MEMBER ITEMS FOR SALE
Custom Knives | Other Knives | General Items
-------------------------------------------
New Posts | New PhotosAll Photos



Go Back   The Knife Network Forums : Knife Making Discussions > Custom Knife Discussion Boards > Knife Making Discussions > Heat Treating and Metallurgy

Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

Reply
 
Thread Tools Display Modes
  #1  
Old 12-31-2014, 12:53 AM
kenshin305 kenshin305 is offline
Registered
 
Join Date: Dec 2014
Posts: 1
Heat Treated Stainless 440C Hole Saw Shattering. HELP!

Hello, I know this isn?t exactly knife related, but it is related to this forum category. I?m an industrial engineering undergrad who is making my own stainless 440C hole saws from 1 inch OD round bar. Using a lathe, I drilled, reamed, and finally used a boring bar to get the wall thickness to 0.021? (I know, it?s very thin). I then used a mill and a v-cutter to machine the teeth. Next, I heat treatment the hole saw to get a martensitic structure. I heat treated at 1038 degrees Celsius for 30 minutes, removed and air quenched, and finally temper for 1 hour at 230 degrees Celsius.

This hole saw was designed to be attached to a T-handle, to manually cut hardwood up to a ? inch thick. It cannot rust, and must have high hardness and toughness, which is why I chose 440C. This hole saw worked well for a year. I recently let a friend try it, who oddly enough is a girl (who isn?t fat), and it broke (see attached pictures). My friend used way more downward force than me when it broke. I feel that my hole saw has way too much hardness (no wear on teeth) but not enough toughness, almost like glass.

Can someone please advise on how to preventing my hole saws from shattering? Many of my engineering professors are baffled.





Reply With Quote
  #2  
Old 01-01-2015, 12:09 PM
TexasJack's Avatar
TexasJack TexasJack is offline
Super Moderator
 
Join Date: Apr 2004
Location: Southeast Texas
Posts: 2,919
I will reply so this stays on the "new" list and maybe one of our resident metallurgists will get a chance to reply. I have to say this is the first time I've seen such a tool posted on here, so it's an interesting thing to see.

Look at where it cracked. (Too bad you don't have a better close-up of that area.) I would suspect that your heat treating is the source of the problem, but I wouldn't dare to claim to be an expert on the subject. I copied the following from a quick google search:

Hardening: Heat 440c stainless steel to 1850/1950f (1010/1066c) soak, quench in warm oil or air cool. Do not over heat, when overheated maximum hardness cannot be obtained. Take care to minimize temperature time at 2000f (1099c) to avoid excessive grain growth. For best corrosion resistance, temper below or around 800f (427c).

Tempering: Hardened 1900 f (1038c) oil quench and tempered one hour (1? rd)


__________________
God bless Texas! Now let's secede!!
Reply With Quote
  #3  
Old 01-12-2015, 09:24 AM
Sergio Segre Sergio Segre is offline
Enthusiast
 
Join Date: Jun 2004
Posts: 73
It could be grain growth; you let the drill at 1038?C for 30 min. The drill is thin and 30 seconds should be enough
Regards
Sergio
Reply With Quote
  #4  
Old 01-12-2015, 11:21 AM
Doug Lester Doug Lester is offline
Hall of Famer
 
Join Date: Sep 2006
Location: Decatur, IL
Posts: 2,612
I would agree with Sergio. In the pictures where the edge of the break are more in focus the grain does seem to be a bit large. You might try tempering your next one at 260? C to reduce the hardness a bit more. Also try two one hour cycles to see if problem is retained austinite converting to untempered martensite with just the one cycle.

Doug


__________________
If you're not making mistakes then you're not trying hard enough
Reply With Quote
  #5  
Old 01-12-2015, 05:07 PM
jmccustomknives jmccustomknives is offline
Skilled
 
Join Date: Mar 2012
Location: Alabama
Posts: 554
The first problem is you are using the wrong steel for the job. 440C (or any of the 400 series for that matter) are not designed for the stresses that come with that kind of tooling. That is why there is grain growth. While any "stainless" material will be inferior to HSS you might try D-2. With a little research you can find a "stainless" that is high temp but working it will be an issue.
Reply With Quote
Reply

Tags
440c, blade, drill, edge, first time, handle, heat, heat treatment, how to, knife, making, material, problem, quenched, stainless, stainless steel, steel, temper, thickness, toughness


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Differential heat treated damascus Dan Graves Ed Caffrey's Workshop 15 03-30-2006 03:41 PM
Tapping heat treated steel... razorhunter The Folding Knife (& Switchblade) Forum 4 03-13-2005 12:25 AM
Need to get it heat treated & tempered! sowilde Knife Making Discussions 5 11-21-2004 02:53 PM
Tapping heat-treated steel AlphalphaPB The Newbies Arena 5 05-05-2003 11:51 PM
Drilling heat treated blades Chris The Newbies Arena 10 06-04-2001 08:53 PM


All times are GMT -5. The time now is 09:08 AM.




KNIFENETWORK.COM
Copyright © 2000
? CKK Industries, Inc. ? All Rights Reserved
Powered by ...

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
The Knife Network : All Rights Reserved