DIY Hardened gears

I wanted to run 6mm bore mod1 pinions against a steel spur, but didn't like the idea of soft metal on metal. After just one run, I could see significant wear on the SDP-SI pinions. I did a little research and found this method of case hardening that works really well and is quite easy. The key is a powder called Kasenit and it cost about $11-12 (available from MSC or ENCO) for a 1 lbs can. 1 can will probably last a lifetime. Case hardening creates a very hard layer of high carbon steel on the outside of the part.

Here are the steps I did: (wear safety glasses!)
Materials needed:
Kasenit
propane torch
vise grips
water
nail
magnet
gear that you want to harden (remove set screw)


Use the nail and vise grips to hold the gear while you heat. Keep turning to heat evenly and heat it until it becomes cherry red. You can check the temp with a magnet. When steel is at hardening temp, it will be non-magnetic.


Dunk it in the powder and coat the gear with the powder. Heat it again and recoat a 2nd time. Then reheat until cherry red and the steel becomes non-magnetic. Keep that temp for about 1-2 minutes. Immediately dunk it into a jar of water and swish it around. Water will spray out (safety glasses!)! Most of the powder will fall off and you will be left with a hardened gear.



The gear will be a matte gray finish and seems to rust pretty easily. Coating it with some oil would probably prevent that. You can check the hardness by using a file. The file will 'bite' into unhardened steel and 'skip' off hardened steel. The whole process takes 5-10 minutes.



So far, the gears I've hardened are holding up really well and show little signs of wear. I've noticed even steel pinions on plastic spurs show wear, so hardening these would probably help too. Hope you find this useful.

[TDC57]

WWoooWW you lost me.. What do you have that uses a 6mm out put shat?? All motors that I’m aware of use 5mm / Mod one pinions gear.. We typical buy them from Mike (RCM)

http://www.rc-monster.com/gears.php

Regardless welcome to the forum.. You’ve tapped into the greatest group of gentlemen known to man kind..

Have a great one..

Yeah, be careful when you run into crap material. A true steel alloy will carburize just fine with your method or using a real heat treating furnace/atmosphere. But I've ran into a problem with gears made of powdered metallurgy. They are already hardened and will not take an effective case. The powdered stuff is sintered with all sorts of different stuff, pinch of this, dash of that, and pressured together and hardened to some degree throughout. But if you look close enough, there will be all sorts of holes and pits and good places to form cracks. I don't know if they do this with pinion gears, I've found this on a differential gear. It's nice to know what kind of metal your metal gears are made from, I'm fairly certain it won't work with stainless steels. Don't want to sound like Im raggin on ya, great thread/idea, its nice you posted it, cheap easy way of adding wear resistance and life to your gears. Never knew they made that kind of stuff.

Also are you just gettin the surface hot or are you heating the entire gear up all the way through?

[gixxer]

kb45 motors use 6mm shafts. I am sure there are probably otheres but thats the only one I know of.

[BrianG]

Can this method be used to harden the surface of aluminum? Anodizing is great and all, but too much work.

[bl-is-future]

Originally Posted by BrianG

Can this method be used to harden the surface of aluminum? Anodizing is great and all, but too much work.

I was thinking the exact thing. but it wouldn't look pretty like the anodizing would.

[TexasSP]

Originally Posted by BrianG

Can this method be used to harden the surface of aluminum? Anodizing is great and all, but too much work.

Aluminum will melt under low heat and the process works differently. I have a guy local that can do hard anodizing of 6061 or 7075 for $100.00 a batch, which is however much he can fit into a large basket. I had a bunch of 7075 machine parts done and the averaged about 6" diameter, 2" thick and there were about 20 pieces total and that didn't near fill his basket so the price is pretty cheap. He can also standard anodize any color you want, same price. The hard anodizing penetrated several hundredths of an inch so it is a good process, very strong.

Originally Posted by Serum

I thought Si and Mg is used to get a harder grade of aluminum.

That is correct although I can't remember the percentages.

It's better to use a tool steel when hardening and preferably D2/A2 or similar. You will get a much better result on the rockford and less brittle material. I would still recommend having it done professionally over DIY as the process is much different.

[Serum]

No, for harding steel there is carbon involved. that won't do the trick with aluminum. I thought Si and Mg is used to get a harder grade of aluminum.

