Cleaning the Blade after Heat Treatment?

[Walt-]

OK I have tried to find out this answer using the search function to no avail. This is my first knife. I have just heat treated a blade of 1084 and oil quenched it. The blade had very little scaly material on it but it turned black. It is in the oven now tempering. What is the best way to remove the black color without scratching up the blade? Is Very fine sandpaper the way to go to get the nice shiny silver color back? Thanks in advance.

Walt

[WynnKnives]

Hate to tell you this but very fine sand paper probably wont clean it off, when I used to oil quench blade this was my least favorite part I was never really excellent at getting them easily cleaned. I switched to an oven, stainless steels, and HT foil, but thats a different page in a different book even.

I don't have any tricks to easily do it besides resanding it, if you got a good hardening and the quench blew most of the scale off, you might be able to start in the 120-220 range.

[NorCal Nate]

220 grit then work your way up. removing all the scratches of the lower grit then go to the next grit. 220, 320, 400,600 etc.

[Tai Google]

If you just clean the oil off real good with lacquer thinner (or even soap and water) and heat some white vinegar in a crock pot or on a hot plate in a non corrosive container (outside because of the smelly fumes), the vinegar will eat the oxides off in a few minutes, along with some soft wire brushing, without doing much of anything to the steel. It's better than sodium bisulfate in that respect.

It won't do anything to speak of about decarb. That needs to be sanded off.

[Ray Rogers]

All of the above, but maybe a better approach is to simply not sand your blade all that fine before HT to begin with. No matter what preventative method you try, no matter what cleaning method you use there will sooner or later be something that will require further sanding (the decarb that Tai mentioned, for instance).

Look at it this way: the HT is part of the process of making the blade. Once you have a blade then you start worrying about putting a finish on it. You didn't put the handle on before HT, did you? Of course not, so why try to put a finish on the blade before HT? Sand it to maybe 220 grit before HT, just enough to get the bad scratches out. After HT you can start at 120 - or maybe 220 if you're lucky - and move forward from there to your final finish.

For what it might be worth, quite a few guys like myself don't do any grinding at all before HT. Doing all the grinding after HT automatically removes all that crud because you get to use your 60 grit belt. It helps avoid any warping that might be caused by an uneven grind AND it automatically removes any pitting and/or decarb that may have occurred.

So, the answer to your situation might well be to change the sequence of steps you are using to something more practical. Think about it: why should we expect a nice shiny piece of steel to be able to remain nice and shiny and smooth even after it is heated red hot and plunged into oil which is pretty certain to burn into crud? That might work out OK but, more often that not, there will be a mess to clean up ....

[Walt-]

Thanks for the great info and quick answers. After the knife came out of the oven and cooled off I went out to the shop and using 400 grit emery paper discovered the black came off with some elbow grease. It will be some work but it is on the way to being cleaned up. Like I said before I am making this knife with files and sandpaper. It is pretty amazing how nice it is coming out with just the most basic of tools. I will post my adventures with the heat treat process after I take a picture of my "forge" tomorrow.

Thanks again folks

Walt

[metal99]

I would love to grind my blades after heat treat but I'm not good enough on the grinder to be able to do that. I always have to correct everything with files after I grind them.

As far as the cleanup goes I have had good luck starting with a good quality wet dry 220 sanding with oil and work your way up the grits like mentioned above.

[Walt-]

I thought about trying to use oil during the sanding. I may give it a go with a higher grit as I am finishing up. Thanks

Walt

[metal99]

I find that using oil really helps make the sand paper last longer and gives a finer looking finish too!

[tuskbuster]

a fine scotchbrite wheel makes shortwork of scale

[Doug Lester]

Sand paper with oil is more polishing than grinding. I grid out to 600 grit with 3M micron belts and either go to a Scot-Brite belt for a satin finish or, if I'm going to etch, I start hand sanding with 600 grit emory paper and WD-40 and continue out to 1500 grit.

As far as getting the crud off I quench the blade in oil then let it cool at least until just slightly warm to allow conversion to martensite to complete and then scrub with a brass brush and detergent before sticking it in the oven. It helps not to bake the crud onto the blade.

Doug

[metal99]

I found that the paper stayed sharper and doesn't plug up as fast when I use oil with it. I noticed that the paper starts to "polish" the steel when it goes dull and the oil prevents that a little bit. I've even had decent results using water.

[Crex]

I'm with Tai on the warmed vinegar to remove scale, but I also take my blades to a 320 finish before HTng. Makes for easier cleanup finish and moving on to the finer grits on the harder steel.
>>>Hundred ways to skin your neighbor's songbird-killing cat.<<<
Try windex or other window cleaner for cutting fluid when hand sanding up to the "polishing" stages. It will cut a little cleaner with less oily mess to clean up.

Play with it all and find what works for you best and easiest, because that's where you will wind up eventually.

[Walt-]

Carl,

The tip on the window cleaner sounds interesting. I would have never thought of that. Thanks

Walt

[Larry Peterson]

I used to send my blades to a heat treat place that "sand blasted" them. They warped so many blades that I no longer use them. My heat treater now used inert gas which cuts down on the oxidation. It is my opinion that heat treating will enhance and deepen the grind furrows so I like to finish the knife to about 400 grit before sending to be treated. This might not be sound thinking, but in my own mind it helps prevent deep gouges and for me it works ok.

Best wishes, Larry Peterson