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View Full Version : TO harden or not to harden... And best method.



.RC.
07-15-2011, 06:42 PM
My Jafo mill came with no handle for the table X feed so this morning I made up the dog clutch portion, but I only made it out of what I assume is 1020 or 1018. ( I bought it as bright mild steel bar)

Should it be hardened?

I assume the only method for hardening is case hardening, and since the bore has been reamed to fit the shaft would distortion rear it's ugly head?

http://img.photobucket.com/albums/v606/OzRinger/jafohandle006Custom.jpg

http://img.photobucket.com/albums/v606/OzRinger/jafohandle007Custom.jpg

Black_Moons
07-15-2011, 07:11 PM
I would think it would be plenty strong to last a long time. I don't think you would want to harden it after reaming if its a precise fit.

You might find it wears a little untill all the teeth engage evenly, then likey lasts forever if you don't change the engagement

PeteF
07-15-2011, 07:14 PM
Since nobody else has yet commented, my 1.5 cents worth is yes, case harden it.

As far as distortion, NFI, but I wouldn't think it would be a factor on a part like that. Personally to be on the safe side I pre-distort all my parts before heat treatment :p

Pete

Edit: Ah I see BM posted while I was typing.

DATo
07-15-2011, 07:19 PM
I'd just roll with it for awhile and see how it works out. If you find that it is starting to wear you can always case it later. About the only time it will really get any serious wear is if it slips out of mesh while you are raising or lowering the table but I find that that does happen to me a lot now that I think of it. Nice looking job by the way !!!

wierdscience
07-15-2011, 07:25 PM
Carbon case pack would be my pick.

gwilson
07-15-2011, 07:48 PM
Case hardening tends to distort less than tool steels that have enough carbon and alloys to harden all the way through.

Fish aquarium charcoal is one of the best media to case harden mild steel in. I don't know why. Possibly it is quite porous,to generate gas better. Do you have a cast iron box or a small crucible with lids? I have found that just a teeny bit of pressure builds up under a somewhat heavy lid,and drives the carbon into the steel better. When it is red hot,the pores in the steel are much more open to let the carbonaceous gas in.

This has been argued before elsewhere,but it is my own real life experience. Without a heavy lid,I have heated parts for hours and not gotten as deep a case. You decide what's best for you.

I had to harden some mild steel parts for a treadle lathe that I was making accessories for at the Geddy Foundry in Williamsburg. We used a crucible about 6" tall,full of bone meal,which turns into carbon when hot. The parts were placed in the crucible,and I inserted some large nails as test pieces.

Once in a while,while the crucible was hot,I pulled out a nail,quenched it,and broke it open. When the case was 1/32" deep,that was plenty.

Kasenite will not give a case that deep,and it isn't available now,from what I've heard.

The proper thing to do is dump the parts out and let them cool. Then,heat them up red hot again,and quench. Brine is best because it prevents the little gas envelope from forming around the parts,and promotes more uniform hardening.

To make it,dissolve ice cream salt in water until a potato will float in it. The best water is distilled,because you do not know what minerals are in tap water. Tap water seems to work well enough,unless your work is critical.

I don't know why ice cream salt is best,a steel hardening book said it was.

To take some of the brittleness out of the deep case,you can sand off a clean spot, and carefully heat the metal to a yellow color,which is the first color to come up. Old timers called this "taking the snap out of it."

Mcgyver
07-15-2011, 08:20 PM
Of the two, it or its mate, I'd rather have it wear/get the corners rounded than the mate plus its duty cycle and the abuse factor will be much lower in the home shop owners hands than a job shop....I'd have use chrome moly and failing that be thinking hardening isn't worth the trouble. Price if I'm full of it: you make a new one in a x years

.RC.
07-15-2011, 08:26 PM
While I had the setup still the same I went out and zipped up one out of 4140.. I will use it and keep the other for a spare... Setting up the dividing head and cutter height takes longer then actual cutting..

A DRO will be nice on this mill...

A.K. Boomer
07-15-2011, 08:41 PM
What about pickling the GD thing?

like a salt bath nitriding - I don't know what all would be involved - im more or less asking a question:p all I know is its much lower temps than conventional hardening processes (1,000 F) - and its damn tough stuff - Crouts used to (or still do?) use it on their crankshafts and camshafts...

Tell you the truth I like Dato's suggestion best - I built a flycutter out of 1018 or some damn heat treatable stuff but had a friend tell me to try it as is first and there she sits - I thought it would get all marked up due to it being soft but it still looks good.

PeteF
07-15-2011, 08:55 PM
Of the two, it or its mate, I'd rather have it wear/get the corners rounded than the mate ...

That's true. I too had thought that the corners may round, but indeed better this than its mate.

Regarding case hardening depth, I'm about to do some with Kasenit after my cup of tea and was wondering what is the significance of the hardening depth, over and above the basic minimum, if the parts aren't going to be subsequently ground? In this case it's some drawbar heads in 1214 steel.

Pete

.RC.
07-15-2011, 09:37 PM
The way I look at it is like this.... The hardness of steel and it's strength are one and the same... The beauty of case hardening is that you can change the strength of one part of the steel (the outside) but keep the inside less hard, but more ductile.. As we know the harder it is, the less ductile it is.. I am sure someone will point out some technical flaw with the above and that alloy xxxx does not do it but as a rule of thumb I believe it...

