Thread: Correct colour to quench steel to harden

Yeah, I know we've been thru this dance a hundred times. but I can't find any posts that explain it simply.

Could some kind person just tell me what colour to take the steel to before quenching, please?

I've just made three lathe tools from old files, I successfully 'annealed' them (this is getting rid of the hardness, yes?), have fashioned them and made handles. I now just need to harden them.

Intend to only (if possible) harden the last 20mm or so.

From memory you go to cherry red?

I'm running our of charcoal for the forge, so want to try shoving them in the pot belly. Not sure if it will be hot enough, and they are bloody great lumps of steel, stock was a 16mm square section file.

Dull red is good enough then quench them
anneal to light straw

Light cherry red then quench to harden it; clean the surface with emery to see the steel underneath; reheat to tempering colour at the tip, which for a turning tool could be straw-dark straw, then quench again.
I'm sure Schtoo and others have posted more detailed approach somewhere!

Cheers

Thanks Bob and Andy. To my surprise, the pot belly got it up to nearly cherry.

After I cleaned it off, the file I tried just skated off the surface. Must have worked

Gotta have a win once in a while.

Skating file?

Puuurfect!

(However, I tried this last time, and the file bit. How was I to know the particular file was up near HRC 67?!?, of course the freaking thing bit...)

But, now it's hard you will need to temper it too, otherwise the first bit of hard stuff you hit in the lathe will make that edge shatter like a glass hit with a bullet.

My latest trick to temper is to take an old deep fryer I had kicking around that has a thermometer in it, fill it with old cooking oil and deep fry the stuff. Seriously...

The O1 I have says to temper at 170-190 for HRC 62, and that's where the deep fryer says things should be cooked. I go a little higher for things that need to be softer, but no more than 220.

Example, a small pig sticker I made was done at 220 and the edge doesn't roll, and doesn't chip.

So, we got hot oil, and I just leave them in there so they are suspended in the oil once the temp has stabilized. Kill the heat and leave them alone for 5-10 minutes. Pull the stuff out, and drop the whole shebang (AKA old sieve) in cool oil till it's cold again. Crank up the fryer to tempering temp and fry them all again. And leave them there till it's all cold. Do this again if you want to get all serious, but a double temper is sufficient for most things. So is a asingle temper, but a double or triple temper makes things a little tougher, without sacrificing valuable Rockwell points. (Plus it is highly recommended with the Starret O1 I have, junk that it is...)

Maybe not stricly kosher, but it's simple, you can't draw too much temper and it works! Once they are cool, give them a scrub with soap and water, quickly take off most of the crud with something gritty and stick them in citric acid to clean them up again.

It must work, because I have a beautiful plane float that's just soft enough for the good files to bite and sharpen (while sacrificing one corner of the file after one sharpening), but harder than the crap files.


One last little thing, if you are not sure what temp to take the steel up to for hardening, stick a magnet to it when it's hot. If the magnet sticks, make it hotter. If the magnet does not stick, throw it back in for 30 seconds and then quench. Never fails on old school (water or oil quench) steel.

Oh yeah, use the pot belly to anneal. It will get hot and stay hot which is perfect for annealing. That, or drop the bits in a pot full of planer shavings, and keep it filled up as the shavings get burned.

My latest trick to temper is to take an old deep fryer I had kicking around that has a thermometer in it, fill it with old cooking oil and deep fry the stuff. Seriously...

......cook up some lunch while your at it.

Have you had a chance at that dovetail blade.

You haven't given it a miss have ya ?

Schtoo

Sounds like a foolproof method. Seems that getting the correct temperature is the hard bit, and the fryer thermostat makes it easy.

Why old oil? The steel to be tempered is probably cleaner than the fryer, so I'm going to cook up the scraper today.

Here's a colour chart, or two.

http://www.woodworkforums.ubeaut.com...ghlight=temper

Thanks Clint, but I found these on a search before I posted. They display the colour changes very well, but to my idiot eye they assume one knows what colour one wants for the treatment. I didn't.

I currently have the scrapers cooking, HI is Outdoors at the moment.

I'll post some piccies of my homemade lathe tools, later this AM when I've finished frying them.

Jake, nope I have not forgotten. Just no so easy combining a heavy skew on the bed and a skew on the blade to match up well and have it still skew into the corner of the dovetail...

I did make a woody up a little while ago that had fatal flaws in it, and it did slice a DT very easily. Helped me get my head around what's important and what isn't at least.

The blade(s) are already made, they were the first to get the KFC treatment.

That, and I have a brazillion things going on that I just can't leave alone. I have a nasty habit of 1/2-3/4 finishing something, then moving on to something else, and not really cleaning up in between. So things get lost and misplaced, and I then have to remake them, etc, etc.

Explains why I have lots of things in the works, but not much in the way of output, unless I manage it start to finish within 5 hours.

I posted the piccies in the Wood Turning Forum. Seemed more appropriate.

Thanks all

Schtoo, get on to Jakes thingo, he needs it bad!