Tempering/softening spine on HSS blade

[Natlek]

Can I do that , guys ? I'm doing this knife for a friend who is not so gentle with knives .....it is relatively long blade so it will be good if I can temper spine ? With torch , of course ?

 

[Willie71]

I have no idea if it would work. Interesting question though.

 

[Coy Ranch]

Try only heating the cutting edge with the torch for heat treat?

 

[Natlek]

Try only heating the cutting edge with the torch for heat treat?

It is 3mm HSS circular saw ... already hard as hell

 

[Natlek]

I have no idea if it would work. Interesting question though.

One good thing is that I don t need to worry that I will ruin edge with torch I have no idea how much to heat spine ... maybe even red color ? Well . . . stupid me I have a lot of this saws .....Who stops me to try on cut of pieces I have

 

[Coy Ranch]

It is 3mm HSS circular saw ... already hard as hell

Gotcha. Never used a saw blade before.

 

[Natlek]

Gotcha. Never used a saw blade before.

Gotcha. Never used a saw blade before.

You should try . . . they cut and cut and cut . .. .. . .and cut not for heavy jobs , more for cutting soft things but they stay sharp for extremely long time

 

[HSC ///]

you have some extra blade there at the bottom, why not try a test piece?
as for your real blade, put the edge in wet sand up the spine area that you want oft, and then torch the spine.

 

[Natlek]

you have some extra blade there at the bottom, why not try a test piece?
as for your real blade, put the edge in wet sand up the spine area that you want oft, and then torch the spine.

Thanks for confirming how stupid I m I don t think that I need to protect edge from heat , this thing are tempered on about 450-550 Celsius .... I think that after I try on scrap piece I will do that on this knife before I full cut it from saw and before I grind bevel ? That way I have full thickness on blade and would be safer to anneal spine , I think ?

Well . . . stupid me I have a lot of this saws .....Who stops me to try on cut of pieces I have

 

[Fred.Rowe]

This proves you should read the OP with your eyes open. ha ha

 

[Natlek]

@Fred.Rowe , tempering range is 1025-1050°F (552-566°C) for most HSS steel ?

 

[Willie71]

@Fred.Rowe , tempering range is 1025-1050°F (552-566°C) for most HSS steel ?

This is why this is an interesting question. These steels have a secondary hardening hump, which makes them more brittle. Will a lower temper under the martensite embrittlement range do anything for toughness?

 

[Natlek]

This is why this is an interesting question. These steels have a secondary hardening hump, which makes them more brittle. Will a lower temper under the martensite embrittlement range do anything for toughness?

When I finish my tempering oven I will make some test with this steel. I just tried with big torch two piece ...one on the left I heat /one corner to red color / Now file can make scratch easy anywhere and I can t break it . Piece in the middle I heated far more then left one . Funny , I barely managed to break it ?? It bend a lot and come straight ? got some elasticity , it bend double compared with regular HSS steel before break ? Piece on the right are regular one , break with little effort .So I think that with acetylene torch I will get what I want . . . ? I wish I can know heating temp . on second piece .....

 

[Fred.Rowe]

@Fred.Rowe , tempering range is 1025-1050°F (552-566°C) for most HSS steel ?

Thanks. I went back and read the original post.

 

[Natlek]

This is why this is an interesting question. These steels have a secondary hardening hump, which makes them more brittle. Will a lower temper under the martensite embrittlement range do anything for toughness?

Willie71 , I will quote you again You mean after hardening to temper on lower temp , or on my problem ? I have this two thing available tomorrow for temperature measurement , one is infrared thermometer , temperature range using infrared: –60 to +625 °C . Another is thermal camera.......temperature measurement range of –20 to +600 °C
accuracy ±2 °C .
Which temperature you suggest me to try ?

 

[Willie71]

Willie71 , I will quote you again You mean after hardening to temper on lower temp , or on my problem ? I have this two thing available tomorrow for temperature measurement , one is infrared thermometer , temperature range using infrared: –60 to +625 °C . Another is thermal camera.......temperature measurement range of –20 to +600 °C
accuracy ±2 °C .
Which temperature you suggest me to try ?

I don’t know what to suggest. Tempered martensite embrittlement is the 500f to 700f Range iirc. (Look it up to be sure though). I don’t temper above 450, or below 900f on any of the steels I use. My questions are: for a steel that has been hardened and tempered at 1000f, causing secondary hardening, would tempering the spine at 450 create more toughness? Secondly, how hot would you have to temper to soften HSS to create extra toughness, 1100f, 1200f? Before you get into annealing temps.

I don’t know. It seems like an interesting problem to seek answers for.

 

[Larrin]

Tempering is a one way process. You can't temper backwards.