Camber vs Rounded Corners (plane blades)

[transatlantic]

I know that a camber is useful for squaring up an edge as you can use the curve of the blade to target where you want to remove material.

But in the context of a smoothing plane, where you just want to get a smooth surface, is there any benefit to a camber over rounded corners?

The reasons I ask is because round corners seems easier maintain, and allows you to keep a square edge.

 

[Cheshirechappie]

The rough rule of thumb (which means that some people's practice will vary a bit, or in other words, it's not the Law of the Land) is for a heavy camber on a jack plane iron to give a deep cut, a shallow camber and intermediate depth of cut on a try plane iron for a surface or edge that's flat enough and true enough for the part's purpose, and either straight across or an almost imperceptible camber on a smoothing plane and corners relieved, with a very shallow depth of cut for a smooth, finished or very near finished, surface.

There is some disagreement about try planes. Some prefer the slight camber, others prefer the straight-across. As with so much in woodworking, whatever works for you ....

 

[Ttrees]

But in the context of a smoothing plane, where you just want to get a smooth surface, is there any benefit to a camber over rounded corners?

Absolutely, the ability to plane in any direction is necessary, if working large areas of interlocking grain timbers.
On many timbers you will get deep tearout if the cap iron is not close which makes scraping a huge task and much effort on large areas.
Any rounding of the corners will prohibit the cap irons ability to work.
It needs to be 1 /32" at the least for me, and if that's not working a 64" will do the job.
A no brainer really and has been for the last few century's.

Tom

 

[MikeG.]

The above advice comes from someone who doesn't make anything, but posts endlessly about his pet subject: cap irons.

The edge of the cap iron is straight. The edge of the blade is cambered, you tell us. Tell me how you can set a straight edge close to a cambered edge and still have the numbers given for distance* make some sort of sense. A straight cap iron edge probably relates better to a straight blade with rounded corners than it does to a cambered blade.

*If using a cap iron to control breakout, then the distance between the edge of the blade and the edge of cap iron relates to the thickness of shaving taken, and not to some arbitrary number.

 

[MikeG.]

...... a heavy camber on a jack plane iron to give a deep cut ....

Really? Scrub plane.....sure, absolutely. But I personally don't equate a jack plane with a scrub plane. And being a jack-of-all-trades, a jack plane has smoothing roles to play as well as flattening/ stock removal roles, so a deeply cambered iron might not be the best plan.

 

[thetyreman]

yes round the corners very slightly, this prevents track marks so perfect for smoothing planes, just a gradual lift is all that's needed, maybe 5-10 strokes on each side should do it. I round the corners on all my plane blades including the no7 jointer and no5 1/2 jack.

 

[Ttrees]

The measurements given is from the centre of the iron.
You will never get close to this if you take the corners off your iron.

 

[Ttrees]

*If using a cap iron to control breakout, then the distance between the edge of the blade and the edge of cap iron relates to the thickness of shaving taken, and not to some arbitrary number.

That's not true

 

[AndyT]

All you need to do is develop a nicely dished oilstone and you can automatically get a cambered edge whenever you want one.

 

[MikeG.]

The measurements given is from the centre of the iron.
You will never get close to this if you take the corners off your iron.

Total and utter twaddle. This displays an enormous ignorance of straightforward geometry. Let me draw it for you:

Black is the cap iron, red is cambered, green is rounded.

 

[Ttrees]

Thats an enormous camber mike where did ya pull that from?

 

[MikeG.]

*If using a cap iron to control breakout, then the distance between the edge of the blade and the edge of cap iron relates to the thickness of shaving taken, and not to some arbitrary number.

That's not true

I'll take the word of someone who actually uses a plane over any theory you espouse, thanks very much:

[youtube]xmDVa5cxq8w[/youtube]

 

[MikeG.]

Thats an enormous camber mike where did ya pull that from?

That's a 32nd of an inch, to scale. That doesn't matter, the geometric principle remain the same whatever the camber.

 

[Ttrees]

I suggest a look at Davids videos for anyone who wants more clarity on the subject

 

[MikeG.]

Video? They were handed down to Tom by DW at Mt Sinai, carved in tablets of stone. Thou shallt speak of no other, and none but TT knows the word of the planing god.

 

[Ttrees]

And thou banished his scrapers away to the press! for use now only on curved surfaces once he stopped doubting, this was after spending forty nights in the desert of sawdust.
This is the word from the scriptures.

 

[Doug B]

All you need to do is develop a nicely dished oilstone and you can automatically get a cambered edge whenever you want one.

If only there was someone on here with years of experience of such stones & sharpening techniques who could delineate such information Andy :-k 8-[

 

[Cheshirechappie]

All you need to do is develop a nicely dished oilstone and you can automatically get a cambered edge whenever you want one.

If only there was someone on here with years of experience of such stones & sharpening techniques who could delineate such information Andy :-k 8-[

**chuckle**

This thread seems to have developed plenty of controversy without resorting to discussion of sharpening methods!

 

[Cheshirechappie]

...... a heavy camber on a jack plane iron to give a deep cut ....

Really? Scrub plane.....sure, absolutely. But I personally don't equate a jack plane with a scrub plane. And being a jack-of-all-trades, a jack plane has smoothing roles to play as well as flattening/ stock removal roles, so a deeply cambered iron might not be the best plan.

Yes - really. (Oh - and I did say it wasn't the Law of the Land!)

Those doing their stock prep by planer-thicknesser won't need a jack plane, except perhaps in unusual circumstances. They probably won't need a try plane that much, either, so could take the David Charlesworth approach of using a jack-size plane as a combined try and super-smoother.

One piece of advice that has been given, particularly for someone starting out or for someone needing to keep the kit minimal, is to have just one bench plane of about jack length, but with two blade/cap-iron pairs. One cambered, for heavy stock removal, and one almost straight across (or with a minimal camber) for try and smoothing work.

That's a bit of a diversion from Transatlantic's original question, though. To which the answer is, "matter of personal preference".

 

[woodbloke66]

Interesting discussion but if you use low angle, bevel up planes as I do (and have done for around 15 years now) the geometry of a BU plane means that with a 12deg bed it's nigh on impossible to camber the blade. As you tip a cambered blade (as illustrated by Mike G) from the vertical back to 12 deg from the horizontal it effectively becomes straight. This means that you have to use a straight blade and round over the corners. That said, it's never, ever been a problem and ALL the pieces in the sig block below were produced with a flat edge on all my planes - Rob