# curved plane iron edge?



## Anonymous (19 Mar 2004)

Hi all

I have read loads of advice that suggests one should slightly curve the cutting edge of a plane iron when sharpening. Whilst this seems to make sense on one level as it will remove raised edges on the wood at the edges of the blade, it seems to me that the resulting surface may undulate from trough to peak.

Anyone tried this technique on their irons? Results?

cheers

Tony


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## Chris Knight (19 Mar 2004)

Tony,
I am sure Alf will have more to say on this subject which is relevant to your question but FWIW it is generally considered good practice to crown the blades of smoothers like your new 4 1/2. We are talking about a very slight curve only and DC makes it by using an Eclipse type honing guide (with a narrow wheel compared with say the Lee Valley guide) and then pressing first on one side of the blade then the other for about a dozen strokes each side - after he has sharpened the blade level first.

Yes, there will be a very slight trough introduced in each stroke of the plane that leads to a microscopically undulating surface but this is less objectionable than the sharp ridges at the sides of the blade.

I much prefer a crowned blade - because it generally cuts better for me. If you look a blade that has been honed straight across, chances are that after a period of use, the centre of the blade will be worn more than the edges (because it has been used on stcok narrower than the blade. If you then want to use this blade on a wide surface it does not perform very well.


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## Philly (19 Mar 2004)

Hi Tony,
I put a slight curve on my bench plane irons (not my block planes though).
I am talking of a very slight curve here! The main usefulness of this is that it allows you to square up edges by altering which part of the blade is doing the cutting. Sorry if this sounds a bit vague, David Charlesworths "Fine Furniture Techniques" books provide all the info you need on this, and also how to achieve a curve when sharpening.
Yes this does leave the surface with slight undulations, but they are very fine. Leave the surface like this for a classic hand planed surface, or scrape and sand for the ultimate finish. (take a look at the latest issue of Furniture and Cabinetmaker-there is an article by David Charlesworth on just this, it should answer any further questions)
Hope this is of some help,
Philly


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## Anonymous (19 Mar 2004)

Well, I'll attempt to post an answer, but I'm sure Alf will be able to add much more!

Generally, on a smoother (#4 or #4 1/2) the iron is ground and honed square, although it's common to just ease the corners slightly on the edge of your stone, just to avoid nasty tramlines where the sharp corners could dig into the wood.

On a Jack, Fore and Jointer plane, it's considered good practice to grind and hone with a slight convex curve - the amount curve varies between the different plane types and uses. For a Fore (#6) or Jointer (#7 or #8), the curve is generally larger than for a Jack. Perceived wisdom is (and I for one agree) that it's impossible to square off the edge of a piece of wood with an iron that's honed square (at least, impossible if the iron is honed correctly and the plane is being used properly). I could explain further on this, but in a nutshell, consider how you use the plane - the sole is always flat to the surface of the wood. So, if the wood isn't square, the sole won't be square, so with a square iron you'd just be taking off material without correcting the un-squareness of the edge.

As for the Jack, it will produce slight undulations in the surface of the face, but of course you always finish off with a few swipes with the smoother, don't you?! I'm not aware of the reason for the curve on the Jack - Alf? - but I do follow the practice.

So, yes you do set some irons curved, and yes it works, and in fact when edge jointing it's the only way to do things properly!


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## Alf (19 Mar 2004)

Not an awful lot left for me to say really!  

I'd have suggested the latest issue of F&C too, but Philly beat me to it. 

The debate between cambering the blade of smoothers and just knocking off the corners is a hotly contested one. Better woodworkers than I haven't been able to decide, so try both and see which you prefer. I have, and I _still_ can't make up my mind...  One theory against the corner method is that you end up with a scraper at each corner, which can produce a rough finish. In practice this is so miniscule as to be irrelevant I think, but FWIW.

Details of using a cambered iron to joint edges can be found here, but DC's books go into it much greater depth. 

Esp, my take on the jack plane's iron is this: The curve is there for a different reason than a smoother of a jointer. A smoother has one to prevent "tram lines" appearing in the work from the corners, and a jointer's is mainly to facilitate edge jointing (unless it's being used as an uber smoother, but let's not confuse things...) However a jack is there to remove quite a bit of wood in order to flatten the board. You want to take quite a chunky shaving to do this, if you don't want to be all day, and doing so with a square iron is hard work. I can't describe it at all well, but imagine a square iron trying to take a thick shaving, and then imagine a curved one. If you have a chisel and gouge of similar size handy you can replicate what happens, although rather exaggerated. The curved shaving will have the full depth of cut in the middle, but it tapers away to nothing at the edges, while the square shaving has to take the full depth right across its width. I'm not sure the exact proportions, but that's quite a percentage more wood you have to push with every plane stroke. A more extreme example of this is the scrub plane, which takes chips more than shavings, and has a really quite pronounced curve to the blade. Does any of that make any sense? :? It's a sort of trade off between finish and speed in the end I suppose.

Tsk, and I wasn't going to say much too... :roll:  

Cheers, Alf


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## Anonymous (19 Mar 2004)

Cheers Alf - that's kind of what I thought about the Jack.

