Should I Case Harden Shredder Teeth?

[staybusy]

All the local metal suppliers I talked to when sourcing steel weren't able to help me so I just moved forward with random 1" plate. I kind of regret that now that it was 10+ hours of cutting time on the bandsaw but at least progress is being made Can always make a better version in the future, this one's low budget as possible.

I was originally trying to get a hardening stainless steel but nobody had any. Even just regular stainless was an issue, because they can't cut 1" plate on their brake - they wanted to waterjet cut it, then the prices start getting crazy. Multiple places didn't bother responding to quote inquiries. Metal shop guy on the phone said regular stainless won't bend or crack against bone.. seems like BS, dunno.

Hardfacing sounds like a good easy solution, didn't know about that. As long as there's no really poisonous compounds that could get into the meat (micro chips or from contact, etc) I'm trying to keep things food grade as possible. How thick does the welded layer need to be and what kind of alloy is it?

Adding hardened tool steel teeth is an option I considered and I think would work well. Making 32 teeth then welding them all on is too much work though.

Here's the case hardening method I planned to use - https://www.youtube.com/watch?v=VpD7NyadLcQ

I don't want the teeth to be too brittle so I think if I temper it afterwards it may have better results.

Added a mock up image of the grinder.

-Single shaft design
-Very compact shredding chamber
-4x 1" thick blades with 8 teeth on each
-2 hp motor
-1:160 planetary gearbox
-feed chute like a juicer (press to apply the cutting force)

[LKeithR]

No point in tempering case hardened material--not that you're going to get much hardening with mild steel. Tempering is a process used to reduce the hardness/brittleness of a block of steel after heat treating. It changes the crystalline structure of the entire piece so, since you won't have any hardness in the core of the material you'll gain nothing by tempering it...

[Ironman]

I think that hardfacing is more benign than case hardening, and the hardness layer is so thin that it would have a short life after wearing through in one spot.
Hardface rods usually contain Chrome, so Chromium hexafluoride gas is something you shouldn't breath. Do it outdoors.

You have to realize that casehardening is about 20 thou thick and underneath is mild steel. Case hardening is done by carbon rich chemicals like cyanide which are used to get carbon into the surface of the steel.
Hardfacing is as thick as you want to lather it on.

[mccutter]

What are you going to use the chopped up bones for?

[staybusy]

Originally Posted by mccutter

What are you going to use the chopped up bones for?

my dog got lyme disease then developed really bad allergies after being put on doxycycline (very strong antibiotic). gonna feed her raw so I can try to run an elimination diet, hopefully it will cure the allergies. also letting her bury lamb shanks in the backyard, trying to rebuild her gut biome. I notice she's food reactive, if I feed her milk bones she itches like crazy, develops sores and her fur is falling out in places.

Originally Posted by LKeithR

No point in tempering case hardened material--not that you're going to get much hardening with mild steel. Tempering is a process used to reduce the hardness/brittleness of a block of steel after heat treating. It changes the crystalline structure of the entire piece so, since you won't have any hardness in the core of the material you'll gain nothing by tempering it...

I'm not trying to temper the whole piece though, just the case hardened exterior that has carbon content

Originally Posted by Ironman

I think that hardfacing is more benign than case hardening, and the hardness layer is so thin that it would have a short life after wearing through in one spot.
Hardface rods usually contain Chrome, so Chromium hexafluoride gas is something you shouldn't breath. Do it outdoors.

You have to realize that casehardening is about 20 thou thick and underneath is mild steel. Case hardening is done by carbon rich chemicals like cyanide which are used to get carbon into the surface of the steel.
Hardfacing is as thick as you want to lather it on.

I was just gonna use the charcoal method of case hardening.

For hardfacing I was thinking of chopping 2-3 mm off the top of each tooth, then welding on hardened material, after I'd using a grinding wheel to reshape the point. Does that sound ok?

[staybusy]

https://en.wikipedia.org/wiki/Case-h...ng#Carburizing

The carbon can come from a solid, liquid or gaseous source; if it comes from a solid source the process is called pack carburizing.

Packing low carbon steel parts with a carbonaceous material and heating for some time diffuses carbon into the outer layers. A heating period of a few hours might form a high-carbon layer about one millimeter thick.

Check this video - https://www.youtube.com/watch?v=aFqdWXDZiq4 (skip to 9:17 it shows penetration depth)

Interesting document - https://www.dce-darbhanga.org/wp-con...5315f6a1c1.pdf

[Ironman]

Originally Posted by staybusy

I'm not trying to temper the whole piece though, just the case hardened exterior that has carbon content

I was just gonna use the charcoal method of case hardening.

