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Sharpening tip – Grinding

Posted by is9582 on May 17, 2012 with No Commentsas , , , , , , , , , , ,

I recently damaged an edge of one of my go-to chisels. It hit something hard enough to cause a small chip.  Even though I always check all of my wood for foreign objects, there can still be the odd piece of rock or the like, that doesn’t show up when using metal detectors.

With the chip, I knew my bench grinder would be the quickest solution, as I likely spend too much time trying to work it out at my water stones. I have a decent sized Craftsman bench grinder that is setup for quick handling of my turning tools, but it takes just a minute to shift it over to handle other edged tools. My grinder is an 8″ with adjustable speed, from 1725 to 3450. I’ve had it for a fairly long time, and were I to buy again, I wouldn’t worry about getting the adjustable speed feature. As long as you use a light touch, and wheels that are friable, you’ll likely not damage the temper of your tools. I personally like the new Norton 3X wheels.

Since the chip was fairly small, I set the angle of the rest so the wheel makes contact in the middle of the chisel/iron. I work with very light touch and don’t try to rush the process. Just remember, if there is a mantra for grinding, it would be “take your time”. I keep contact with the tool with a finger, up close to the working area, so i can feel if I’m starting to overheat the steel.

One tip I want to make sure to share has to do with how I know I’m ready to move on to the next stage of the process. I work the chisel’s bevel until I am just a hair’s width from the tip, so I don’t introduce heavy grooves from the wheel, at the tip. If the damage to the chisel/iron is significant, and not just a minor chip, I change my plans a bit. For these, I change the rest so it is 90 degrees to the wheel. Again, I use a very light slow touch, but with this technique I am ultimately blunting the chisel. I remove as little from the front edge, as possible, to get past the chip. After this is complete, I change the angle of the rest to match my intended bevel angle. As always, I will just take it slow and easy, gradually working up towards the very edge of the chisel. When a hair’s width away, I again stop this process, and move to my sharpening stones.

Some ask why I don’t take it all the way to the very edge, and I think that’s a fair question. The wheels I use, and many use, are usually between a 46 grit and a 120 grit. When you are working the whole bevel, and are closing in on the tip of the tool, it takes some time on the grinder. With this, the more time on the grinder represents the chance for more heat build up. The tip being so thin, just can’t stand much heat at all, before potentially starting to lose the temper in the steel. This is the the biggest concern, when working towards the wanted shape, say, after blunting past a chip. If the issue bringing me to the grinder, didn’t require blunting, I’d be more concerned with the size of that grit. If I grind all the way to the edge, I’ll have a lot of extra work on my water stones, to remove the grooves from the wheel’s grit. If I stop just before reaching the edge, I can quickly use my water stones to work the tip area, which is all that cuts anyways. It is all personal preference, and if you’ve already found a different technique that works, I wouldn’t change. For those who are either on the fence, having trouble, or just interested to try something new. give this a try and see if it helps your sharpening process, like it did mine.

Feel free to leave a comment and let me know your thoughts.