Troubleshoot bent knives

[Smashmasta]

Talk to me about the best ways to correct bent knives, from accute bends at the tip, to gentle curves along the spine, to twists, etc. I've come across a couple bent tips for customers that I can usually get nearly true again by covering in a towel, and gently using a ballpen hammer on a vice base (or other hard surface). Bigger gentle curves along the spine, and twests are somethings I'm hesistant to touch right now. I don't have a tempering oven (although I have a kitchen oven), and many of the knives I encounter have Western handles, so removing those handles is PIA. Not sure if such an option with ovens even exists, but if so, I might not be able to make it work. Thanks for the input. Direct me to another thread if there's one indentical.

 

[RDalman]

The techniques and amount of force you can use will vary depending on steel and HT, for example iron san mai, you can quite safely give quite the beating. Always best with the blade at tempering temp. Better than nothing is halfway there (boiling water maybe?) sample of useful techniques:
Three brass rods in a vice. Hammer. Stick with channel sawed, like the japanese use sometimes. Sometimes just a table will do, or even in hand for a long slight bow on thin san mai.

 

[Dendrobatez]

I usually fix curves by laying the tip on a plastic cutting board, putting weight on the palm of my hand where it's the worst and pulling up on the handle, it takes a while as the blade springs back to mostly where it was. For tips I'll usually clamp the tip between 2 peices of hard wood and bend it back. I've never broken anything but then again I also haven't done this on other people knives, I'd probably be hesitant to do so.

Aframes uses these not sure how it works on a tip though.
https://www.instagram.com/p/BcTKLyDgLYD/?utm_source=ig_share_sheet&igshid=1fp0irsibtxuf

 

[LucasFur]

I've had a minor bend that was able to be repaired by thinning. Be careful if its a totally bent blade then it will develop a over grind like this.
BUT I had a wave in a blade from say forcing my way through cheese. Thinning removed the wave, and now i use a thicker knife for the task.

 

[captaincaed]

Can light hammering on a concave surface help straighten a blade? Are there any makers out there watching this thread? I've seen smiths use a concave wooden stump and a soft-faced mallet to help bring something into true.

I have a vintage Sab that's about 13" long with a subtle curve. Would really love to get it worked out, but I'm worried about putting a new curvature into the blade.

 

[Smashmasta]

I usually fix curves by laying the tip on a plastic cutting board, putting weight on the palm of my hand where it's the worst and pulling up on the handle, it takes a while as the blade springs back to mostly where it was. For tips I'll usually clamp the tip between 2 peices of hard wood and bend it back. I've never broken anything but then again I also haven't done this on other people knives, I'd probably be hesitant to do so.

Aframes uses these not sure how it works on a tip though.
https://www.instagram.com/p/BcTKLyDgLYD/?utm_source=ig_share_sheet&igshid=1fp0irsibtxuf

Any idea how it works in general? Do you just put the blade in a slot and leave it there until it straightens itself out?

 

[Dendrobatez]

You put the spine into a slot and use it as a lever to straighten the blade. It's best to have the handle or if you can another part of the blade in a vise

 

[JBroida]

I know there is a lot of encouragement for people to straighten blades themselves, and in theory, it shouldn't be that hard. I often try to dissuade people from doing this themselves. It takes a lot of practice to do it well and to do so without causing additional problems. Learning how and where to apply pressure takes time. Blades can break, additional bends can be harder to fix, and so forth. But the most difficult thing is training one's eyes to see bends, twisting, and other kinds of warping better... this takes time no matter how you do it.

In this case, you're sharpening professionally, so clearly taking the time to learn how to do this well will be very important. But in most cases for people not experienced in this, unless you feel very comfortable with the risk of further damaging or even breaking your knife, I would recommend not doing this yourself. I straightened a few hundred blades before starting to do this for customers.

 

[Smashmasta]

Thanks everyone for the input on possible solutions to bent knives. Definitely feeling more confident to (carefully) repair some. But, a bent knife seems to be the easiest skewed problem to solve - what about twisted knives where the spine may be somewhat straight, but the axis of the spine to edge is out of allignment?

 

[JBroida]

those are much harder... the best way to fix them requires some serious refinishing afterwards (chisel hammer) and the easiest way can cause huge amounts of damage very quickly (clamping and twisting).

 

[HRC_64]

Worth mentioning in this thread in case anyone isn't aware of it -- Hammers used for metal work are typicall faced and polished (to semi-mirror). Often times the necessity of this step is only obvious in hindsight, or to people who have been trained in some way.

 

[JBroida]

very true

 

[Smashmasta]

those are much harder... the best way to fix them requires some serious refinishing afterwards (chisel hammer) and the easiest way can cause huge amounts of damage very quickly (clamping and twisting).

Jon, you should do a bent and twisted fix video, with a banner moving across the top saying, "don't try this at home." To which I will certainly try at home (but on my own knives first). But seriously, that would be awesomely helpful.

 

[JBroida]

i've thought about it, but i know that people will take that and try these things at home... and i cant teach people how to see things better. I cant emphasize enough the importance of training your eyes to see better in the scope of what you are doing. That takes a long time.