For hardfacing I was thinking of chopping 2-3 mm off the top of each tooth, then welding on hardened material, after I'd using a grinding wheel to reshape the point. Does that sound ok?

for your dog, feed him garlic chopped fine, 10 minutes in the open air to convert the alliin into allicin. Then mix with ground beef and feed it. Eliminate grain from his diet, it's a filler and does no good for a carnivore.
I had St Bernard with issues like that. I know garlic will cure the hair falling out and oozy wet spots. Took about a week.


I would hardface the top and frontside and leave the backside soft. Camdigger may have a better idea. Then tweak the edge with a grinder to sharpen the edge. If you leave one side of the tooth soft it will wear sharpen.

[Ironman]

Originally Posted by staybusy

https://en.wikipedia.org/wiki/Case-h...ng#Carburizing

The carbon can come from a solid, liquid or gaseous source; if it comes from a solid source the process is called pack carburizing.

Packing low carbon steel parts with a carbonaceous material and heating for some time diffuses carbon into the outer layers. A heating period of a few hours might form a high-carbon layer about one millimeter thick.

Check this video - https://www.youtube.com/watch?v=aFqdWXDZiq4 (skip to 9:17 it shows penetration depth)

Interesting document - https://www.dce-darbhanga.org/wp-con...5315f6a1c1.pdf

I was wrong in my 20 thou estimate, 40 thou. I used to work in a drill shop where they forged ends on square drill steel, machined a thread on a turret lathe and case hardened in a bath of molten cyanide salt.
This was an open bath with a hood and fan. Times have changed

I hope you plan on broaching a keyway into these cutters before you harden. Afterwards is not a good plan.

[greywynd]

Years ago I had access to a cyanide bath for case hardening, and yes, if things were ideal, we could get around .040” or one millimetre of case.

I’ve also used Kasenit, however it’s no longer sold. Charcoal and bonemeal can also be used.

The toughest part I find for case hardening is finding metal containers to use, along with a heat source that will run long enough, with enough volume of heat. Tool steels one just has to get hot enough then quench, followed by a lower temp heat for tempering. (Tempering can sometimes even be done in kitchen ovens.)

Case hardening requires holding the high temperature long enough to allow the carbon to soak.


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[staybusy]

Sorry for delay in response I think I got covid again, been all dizzy and tired.

Originally Posted by Ironman

for your dog, feed him garlic chopped fine, 10 minutes in the open air to convert the alliin into allicin. Then mix with ground beef and feed it. Eliminate grain from his diet, it's a filler and does no good for a carnivore.
I had St Bernard with issues like that. I know garlic will cure the hair falling out and oozy wet spots. Took about a week.


I would hardface the top and frontside and leave the backside soft. Camdigger may have a better idea. Then tweak the edge with a grinder to sharpen the edge. If you leave one side of the tooth soft it will wear sharpen.

Thanks for the tip, I'll try out the garlic. I already have her on a premium "no grain kibble" but it's still got fillers like peas and oils, and other random crap. It definitely reduced her symptoms but didn't fix everythng.

My only worry about hardfacing is that I'm gonna make a mess of the teeth and add "worm holes", and shitty welds that will make the teeth hard to clean. I'll have to practice welding a bit more before attempting it.

Originally Posted by Ironman

I was wrong in my 20 thou estimate, 40 thou. I used to work in a drill shop where they forged ends on square drill steel, machined a thread on a turret lathe and case hardened in a bath of molten cyanide salt.
This was an open bath with a hood and fan. Times have changed

I hope you plan on broaching a keyway into these cutters before you harden. Afterwards is not a good plan.

Oh LOL I thought you meant 20,000 of an inch. Like a fraction of a hair. I don't know anything about these types of fractions, only ones I use are on a tape measure. Where's a good place to learn?

Originally Posted by greywynd

Years ago I had access to a cyanide bath for case hardening, and yes, if things were ideal, we could get around .040” or one millimetre of case.

I’ve also used Kasenit, however it’s no longer sold. Charcoal and bonemeal can also be used.

The toughest part I find for case hardening is finding metal containers to use, along with a heat source that will run long enough, with enough volume of heat. Tool steels one just has to get hot enough then quench, followed by a lower temp heat for tempering. (Tempering can sometimes even be done in kitchen ovens.)

Case hardening requires holding the high temperature long enough to allow the carbon to soak.


Sent from my iPhone using Tapatalk

What temps did you case harden at?

I have a dual burner forge setup with 100lbs propane tank. I could use the 2 burners + extra charcoal on top of the container with forge blower blasting air onto the coals.