Hello
After playing with my small grinder I bought (see below) I was finally able to grind my plane irons to 25 degrees (primary bevel) so I can move on sharpening them. Actually, I had to use a little bit of coarsy sandpaper and a sharpening jig at the end, since I am just not able to get completely straight grinded edge of the iron (it looks a little bit woobly directly from the grinder).
My problem is once I get to the sharpening, I start getting camber which I do not want (I did not notice this until I got problems with too narrow shavings). I am not sure what I am doing wrong. I have cheap sharpning jig which I have to grind in order to properly put iron in it. I did not put much pressure on the jig, so the iron is not bent. My fingers are pressing the iron in the middle during the sharpening process. It sits nice but somehow I take more material on the sides. The camber gets bigger and starts “falling” on one side so the edge on the plane iron is just not straight.
How to fix this?
Replies
The wobbly edge is because the tool rest on the grinder is bad. Build a replacement that you can change the angle of in relation to the wheel.
It sounds to me like whatever you are sharpening / honing on is not flat. A description of your process including the stones and a photo of the jig you are using might help.
Here is the small grinder which I changed to suit my needs. I played yesterday a little bit with mounting additional piece of plywood to rest the iron on it. Now, the edge is not wobble anymore, but somehow is the iron still not square. I will try to pay more attention and control on which side I have to take more material in order to have square edge.
Not sure though if square edge is that important, since the fine adjustment will be done on the plane itself once the iron is in.
I hate to say this buy in this case throwing money at the problem may be the solution. I use a sharpening guide from Veritas to sharpen my chisels and plane irons. They have a basic straight holder and setup tool for square blades as well as options for bevel blades and cambered blades. Not cheap but worth it. Here is the deluxe set, but you can also buy the components separately:
https://www.woodcraft.com/products/veritas-deluxe-honing-guide
They have developed a similar system for use with bench grinders as well. The tool rest in their deluxe version controls the angle of the tool as well as holding it square while you slide it across the wheel on a track.
https://www.leevalley.com/en-us/shop/tools/sharpening/jigs-mounts-and-rests/32972-veritas-deluxe-power-sharpening-set?item=05D1201
Adding credence to ct_engineer's post. The "stock" support platforms on a lot of low and mid range grinders are not very precise. I use the Veritas grinder rest he shows and the MK-II honing guide (among many other items) with good success.
Agreeing with the better tool rest - you can make one that is just as good as the bought one.
Some tips, which I find useful:
- A white/friable wheel is better if you can afford one.
- I grade a very slight crown on the wheel so I'm only cutting in the centre. This improves control and it's cooler.
- Don't trust your jig - instead, mark a square line on the blade with a square, and a sharpie. Grind to that.
- The grinder is for bulk removal only. You will need to move onto stones after.
If money is tight, buy a good quality 400/1000 grit diamond stone and a leather strop with diamond paste. If that's too much then wet or dry paper on glass will do.
First make sure tool rest is square to the wheel. Try clamping a stick to the iron that will ride against the grinder platform.
But that may not be the problem.
What stones are you using? Are they flat?
I'm wondering if you use sandpaper for all your honing? If so, it must be adhered to the flat surface under it (not just resting on it) to avoid rounding over slightly anything you sharpen on it. I discovered this trying to flatten the bottoms of my planes with sandpaper on glass (but not glued down.)
So again, we ask what are you using/doing to hone after grinding?
By the way, unless I am repairing a damaged edge, I never grind the actual cutting edge of a tool once it is established. I only grind material back of the cutting edge to speed up honing. Doing this makes it easy to grind evenly because the remaining honed edge is your guide to evenness.
I go through 600/1000/1200 diamond stones, then I go about 50 times on a strop (leather) with green compound. I got pretty sharp edge for a noob, but of course I do not know exactly what sharp actually look like to be honest.
There are lots of methods used to test an edge for sharpness. In wood working, with edges on plane blades, chisels and the like, perhaps the best method is to cut a piece of wood with the newly sharpened edge - having the plane blade out of the plane and hand-held like a chisel when doing so.
The best wood to use in a test is, strangely, not the most difficult hardwood but rather the end grain of a piece of softwood. End grain is harder to cut than parallel (to the cutting action) grain because the edge has to sever all of the wood fibres of end grain. In addition, softwood fibres will distort or bend much more easily under sideways pressure so an edge must be very sharp to cut a clean slice of end grain rather than just put a dent in it or cut badly with lots of "rag".
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Other methods:
Will your edge shave the hairs off your arm? (Be careful)!
Will the edge cleanly cut a page of foolscap paper without hesitation, stall or leaving tears rather than clean cuts?
Lataxe
Yes, I can shave hairs off my arm. The question is of course angle and pressure, but as I saw on YT, yes, I am able to shave without problems.
Also I can cut the paper properly (clean cut). Again, the paper has to be hold properly so the edge will engage properly in the paper sheet, but yes, it cuts.
Preventing camber.
If it's square coming off the grinder camber most usually occurs due to two issues. A quick check with a small machinist square can verify squareness coming off the grinder.
1. "FLAT" sharpening surfaces are a "MUST". If you're using lapping paper or sandpaper the surface below must be "FLAT". 1/4" or 3/8"Float glass or a "Flat" granite stone work well here.
If you're using stones then they have to be continuously flattened with a known flattening tool. Diamond plates or a flattening stone work well.
2. The second issue creating camber is uneven hand pressure (too much on left or right edge) or direction of motion (skewing). It sounds as if you're able to achieve "Sharp" edges but can't eliminate camber.
Try a lighter grip and less pressure when sharpening. You don't need fancy "GUIDE$$$$$". Your hand and your brain are the best tools you have. Most of us use our sense of "Touch", not our eyes, to line up edges with a very high level of accuracy. IBM would train their field tech's to use their sense of touch (no eyes, gauges or special tools) when adjusting the "Selectric" typewriters. The adjustment required settings to be within a couple of thousandths of an inch.
I teach newbies and Ole' timers to close their eyes and use their senses (hand and brain) when sharpening. Your sense of "Feel and control" are much more heightened with your eye's closed. It's amazing how much more precise you can be using this technique. It challenges you to feel the process. It only takes the students a short while to make this work. They mess it up at first but once they get the feel for the process, which doesn't take long, they get started with their eyes closed and open them while they finish. At this point their eyes are not used for feedback or control. Their hand and brain are still in control.
Sometimes a very slight camber can be a good thing to help prevent "Plane Tracks".
I'm not suggesting this technique for the grinder, only for the sharpening process once the grinding is completed.
Good luck to you.
Yes, I tried this and got pretty much straigth edge. I guess I was bending the iron (old thin Stanley blades).
But would you consider a square edge very important? I mean there is always a lateral adjustment on the plane?