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T_henry
11-21-2009, 08:37 PM
Hi, I am trying to make the button cutter in Ivan Laws book on gear cutting.
I have some O1 drill rod that I made the buttons with. Well my first attempt at cutting the tool didn't go so well. I didn't get the buttons hard enough.
On this post I read that when hardening when the steel looses it magnetism it is at the right temp to drop in the oil . So what I did was put the button on a magnet over the oil and heated (it was also cherry red) it until it dropped off. So is that correct? Also I tempered by putting it in my oven at 400 for 1 hour.
Thanks
Tim

dp
11-21-2009, 08:49 PM
Sounds like you were also heating the magnet so it's not possible to know which demagnetized first, is it?

Frank Ford
11-21-2009, 09:02 PM
Some folks hang a magnet from the ceiling, and test the heated part as it gets hotter to know when it's reached the nonmagnetic state.

For what it may be worth to you, I harden small O-1 items by using a propane torch, and heating the part until it gets as hot as I can get it - usually bright orange, then dropping it in the oil.

Test it with a file right after quenching and cooling. If the file simply can't scratch it, you're good to go. Then tempering at 400F for an hour will finish the job.

As an interesting alternative for more casual jobs, I've had very good results by using W-1 steel, heating it to bright orange and quenching in oil. That's the end - I skip tempering because it never gets to be truly file-hard. Works for me. . .

gwilson
11-21-2009, 09:05 PM
The magnet should NOT be heated. Some tie the magnet onto a wire,and periodically touch the hot steel to the magnet to see if it stops sticking. Heating the magnet will demagnetize it pronto!!

I just heat the 01 to an orange color,and quench in oil. Vegetable oil or automatic transmission fluid will do. The quench needs to be big enough so that the steel doesn't warm it appreciably. Polish off a face of the tool you just hardened,and slowly and carefully heat it to a medium brown color. If it goes past brown,it may be too soft,and you have to re harden and re temper.

To make a tap,heat the 01 to purple for the temper.

If you got blisters on the steel when hardening,you got it too hard and ruined it. That is called burning the steel.

T_henry
11-21-2009, 09:07 PM
I have one of those magnet pick up rods and held the button on the small end and heated the top, but that could be what happened it just didn't get hot enough. So can I re-harden it or do I have to make new buttons.

gwilson
11-21-2009, 09:12 PM
:mad: Read the post I apparently wasted my time writing. You had better start cracking some books if you want to play with metal and machinery.

T_henry
11-21-2009, 09:40 PM
I was answering Franks post.
What a ass you are.

gwilson
11-21-2009, 09:43 PM
Yes,an ass who tries to help you,and gives you PERFECTLY GOOD ADVICE. Educate yourself.

If you addressed your post TO FRANK,maybe it wouldn't be so vexing to see you still asking a question I just took the trouble to inform you about.

Another god way to educate yourself is to ask how you do something properly BEFORE you do it and ruin your magnet.

Doozer
11-21-2009, 09:53 PM
The temp when the steel looses its ability to stick to a magnet is called the Currie point. Actually if you keep heating the steel more, eventually you will reach a temperature where the steel will again be attracted by a magnet. Google Phase Diagrams for Steel and find some good info.
--Doozer

T_henry
11-21-2009, 10:06 PM
Thanks Doozer and Frank for the help I will try again.

J Tiers
11-21-2009, 11:36 PM
You can use a piece of steel rod between your magnet and the part. Make sure the part is hotter than the steel rod, and it should work OK.

I usually go by color, but there is a lot of variation depending on ambient light, so that can be problematic. I've had parts not harden because I didn't see the color the same as before due to different light. There's a reason blacksmiths forge areas were dark and shadowed. Colors look different to the eye in different lights.

As for the idea of touching to a magnet, there are problems with that, too. if the part is small, it cools off while you are diddling with it and the magnet, and so you may get a bad 'reading". And naturally you may not be able to do the rod trick because the rod gets just as hot as the small part, so you have doubt as to what was really the hotter part.

juergenwt
11-21-2009, 11:39 PM
Henry - you harden O-1 at 1475 deg. F. Sherry red! Quench in oil. Clean with emery and draw to a straw to light brown collor. But do read some books or have someone advise you!!!!!!!!!!!!!!.

Boucher
11-22-2009, 12:17 AM
Being color blind and trying to heat treat by colors is a bummer but with practice one can sort it out. This has allways been a problem for me. The tempra crayons that melt at certain temperatures can be a good work around. I haven't been looking for them but I have not seen them advertised in a while.

lazlo
11-22-2009, 12:32 AM
The tempra crayons that melt at certain temperatures can be a good work around. I haven't been looking for them but I have not seen them advertised in a while.

Any welding store carries them.

boslab
11-22-2009, 02:41 AM
the point steel looses its magnetic property is called the curie point [yes them radioactivity curies the clever things] its 910 degrees centigrade also where theres a transformation to austinite apparently but i;d have to check what.
from a hardening perspective you are well above the upper critical limit an on the way to meltdown!
the next thing to consider is that steel is like a clock, you just cant heat it till it glows then dunk it, though most people do an wonder why thier cutter is lousy
once at a temperature allow the steel time for all the transformations its going through to finish, just because its glowing on the outside dont mean the core is at the same temp so give it a minate or two to settle.
next quench in light oil, not gear oil! dont laugh ive tried it!
keep the part moving in the oil, a tin canfull in not enough, a gallon or 2 is more like it.
have a look at TTT diagrams, these show what transformations atr happening as metal cools, Time Temperature Transformation is what it stands for, you can see from these how to get the crystal structure you want.
a straight quench gives the hardest crystal you can get, Cementite [Fe3C] its glass hard and brittle, but the start point for all the secondary heat treatments, tempering, austempering, martempering, annealing normalising etc etc
if you have ****e colour vision use a tin lead bath to temper, variation of percentages will give you the correct tempering temperature and allow you to soak the item at that temp, water quench usually follows though iced water ,brine, liquid N2 and air last can be applied. oil is too slow to temper quench
mark

Forrest Addy
11-22-2009, 02:50 AM
Manetic attraction may sound real scientific but it's not all that reliable. The Curie point may vary somewhat from the optimum quenching temperature for different alloys. I think the work's color under ordinary light is more reliable. One old metallurgist (Mike Brixen) told me that there a small change in the thermal properties of steel when the carbon goes into solid solution. Circular charts from the older heat treat furnace controller recorders often showed a "hump" at the transistion temperature. You can spot this change by eye alone when the darker red of a heated zone intensifies to bring the whole heated portion to about the same temperature and color. The effect is subtle but very visible to an eye attuned to it.

This is the temperature you're shooting for.

Quench at the moment of transition of carbon into solid solution is not a universal rule. Some steels should be held at heat for some time both to enure uniform heating to the interior of massy parts and to ensure the transition is complete for the chromium, vanadium, tungsten etc before the quench. While it's not a big concern for oil hardening tool steel it should be borne in mind for subsequent projects requiring heat reatment were other alloys are involved.

Walter
11-22-2009, 03:43 AM
Welding suppliers and or McMaster Carr for these.


Being color blind and trying to heat treat by colors is a bummer but with practice one can sort it out. This has allways been a problem for me. The tempra crayons that melt at certain temperatures can be a good work around. I haven't been looking for them but I have not seen them advertised in a while.

gwilson
11-22-2009, 10:52 AM
I haven't used the Tempra crayons,but the Tempra liquid form eats up your metal like acid when it melts,leaving a eaten out,PITA spot to polish out. I quit using it for that reason.

Juergen,I see that we agree on studying some books!