Blade alignment when HT?

[JimDiGritz]

So I've finally bagged a HT oven to replace my old blowtorch setup:

It's not the standard deep Evenheat design, instead as you can see it opens length ways.

I bought it because it was less than half the price of a Paragon or Evenheat, also the chamber is quite large 20x20x40cm (8"x 8"x 15") and my wife wanted a small kiln to get back into ceramics.

The question I have is how best to align the blades when HTing. In a standard knife HT oven you line them up in between small posts/rods and the blade only touches at the spine (which I understand is essentially the least important part of the blade to HT)

Like this:

1. Given that I need to remove the (1095) blades and quench quite quickly, I was thinking of laying the blade flat with the blade running left to right like a shelf on a couple of small firebrick pieces, so I can grab it with blacksmith tongs as soon as the door opens. If I stand it up on it's spine left to right it's going to be really tricky to grab the steel with the tongs, especially with the heat rapidly escaping.

Do you foresee any issues with part of the blade lying flat on and being in contact with a brick? Might it create a weak hot/cold spot?? This isn't something that I can test to get the answer.

2. Given the 855c/1571f temperatures, so you think that the steel might sag or warp if not supported fully across it's length?

I could run some test but 1095 is pretty expensive in the UK and I thought some of you might have experience!!

Jim

 

[Stacy E. Apelt - Bladesmith]

Make or buy a set of right-angle tip tongs, or use right angle tip long handle needle nose pliers. Setting the blade on pieces of brick could cause warps because the whole blade isn't supported.
These are from Blacksmith Depot:

 

[JimDiGritz]

Make or buy a set of right-angle tip tongs, or use right angle tip long handle needle nose pliers. Setting the blade on pieces of brick could cause warps because the whole blade isn't supported.
These are from Blacksmith Depot:

Thanks Stacy, that's good info.

Picking up a horizontal blade in a ready to quench position for my ammo can is harder than I thought.

Those design tongs won't help since the blade will be on it's spine, left to right as you open the oven. I was pretty sure that as soon as I got the oven I'd figure the order of operations out but I'm still staring at it trying to figure out how to quickly grab and quench a blade that is in that position....

I know, I know, if I'd bought the £1,800 purpose built unit I wouldn't have this issue!!

 

[JimDiGritz]

This is a 30cm chef knife in the heating position (just propped up with a bit of angle iron for the photo)

https://flic.kr/p/2mN9bY2

I need to grab it at the tang end, from behind and above to then quench spine first into my 50. cal ammo tin.
To be fair I can angle it so that the tang is more facing the opening, but it does limit the number of blades I can HT easily at once....

 

[Stacy E. Apelt - Bladesmith]

Just make a pair with the 90° bend in-line with the reins. They are called knee tongs. Here they are from Blacksmith Depot:

Knee Tongs

Knee tongs in 3 sizes

www.blacksmithsdepot.com

 

[Natlek]

1. Given that I need to remove the (1095) blades and quench quite quickly, I was thinking of laying the blade flat with the blade running left to right like a shelf on a couple of small firebrick pieces, so I can grab it with blacksmith tongs as soon as the door opens. If I stand it up on it's spine left to right it's going to be really tricky to grab the steel with the tongs, especially with the heat rapidly escaping.

You don't have to hurry with that, 1095 needs fast quench oil not fast hands.

 

[JimDiGritz]

You don't have to hurry with that, 1095 needs fast quench oil not fast hands.

I didn't know that, the guides I've followed so far all say that you need to get the blade into the Parks 50 (I use a UK equiv here) within a few seconds otherwise the steel drops below temperature....

Thanks

 

[Natlek]

I didn't know that, the guides I've followed so far all say that you need to get the blade into the Parks 50 (I use a UK equiv here) within a few seconds otherwise the steel drops below temperature....

Thanks

What is important is to cool steel fast/under one second for example from austenitizing temperature to bellow 1200 F. That doesn’t mean you only have 1 second to get from your heat source to your quench , the steel will retain heat and will survive a few seconds in the air as you move from heat to quench.
Here you will find all reliable data you need about HT of most steel , and more .........

Categories - Knife Steel Nerds

knifesteelnerds.com

 

[JimDiGritz]

What is important is to cool steel fast/under one second for example from austenitizing temperature to bellow 1200 F. That doesn’t mean you only have 1 second to get from your heat source to your quench , the steel will retain heat and will survive a few seconds in the air as you move from heat to quench.
Here you will find all reliable data you need about HT of most steel , and more .........