Personally, never cambered a smoother, just knocked the corners off, as I described. Do you use a smoother for shooting? If so, I guess you'd need a separate iron (square) for shooting?


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## Philly (19 Mar 2004)

Alf,
It pays to subscribe to F+C-you get it at least a day earlier than in the shops, so can scoop your forum buddies on articles.
(that was almost a gloat! :? )
Thanks for posting the link, a picture truly says a thousand words.( or more in my case!)
I've never really understood the "just draw the corners gently over the stone to remove them" approach to plane irons. That can't be a help when it comes to tram lines, a slightly curved iron being the "obvious" answer.
Cheers,
Philly


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## Alf (19 Mar 2004)

Esp, I tend to use a jack for shooting long grain and my L-N low angle smoother (#164) for end grain. I, er, have sufficient jacks not to require a different iron, if you see what I mean...  The 164 hasn't been used for anything _but_ shooting so far, but another blade or two would be useful. One cambered and one ground at a higher angle for noxious woods. Just waiting until I feel the need, rather than just the want! :wink: 

Philly, I _am_ a subscriber! Just didn't log on early enough  DC's article on finishing was a bit of an eye opener I thought. Never given that much thought to a sanding block before :shock: :? :lol: 

Cheers, Alf


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## Anonymous (19 Mar 2004)

Thanks all. I might try it out tonight..

Shocked tha tyou were only the forth respondent when planes were mentioned Alf :shock:


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## Alf (19 Mar 2004)

Tony":24zmbp84 said:


> Shocked tha tyou were only the forth respondent when planes were mentioned Alf :shock:


I know, I know. The humiliation. Obviously I'm going to have to get up much earlier in the morning to beat the rush :lol: 

Cheers, Alf


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## Aragorn (19 Mar 2004)

Alf":15hob2s5 said:


> The 164 hasn't been used for anything _but_ shooting so far, but another blade or two would be useful.


Sorry Alf - I didn't understand that. Don't you mean another _164_ would be useful?

A


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## Alf (20 Mar 2004)

LOL! :lol:


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## Anonymous (21 Mar 2004)

Tried it and it works! Definitely smoother boards and cannot feel any lumps or bumps nor see them

Thanks for the help you lot, much appreciated

Cheers

Tony


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## Steve (22 Mar 2004)

I use a Tormek for my plane irons, which end up square of course. I've often wondered about the slight curve - it certainly makes sense to me. Has anyone got a nifty technique I could use to facilitate achieving this using a Tormek? Would it be a question of 'Tormekking' and then finishing with a few strokes on the stone? 
Any suggestions would be most welcome! (Alf - that was a hint!)

Steve

(PS - posted this under the wrong thread and it was roundly ignored. Are you trying to tell me something people?)


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## Chris Knight (23 Mar 2004)

Steve,

Don't do it on the Tormek. Use that for establishing your primary (hollow ground) bevel then take the iron to a stone and work the secondary bevel on that using an eclipse type guide and pressing down harder first on one side then the other, to maintain a symmetrical condition. Use as many strokes as it takes to put suitable curve on the seconday bevel. Swap to your finest stone and put on a microbevel of perhaps one degree steeper than your secondary bevel.


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## Alf (23 Mar 2004)

Steve":lljlehgo said:


> (Alf - that was a hint!)


No good hinting to me, I'm in a Tormek-free zone  Come back when you acquire a hand grinder :wink: But FWIW, I do as Chris describes. For in-depth to the point of obsessive descriptions of this, you want David Charlesworth really (heavens, I hope he doesn't lurk round here... :shock: )

Cheers, Alf


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## Anonymous (23 Mar 2004)

With Alf here - DC's method seems the best I've seen, and the ruler trick is a good one for altering angles subtly! Mark Finney's book (heavily Stenleyised, but still worth a gander) kinda follows DC's method.

(tormek? wassat then? It got 'lectricicicity goin through it?  )


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## Steve (24 Mar 2004)

Cheers chaps!
I'll give Chris's advice a goodly try and let you know the results. Interestingly, DC has just made a video shot at Lie-Neilsen about this very subject which is available in PAL format. I think I'll give that a spin.
I'm _fairly_ successful with my planes, but it's an area that I know could be improved. I'm a real Tormek fan (it has got lectricicicity goin' through it, but not so much that you'd notice), mainly for my turning habit. The results are unbeatable IMHO. All I have to do is show the chisels to the wood, and it peels away all by itself! Well - almost!
My plane blades _look_ fantastic and cut well, but it's high time I got my head round the curve and started using them properly. It's a part of my technique that's not up to scratch. 

Steve


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## Philly (21 Apr 2004)

Hi All,
Just a late addition to this thread. Found this link on the Gordon Planes site on sharpening a Smoothing plane iron.

http://www.hntgordon.com.au/sharpenings ... gblade.htm

And this one on Jack/ Scrub planes.

http://www.hntgordon.com.au/sharpeningj ... eblade.htm

hope this is of some use,
Philly


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