Shop Floor Talk  

Go Back   Shop Floor Talk > Welding and Metalworking Forums > Fabrication

SFT Search:   
Reply
 
Thread Tools Display Modes
  #1  
Old 07-15-2022, 09:25 PM
staybusy staybusy is offline
Member
 
Join Date: Oct 2020
Location: Ontario, Canada
Posts: 78
Default Should I Case Harden Shredder Teeth?

I have some 1" plate I cut into teeth for a shredder / grinder. As far as I know it's mild steel (sourced from a junkyard). This steel doesn't harden well from heat treatment.

The shredder will be for processing meat, bone, hooves, etc.

I'm wondering how mild steel teeth would hold up to dense bone - lamb shanks, deer femur, cow femur, pigs feet, etc. Will the teeth eventually get warped and chip if I don't harden them?

Is it worth it to case harden the teeth?

Case harden then temper?

Setup will be extreme high torque, very low RPM so no high speed impacts. I don't care about grinding speed at all, only that it can process material.

See pic for tooth profile.
Attached Thumbnails
Click image for larger version

Name:	20220715_202720_HDR.jpg
Views:	87
Size:	203.5 KB
ID:	165248  
Reply With Quote
  #2  
Old 07-15-2022, 10:16 PM
LKeithR's Avatar
LKeithR LKeithR is offline
Hey...wait...is there a prize?
 
Join Date: Aug 2011
Location: Langley, B.C.
Posts: 5,618
Default

In my experience mild steel doesn't case harden well either. The other problem you may have is with the depth of the case hardening itself. The surface of the material may harden somewhat but the underlying material will still be soft and, depending how much load and impact there is, the sharper edges may just break away while the softer material slowly deforms.

I would certainly have made those teeth out of a better material but, since you've already got them made you don't have a whole lot to lose if you use them. The time to ask questions like this is before you buy the material...
__________________
Keith

Measure twice and cut once...or...wait, was that the other way around?
Reply With Quote
  #3  
Old 07-16-2022, 01:16 AM
Shade Tree Welder's Avatar
Shade Tree Welder Shade Tree Welder is offline
Grumpy Bastard
 
Join Date: Jun 2004
Location: Kankakee County, IL
Posts: 22,215
Default

Quote:
Originally Posted by LKeithR View Post
In my experience mild steel doesn't case harden well either. The other problem you may have is with the depth of the case hardening itself. The surface of the material may harden somewhat but the underlying material will still be soft and, depending how much load and impact there is, the sharper edges may just break away while the softer material slowly deforms.

I would certainly have made those teeth out of a better material but, since you've already got them made you don't have a whole lot to lose if you use them. The time to ask questions like this is before you buy the material...
Mild steel will not harden.

I agree use them when they fail, and the only unknown is when not if.

Buy some A2 tool steel and make your next set.
__________________
Shade

"Prepare to defend yourselves."
-- Sergeant Major Basil L. Plumley, Ia Drang Valley
Reply With Quote
  #4  
Old 07-16-2022, 01:51 AM
LKeithR's Avatar
LKeithR LKeithR is offline
Hey...wait...is there a prize?
 
Join Date: Aug 2011
Location: Langley, B.C.
Posts: 5,618
Default

Quote:
Originally Posted by Shade Tree Welder View Post
...Mild steel will not harden...
You can in fact create a very thin skin of hard material on a piece of mild steel by case hardening but it won't stand up to anything more than mild abrasion. If there is any impact involved it will fail quickly because the underlying core is soft and won't support it. So for all practical purposes Ron is right, you cannot harden mild steel--it's just not worth the effort...
__________________
Keith

Measure twice and cut once...or...wait, was that the other way around?
Reply With Quote
  #5  
Old 07-16-2022, 06:49 AM
GWIZ's Avatar
GWIZ GWIZ is offline
SFT Historian
 
Join Date: Feb 2006
Location: USA
Posts: 7,418
Default

Quote:
Originally Posted by Shade Tree Welder View Post
Mild steel will not harden.
I think you missed the question.

Yes, Case harden will help but from the pictures there may be too much back clearance on the teeth.
as Keath mentioned "won't support", may not be enough back support for the pressure generated. "its hard to tell from the picture because I cant judge size or pressure angle.

I had a motorcycle sprocket case hardened, about 0.030-0.050 it did help but the teeth still bent.
its Hard to explain,
with case hardening the teeth bent symmetricly (all the teeth bent the same amount).
stock non hardened sprockets some teeth would bend more than others and stretch the drive chain in spots, the chain would slap up and down so you could not adjust the slack out of the chain.
__________________
*
*
The factory of the future will have only two employees, a man and a dog. The man will be there to feed the dog. The dog will be there to keep the man from touching the equipment. ~Warren G. Bennis

Last edited by GWIZ; 07-16-2022 at 06:59 AM.
Reply With Quote
  #6  
Old 07-16-2022, 07:28 AM
digger doug's Avatar
digger doug digger doug is offline
Banned
 
Join Date: Jan 2008
Location: NW Pa
Posts: 14,033
Default

OH GOD NO !!!!!

"Hard Facing"

OH GOD NO !!!!!
Reply With Quote
  #7  
Old 07-16-2022, 07:41 AM
Shade Tree Welder's Avatar
Shade Tree Welder Shade Tree Welder is offline
Grumpy Bastard
 
Join Date: Jun 2004
Location: Kankakee County, IL
Posts: 22,215
Default

Quote:
Originally Posted by digger doug View Post
OH GOD NO !!!!!

"Hard Facing"

OH GOD NO !!!!!
Doug, I did think about that but this is a shredder, so you have to have them somewhat sharp. So weld and then try to grind hard facing...

Run them like they are. The buy some tool steel and do it right.

(PS he likely is not going to want to spend that kinda cash on 10 lbs. of hard facing rod, I have never seen HF rod in small paks.)
__________________
Shade

"Prepare to defend yourselves."
-- Sergeant Major Basil L. Plumley, Ia Drang Valley
Reply With Quote
  #8  
Old 07-19-2022, 08:54 AM
greywynd's Avatar
greywynd greywynd is offline
I can dig it
 
Join Date: Dec 2005
Location: Wainwright, Alberta
Posts: 6,267
Default

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
Reply With Quote
  #9  
Old 07-21-2022, 06:30 PM
staybusy staybusy is offline
Member
 
Join Date: Oct 2020
Location: Ontario, Canada
Posts: 78
Default

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

Quote:
Originally Posted by Ironman View Post
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.

Quote:
Originally Posted by Ironman View Post
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?

Quote:
Originally Posted by greywynd View Post
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.
Reply With Quote
  #10  
Old 07-22-2022, 11:00 PM
staybusy staybusy is offline
Member
 
Join Date: Oct 2020
Location: Ontario, Canada
Posts: 78
Default

Had an interesting thought.

If you can heat mild steel in a carbon pack and have it absorb carbon, what would happen if you added chromium powder with the carbon?

Is it possible to create a stainless surface layer that way?
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Web Search:

All times are GMT -5. The time now is 03:28 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.