Replies

1. 
   Hopster | Jan 13, 2005 06:08am | #1

   I suspect the jury is still out as to the effectiveness of cryo. Nevertheless, from the articles I have read, a final tempering is required after the cryo treatment.

2. 
   eddiefromAustralia | Jan 13, 2005 07:11am | #2

   Bob,

   If you can get the chisels handles off and have access to a household stove, temper at 180C for 1-1.5 hours - if still chipping, repeat the tempering process until they don't

   (180 x 9/5)+ 32 = 456ºF

   Cheers,

   eddie

1. 
   UncleDunc | Jan 13, 2005 07:27am | #3

   The formula looks right, but I think you slipped a digit transcribing. I get 356F.

1. 
   eddiefromAustralia | Jan 13, 2005 09:30am | #5

   Thanks Uncle Dunc,You're right on the maths - minor slip of the fingers would make a major difference in the result.Moderate oven heat - if done properly, it shouldn't raise an oxide colour - the temper colours are for instantaneous flame heat at the surface - the centre is slightly colder.Basically, to keep the hardness, you want to temper the minimum amount possibleCheers,eddie

   Edited 1/13/2005 1:34 am ET by eddie (aust)

1. 
   UncleDunc | Jan 13, 2005 05:30pm | #10

   >> ... if done properly, it shouldn't raise an oxide colour ...My own experience and all my metalworking references reach the opposite conclusion. I don't think any ordinary tool steel chisel subjected to the temperature and time you describe could fail to turn color.

1. 
   eddiefromAustralia | Jan 14, 2005 02:26pm | #15

   Hi UD,Nae dramas - I'm dual-trade, one of which is a degree metallurgist - This time and temp shouldn't form a thick enough oxide film to cause the steel to change colour - I've done it several times when the boss was out so she couldn't see what I was using the oven for.A bit hotter and it would but.Cheers,Andrew(off to bed after working in 44ºC/111ºF heat all day - waiting for autumn to arrive)

2. 
   GRW | Jan 13, 2005 04:30pm | #7

   I just bought some old socket chisels which I will be putting new handles on. Do you folks suggest I temper them in my oven at 356F before I install the handles?

   Are there other tools that you think this process would help? (plane irons, ect.)

   Thanks,

   Stuart

1. 
   UncleDunc | Jan 13, 2005 05:02pm | #9

   >> Do you folks suggest I temper them in my oven at 356F before I install the handles?Only if you're having trouble with the edges chipping. I think I would fit the handles first so I could test the edges, and then temper the blades if necessary.>> Are there other tools that you think this process would help?Any hardened steel cutting tool needs to be tempered at least to the point that the edge doesn't chip. If your cutting edges aren't chipping, your tools are soft enough. (If your edges are folding over, your tools may be too soft and need to be rehardened, or maybe you just need to sharpen them to a blunter angle, or learn to take smaller bites.)

   Edited 1/13/2005 9:11 am ET by Uncle Dunc

3. 
   UncleDunc | Jan 13, 2005 07:31am | #4

   Here's a table that relates oxide color to temperature, if you don't trust the dial on your oven. Scroll to the bottom.

   http://64.78.42.182/sweethaven/BldgConst/Welding/lessonmain.asp?lesNum=2&modNum=4

1. 
   cherryjohn | Jan 13, 2005 04:12pm | #6

   Dunc, you never cease to amaze me......a living , breathing Dewey Decimal SystemWicked Decent Woodworks

   Rochester NH

   " If the women dont find you handsome, they should at least find you handy........yessa!"

4. 
   Crunk | Jan 13, 2005 04:52pm | #8

   You're kidding I hope. You mean you literally shipped chisels to have them cryo treated?

   Buy some Two Cherries or something along those lines (a medium priced quality chisel) and get back to woodworking.

5. 
   JohnWW | Jan 13, 2005 08:33pm | #11

   Two things:

   1.  What did the company that treated your chisels say?  It would seem that they should have some expertise in this area.  At a minimum I think they should have warned you about the likely damage to the handles.  It would also seem that they did something wrong and should correct the problem, they were supposed to improve the performance of the chisels not make them worse. 

   Like heat treating, cryo treating is an exacting fussy process.  if these guys were amateurs who just dumped your chisels into a bucket of liquid nitrogen for a few minutes, and then warmed them up and shipped back to you with a bill, it would explain why you are getting a poor result.  It may also be that not all steels cryo treat equally, but they should know that also.

   2.  Using all capitals in your posting makes them considerably harder to read.

   John W.

6. 
   sharpblade | Jan 13, 2005 10:54pm | #12

   There are a few things here that don't make sense, here's my comments:

   1) Freezing  a chisel down to -300 deg F in & by itself isn't supposed to improve its performance, as you just found out.  Cryo treatment only works on the higher alloy steels (high Cr steels such as D2 and the stainless steels), and should be done as part of the heat treating process, typically immediately after the hardening step.  

   2) I am guessing that your chisels are most definitely NOT made from one of these steels.  Simply not typical.   Deep freezing isn't supposed to make any hardeneable steel tougher, so your expectation was off to start with.  It isn't supposed to make it any more brittle either according to my experience & the stuff I've read, are you sure the chipping on the Marples is worse than before?

   3) If toughening the chisels is what you want to do, then tempering them further (as others have suggested) if done properly ought to do it.  You may want to remove the handles if possible before you do that.

   4) I am curious as to the folks who did the treatment for you, a pro shop or some hackers? You paid for it in $  (other that the degradation of the tools?)  Many plastics and synthetics are ruined by deep temps, they become brittle and can break like glass.  I would assume that a serious HT shop would ask you what you're trying to achieve instead of blindly taking your $ and doing what you ask of them.

   Also as someone else mentioned, please turn of the ALL CAPS (leftmost key, middle row on keyboard). thanks.

1. 
   GHR | Jan 14, 2005 02:02am | #13

   From a very good steel site:A2 and D2 are two common grades which may contain significant (20% or more) retained austenite after normal heat treating. Retained austenite may be undesirable for a number of reasons. By cooling the steel to cryogenic (sub-zero) temperatures, this retained austenite may be transformed to martensite. The newly formed martensite is similar to the original as-quenched structure and must be tempered. Cryogenic treatments should include a temper after freezing. Often the freezing may be performed between normally scheduled multiple tempers. Technically, cryogenic treatments are most effective as an integral part of the original quench, but due to the high risk of cracking, as discussed in the “Quenching” section above, we recommend tempering material normally at least once before performing any cryogenic treatments.

7. 
   NARDO | Jan 14, 2005 06:00am | #14

   I don't think cryo works on chisels that are already hardened,I thought it was part of the manufacturing process and needed to be done just after tempering stage.I willing to bet Lie-Neilsen would know the answer to that since they use the process themselves and usually they're good about answering questions.