Edge Thickness When Hardening , Your Preference?

[Herr_Mingus]

I say u chaps


I was browsing some knifemaker webpages the otherday and was reading that some smiths knock there edges off to about 1/16th thickness before quench to help prevent warpage , personally (quenching in the urine of 100 virgins) i do occasionaly get a bit of a kinky blade (using 01 , is it true ure not sposed 2 normalise 01?) and only slightly blunt my blades before quenching. Does ne one take there edges/tip down to or near as much as 1/16th?

cheers u chaps

:noggin: :noggin: :noggin: :noggin: :240: :noggin: :noggin: :yikes: :noggin:

Nathan

[narsil]

I have left blades with very thick edges in the past but I've pretty much stopped doing it now cos of the huge ammount of efort it takes to sharpen tham again. Now i just make them quite blunt for quenching. I always normalise O1, in fact the data sheet I got from the supplier reccomends it.

[Herr_Mingus]

tnx for ure reply , like u say i thought it would require alot of grinding afterwards tho i may give it ago

nathan

[Underhay]

I have always left just under 1/16 edge when hardening, because all the books I have read and anyone I have spoken to in the past has recommended it.

It is a pain, because you have to remove so much hardened steel afterwards. I tend just do a rough grind to shape the blade, smooth off the deeper grit marks with 80 grit and then harden and temper it. I then thin the final edge down with the belt grinder taking care not to let it heat the blade.

I would love to harden the sharpened blade, but I'm not that brave :yikes:

Duncan

[Herr_Mingus]

eheh thanks for ure reply duncan i will try doing that in future see how it goes

[MushiSushi]

A lot of it, I think is also dependent on what type of primary grind you have ..... I have gone a lot thinner than 1/16th and no warping ... but i have only done this on flat grinds ... if you have a hollow grind then there will be less resistance to warping ..... a flat grind tapers quicker and by the time you have gone back 5mm from the edge you've got around 3mm thickness ... for a hollow grind the difference in thickness to edge is a lot smaller leaving the edge more susceptible to warping.

[Andrew]

When I prepare to harden I always have gone through the proper heat treatment to anneal the blade. With O1 (or the EU equivalent 1:2842) and W1 it also helps. I usually grind the blade fully to shape and finish the blade to 600 grit all over. I charge the blade to a temperature some 200C below the AC1 temperature, hold for 2 minutes to allow to soak then take the blade to AC1. Then immediately remove and quench. In either oil or water. In oil I found doing an interupted martensite quench to be the best with O1. That is to heat the oil to around 90C and quench the blade into the oil. Hold in the oil for 2 min, remove cover with insulation white blanket, allow to cool to 30C and then temper to required Rockwell hardness. With W1 I use water, normally the water is 25C. The blade is quenched rapidly, removed from the water whilst hot and then tempered to the required Rockwell hardness. I found by using this method I can take my cutting edge down to .8 mm slightly thickening at the point to around 1mm. I don't get many broken blades in the water quench now (maybe 2 out of 10). With the interupted martensite quench I had no problems in the last 5 years.

[Kevin]

I say u chaps


I was browsing some knifemaker webpages the otherday and was reading that some smiths knock there edges off to about 1/16th thickness before quench to help prevent warpage , personally (quenching in the urine of 100 virgins) i do occasionaly get a bit of a kinky blade (using 01 , is it true ure not sposed 2 normalise 01?) and only slightly blunt my blades before quenching. Does ne one take there edges/tip down to or near as much as 1/16th?


Nathan

I know at least one maker who forges then forges then hardens/temper berfore any grinding.

Personaly, I take it as far as I can, but not to full sharpness as the edge may burn. Besides, I always think its useful to touch the grinder on the edge after hardening to clean steel.
As to your question about normalising O1... :yikes: ...Any steel you forge, I suggest going through a correct thermal cycling process .

What you may have heard of is that some recommend not 'annealing' certain alloy steels.....maybe O1 is one of these...I think its something to do with carbides and the effects it has on martensite formation..but I cant be sure.

I use 52100 alloy steel....I do not anneal it as my own testing proves to me its not necesssary......

If you had a room full of bladesmiths.....each would have a different opinion :) ....The only way to find out is to do your own experimentation and find out what works best for you.

[Herr_Mingus]

thanks coutel

the discussion on not normalising 01 is on here
http://www.britishblades.com/forums/showthread.php?t=5007&highlight=normalizing

[Kevin]

Mushisushi mentioned it :) .

Experiment and see what works best for you.......

I have formed my opinions from my own testing but its better for each maker to decide for themselves what works best.