Parks 50 and Post HT Grinding

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Dave Hub

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Dec 10, 2014
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I have been doing a ton of research on this forum and am still unclear on a few (ok a lot) of questions. I have made about 40-50 knives out of AEBL and now I want to try some 1095, 15n20, and maybe 1084/5160 steels. I have a forge and some Parks 50 that I plan to use for my heat treat.

My first question is can I use Parks 50 for the 5160 and 1084? I know it's good for 1095 and w2/w1. If it isn't ideal for these steels, how detrimental will it be if I use it anyway?

My next question is how thin can I grind my 1095 blades before heat treating? Or should I grind post-heat treat? If post HT, should it be after I temper?

thanks for your help and patience.
 
I use my Parks #50 for most steels with no problems. Use it at room temp ... 50-90F. If it is colder, warm it a bit. If it is 100F at your shop, it will be OK.

On 1095, grind the edge to about .030" pre-HT on a blade that is .125" or thicker. On .100" and thinner blades, just grind the bevel post-HT.
Using aluminum quench plates immediately after the quench will pretty much eliminate warp.
Quench the blade in the Parks#50 and count to eight. Pull the blade and set right in the aluminum plates and apply the clamp.
 
Stacy E. Apelt - Bladesmith said:
I use my Parks #50 for most steels with no problems. Use it at room temp ... 50-90F. If it is colder, warm it a bit. If it is 100F at your shop, it will be OK.

On 1095, grind the edge to about .030" pre-HT on a blade that is .125" or thicker. On .100" and thinner blades, just grind the bevel post-HT.
Using aluminum quench plates immediately after the quench will pretty much eliminate warp.
Quench the blade in the Parks#50 and count to eight. Pull the blade and set right in the aluminum plates and apply the clamp.
Click to expand...

Counting to 8 would be like in seconds?

Also, what will the temp of the blade be after counting to 8, if measured with an infrared thermometer?

Thanks in advance,
Constantin
 
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A count to eight will probably take 5 or 6 seconds. Most knife blades have dropped below the pearlite window at 1000F by that time. The temp should be around 800-900F. This is perfect, because the blade is still 100% austenite and as flexible as rubber (almost). It will stay that way until it reaches 400F, and start to convert into martensite. By 200F it is mostly martensite, and the steels you listed are fully converted by room temp. Placing the blade in the quench plates while still austenitic, but below the pearlite nose will allow the blade to harden straight. It will be down to room temp in 60 seconds in most plates, but leaving it for a couple minutes is a good idea.
 
Stacy E. Apelt - Bladesmith said:
A count to eight will probably take 5 or 6 seconds. Most knife blades have dropped below the pearlite window at 1000F by that time. The temp should be around 800-900F. This is perfect, because the blade is still 100% austenite and as flexible as rubber (almost). It will stay that way until it reaches 400F, and start to convert into martensite. By 200F it is mostly martensite, and the steels you listed are fully converted by room temp. Placing the blade in the quench plates while still austenitic, but below the pearlite nose will allow the blade to harden straight. It will be down to room temp in 60 seconds in most plates, but leaving it for a couple minutes is a good idea.
Click to expand...

Thanks again Stacy. Just to make sure I understand, the rapid/most violent part of the quench is critical from the aus temp to below pearlite nose and it's done in the liquid, after that plate quenching like with air hardening steels is ok, did I get this right?

Is anything wrong to use the same approach with O1 steel, to fix a warp?

And if I'm going to generalize this for carbon, oil quenching steels, it is safe to "interrupt" the quench in liquid once the pearlite nose has been passed and temps are below it, is this correct?

Thanks,
Constantin
 
Yes. Once the pearlite nose has been passed you can cool the blade as you wish (within reason). It can hang in cool air, sit in the oil, go into plates, etc. During that time the blade can easily be bent to remove warp and twist. I have a piece of wood that clamps in my post vise. It has slots in it to slide the blade in to twist or bend as needed to straighten the blade. Because the wood doesn't suck away much heat, it doesn't cool the blade much while straightening.

If fixing a warp in a hardened and tempered blade, you can try putting it in quench plates with dowels under and over it to reverse-bend the blade. Do this at 400F. Repeat as needed to get the warp out.
 
Stacy E. Apelt - Bladesmith said:
Yes. Once the pearlite nose has been passed you can cool the blade as you wish (within reason). It can hang in cool air, sit in the oil, go into plates, etc. During that time the blade can easily be bent to remove warp and twist. I have a piece of wood that clamps in my post vise. It has slots in it to slide the blade in to twist or bend as needed to straighten the blade. Because the wood doesn't suck away much heat, it doesn't cool the blade much while straightening.

If fixing a warp in a hardened and tempered blade, you can try putting it in quench plates with dowels under and over it to reverse-bend the blade. Do this at 400F. Repeat as needed to get the warp out.
Click to expand...

Awsome, thanks again Stacy, really appreciated. You are such a wealth of knowledge!

Constantin
 
If you quench deep hardening steels like 5160 in Parks #50, you run the risk the your blade exploding, especially a thin blade. I used #50 for Cru Forge V, but in 1/4 inch cross sections with no ill effect. I tried that with a .85 thick kitchen knife blade and it cracked lengthwise down the spine about 2.5 inches.
 
I use lower austenitization temps on steels like 5160 when using Parks #50. I have never read a clear explanation of why a blade sometimes will split down the spine. It happened a few weeks ago on a suminagashi blade with Blue core. I tend to think that overheating is the cause. I have only had it happen on blades done with forge HT.
 
Stacy, problems with drying wood are similar . You can have a piece of wood split down the center ! This often comes from mixing wood of different thickness Sub critical anneal would certainly minimize the problem.
 
Heh, mete mete , how do you go about sub-critically annealing laminated African Blackwood and Purple Heart?
 
I had some mahogany and hard maple and I needed a small table with them . I said 'you're not going to just glue the two together' . NO we'll have floating panels like other types of furniture . It's perfect , looks great and no panels !
 
Yes, it makes sense that forging the blade and not fully relieving all stress and structure issues may be a cause. I have found this issue most often in san-mai constructions. What is so interesting is the split is exactly in the center. I had one W2 core blade come apart all the way from ricasso to tip. It split about 1/2" deep into the blade. The edge area was fine.
 
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