sharpening neophyte with chipped mortising chisel

[Gil Liu]

Hi All,

I ordered a MHG mortising chisel set during a "scratch and dent" sale and a few are chipped at the cutting edge.

I plan to take them with me to a Rockler sharpening class next week, but thought I'd seek the communal wisdom of this group and ask how you would start to repair such damage. I've read about the "Scary Sharp" process and saw a post that there's a Tormek sale going on at Hartville Tool. I don't have a grinder and am not eager to spend much for powered sharpening supplies, but I'm open to suggestions.

Thanks,
Gil

[Zahid Naqvi]

Gil, the Scary Sharp method is based on sandpaper and is used for honing. For a chipped cutting edge you need some sort of a grinder to grind the primary bevel beyond the chipped edge. Unless you have an imminent need to use these chisels I'd suggest you wait until you are in that class. These chisels will provide a good opportunity for you to experience the full cycle of sharpening. I am sure Rockler will have powered grinders that you can use.
Do a search on SMC and you will find plenty of discussions on scary sharp. There are other options to dedicated grinders, since grinding primary bevels on chisels is mostly a one time activity, that is until you drop one. The point is it is done much less frequently, honing is a something that you will need to do real well. As I said earlier just wait for that class and I am sure you will learn and do a lot of hands on work.

[John Schreiber]

You want to return the shape to where it was before it was chipped and all you can do is remove steel. Depending on the size of the chip, really for any chip in a mortising chisel, you are going to have to remove a lot of steel.

It can be done with Scary Sharp. I'd use 50 grit paper and go at it. Keep monitoring to make sure you are maintaining the right angle. Might take an hour or more.

It can be done much faster with a grinder, but you must be very careful to not overheat the edge.

In the situation you describe, I would use my belt sander. You still need to be careful not to overheat the tool, but it doesn't happen quite as fast as on a grinder. Keep a cup full of ice water handy and touch the bevel to the sand paper, then dip it in the water. Eventually, you will develop a rhythm where you can remove steel fairly quickly without making the edge too hot to hold.

Good luck.

[wells conklin]

Gil Please, share your results here because some of the rest of us (like myself!) are looking at the same kind of repairs. And thanks!

[Gil Liu]

Thanks to all for your quick input -- I'll definitely post some follow up and maybe even some pics after the Rockler class

Gil

[Wilbur Pan]

There is only one way to fix the chip -- you're going to have to grind it out. Of the various ways to grind the chip out, your can break them down into manual and powered methods.

Manual methods include the Scary Sharp system, waterstones, and oilstones. The advantage of manual methods is that you have a lot of control over what happens to the chisel. The disadvantage is that it can take a long time to grind out a chip. I've ground out chips from used chisels/plane blades that I bought. One time, it took me the better part of an evening to do this. But it can be done.

Powered methods include grinders, belt sanders, and "powered waterstones" (Tormek, Borg, Jet). Most people seem to choose grinders. The advantage of grinders (and belt sanders) is that it will take care of a chip quickly, and they are inexpensive compared to the powered waterstone type machines. The disadvantage is that they can make the edge of the blade very hot if you're not careful, and ruin the temper of the blade. You can also grind the blade in a way you might not expect because of the speed of the grinder. I'm also worried about the effects of breathing in grinder dust. (I'm a doctor, so I tend to be a little paranoid about these things.)

The disadvantage of the powered waterstones is primarily their cost, and that they are slower than grinders. The advantage is that you don't have to worry about overheating the blade, and they don't go so fast that I feel that I am out of control of the sharpening process.

As for me, I mainly use waterstones for sharpening. I do have a Tormek, but I bought this to deal with turning gouges, which are difficult to sharpen by hand because of the curved profile. I don't use it for chisels or plane blades, except to take a chip out.