Sharpening the plane iron: the back face
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I’ve just recently completed the restoration of my first hand plane, a Stanley No. 5 that I got off eBay for twenty dollars. It was a lot of fun “making it mine,” following Paul’s techniques. And I managed to get the iron relatively sharp. I’m sure with practice, I’ll be planing like a pro.
My question is about sharpening the plane iron versus something like a chisel. In Paul’s chisel sharpening video, he stresses getting that mirror-like finish on the back face of the chisel. This means that when the back face and the bevel meet, you’ll have the ultimate sharp edge. Is the same true when sharpening a plane iron? Do I need to start by getting the mirror finish on the back face before actually honing the bevel?
Granted, this is my first plane, and my first time actually sharpening a hand tool by hand. But it seems I’m really having to force the plane through the wood (3/4″ edge of a pine board).
Thanks for your tips.
-Mark
I don’t believe it needs to be as polished as a chisel?
Did you strop the iron? I managed to round over the edge on my iron on the strop, and the blade just skidded over the wood.
Have a look at Paul’s Q&A 6 video, he talks about this problem.
Regards,
Darren.
7 November 2016 at 5:17 pm #142259I would say strop it glossy. It really does not take that long to do it and once done, you will not have to do it again.
7 November 2016 at 6:23 pm #142265The flatter the better, where the back meets the edge. Get the back flat and shiny for the last 1/4″ or so, towards the edge. The rest of the back will be hidden behind the cap iron anyway and does not matter. And also have a look at the cap iron. It should meet the blade without a gap and it is worth polishing the upper side where the shavings slide along.
And, yes, see the video by Paul Sellers, it tells you more details, such as rounding the corners etc.
And be patient. What you consider sharp today will cry out for sharpening soon.
Dieter
There’s more to this question than meets the eye.
Whilst a plane iron cuts wood, it ain’t a chisel. However, the surface of the back section of your iron performs two essential functions:
First, it is one side of the cutting angle so it needs to be as free of scratches and minute surface marks as possible. This is often translated as “polished”, because that is how it appears. You are already spending a lot of energy on polishing the front bevel, so do the same on the back. The good news is that, unlike chisel-backs, it’s only necessary to maintain the surface in this condition for the first ¼ inch or so. If you get the important front bit flat initially, maintaining it on each sharpening is simply a few wipes on a strop.
Secondly, it is the mating surface of the curved tip of the backing iron which needs to sit on the aforementioned polished back with absolutely no gaps at all. (It can help the passage of shavings if the front nose of the backing iron is also polished to reduce friction). So it helps to give some attention to the backing iron, too, fettling it for a good fit.
Next, rounding the corners of your blade to get rid of ‘tram-lines’ is a matter of personal choice, but overdoing it forces the backing iron tip to sit further up the blade.
Hope this helps.
Thanks for all of the great advise. I’ve posted a couple of pictures of the iron’s back face. This is after a bit of time on three diamond plates (coarse, fine then extra fine). My personal assessment is that it needs more polishing. It appears that the polished portion has not yet reach the edge. Also, if you look closely on the half of the face farthest from the camera, about 2-3 mm from the edge, there are some very tiny pits. I assume these need to be worked out? I would appreciate hearing from anyone else about whether I am correct on both counts. Thanks.
-Mark
Attachments:
You must be logged in to view attached files.8 November 2016 at 2:20 pm #142284I know lighting makes things look different, but it looks to me that you need a lot more time on the plates, especially the fine grit. The fine grit does get a fairly polished look on it’s own. If I remember I will take a picture of a iron only sharpened on the fine diamond plate.
Depending on the condition of the iron, I have spent an hour on an iron before and earned a few blisters.
8 November 2016 at 2:43 pm #142287Looking at the photo (hard to tell) it looks like the middle of your plane iron is polished and not the edge which means the middle is higher than the edge. If this is the case I had one similar, it took me hours on the flat stones to get the polished area to the edge. About a week later Paul released a video ( I think it was his plane restoration vid ) where he had a blade which was bellied out in the middle, one well aimed blow from a hammer took the belly out and he was able then to polish the edges in minutes.
……Just had a look. Watch this video, it will help you. Paul starts restoring the blade at 42.00 mins in, he takes the belly out with a hammer at around 47.00 mins.
It will save you a lot of hard work 🙂@putnamm
Diamond plates or abrasives will do equally well.However, abrasive sheets can be expensive and require firm bonding all over to an absolutely flat surface. I would expect good quality diamond plates to be flat enough for your purposes – though I’d advise avoiding cheap ones for this. They wear out quickly and may not be flat.
Looking at the scratch marks on the front portion of your blade, I’d suggest that a previous owner has attempted to remove pitting and gone below the flat-line of the blade. If this is the case, I’d personally admit defeat with this one and replace it. Check it with a flat edge against light to see how much is removed.
The hammer trick works on slight bows on the blade, but it looks as if yours is a bit more stressed than that.New Stanley-type blades are not expensive (go by the width) and they also appear regularly second-hand. Then you need to go through the flattening process again, but just concentrate on the front 1/4 inch.
For what it’s worth, my current sharpening set up for most blades, chisels and planes, is successively medium, fine and extra-fine Eze-Lap plates, followed by a hearty stropping on leather.An alternative I use to leather is a piece of 1” MDF about 10 inches square: lightly oiled on the surface, one half has carver’s stropping compound, the other a well-known metal polish, Autosol. Used flat, back down, this will give a mirror finish on backs.
@howardinwales I’m afraid the scratches are my own fault. I actually began the polishing with abrasive paper (grits 120 to 1500). On the paper, I polished perpendicular to the length of the iron, going side-to-side, because that is how my granite block and bench positions allowed me to do it. And then I took to the diamond plates. (NOTE: This was due to an error in my memory. I thought I recalled Paul using paper and then plates. However, upon reviewing, I realized he advocated EITHER abrasive paper OR diamond plates.) On the diamond plates, I polished moving the iron forward and back parallel to its length (i.e. perpendicular to how I polished it on the paper). I did not spend much time on the diamond plates because I noticed the scratching and stopped.
I would really like to avoid buying a new iron, since the whole reason for this endeavor was to get a usable plane in an inexpensive manner and avoid spending a bunch of money on a new one. But if this iron is scrap, then maybe that’s just what I have to do.
@putnamm
Nothing wrong with a side to side motion – that’s how I do it on the backs of plane irons.However you must, absolutely must, keep the back absolutely flat on the surface. Don’t tip it at all –otherwise you’ll end up with a back-bevel.
Go back to your coarsest grit and just engage the first ½ to ¾ inch in the surface, going sideways. It may help to run an indelible box-marker on the metal to see how much is engaging with the grit. Keep it flat at all times and don’t go to the next finest grit until you have a uniform rub pattern. Ultimately you only need the front ¼ inch polished – not the whole back of the blade; that’s a waste of work.
I think that it’s going to be a lot of rubbing. To stop your grits clogging, use some water or very light oil.
If you still have a bevelled back closest to the edge after all that rubbing, you may consider going to Plan B………
@howardinwales Thanks for the tips. I have no problem putting in the elbow grease to get it where it needs to be. I will go back at it tonight as you suggested and report my results. Thanks for all of your suggestions.
8 November 2016 at 4:18 pm #142292I’m with you on that one, see it through from start to finish, a sense of achievement and lots learned. Your next one will be a doddle 🙂
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