How to assess straightness, bowing, twist or other concerns with a knife?

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Hey knife fam,

I received a new knife in the mail today. The spine appears (ever so) slightly bowed to my eye. Are there easy ways to assess or test for straightness? Should I evaluate both spine and edge? On that note, are there other structural problems I should look for (e.g., twist or others) when evaluating a new knife? Thanks for your help. Cheers!
 
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Lay the knife on the edge of your cutting board, handle off the edge so it rests on the blade only (if the size of the knife can support it), spine facing you. Is it flat?

I did this with the new knife and four other gyuto, all side-by-side. The new knife stuck out bc it had the least spine-to-board contact of the group. I'll temper that with the knowledge that my cutting board/counter/etc. are not perfectly flat, but this was helpful.



This was also helpful. I need better light I think, so I'll try looking at this more in the morning. Maybe I noticed a little twist?

I understand these are handmade tools, so not perfect. Just trying to assess if the knife is straight within reason.

May have to get a second (professional) opinion tomorrow.

Thanks for all the help!
 

tostadas

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Even if it's not straight, it's not necessarily a problem. My cck cleaver was both bent and twisted and I used it for a year without even noticing. Sometimes fixing the bend is as simple as laying the tip of the knife on a sturdy surface and applying force to bend it back
 

Pie

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Twists and bends will affect your sharpening, although it can be overcome with a bit of extra attention. Performance may vary by case I suppose.
 

blokey

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Even if it's not straight, it's not necessarily a problem. My cck cleaver was both bent and twisted and I used it for a year without even noticing. Sometimes fixing the bend is as simple as laying the tip of the knife on a sturdy surface and applying force to bend it back
CCKs are cheap tho, I have never seen a straight CCK 1302, all of them have slightly bend grind or spine.
 

Corradobrit1

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Deviations in the spine are not that critical, particularly if barely perceptible to the eye. If the distortion extends through the blade road down to the edge then you have a problem. Cuts can be affected, the ability to sharpen properly will be impacted and for me its a deal breaker, together with overgrinds that hit the edge. To check this place the knife on its side on a flat surface like a chopping board, with the handle over the edge. Press the heel with the thumb so the blade road falls flat against the board. Repeat on other side and note the difference along the edge and especially the tip. Here's a good example of a bent TF Morihei Ku 210 Fine Finish I received. This deviation made the knife contact with the board, when rocked, really weird.

bent2.jpg
bent1.jpg
 
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