DIY case hardening....

[davee1]

OMG....somebody please help me!!! I can't believe what just happened to me. I've been "expanding my horizons" so to speak. I have found a few other forums of interest, and stumbled upon a topic about a guy that puts 2 washers on each end of the mainspring like I do. Asked some questions and found out that he case hardens his own washers. When getting down to the nitty gritty about how to do the process, my post was edited...my 3 questions removed...and it was "suggested" that I ask my questions in another forum. This was after I had spent quite a while organizing the questions in a fashion so that I did not need to keep asking questions. I am so used to the helpful nature of the guys here that I forgot that not everywhere is like the GTA Wow, I also forgot how quickly my blood can boil too...

So its my understanding that a guy can take some mild steel washers and case harden them quite easily. My recollection goes like this:

You heat your washer(s) red hot, and then quickly transfer the redhot washer(s) into a mixture of carbon and oil. Let them cool and you are done. One guy used powdered charcoal briquettes for carbon, and mineral oil for oil.

So I asked:

Can you use a propane torch to heat the washers red hot? Can you use motor oil mixed with charcoal....and should that mixture be cool or hot? And my questions were blown away. Could anyone here answer my simple questions?

[davee1]

I've already done a search and have the questions that I asked before. I know that if you put too many washers on either end the gun won't cock...been there done that...just lookin for some answers to my questions. And yeah, I know that you can use grade 8 washers and have used them...just curious about the quick and dirty case hardening methods.

[Bhawanna]

not difficult but can be dangerous if caution and safety are not used.....i won't post instructions on this as there are some people that would not follow precautionary measures and end up getting injured.  pm me and we'll talk.

[davee1]

Ok, thanx Roger...will send PM in a few.

[gamo2hammerli]

Hey Davee1....why do you want to put washers in the front or/and in the back of the main spring?  Just opened up my Sierra Pro....if there's some kind of benefit...I might try it.  Thanks.

[davee1]

Hey Stan...yeah!!! Back at ya there buddy, fell asleep for a little while. Yes, the washers act like a thrust bearing and allow the spring to torque/twist, but not transmit all of that action into the airgun. So it reduces felt torque or twisting. You can use more than one or two washers if you want to...and it results in spacing of the spring, which can increase your velocity. If the spring is spaced too much though, the airgun may not cock...and then you just take away washers until it does cock. Don't have a Sierra Pro, so I cant give you exact numbers of washers, but I always try 2 on each end of the spring and use grade 8 or stainless steel, with moly on the spring ends and all over the washers. You can scratch n polish the washers too...so the moly has microscopic places to squish into...and make the washer surface nice n slick. And...there may or may not be a more harsh felt recoil from a lot of spacing, particularly if a stack o washers is in the piston end...because that makes the piston heavier. But I've never noticed anything negative in any of my guns that had just 1 or 2 washers on each end. Worst case is piston slam when the piston is too heavy and overcomes the compressed air cushion ahead of it, but again, I haven't seen that with one or two washers. If you find out that you have a lot of space in there to take up, you can use other stronger lighter materials after the original spring end washers to keep the weight down...experimentation is key here. You may have to take her apart several times to get the sweet spot...but in the end it always feels good to me.

[davee1]

Is that there may be a "tophat" on the end of the spring inside of the piston. In that case you have to decide where to put the washer(s)...either on the tophat, or after the tophat, or a combination thereof. If a washer(s) interferes with a tophat's fit onto the spring...then I put the washers after the tophat, or make a new tophat, if everything will fit without making it uncockable. And once again, moly is good stuff...but we dont slather it on like butter...more like a nice layer ofpaint is the way I like to describe applying it.

[gamo2hammerli]

Thanks Davee1...that's very good info....I'm going to try that....my Sierra Pro was always a  bad shooter....3 flyers out of 10 all the time....until a few weeks ago....and then the spring died.

[kiwi]

The carbon rod from a dry cell bat can be used
Use old dirty engine oil as it has a lot of carbon in it from
the engine.
You can buy a carbon enriched paste for harding.
But why not just buy hardened shim washers in
the size you require.

[davee1]

Ok, I can see where I made my mistake. It appears that I want to make my own hardened washers. That is not really what I want to do. I would just buy grade 8 washers if I needed them.

But washers can be cheap to experiment with...yes? With the hardening methods learned by experimenting with cheap washers, I can then apply what I have learned to the items which I actually really want to case harden.

Please stop telling me that I can buy my own hardened washers. I know that. That has nothing to do with the questions that I asked originally.

So one of the things thatKiwi mentioned is that used motor oil could be good. Guys...I know that if you take a cherry red hot washer and drop it into a charcoal/used motor oil mixture...that there is going to be fire. So caution is needed, everything should be as small as possible, metal container, safety glasses, fireplace tongs, propane torch well away from the fire...and I understand why folks are reluctant to discuss these methods on an open forum on the internet for somebody to read who might not take the same safety precautions that are needed. So lets end this thread here. I have my answers and know what to do. Thank you.

[gamo2hammerli]

You guys really know your stuff.

[davee1]

You are very kind Stan. Learning something new everyday keeps me humble, and continually learning...however, at 50yrs old,my memory is starting to get filled up, and it seems that some of what I used to know, has made room for something else that I can't remember.

[RedFeather]

There's a product called Kasenite that you can use to surface harden steel.  Muzzle loaders use it to re-harden the frizzens on flintlocks, for example.  One thing, though.  As I understand it, case hardening can make some metals brittle.  Where you are subjecting the washers to a lot of impact stress, might an over-hardened washer tend to crack?  What wear do the washers impart to other parts of the gun?  That is, why do you want to harden the washers in the first place, aside from just a hardening trial?

[davee1]

Yes I am aware of that product. Thank you for suggesting it. Was just curious of how to do the process with some stuff laying around(experimenting), and not buying anything. A very nice gentleman was kind enough to explain his method ofa DIY case hardening process to me in detail. But as that very nice gentlemanstated, there are safety precautions that must be taken, andfolks are not comfortable discussing the process on an open internet forum...becausesomebody might take some shortcuts and hurt themselves/others. And...as I stated before, I could use unhardened washers that I already have to experiment with, to become familiar with the process...And I already have grade 8 washers laying around to use as thrust bearings on the ends of mainsprings. I use grade8 washers on eachend of a mainspring. I discussed my methods of doing that in the answer to gamo2hammerli's question, earlier in the thread.

As I was relating the censuring story that happened to me...I believe that I have given the impression that I want to case harden my own washers to use in an airgun. No, that *is not* what I want to do. That is what someone else on another forum does. What I actually want to do isjust become familiar with simple DIYcase hardening processes. There was a little more to the process, as I suspected, than what I had originally read about. Then comes myquestions...and the subsequent censoring(on the other forum)which really made my blood boil. It would have been much nicer to simply move my questions to the other forum suggested by the moderator, rather than deleting my questions, or discussing through PMs, like what was done here on the GTA.

Yes, parts are brittle after the intitial hardening process, and then the final process involvesstress relieving said parts. It is here on the GTA, because of that nice gentleman, that I finally learned what I wanted to know.

[MEHavey]

Done properly, case-hardening affects only a very (very) thin surface layer, leaving the rest of the metal thickness tempered softer w/ the normal quench effect.

That thin surface layer, however is *extremely* hard/scratch-resistant which is why it makes for a slick bearing surface.  The trick is getting that thin layer to carburize *before* the final tempering quench.  

See http://www.youtube.com/watch?v=9tlsq2ESQz0 for one possible modern product to use for that pre-quench carburizing.