Straightening after temper?

J

James Hall

Joined
Sep 18, 2013
Messages
85
I had my first successful 1095 quench yesterday using veg oil after cracking one in water. It wasn't until after two 1 hour temper cycles that I realized the blade had a slight warp (I had left the clay on). I saw a post about straightening the warp during tempering, but does it matter if I just throw it in for another cycle to straighten?
 
If you end up with a high enough temperature and long enough time, you can bring the hardness down a bit (time+temp=lowering your hardness). But, you can still help yourself out by using some heat to minimize the possibility of breaking the blade during straightening. I've used a piece of wrought iron wagon wheel rim to help straighten a warped blade. It had a natural curve, so I just clamped on either side of the bend and left it that way during the tempering cycles.





I've also heard of guys using a straight piece of steel. Put a metal rod near the bend between the blade and steel, then clamp appropriately on either side. Good luck, hope it all works out for you.


Jeremy
 
To add to the question, if James doesn't mind, what happens if we temper a knife at, say 400F, and we notice the warp afterwards. Does the temperature then need to be bumped up maybe 10-15 degrees every try, or can the same temp be used to straighten the warp, time and time again, if we aren't successful the first go-around?
 
I'd stay with the same temp to avoid losing too much hardness while doing your multiple temper cycles. Bumping up 25 or 50 degrees isn't going to somehow drastically help straighten the warp, but it will effect your hardness. If you completed your temper cycles already, I'd even try 350. I've seen guys get the knife to temp, then take it out and clamp it (or remove it already clamped) and allow it to cool to room temp that way. Then you can un-clamp and see how it went. Doing it that way, you really have less to worry about as far as losing more hardness, but may not have as much success in straightening in a single cycle of doing that.

Just my $.02.


Jeremy
 
It's safer if you do any bending at 400F or higher if it's a hardened blade. NO cold bending !
 
samuraistuart said:
To add to the question, if James doesn't mind, what happens if we temper a knife at, say 400F, and we notice the warp afterwards. Does the temperature then need to be bumped up maybe 10-15 degrees every try, or can the same temp be used to straighten the warp, time and time again, if we aren't successful the first go-around?
Click to expand...

Here is my experience, YMMV:

I was told that you have to heat the blade @ 400˚ for 2 hours then QUICKLY put it in the vise with a 3 pin set up to bend it straight. I lost a few blades trying that. Now I do as others do. First thing I do is throw the blade in for the first temper cycle, warps and all to relieve stress. starting with the second temper cycle I clamp to a flat bar with appropriate counter-bend using spare change as a jack. Sometimes it takes more than one try to get it just right. I had one blade recently that took 9 two hour temper cycles to get all the wiggles out but I got 'er straight. All those temper cycles were at 350˚. So you don't necessarily have to raise the temp with each successive cycle. I haven't lost one blade this way. Some steels are trickier. I find that 52100 is VERY stubborn. You may have to raise temps in those kinds of cases.
 
Yup... Cold bending=bad things....ask me how I know ;). The exception to that rule for me has only been on edge quenched blades. I've had some success with a 3 pin setup in a vise with that, FWIW.


Jeremy
 
I always run my first temper short of target temp. That way, I relieve stress and have room to straighten AND increase temp and still be at my target temperature.

Know what I mean??:)
 
I used to worry about straightening after a temper and if the blade was still hot enough to do it safely. Then it finally dawned on me to do a draw on the spine of the blade and straighten at the same time. ;) No risk.

Gary
 
I've had to do a BUNCH of shimmed tempers on a few blades, only one or two on most that have a problem. With the stubborn ones, I've found that it works to re-shim and then temper for 45 min. or so- after your first two cycyles, 2 hours at temp isn't necessary. Just getting the blade to temp and soaking it for 1/2 hour saves me a lot of time over say, 6-8 cycles.

It also seems that it works better for me if I leave the blade in the clamped setup hot, and water cool everything down at once. Like, it sets the bend I've shimmed into it a bit more. Maybe it's just me. I do quench after temper cycles anyway, so no harm done.
 
I quench the blade in the clamp set up as well. I do think it helps to set the correction. I suppose you're right about not needing to go 2 hours. But I feel better doing the first two or three at 2 hours. Anything after that, the concern is not with converting RA so just need a quick soak at temp to deal with the wiggles.
 
Just wanted to say thanks for a great thread on this - Ive got a 1080 blade that has a slight warp that I only noticed after 2 temper cycles, so I am going to try this myself. Its all learning for me at the moment, so this advice is awesome! Much appreciated.:):thumbsup:
 
You must log in or register to reply here.
Back
Top