Starrett tool steel

[Tim Passmore]

A gentleman gave me a couple of pieces of flat stock steel. They are imprinted with "Starrett Oil Hardening Steel". I'm assuming that this material has not been hardened. Here are my questions: 1. Can I harden it? If so, how? 2. Would this be a good material for making scrapers? I'm sure some tool and die makers out there can assist me----thanks in advance.

[David Gilbert]

The steel that you have is probably (hopefully) O1. It is easily hardened and then tempered and can make very nice tools. All you really need is a MAPP gas and an oven. I think that you could make a scraper but not a large one. The largest size that I would suggest is 3/16 x 1" and you will need two or three MAPP torches to effectively heat up the steel. My suggestion is to test a small piece and make sure that this process works.

Last weekend I helped give a tool making class where we covered this. I pasted in the handout that we used. By no means am I an expert but have successfully made a variety of tools in this way. (I also have advanced degrees and have stayed at a Holiday Inn, so that is all you need!)

Making Edge Tools with O1 Tool Steel Workshop Info

February 7, 2015

O1 Tool Steel Sources: McMaster-Carr http://www.mcmaster.com
MSC http://www.mscdirect.com
Enco http://www.use-enco.com

MAPP Gas: Hardware stores (Yellow can)
Bernzomatic TS8000 torch works well

Quenching oil: Wegmans corn oil (not machine or motor oil because of fire risk)

O1 Steel: Annealed – As purchased, soft, easily cut and machined
Hardened – Heat to bright orange with MAPP gas (1450° to 1550° F) and quench in oil. As quenched Rockwell Hardness is Rc = 63-64
Tempered – Reheated to relieve stress and brittleness (McMaster-Carr)
Temperature Rc Hardness
300° F 63-64
400° F 59-61
500° F 57-58
600° F 54-56
800° F 47-50
1000° F 42-43

Process:


Decide on the tool you want to make.
Select the appropriate steel and layout the design.
Use magic marker or layout fluid to provide a background for laying out shapes. We’ll have Dye-chem layout fluid available.
Lay out shape using scribe, awl, marking knife, etc.
Saw, grind, and file the steel into general shape of tool. The edge shouldn’t be sharp but close to the final shape (~1/32”). If the part is small, drill a hole in it to help you to hold it when it’s heated up.
Hold steel with a pair of vise grips away from where you will heat it. With a MAPP gas torch, heat the end of the steel until it is red hot. As you continue the heat the color will jump to a bright orange and then maintain that color for a minute or two. The recipe calls for heating it for 20 minutes per inch of steel but since we are working with small pieces only a short time is needed. If the piece is large, use two or three MAPP torches.
Once it is heated, plunge it into the corn oil and rapidly stir it around to cool it down. Try to keep the piece submerged until it’s cooled. This will prevent fire. The chances of a fire are pretty slim with corn oil, but they’re not zero. The chances would be much higher with motor oil.
Remove the tool from the oil, wipe off the oil and then clean off the scale that will be on the heated end. At this point test the steel with a file. It should cut the untreated area but will skid off the hardened area.
Once the tool is cooled, place the tool in the toaster oven at 400° F for 30 – 60 minutes to temper the steel (recipe calls for 60 minutes per inch of steel).
Watch the steel’s color as it cooks and remove it at the “light straw” stage. It is possible to temper a tool using a torch by slowly reheating and observing the color change. The toaster oven is easier, takes less skill, and is more reliable. If the tool is too hard, it can be retempered at a higher temperature to give a softer steel.
Remove the tool from the oven, let it cool, then sand and polish.
Sharpen the edge on a grinder or sharpening stone and use your new tool.
Mount your tool in a handle if desired


If you have questions, send me a PM and we can talk.

Cheers,
David

[Thom Sturgill]

David is right on. I would add that you can re-heat and re-harden/re-temper the steel. I saw Alan Lacer a couple of weeks ago at the Florida Symposium doing a demo on making hook tools and he made that point as he only hardens the hook and said that after several sharpenings when there is nothing left to sharpen cut off the end and re-shape, re-harden and re-temper.

He also pointed out that the resulting tool is carbon steel NOT HSS. You need to hone every time you use the tool.

[Tim Passmore]

Thanks David and Thom----I appreciate your willingness to share your knowledge.