|
Post by ron on Apr 26, 2007 10:20:11 GMT
Hi Everybody I need to case harden some of the motion parts for the Simplex I'm building, I haven't done this since I was an apprentice and we used [or in my case avoided] a molten cyanide bath. I have bought some of the powder which is a bit short of instructions, can anyone post some hints and tips on how to do this please. Ron
|
|
paul
Member
Posts: 8
|
Post by paul on Apr 26, 2007 10:38:40 GMT
Ron Wikipedia says.... "Small items may be case hardened by repeated heating with a torch and quenching in a carbon rich medium, such as the commercial product Kasenit / Casenite."
I have been told that some suppliers have stopped stocking it as it may be carcinogenic - how accurate that is I cannot say but I'd be careful just in case (no pun intended) ;-)
|
|
|
Post by greasemonkey on Apr 26, 2007 13:05:13 GMT
|
|
|
Post by ron on Apr 26, 2007 14:12:58 GMT
Hi Paul I got a tub of powder from EKP, it isn't Casenite, it's a generic replacement, and short on instructions [and the hazards, surprisingly!] Andy Thanks, I'd read that thread but it doesn't have a great deal of info about how to actually go about it. Ron
|
|
|
Post by baggo on Apr 26, 2007 15:09:55 GMT
Hi Ron,
the way I do it (and I think this is the way I was taught at school) is to heat the component to a dull red and then dunk it in the compound (or sprinkle the compound over it). After a few seconds remove the component from the compound and reheat to red again. This can be repeated to increase the thickness of the hardened layer. Then quench in cold water (or oil?). Not sure if this is the 'correct' method but it works for me!
Incidentally I use gauge plate (oil hardening tool steel) for slidebars and other motion bits as it wears well even if not hardened and is nearly as easy to machine as mild steel. You can always harden it if you want to.
John
|
|
Lurkio
Seasoned Member
Posts: 101
|
Post by Lurkio on Apr 26, 2007 15:54:51 GMT
Ron,
Just to add weight to baggo's comments - that's almost how we used the Kasenite stuff as apprentices. Rather than dull red though, heating to bright red was preferred. Then, as baggo suggests, subsequent dunking while keeping the part (bright) red hot increased the depth of penetration. Sometimes (small) parts would be buried in the stuff and kept at bright red heat for a period of time....this achieved even deeper case hardening. Rapid cooling by quenching in a decent volume of cold water finished the job. This was suitable for mild steel - I can't comment on it's use on other steels.
You could experiment with some scrap bits.....you'll know how succesful you've been, an old file will slide off a properly case hardened part as it would off glass, as I'm sure you'll know.
The downside.....distortion.
Lurkio.
|
|
chris vine
Elder Statesman
Posts: 2,107
Member is Online
|
Post by chris vine on Apr 26, 2007 21:19:29 GMT
Hi Ron,
One thing to watch out for on our tiny parts is getting the case too thick. I did this once on a small link (mild steel) and when I nipped it in a machine vice (gently) for some reason, perhaps to polish it up, it shattered like glass.
As Lurkio suggests, try it on some scrap parts first and make sure that it isn't brittle through.
Having always used kasenit, it comes up a rather satisfying mottled grey when it has been treated, although this can be polished of in a few seconds.
I remember having the slide bars for my little Bridget locomotive hardened in the cyanide bath at the works when I was an apprentice. When I got them home I went to polish them up with a bit of wet and dry to find that they were so hard that the abrasive was blunted almost immediately....
Chris.
Chris.
|
|
|
Post by chameleonrob on Apr 27, 2007 7:58:00 GMT
for a small part heat it indirectly in a metal tray while covered in case hardening compound and quench vertically (assuming its a shaft), you shouldn't get any distortion like that. one point to bare in mind is that if the component has to be very accurate its worth testing to see if you lose any metal from the outside. last time I did any case hardening the 1/8" dia shaft shrank by about 2 thou, which took it way out of tolerance (lubricator shaft running in roller clutches)
rob
|
|
|
Post by ron on Apr 27, 2007 9:23:15 GMT
Hi Thanks for the replies, it's mainly motion parts like the radius rods and eccentric rods etc, he suggests case hardening the reamed holes in the end of them, I'll do some trials on test pieces first to see how it goes. Ron
|
|
abby
Statesman
Posts: 927
|
Post by abby on Apr 27, 2007 14:21:18 GMT
For small parts I get a short piece of steel tube , large enough to put the pieces in , and pack the tube with Kasenit , ramming it tightly around the parts to be hardened. I stand the tube in the brazing hearth on a piece of flat fire-brick and put a piece of steel sheet over the top of the tube. Then heat to cherry red for 15 to 20 mins and dump the whole lot in a bucket of cold water. Fish out your bits and they will have a glass hardness. Many things are labelled carcinogenic today , even Blackpool rock , if you eat a million sticks , I doubt any harm will come to anyone using Kasenit on a model making scale. Abby.
|
|
waggy
Statesman
Posts: 744
|
Post by waggy on Apr 28, 2007 18:37:46 GMT
At one of our club meetings some years ago, the case hardening issue arose. Among our membership at the time was a retired matallurgist. He informed us that case hardening and "free cutting" mild steel didn't mix too well. Something to do with the composition of the steel, can't remember what though. I'm sure the answer will appear on the thread, though.
Waggy.
|
|
|
Post by Shawki Shlemon on Apr 29, 2007 10:20:20 GMT
Reaming and case hardening is over stated on many plans ( that is my humble opinion ) . I have case hardened few items using a product called HARDITE , but for most motion parts I use bronze bushes and silver steel pins . They last a long time and are repairable if needed after a long time . The amount of running we do this process lasts a very longtime .It is up to you of course and best of luck .
|
|
abby
Statesman
Posts: 927
|
Post by abby on Apr 29, 2007 10:27:14 GMT
Leaded free-cutting steels are unsuitable for case-hardening , but any other low carbon steel should be fine, I have found the most useful application for case-hardening is in filing jigs or templates , drill plates and the like , you can make them up from almost any scrap sheet steel you have handy , case harden and they last forever. Abby.
|
|