Heat Treated Blade from Start to Finish or dud?

[onotoman]

Hi Guys,

I'm quite new to blade grinding, so go easy :-)

About a year ago, a Blacksmith over here in 'Middle Earth' kindly forged me a razor blank. As I didn't have a belt grinder at the time, it sat in my workshop forgotten.

After my new grinder arrived and I did some practice on mild steel blanks, I decided to give the forged blade a go.

It took a really long time to hollow grind - I'm down to about 2mm at the edge now - I know why it took so long.

I re-read the email from a year ago and the blacksmith had hardened and tempered the blade before sending to me :-).

Questions - have I likely ruined the original heat treatment - I have been cooling and using my hand - dipping in water when too hot to handle?

Shall I continue to shape and then finish-grind, or should the blade be heat treated again. I suppose I could just try finishing, honing and shaving?

Any thoughts appreciated

[randydance062449]

My guess is that you have now destroyed the temper thus making it to soft to hold an edge for very long. However, you may luck out. It sounds like the edge thickness is still adequate for another heat treatment and tempering. Then you can finish grind but with a heck of a lot of care in keeping the blade cool.

Good luck

[Substance]

If you have kept it cool with no colouring of the blade it should be ok but
If it has blued it is toast and would need redoing

If at no stage it got hotter than about 200 -230 degrees C (yellowing on clean steel)
I'd continue keeping it cold enough to touch bare hand

You will want to keep the edge at about 1.5mm if HT is needed again

Otherwise either zero grind or get it down to at least 0.1mm (5 thou") or less to keep the bevel narrow

[onotoman]

Hi Guys,

I've just had a thought.

Presumably it's just the tempering that would need re-doing once I get to 1.6mm (1/16 inch) at the edge?

Possible in a domestic oven, rather than sending back to the heat treaters?

[bluesman7]

Hi Guys,

I've just had a thought.

Presumably it's just the tempering that would need re-doing once I get to 1.6mm (1/16 inch) at the edge?

Possible in a domestic oven, rather than sending back to the heat treaters?

No, once it is over tempered from grinding you would need to re heat treat it. You can go down to 1mm prior to heat treating, and if you are going to re heat teat, I would do as much grinding as possible while you don't have to worry about over heating. Do you know what alloy of steel it is? It is possible that you did not over heat it if you never saw temper colors above straw.

[onotoman]

Ah, OK, thanks bluesman7.

I believe that the steel is 01 Tool Steel, but I'll double check with the Blacksmith who made the blank.

If 01 Tool Steel - should HT be 780 to 800 degrees C (how long before quench?) to harden then temper at 230 degrees C for a time?

Also, what grinder speed is good for finish grinding (with least risk of overheating)?

Apologies for so many questions.

No, once it is over tempered from grinding you would need to re heat treat it. You can go down to 1mm prior to heat treating, and if you are going to re heat teat, I would do as much grinding as possible while you don't have to worry about over heating. Do you know what alloy of steel it is?

[bluesman7]

O1 is a through hardening steel. Check to see if you can skate a file everywhere on your edge. Compare the file test with thicker portions of the blank where you have removed some material, sometimes the unground 'skin' can be a little soft due to decarborization. If this all checks out, I would say just finish it. If it doesn't hold an edge call it a practice blade. Your going to want to make another one anyway. Did you ever see any color when grinding? As thick as you still are, I would expect it would have been quite obvious.

[bluesman7]

Also, what grinder speed is good for finish grinding (with least risk of overheating)?

.

I like ~ 900 SFM with light pressure, the slower you go the less risk. Control your heat with pressure and continually moving your pressure point. Keep your bare finger tips directly behind the thinnest pressure point so you can feel the heat. Coarse grits [60] cut cooler than fine, new belts cooler than old.

[onotoman]

Hi Bluesman7,

The file skids off the edge everywhere along the length and also, anywhere else on the blade. I can't really get it to mark without considerable effort.

Once my new VFD arrives (my current one blew) I'll continue and see how far I get.

Thanks again for all the advice.

O1 is a through hardening steel. Check to see if you can skate a file everywhere on your edge. Compare the file test with thicker portions of the blank where you have removed some material, sometimes the unground 'skin' can be a little soft due to decarborization. If this all checks out, I would say just finish it. If it doesn't hold an edge call it a practice blade. Your going to want to make another one anyway. Did you ever see any color when grinding? As thick as you still are, I would expect it would have been quite obvious.

[caltoncutlery]

if it skates a file, then you are probably ok. also if you were to put a quick 400 grit ish finish on the blade, and then etch it in ferric, or vinegar, you would be able to see any areas that were grossly overheated. if you don't see any of those, and the file says its good, then it is likely good.