Another quenching question - too soft

D

DWah

Joined
Feb 27, 2022
Messages
7
Hi,

Found a lot of interesting threads here, while searching information. I'm very unexperienced in this area and have just performed my first tries to harden steel. In this case actually not even a knife, currently I'm trying to create a tapered reamer. Unfortunately a lot of unknown data and unprecise methods, but I was hoping for some tips or at least guessing for next step. I have made the cutting fluits on the reamer and now want to harden it, then I plan to sharpen the cutting edges and finally use to create two tapered holes in a cast iron part. I'm happy if it survives these two holes, I don't need it to be more long lived.

First of all, I don't even know which steel I have used, picked it up from the scrap bin. However, I did perform a grind spark test, comparing with another known steel. The known steel is a low carbon structural steel (S355J2). Grind sparks from this were quite long and not very "sparky". My unknown steel gave shorter sparks, much more "sparky" (more like fireworks). Based on this I assume I have some sort of high carbon steel.

First I created a small "soup can forge" which I heated by a propane torch. Unfortunately this was not enough to generate an even heat for the complete lenght of the reamer. One end got yellowish (and not magnetic), but the other end was clearly cooler. I did try to quench it anyway, in oil (canola oil). Tried it with a file, and not very surprising the cooler end was still soft. The other end felt good though, I was satisfied with the hardness.

For the second test I made a larger forge, heated by coal and blew air through the bottom of the forge (used air compressor). Checked when it was not magnetic and quenched in canola oil again. Tried with the file, it felt quite okay. Couldn't feel any difference between one side and the other, but it felt a little little bit softer than the best side from the first try. However, I judged it good enough and put it in the oven for tempering. Regular kitchen oven, 200 degrees celsius (=392 degrees farenheit) for 1,5 hours. Then turned off the oven and let the reamer stay inside cooling down with the oven. Tried the file again, but now it feelt too soft again...

Today I performed my third try, same coal forge but I believe I heated it up too much. For sure the reamer got warmer than last time. Quenching in the same canola oil. But this time it felt much softer when testing with the file... Could it get softer if heating too much (I would have guessed it should get more brittle)?

So here I stand :) Sorry for a very long introduction. I would really appreciate some tips or guesses for what to do next. Have I destroyed this part or is it possible to perform several heating/quenching operations on the same part? I really want to avoid making a new reamer (an awful lot of time on my manual lathe). What are my best chances to succeed in the next try? Even though I'm fairly sure I heated it up too much this time, I didn't feel any brittleness. If I try to heat it up again, with a magnetic test more often trying to be more correct in temperature - should I go the with the canola oil again or do you think I should try with water instead? All input and tips are greatly appreciated :)
 
DWah said:
Based on this I assume I have some sort of high carbon steel.
Click to expand...
more accurate to say "some sort of higher carbon" which doesn't necessarily mean what's considered 'high' carbon. Sorry.
 
Sounds to me like you should have done additional tests before investing your time. Please understand that it not that we dont want to help , there's just too many unknowns.
In addition to spark test you need a snap test. Heat up to temp above magnetic, quench, the place in vice and try to break off a piece . If it breaks its a hardenable steel BUT it might not have a high enough carbon content to make a reamer. If you have a remenent of the steel you might try this before expending more time.
Did you warm the canola oil before the quench?
You could try another heat treat and temper at a 350f. That should give you a higher hardness. Would it be hard enough to make a good reamer, thats a crap shoot. But i would buy an oven thermometer to double check the ovens temps. Oven temperatures are notoriously off.
 
DWah said:
Could it get softer if heating too much (I would have guessed it should get more brittle)?
Click to expand...
repeated heating and quenching can have complex effects on the structure of the steel. you can also have build up a layer of decarburisation on the outside of the part, which will be softer. that will need to be ground away.

unfortunately without knowing the steel all we can say is to keep experimenting. rather than use the same sample repeatedly do multiple samples at the same time.
canola oil could be ok, if the parts are thin enough, but getting a professional quench oil would remove that variable.

honestly; 1080/1070 is cheap, makes a good knife, and steel is the cheapest part of knifemaking anyway. get some of it.

edit: i would start tempering at 180c, 200c is often a bit hot
 
You have too many unknown variables. Buy or find a known steel for your purpose and then experiment. I would also use a better quench if possible...Brownells tough quench, or something you can get in small quantities for less money. Then you only have to experiment with your forge and temper.
 
