Blade heat treating

[Markkdw]

Hi, I'm just getting into knife making and am wondering if anyone on here knows where I can get my blades hardened and tempered please. With me just starting and focussing on stock removal and not forging I don't really have the equipment to perform this myself but would obviously like to ensure the process is completed correctly. I have performed a Google search for heat treating companies but can only really find large scale industrial companies who I'm sure wouldn't be interested in treating a couple of blades.
Thanks

Mark

 

[Mesquite]

Try some of the knife makers on here.

I'm pretty sure you'd be able to come to a suitable arrangement with one of them to get your blades treated

 

[Markkdw]

Great idea. Tyvm

 

[Peter Eaton]

Hi Mark
What steel are you using, if 01 why not try to do it yourself? Its not difficult and you will learn as you do it. You just need to make a small HT oven, even a few thermolite blocks can be used, a blow lamp, a magnet and some cooking oil.

I get my blanks cut now and heat treated in bulk and so grind the steel in the fully hardened state but this is expensive and of course you need a decent linisher and ceramic belts when using hardened steel.

You could also ask Shing Chan as he is doing some Damascus steel I the future for me and will do single blades.

https://shingcrafts.weebly.com/

 

[Broch]

As Peter says it's possible to do this yourself with a blowtorch; it's not as accurate as using a kiln but does the job; there are plenty of videos and articles on how to get to the right temperature.

As for tempering, a modern oven is more than capable of holding 200 to 250C reasonably accurately so you can choose the end hardness yourself even if you get the high temp stage done by someone else (be aware though that after quenching the blade is fragile until tempered).

I wouldn't do much grinding work on a hardened blade - I do as much 'sharpening' before hardening so the edge just needs light honing and polishing. The problem with grinding hard steel is that it gets hot and you've no idea how hot so you don't know the tempered hardness when you've finished; just the way I prefer to work, we all have our own methods

 

[Peter Eaton]

Blanks can be safely ground from pre hardened steel and will not be affected if it is done correctly. Yes, if the blade is ground out without the correct process it will of course loose points of hardness due to over heating but it must be remembered that it would only be in the area that over heated and that will only occur if in excess of the tempering heat to which blank was heat treated. There are fool proof measures to ensure that cannot occur.

Firstly my thumb is on the back of the blank and it would let me know the blade was warm wayyyy before it got to tempering as my skin would burn and the steel would have the tell tale straw colour if the temperature was exceeded.

The majority of the heavy grinding (roughing out) is done on 36-60 grit ceramic belt which are structured to cut fast and keep cool and after each 'sweep' across the belt the blank is dipped water in order the blank is once again cool. The process then carries on through the grits with ceramic Gator belts which once again are structured to cut fast and keep cool.

The finer grits heat up quicker than course grits which is why the majority of stock removal is done on the coarser grits.

Also ditch your metal platen and use a ceramic glass platen as there is a dramatic drop in temperature compared to a steel platen. This will also save wear your belts. I looked into a water cooled platen but most folk are using glass now.

Or use a water spray to cool the blank and belt like Travis Worth advocates, he has plenty of videos on YouTube showing his set up. Personally I regard ceramic glass plattens and dipping adequate for the process and couldn't warrant setting up a spray system.

My blanks are heat treated in bulk in industrial ovens in Sheffield which ensures each blank is the exact same as the next, the last batch I got from another maker who grinds pre heated blanks and were 52100 steel @ 62-3 HRC and Elmax @ 62 HRC. They were exactly the same after grinding as I took them into the laboratories where I worked and they were tested on a Rockwell machine. I sold a blade to a deer stalker recently and he is has so far done 18 Red and Sika Deer with it and it still shaving sharp.

As a matter of interest I was reading the other day about excessive buffing and apparently a blade is more likely to lose 'temper' on a buffer used carelessly than other methods, though this would be right on the blade edge where it is micro fine. Once again the rule of if you cannot put you thumb on the blade or hold it in your hand without pain it is getting too hot.

If your doing lots of blades have a look into grinding pre hardened blanks, there are lots of makers who do , especially in the States.

Regards

Pete

 

[Broch]

To each their own
No criticism intended.

 

[Markkdw]

Thanks for the replies, very informative. I am planning on using 1095 which is readily available from the supplier I plan to use. On their website it says a hardening temp of 800-830°c followed by oil quench then a tempering temp of between 200-260°c is required for 63-60HRc respectively so the tempering wouldn't be an issue in the wife's oven (when she is out obviously ). I have been reading about 2 brick forges and I do already own a propane bottle and gas torch, if I were to buy some insulation kiln bricks and use said torch do you think I could obtain the 800 or so °C temp I require to harden myself??
Whilst watching some of the YouTube videos I've seen I did come across a reasonable amount about heat issues from grinding and saw them using water to cool after nearly every sweep of the blade across the belt so will probably try a similar thing to protect my hear treat.
Also I read on a post not to grind my blade to it's final thickness until after heat treat, leave it around 0.5-1mm is this correct?
Thanks

 

[snappingturtle]

I use spring steel (old car springs) and take the edge to just under 2mm, normalize then heat treat, I go by colour, and quench in oil then off to the over going by colour again then final finishing cool after each sweep and do the edge by hand.