I think the gears you are using are from a steel that makes it possible to be hardened, not all sorts of steel are suitable for hardening. My guess is that the kasenit adds carbon to the steel.

[Serum]

You can DIY hard anodize aluminum. Not all grades of aluminum are suited for anodizing though. Colors are also doable.. (one of the reasons i installed a sink in my hobby-room!)

[bl-is-future]

i have looked up DIY alloy anodizing and it seems like a complicated process. I think if i ever seen it done i could do it though. I just get mixed up with all of the steps and i dont want to mess anything up.
TexasSP -
So can i fit a whole FLM chassis and a arms and the bulk heads in this basket?? And is there a blue anodizing this guy has???

I should have prefaced by saying this only works with carbon steel. As others have said, the quality of steel makes a difference. The sdp-si gears seem to work well and doesn't rust afterwards. However, the traxxas gears I've done rusts within a day or 2 just exposed to air. They are probably using cheap steel, but the surface does seem harder (using the file test) than before hardening.

The hardened layer with this method is going to be much thinner than if done in a factory with a controlled environment. The way this works is that the powder creates a carbon rich environment as you heat it to hardening temperature. The more carbon in steel, the better it is for quench hardening. The longer you heat it, the deeper the carbon penetration and thicker the hardened layer.

I would think things like dogbones and drive cups could be hardened as well, but haven't tried. Would hardening the spur and the pinion be beneficial? As with anything, experiment and your mileage may vary.

Originally Posted by kona

I should have prefaced by saying this only works with carbon steel. As others have said, the quality of steel makes a difference. The sdp-si gears seem to work well and doesn't rust afterwards. However, the traxxas gears I've done rusts within a day or 2 just exposed to air. They are probably using cheap steel, but the surface does seem harder (using the file test) than before hardening.

The hardened layer with this method is going to be much thinner than if done in a factory with a controlled environment. The way this works is that the powder creates a carbon rich environment as you heat it to hardening temperature. The more carbon in steel, the better it is for quench hardening. The longer you heat it, the deeper the carbon penetration and thicker the hardened layer.

I would think things like dogbones and drive cups could be hardened as well, but haven't tried. Would hardening the spur and the pinion be beneficial? As with anything, experiment and your mileage may vary.

Hey, you should probably toss your newly hardened gears in your oven at home and leave them in there for 2 hours at 400 deg. or so. Right now they are probably pretty brittle and you wouldn't want to start shearing off teeth.

Originally Posted by 1maxdude

Hey, you should probably toss your newly hardened gears in your oven at home and leave them in there for 2 hours at 400 deg. or so. Right now they are probably pretty brittle and you wouldn't want to start shearing off teeth.

to remove the brittleness you need to temper the gears after you harden them, also quenching in water causes a fast temp drop which gives the you the hardest result but makes it the most brittle and gives you the highest chance that you will get warping...in the past I have heated parts to about 1500 degs and than quenched in motor oil, I than brush off the carbon residue and reheat to about 500 degs to temper

here is a link to help explain the hardening process

http://www.armourarchive.org/essays/...treating.shtml

[TexasSP]

Originally Posted by bl-is-future

i have looked up DIY alloy anodizing and it seems like a complicated process. I think if i ever seen it done i could do it though. I just get mixed up with all of the steps and i dont want to mess anything up.
TexasSP -
So can i fit a whole FLM chassis and a arms and the bulk heads in this basket?? And is there a blue anodizing this guy has???

Yes and Yes. If you want I can get you his number.

He does a lot of parts for a friend of mine that builds cars, so he can fit some pretty big parts. I saw some really nice tie rods he did for him in blue not long ago, they looked sweet!

[mothman]

Originally Posted by bl-is-future

i have looked up DIY alloy anodizing and it seems like a complicated process. I think if i ever seen it done i could do it though. I just get mixed up with all of the steps and i dont want to mess anything up.
TexasSP -
So can i fit a whole FLM chassis and a arms and the bulk heads in this basket?? And is there a blue anodizing this guy has???

Do yo think its ok to hard coat the bulk head? I was thinking about that too but then the coat will add thickness to the surface. This might be a problem when it comes to the bearing area on the bulk heads. The bearing might not fit after that. Can someone shed some light? I would really love to hard coat my FLM hybrid bulk.