Wow, thanks for all response and input. Of course it would have been smarter to get a proper, known, material and for sure I would have been better of also with professional equipment. I could also just buy the reamer :) Which actually is my backup solution if this fails. So, this is more of a "the journey is the goal" kind of a project. Even if it fails, firstly I've learned a lot and foremost: I had really fun doing it. Well spent time in my opinion :)

Unfortunaly I don't have more material which I'm certain is the same, so I can't really experiment with another sample. I did now warm up the canola oil before quenching, rather it was quite could, ca 10 degrees celsius (live in Sweden, that's the temperature in my little workshop during winter :)). Compared with the blade of a knife this is really thick material. It is like a tapered pin, with the small end beeing diameter ca 14mm and the large end being ca diameter 17mm. Since my last try, probably from too high temperature, did not end up in a brittle part - would it be completely wrong to try next quench in water instead? As someone pointed out, this is some sort of higher carbon steel compared with a very low carbon steel. Still it could be too low for satisfying hardening...

Again, thanks for all response, I understand it is impossible to answer with certainty due to all the missing information.
 
Welcome to Shop Talk.
The other chaps have told you a lot, so I will only add that your tempering was also wrong. 200°C was a good temperature, but after the 1.5-hour time was up you should remove the piece and either cool it in water or let it air cool. A slow oven cool is not wise. Then, you need to do a second temper like the first one.

I would suspect the steel type was the biggest issue. You should be able to get a piece of W-1 / T72301 / C100W1 steel at many welding or tool places.
For W1/W2 you can quench a piece of steel the size you are using in 40-45°C brine. Canola isn't a suitable oil for quenching such a large mass of steel.

Fill out your profile. Someone near you may be able to help with steel and proper hardening.

Places like ebay often sell used reamers very cheap. The industrial places dump them when they are a bit dull or worn past specifications.
 
Tell us more about what it's for.

I'd look at
D bit grinding
D bit
D bit grinders
Deckle d bit grinders

I'd start with a hard part and grind it to size

High carbon steel toolbits have been out of style for a hundred years or more.
I'd use HSS High Speed Steel

It will grind with normal grinding equipment.


carbide would need special diamond wheels.

Look at SHARS for the catalogue
There's photos and you can learn the proper names for things.

Home page

Shars Tool
www.shars.com www.shars.com

There are HSS drill or reamer blank rods - in those diameters they will be expensive.
Grind on the lathe with a toolpost grinder
Then grind them flat.

14 to 17 mm
that sounds like 20 gauge shotgun shell size range.
Look at preexisting tools.
Although they will be expensive.

how much taper ?

I'd start by just boring the hole out on a taper and polishing with abrasive paper- or finish with an ID toolpost grinder
How close of a fit do you need ?

If not I would silver solder or silver braze a HSS square lathe toolbit onto a carbon steel tool blank.
then a toolpost grinder to grind the taper and edge on the lathe


get that book and read it
 
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wow 17mm that is like a 5/8 - 11/16 maybe a used drill bit ?? re grind the taper of it for what you need and add the flutes. start with a hardened steel
how about a piece of low carbon steel (Like it sounds like you are using) and weld /braze 2 harder pieces in place to make the flutes for cutting.
after arc /mig/tig welding you could easily shape the 2/3 blades and sharpen .. you say you only need to use it for 2 holes..
another option would be a carbide burr with a taper already on it.. Good luck on your journey to make the part to use once.
 
Thanks for all the input! I will use the reamer to customize a car wheel upright, I will replace the upper ball joint with a tie rod end from another car. The latter one has a larger cone, hence the hole in the upright is too small. I will start using a regular drill bit to get the smallest diameter as close as possible and then the reamer to add the taper. So, correct taper is cruical, should be 1:8 (not too easy to find I’ve realized).

To grind a taper on an existing drill bit may be a way. To use a square HSS lathe tool bit and grind may also work. Actually, re grinding a threading tap could also work, the fluits are quite deep…

However, since I’ve already made the first one I will give it another hardening try and test it. If it fails I could try re grinding existing hss tools.

Again, thanks a lot!
 
Just one more thing… generally, will the steel get softer after each hardening attempt if heated up and quenched multiple cycles? Or does that differ between materials as well?
In my case it has gotten noticeable softer each time, but of course it could be that I was lucky with the temperature the first time…
 
DWah said:
Just one more thing… generally, will the steel get softer after each hardening attempt if heated up and quenched multiple cycles? Or does that differ between materials as well?
In my case it has gotten noticeable softer each time, but of course it could be that I was lucky with the temperature the first time…
Click to expand...
Generally speaking it shouldn't get softer, if you are using the same temperature and time.

Check out www.knifesteelnerds.com for info on heat treating procedures.
 
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