bed. After that, no more loosening blade & the plane had a much more solid feel.

Bob, there are many millions of planes that have been able to keep their blades in place very firmly with wedges, I'd say at least a couple of orders of magnitude more than the ones wearing lever-caps! So I don't think you need to fear your wedge won't do the job perfectly satisfactorily. If you are using the 'lamination' technique, at least you can cut & refine the blade bed part before assembly. If the bed is perfectly flat, but you get your pin slightly off-parallel with the bed, you should be easily able to pare a little off until there is even pressure from the pin all the way across. If you "spring" the wedge a little, so that it is applying most pressure at either edd whhen tapped home, I don't think you'll ever have problems with the blade coming loose in action....

Cheers,

Hi Ian. Funny you should be talking about flatness. I spent over an hour this morning trying to remove rocking in my challenge plane. Both the depth adjuster/front of throat and blade/bed connections were assumed to be flat but guess what?....there is flat and there is FLAT! Pivoting of the depthe adjuster is driving me a bit batty but hopefully the re flattened parts will now stop this. It was much improved when I left the workshop this morning anyway.

Yup - believe me, I know the feeling! Nothing I can offer to help, just keep at it, marking the high spots with soot or whatever you are using (chalk for dark woods) & carefully, ever so carefully, refining the fit. It can be a very tedious & exacting task at times, so I tend to work at this sort of thing in short bursts so I can remain patient & not be tempted to rip into it too energetically....

Cheers,

Can't seem to get away from filing! Because of access, I can't use a plane and instead are using the file teeth on the back of one of my rasps. Even got desperate enough to hunt down my feeler gauge set and after cleaning off some serious gunk, used the 0.015mm one to check. Actually quite helpful to find the lumps, may have to remember this

Originally Posted by Mountain Ash

Can't seem to get away from filing! Because of access, I can't use a plane and instead are using the file teeth on the back of one of my rasps. Even got desperate enough to hunt down my feeler gauge set and after cleaning off some serious gunk, used the 0.015mm one to check. Actually quite helpful to find the lumps, may have to remember this

Would a metal file, work, especially a fine cut.
I can’t imagine your having to take too much wood off.

Cheers Matt.

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Cheers Matt.

Originally Posted by Simplicity

Would a metal file, work, especially a fine cut.
I can’t imagine your having to take too much wood off.

Cheers Matt.

I was thinking along the same lines but the rasp I'm referring to (Bahco "Oberg") seems to be just the right amount of bite. Some of my files just seemed to polish

Originally Posted by Mountain Ash

Can't seem to get away from filing! Because of access, I can't use a plane and instead are using the file teeth on the back of one of my rasps. Even got desperate enough to hunt down my feeler gauge set and after cleaning off some serious gunk, used the 0.015mm one to check. Actually quite helpful to find the lumps, may have to remember this

Sorry all. I think my feeler gauge was 0.15mm

Originally Posted by Mountain Ash

Sorry all. I think my feeler gauge was 0.15mm

We’re not going to worry about a 0 hear,

Don’t worry about it lol.

Cheers Matt.