Blade bow pre heat treat

[Bill Thomas]

I have ground two chef knifes, 12" oal to about .020 edge thickness. Before grinding I marked the center of the 1/8" x 3" Aldo 52100 stock on the spine and the blade side. I hit the mark on the tip of the blade perfect leaving the scribe line. I did some 150 hand sanding to take the plunge and the 80 and 120 grind lines out. I put the blade on a granite slab to check the tip with a piece of soapstone. I have an approximate 1/8" tip difference on both blades. I placed a clamp on the tang and another about 2/3rds down towards the tip. If the blade would retain this shape it would be dead perfect. I send my blades to Peters for heat treat. Is this something that I can/should straighten before sending, or can this be done during heat treat? I have another 4' section of 52100 that I laid on my bench and noticed it has a bow. I am not sure if it came bowed, but I have a feeling it bowed because I left it in the shipping tube leaning in the corner of my shop for 6 months. Is that possible? Can I clamp the blade to a piece of angle iron and put it in the oven or will this harm the steel? What would you do to get these blades straight? It's too late to surface grind. Thank you.

 

[P.Brewster]

In my experience, Peters will correct any existing bow. They told me that I am not saving them any time by straightening knives before HT.

You can find a lot of info about cold/hot straightening by doing a search.

 

[Bill Thomas]

Patrick
Thanks for the info, that is very helpful to know. I assumed that once it was heated a bow could be straightened. I was afraid if I tried to straighten it cold I might end up with an S bend rather than a U. I did plenty of reading but found nothing as helpful as what you said about Peters.

 

[Maelstrom78]

I have been on an AEB-L chef knife kick lately and those long and thin blades will bend as you grind them. It seems to be lessened if you alternate sides frequently while grinding but from those more knowledgeable than myself AEB-L is known to bow while grinding.

This big dude wanted to curve during initial grinding for sure.

Also be aware of the bending if you can't seem to get some part of the blade how you like it. Chances are it is concave there and your belt isn't contacting it squarely. So for accurate grinding keeping an eye out for bowing might be one reason to keep them straight IMO.

I'm no He-Man (I had a considerate person describe my hands as "dainty" )but I just bend the blade back with my hands or gently against my knee. Seems to keep them straight.

I did use a rubber mallet on a flat surface but doing it by hand is easier and straighter for me.

 

[Bill Thomas]

Thanks Maelstrom78
On my next chef knife I am going to make it a point to check my tip with the soapstone after I have ground to my center line scribe reference and before I start hogging away metal. This should tell me at what stage I am getting the bow. Is it the stock, is it from the 80-120 grind, or is it during hand sand pressure.

 

[Maelstrom78]

I would lay the profiled blade on a flat surface and straighten it first before even starting to grind personally. Some more experienced ppl probably don't need to but I need all the help I can get to get nice grind lines.

I do FFG almost exclusively, but to keep practicing my bevels I do my best during the different stages of bringing the bevel back to the spine to keep them even. Like if I wasn't going to do a full flat grind (which is forgiving of uneven grinding as there is very little left to compare to side to side when complete) how would my bevels look? I'm getting better but don't let a FFG allow you to short change yourself in improving your grinding. My .02 (Doing so has shown me I have a long way to go! )