Is the depth of case hardening is too small what may happen is when the load comes on to your hardened part it will deform the soft underneath section and cause the hard outer section to peel off so to speak...

beckley23
07-15-2011, 09:48 PM
I've made several dog clutches for handles, like shown, out of 1018, no heat and no problems.
Harry

JoeLee
07-15-2011, 10:16 PM
I have been thinking of T-slotting both halves of mine. This way they would lock in in either direction. That would solve the problem of the darn thing working it's way off when your cranking the knee up.

JL.....................

lynnl
07-15-2011, 10:30 PM
Kasenite will not give a case that deep,and it isn't available now,from what I've heard.



Apparently that's true. i.e. it's been discontinued. ...at least according to Brownells. I also saw another equivalent product "Cherry Red" listed as discontinued by another vendor.

Anyone know why? It has always been described as non-poisonous.

(added) ...never mind. I found a discussion about this from a couple of months back. Was a mystery then, and I guess it still is.
Just our bureaucrats looking out for us I guess.

lazlo
07-15-2011, 10:46 PM
Apparently that's true. i.e. it's been discontinued. ...at least according to Brownells. I also saw another equivalent product "Cherry Red" listed as discontinued by another vendor.

Bizzare -- if you Google "Kasenit discontinued" almost all the links point back here :confused:

Piehl Tool, one of the blacksmith suppliers I frequent, claims to have it in stock:

http://www.piehtoolco.com/contents/en-us/p9738.html

I'll call them on Monday and ask what's going on. I'm wondering if I should treat my can more sparingly? :)

As far as the case depth, it depends on how long you soak it:

Rates of penetration:
After heating the component to 1650 degrees

Case Depth Time
.005 15 minutes
.010 30 minutes
.015 40 minutes
.020 50 minutes

PeteF
07-15-2011, 11:36 PM
Bizzare -- if you Google "Kasenit discontinued" almost all the links point back here :confused:

Piehl Tool, one of the blacksmith suppliers I frequent, claims to have it in stock:

http://www.piehtoolco.com/contents/en-us/p9738.html

I'll call them on Monday and ask what's going on. I'm wondering if I should treat my can more sparingly? :)

As far as the case depth, it depends on how long you soak it:

Rates of penetration:
After heating the component to 1650 degrees

Case Depth Time
.005 15 minutes
.010 30 minutes
.015 40 minutes
.020 50 minutes

Ah Lazlo, that was precisely the question I was going to start a new thread on, now you've mentioned it however I'll continue here. From what I'd seen previously, the recommendations from the manufacturer are to go through the heating/coating/quenching cycle more times in order to increase case depth. However I was just doing some parts then and as I was mindlessly watching the part heat up wondered if the recommendations actually made any sense. It seemed to me to be far more logical that the part would have to be held at the temperature with the Kasenit coated on it for longer in order for it to penetrate further. But I had no idea how long. I was using a MAP torch and it was struggling so I kept the heat on for about 5 minutes and 2 cycles. The parts hardened just fine, but I have no idea how deep the case is (and arguably don't really care).

Which brings me to my next question. I don't have a hardness tester, but my neighbour does. I wondered if they give unreliable readings of hardness with parts that only have a thin case? Or does it depend on the type of hardness tester?

Pete

lazlo
07-15-2011, 11:49 PM
Pete, there's two ways of using Kasenit -- they refer to it as type A and Type B on the can. In the first method, you heat the part up cherry red, paint in with Kasenit, and then reheat it. That leaves a thin, but perfectly usable case.

The second method, type b, is pack hardening -- you bury the part in a box with the Kasenit (or Cherry Red, or a dozen other similar compounds), seal it, and put it in a heat treat oven for X minutes. You can get a much deeper case that way.

PeteF
07-15-2011, 11:58 PM
Ah, it's just another carburising media in "method B"? I didn't know it could be used like that, but it makes sense that it could. There are instructions? :p

I don't have a furnace (but am keeping an eye out for a kiln) so I just use the dip and heat method, it seems to work just fine, but know it's not very deep. I can't see it's very important with things like I was just doing. They're just drawbar bolts so I just hardened to help prevent them getting knocked around too much.

I'm thinking of borrowing the hardness tester, just for a giggle, but suspect with a thin case like this the tester's results will be meaningless anyway. The file skid test is all that matters in this application anyway, but it's nice to file these things away (excuse the pun) for other times.

Pete

TexasTurnado
07-16-2011, 12:07 AM
While I had the setup still the same I went out and zipped up one out of 4140.. I will use it and keep the other for a spare... Setting up the dividing head and cutter height takes longer then actual cutting..

A DRO will be nice on this mill...

Did you use 4140PH (pre-hardened, Rc ~ 30)? That would be my choice for something like this - if you wear that much, then it might be time to invest in a power drive like a Servo.....:)

darryl
07-16-2011, 01:33 AM
A method I've used a few times to harden a part is to have the hardening powder in a container not much larger than the size of the part. With the part held in vise grips and the 'end' of the part heated to cherry, I physically grind the part into the powder using some elbow grease. After a few cycles of reheating and grinding into the powder, I carry on with cleaning, reheating, quenching, cleaning again and tempering.

Obviously not every part can be treated this way. I don't know to what depth the hardness goes, but I've re-sharpened some tools hardened this way a few times and not gone through to the soft core.