 

[Stew]

https://bushcraftuk.com/community/index.php?threads/heat-treating-carbon-steel-blades.149653/

 

[Markkdw]

https://bushcraftuk.com/community/index.php?threads/heat-treating-carbon-steel-blades.149653/

Thanks Stew, i maybe in touch soon

 

[Peter Eaton]

https://bushcraftuk.com/community/index.php?threads/heat-treating-carbon-steel-blades.149653/

That's a great price Stew. I might try some of the steels you list and get you to HT them in the future if OK.

 

[Stew]

That's a great price Stew. I might try some of the steels you list and get you to HT them in the future if OK.

Yep, no problem.

 

[Peter Eaton]

To each their own
No criticism intended.

No probs Broch, I didn't think you were being critical. Have a look at grinding in the hardened state as although it is an initial outlay to get blanks cut and heat treated in bulk it does have its benefits. Even if you don't, look into getting a glass platen as it saves wear and tear on belts. Just look for ceramic fire glass on the net and use JB Weld epoxy to bond it to you present platen, of and dull the edges once on with wet n dry to save yourself a cut.

Regards

Pete

 

[C_Claycomb]

Leaving an edge 0.75mm before heat treatment works well for blades that are oil quenched and treated without foil wrapping, especially in simple forges. It is fairly easy to reach and exceed 800degC temperature with a one-brick forge and small propane torch. Two brick is even better. The problem is that the area heated is not large. Bigger burner and larger volume can also get hotter fairly easily. If your edge is really thin it may over heat while you are waiting for the rest of the blade to come up to temperature. You will also get some degree of decarburisation on the surface of the steel while it is at temperature. Start with an almost finished edge (as you can with foil wrapped stainless that is air or plate quenched) and your blade won't cut properly until you have sharpened off that outer low carbon layer.

Good call using 1095 rather than O1 to start with. I started with O1, as do many, and it can be made to work using simple heat treat methods, but it should really be soaked at temperature for over 10 minutes, which is very hard to do without a kiln. I managed an approximation by performing three quench cycles.

Rather a good source for info on simple steels and their heat treatment.
http://www.cashenblades.com/info.html

And for the seriously technical:
https://archive.org/details/Metallu..._Others_who_Heat_Treat_and_Forge_Steel_By_Joh

 

[Peter Eaton]

Leaving an edge 0.75mm before heat treatment works well for blades that are oil quenched and treated without foil wrapping, especially in simple forges. It is fairly easy to reach and exceed 800degC temperature with a one-brick forge and small propane torch. Two brick is even better. The problem is that the area heated is not large. Bigger burner and larger volume can also get hotter fairly easily. If your edge is really thin it may over heat while you are waiting for the rest of the blade to come up to temperature. You will also get some degree of decarburisation on the surface of the steel while it is at temperature. Start with an almost finished edge (as you can with foil wrapped stainless that is air or plate quenched) and your blade won't cut properly until you have sharpened off that outer low carbon layer.

Good call using 1095 rather than O1 to start with. I started with O1, as do many, and it can be made to work using simple heat treat methods, but it should really be soaked at temperature for over 10 minutes, which is very hard to do without a kiln. I managed an approximation by performing three quench cycles.

Rather a good source for info on simple steels and their heat treatment.
http://www.cashenblades.com/info.html

And for the seriously technical:
https://archive.org/details/Metallu..._Others_who_Heat_Treat_and_Forge_Steel_By_Joh

Just looked at the links, some good reading there. Thanks for posting.

 

[C_Claycomb]

Kevin Cashen used to post on Bladeforums, some of the best threads in the Shop Talk area. All about heat treating and metallurgy.

 

[Peter Eaton]

Kevin Cashen used to post on Bladeforums, some of the best threads in the Shop Talk area. All about heat treating and metallurgy.

Thanks, I will have to take a look as often on there. I have often wanted to do a bit of my own heat treating but not sure if I can justify the cost but I also want to turn a few coil springs into knives, maybe I will get round to it some day and when my tendons in my arm aren't screaming at me as the case most times I swing a hammer. I really should have an arm like Arnie the amount of bloody cortisone the doc has put into the tendon )))