Categories - Knife Steel Nerds

knifesteelnerds.com

Again as a novice knifemaker this is all really useful.

In my old blowtorch/firebrick setup I was heating to just past non-magnetic (another 2mins ish) and then moving it into the oil (roughly heated using a previous heated piece of steel) as quickly as possible.

I'm trying to get a little more accurate (hence the oven) and this data is really helpful...

Jim

 

[samuraistuart]

Jim, just to add to what Natlek was saying, steels like 1095 and W2 have a very fast "pearlite nose" of about 1 second. What that means is that when you insert your blade into the quench oil, the quench oil must be able to cool the blade from the hardening temp down to ~1000°F in about 1 second. You still have time to smoothly (but quickly) remove the blade from the HT oven to the oil.

I would do anything I could to make sure the blade is not laying on the side, but make a fixture that will hold the blade edge up.

Also, I noticed you mentioned the temperature of 855°C/1571°F. I'm not sure where those numbers came from, but those are approaching normalizing temps for 1095, which should be closer to 870°C/1600°F.
For hardening 1095, you'll want to use 800°C/1475°F with a 10 minute soak, and then quench. Just FYI.

 

[fitzo]

A couple of something like this make for a nice edge-up rack in the furnace:
https://www.theceramicshop.com/product/1669/tile-stand-holds-5/

 

[JimDiGritz]

Jim, just to add to what Natlek was saying, steels like 1095 and W2 have a very fast "pearlite nose" of about 1 second. What that means is that when you insert your blade into the quench oil, the quench oil must be able to cool the blade from the hardening temp down to ~1000°F in about 1 second. You still have time to smoothly (but quickly) remove the blade from the HT oven to the oil.

I would do anything I could to make sure the blade is not laying on the side, but make a fixture that will hold the blade edge up.

Also, I noticed you mentioned the temperature of 855°C/1571°F. I'm not sure where those numbers came from, but those are approaching normalizing temps for 1095, which should be closer to 870°C/1600°F.
For hardening 1095, you'll want to use 800°C/1475°F with a 10 minute soak, and then quench. Just FYI.

Thanks I was referring to normalising, but appreciate the clarification - you are of course right!

I've typically based my data on sources like this SAE AISI 1095 Steel, High Carbon Steel Heat Treat, Properties & Hardness show that the temperatures are:

1095 Heat Treat Temperature
Steel	Austenitizing temperature for direct hardening, °C (°F)	Normalizing temperature, °C (°F)	Full annealing temperature, °C (°F)
1095	790-815 (1450–1500)	845-900 (1550-1650)	790-830 (1450-1525)

Until now I've relied on the colour of the heated steel and getting it 'past' non magnetic.... now that I can theoretically get it to a specific temperature I'm trying to get the science bit right!!!

 

[JimDiGritz]

A couple of something like this make for a nice edge-up rack in the furnace:
https://www.theceramicshop.com/product/1669/tile-stand-holds-5/

Exactly what I need!!! Sadly can't find the same thing here in the UK.... the closest is this:

But I'm pretty sure they're not tall enough and the blade will probably fall over!!

I guess I could carve slots in a fire brick?

 

[JimDiGritz]

Another small question that's bugging me - would you leave the blades in whilst the oven heats up? Or is best practice to wait until the correct 800c is reached then place them in???

Jim

 

[Natlek]

Exactly what I need!!! Sadly can't find the same thing here in the UK.... the closest is this:

But I'm pretty sure they're not tall enough and the blade will probably fall over!!

I guess I could carve slots in a fire brick?

You can make it from stainless steel , like from 316 ? Something like this ,It is for my tempering oven so don t look that thick part in middle in which TC are inserted

 

[Natlek]

Another small question that's bugging me - would you leave the blades in whilst the oven heats up? Or is best practice to wait until the correct 800c is reached then place them in???

Jim

Wait

 

[JimDiGritz]

Wait

Awesome, thanks.

That stand looks nice! I've made do for now by cutting some 1/2inch deep slots in a firebrick so that the blade can lie spine down

Looks good to go!

I'll get the oven up to 800 later and get my first quench with the new kiln!!

 

[Natlek]

Awesome, thanks.

That stand looks nice! I've made do for now by cutting some 1/2inch deep slots in a firebrick so that the blade can lie spine down

Looks good to go!

I'll get the oven up to 800 later and get my first quench with the new kiln!!

You can also use piece of stainless sheet to make one ....something like this one , just cut and bend ?
Good luck with first quench