problem with edge chiping during sharpening

[ronald mccormack]

Hi all, I was hoping someone can shed some light on a problem I'm having that I've never encountered before. I made a blade for a half round moulding plane and when I sharpen it the edge chips. Basically as soon as the wire edgeforms is when the chips develop. Could it be I didn't temper the blade enough? If it matters I use water stones and the bevel angle is 25 degrees. I've made a lot of irons and haven't had this problem before.

[David Weaver]

Either the angle is too shallow or the edge is just too hard regardless of the angle (unless you go really blunt). If you're using 01, did you temper it to 350 or more?

It could also be starved of carbon right at the edge, but that's usually not that much of a problem unless you left it soaking at high heat for a long while.

[Mike Henderson]

I had that problem a while back and it was because the edge was too hard. Once I ground the edge back with a few sharpening, the edge was okay.

Mike

[ronald mccormack]

I tempered at 380 for an hour and 20 minutes and no I didn't leave it to soak to long. I guess I'll try retempering. Should I do the same temp or increase a little. It is o1.

[george wilson]

Maybe you got it too hot while hardening. It's possible to BURN the steel. Try tempering it after sanding with fine wet or dry. Temper it to a dark brown color. 350 isn't very hot for tempering. But,how sure you that you got that hot? Using a kitchen oven is VERY unreliable. They can be 75º OFF.

I suggest you rely upon the dark brown color,and not some gauge you might be reading. I use a toaster oven with an accurate Brownell's Gunsmith high temp thermometer probe in it. And,do let it soak longer. It takes a while for the iron to actually get as hot as the oven.

[ronald mccormack]

Yeah I use the kitchen stove and actually I usually set it higher and now that I think of it I did come out a very faint straw. Thanks for the input I'll try retempering. I did try grinding the edge back and same problem.

[David Weaver]

If it's O1, faint straw should be plenty tough to avoid chipping on sharpening. Give it a retemper (put it in the oven for 45 minutes or so, even though it really shouldn't take that long) and see how it comes out.

If that doesn't work. steepen the bevel to 30 or so and give it a shot.