Case hardening question

[cessna]

Hi, I am working on a small four cyl horiz opposed engine ( 1/2" bore ) the plan calls for case hardening the cam lobes before installing on the cam shaft. For an engine that will not be run very much is it really necessary? If so does anyone have a simple method possibly using casenite. Appreciate any input.
Thanks
Terry

 

[gbritnell]

If you're going to go to the trouble of hardening just the lobes I would recommend using W-1 drill rod and harden it. Case hardening is generally done to low carbon steels, 1018 for example. The metal is heated, then coated with Kasenite then brought up to hardening temperature. Once there it is quenched as with tool steels. The only difference is you don't draw out the material after case hardening.
I make all of my cams out of drill rod and leave them in an unhardened state. I harden the cam followers/lifters so that I don't have the same material running against itself. Even with splash lubrication and many hours of running I haven't had any excessive wear on my cams.
gbritnell

 

[cessna]

Thanks for the reply, I have already made the cam lobes from ordinary steel possibly 1018, I was hoping to get away without hardening them, but I have a lot of hours in this project, so I will have to weigh it out.
Terry

 

[Generatorgus]

I would approach this subject with a "How difficult would it be to replace the parts if they do wear out?" attitude. A simple cam on a hit and miss model would be an easy fix, but inside a little tiny 4 cyl? Not to mention the more complex machining.
But I myself, as a real amature, am put off by the hardening task. Heating stuff up sometimes messes things up. I can see why your on the fence.

Gus

 

[Mainer]

I attempted to solve this problem when I made the cams for "Kiwi" by using pre-hardened 4140 as the stock. I never got Kiwi finished to the point of running so I don't know how they would stand up in use.

FWIW I made the rocker arms out of pre-hardened 4142 ground stock, again to avoid (I hope) the need for hardening.

1018 may need hardening of some kind; it's pretty soft.

 

[metalmad]

Hi Cessna
you could just have the Cam chromed Mate.
would only need a few thou to give a nice hard coating.
Might look real nice too. th_wav
Pete

 

[Swede]

Chroming is an option... Kasenit and the like rarely penetrates more than a few thousandths anyhow. The case skin is very thin when the object is hardened according to the typical hobby practice of using a torch. It's hard to hold the heat at the proper temperature for any length of time.

Kasenit is fine for smaller objects. For larger, an oven is best, and kasenit can be used as a pack medium. Better yet, as mentioned... make the part out of tool steel so you can through-harden it. Don't forget to temper.

Regarding the original question, the mild steel cam will work for occasional running, especially if lubrication is adequate. But for any significant running, hardening is required.

 

[jonesie]

using 4142 or p-20 would be and option. when heat treating small thin or cut out parts like a cam or crank it is important to cool them so they to not warp or bend. cans or cranks should be hung to cool. you might have to leave extra material to grind or hard turn after heat treating to get them straight and to correct size. you could also have them flash chromed or nitried as they are only a few tens deep and real hard. using o-i or w-1 cooling then will likely cause them to bend or warp. good luck. jonesie

 

[cessna]

Thanks for your input, much appreciated. I have ordered a can of Cherry Red compound, if nothing else it will give me some experience with the process.
Terry

 

[bob ward]

You would probably have found that your cam lobes, if made from 1018 would have worn surprisingly quickly. Cherry Red works well when hardening mild steel, I've used it myself to good effect. After you have dipped the lobes in the powder hold them at red hot for about 3 minutes before quenching.

 

[Swede]

To add to Bob's comment, something to keep in mind with case (or pack) hardening and through hardening is that the depth of the case, the skin, is dependent upon how long the part is kept at or above the correct temperature. If something like a little cam is held only for a few seconds before quenching, the case thickness won't be more than a couple thousandths, and once that wears away, soft steel is exposed and the wear will accelerate.

So a one-lobed cam for a small IC engine that is maybe 0.500" OD would be best kept at temperature for 5 to 10 minutes, and this can be tricky. Too high and the steel can be harmed.

Also, the Kasenit or other compound melts and forms a protective shell, but any areas subject to dull red heat without the molten salts can oxidize badly - you get black scale, iron oxide, that can be up to .005" to 0.010" thick; it'll flake off and ruin fine dimensions if care is not taken. It looks bad, too. So gob that stuff on there as the part heats up, and add more during the process. The part will look like a badly crisped BBQ item, with a thick shell so that you can't even see the shape of the part very much anymore!

For O-1, W-1 and the like, a borosilicate glass like KeepBryte saves the day from scale. All that said, my favorite higher carbon steels for small parts these days is A-2, an air-hardening steel. You can wrap these up in stainless steel foil during heat treatment, and there is no liquid quench, no scale, no spatter, no fuss. The parts come out greay to purple, attractive, and squeaky-hard.

 

[petertha]

All that said, my favorite higher carbon steels for small parts these days is A-2, an air-hardening steel. You can wrap these up in stainless steel foil during heat treatment, and there is no liquid quench, no scale, no spatter, no fuss. The parts come out greay to purple, attractive, and squeaky-hard.

So with the foil on, I assume that rules out a torch heating method to 'see' the color while heating? You require an oven with this setup, right?

Between air/water/oil type tool steels, is air appreciably better than the others for mitigating distortion on finicky, small & un-symetrical do-dads like camshafts?

 

[Swede]

So with the foil on, I assume that rules out a torch heating method to 'see' the color while heating? You require an oven with this setup, right?

Between air/water/oil type tool steels, is air appreciably better than the others for mitigating distortion on finicky, small & un-symetrical do-dads like camshafts?

I do have an oven and it's a luxury, but for small parts, you can possibly get away with the magnet trick. In theory, you bring the A2 part to 1450 f., then raise it to 1750 f. Here is some data for A2:

http://www.steelforge.com/alloys/?alloy=A2

Even if you don't nail it, it'll still probably do as well, or better, than O1 or W1 using a torch. Another interesting thing about A-2 are the very high annealing temps, several hundred degrees F. higher than O-1. This makes tempering more challenging, but you do have a steel that can hold its harness at much higher working temps.

It exhibits excellent resistance to distortion, if my memory serves me... need to check Machinery's Handbook.

I know furnaces cost pretty hefty bucks. One good thing is that you can now buy both pyrometers and PID temperature controllers at ridiculously cheap prices off the internet. A good digital PID controller and a type K thermocouple can be had for less than $100. Combine those with an inexpensive knife furnace, and you can replicate a $2,000 shop furnace for a small fraction of that. And all of a sudden, a small shop's capabilities go way up. You can heat treat just about ANYTHING with confidence.

 

[jonesie]

you could also check with any local tool shops or machine shops to see if they will heat treat you parts for you. they might be able to run them with some of there stuff, and save you doing a single run for you .there might be some local places that only do heat treating, who sometimes charge by the pound. the 1018 can only be case hardened. good luck jonesie

 

[crab]

This might work.
http://www.viddler.com/explore/rashid11/videos/3/

Crab