Hi there,

This post doesn't really relate to machining as such, but I think it's the best place to post it...it is metalworking.

I need to harden a shaft that a needle roller bearing is going to run on. I have seen some things here and there that can be used to case harden low carbon steel at home (funny powders etc...), but most have been adverts from back in the day (like long before I was around). Does anyone know of any of these 'chemicals'/'mixtures' that can be bought in the 21st century and how effective they are???

Am i better off just getting someone experienced to do it for me?

Thanks
Warren

Hi there,

This post doesn't really relate to machining as such, but I think it's the best place to post it...it is metalworking.

I need to harden a shaft that a needle roller bearing is going to run on. I have seen some things here and there that can be used to case harden low carbon steel at home (funny powders etc...), but most have been adverts from back in the day (like long before I was around). Does anyone know of any of these 'chemicals'/'mixtures' that can be bought in the 21st century and how effective they are???

Am i better off just getting someone experienced to do it for me?

Thanks
Warren

Case hardening requires heat to migrate carbon into the surface of the steel. THe other alternative is nitriding which is heating the part in a nitrogen atmoshere.

If the shaft has value then a professional should do it for sure, the cost should be fairly low.

This is the stuff your looking for:
http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=12400521&PMAKA=DK505-0271

bobgerman...that was the stuff I was thinking about...though I've never used it....you have to heat the part and pour this over it....I believe it's a fine powder...

In the early 70 ties, [apprenticeship in Switzerland] I had to caseharden a section
on some kind of rods or levers for Ferguson Tractors, all I know is, heat up nice and bright red with a torch, then sprinkle the powder over it, then quench in water.
Konrad

used it, it works ok, problem is it will only harden the outer thou or 2. casehardening is a soak process, so many thou depth per hour of soak…carbon is soaking into the outer layer while the grain structure is altered (high temp) with that thin a case you have no room for grinding.

basically drop the bright red part into the stuff and role it around (i used an old pie plate or the like) and the kasenit sort of fuses to it. you can repeat this a bunch of times before the quench for a thicker case, or so says the package (i was always doubtful as you aren't really giving it a soak - no short cut around that that i know of

i think are right though, the torrington bearings need a hardened shaft. obviously there are advantages to case hardening, but if its just a simple shaft, you could use drill rod, harden and temper it.

tell us more about the application - if it really needs a proper case hardening job (ie 20-40 thou), kasenit won't do and imo its a lot easier to send it to a heat treatment shop than to do a real caseharden yourself (messy, smelly, time consuming).

Mcgyver is mostly right about how to use the kasenit. Heat your work piece bright red and roll it in the kasenit untill you get a nice coating all around. Re-heat it to a nice red again and soak it that way for a good five-ten minutes. Remove from the heat and while it is still hot scrape or wire brush the powder off. Re-heat bright red again...roll it in the kasenit again....you can repeat this several times soaking a little longer each time and can acheive up to .005" case. Finally quench in water (or oil if you prefer) and temper to your liking. I have use this stuff many times (mostly for hammer heads) and know it to very forgiving and easy to use. The big problem I see that you might have is warping your shaft. Quenching from end to end (rather then dropping the shaft in sideways along the length will minimize warpage and with a still soft core it can still be straightened with minimal effort.

Hi there,

I need to harden the lobe on the eccentric shaft for a wankel rotary engine. It is the needle bearing that supports the rotor that runs on the shaft. It is a relatively high load/high speed application, so a good solid shaft is in need.

Unfortunately it is not just a simple shaft, so drill rod won't do and warping is not really an option if I want this engine to work. I think I might have a look at the professional options to see what it would cost and then go from there.

Thanks for the help!

Regards
Warren

for any hardened part, we're just hoping for the best on the warping when it's quenched. the right way to do it is to build it oversized and grind afterwards, although then again sometimes on the quench the warping is negligible and not everyone has a tool post grinder…just that you should know this because it sounds like complex part in a demanding app.

I find it hard to believe you could get more than a couple of thou with Kasenit, the heat treating shop I use tells me the deepest they could give me is around 50 thou and that’s soaking at temp all day….then again you may know more about than i.

It looks like the shaft is getting fancier, not something of a low carbon steel
I would use...

You need a good alloy steel, something like 4140H or 4145 and have the bearing journals induction hardened.

Konrad

I'm with Konrad....induction hardening is probably the way to go on the Wankel...

I'm wondering if this metal induction hardening can be homebuilt? Where can I find something to read about it?

http://www.deform.com/displayapp.php?appsel=11

Curious to learn more about this… I've seen induction welding of tube and this looks similair - isn’t this more production process – ie can you get this done for one of parts at the local heat treat shop?

Although they say it’s a case hardening process, it done to tool/heat treatable steel, right? i.e. only the outer part of the tool steel is changed…..but you're are still starting with a steel that can be heat treated....or is carbon added (or leached from surrounding material) to mild steel?

Finally, as a quench is still involved, isn’t warping still an issue?

To answer a few questions from different people. Case hardening, the old fashioned style was done by packing the low carbon steel part in charcoal and heating to red heat for many hours. The powders that came available made the process a bit easier but no matter what technique is used the depth of the hardening is only a few thousandths. It is not deep enough to grind to the type of finish needed to run needle roller bearings on nor is the underlying material strong enough for the concentrated roller loads. Remember the rollers only contact for a very small portion of their circumference. Think of a log on a layer of ice half an inch thick over soft mud.

Induction hardening only heats the surface of the shaft material being treated and a high carbon or alloy steel is needed because nothing is added. The case depth here can be several hundredths of an inch, it is deep enough for a ground finish and the hardened depth is thick enough to handle the concentrated roller loads. Distortion is minimised with induction hardening because the heated region does not extend all the way through the material, the heating is very even and the quenching is arranged to be even also.

For the shaft in question it may be possible to make it from low or medium carbon steel and press on hardened steel sleeves for the roller bearings to run on. The sleeves should be available from the same source as the rollers.

Geof...I agree with you on that...."bearing races" are the way to go...

Geof, thanks for better my understanding on induction hardening.

Have to disagree on the case hardening though. even the old pack hardening could have thicker cases, the box had to be airtight, after that it was a matter of how long it soaked for. Nowaday it just sits a vat of nasty (cyanide?) stuff and the depts of 50 thou are possible. using the powders however will only get you a few thou

Carbonnitriding starting with low carbon steel (SAE 1008):

1 hour @ 1425 to 1450°F results in a case .004" deep.
2 hours @ 1425 to 1450°F results in a case .006" deep.
3 hours @ 1425 to 1450°F results in a case .009" deep.
4 hours @ 1425 to 1450°F results in a case .011" deep.

1 hour @ 1600 to 1625°F results in a case .015" deep.
2 hours @ 1600 to 1625°F results in a case .021" deep.
3 hours @ 1600 to 1625°F results in a case .026" deep.
4 hours @ 1600 to 1625°F results in a case .030" deep.

for Heat Treaters Guide

Mcgyver;

I concede; more than 0.010 does not qualify as a few thou.

ah, your a gentleman. no need for the duelling pistols then :)