Blade Thickness Before Sharpening

[Ploppy Blobby]

Hi all,
this may be a REALLY dumb Q, when grinding the blade how thick do you leave the edge before sharpening. Seems wrong to grind all the way so the 2 planes meet. Have ground it down to 0.4mm/0.1575″ and am not sure whether to reduce further. Any pointers would really help.
Pic to follow cos that ^ may not make sense

 

[Ploppy Blobby]

It really is hard getting those shots

 

[ma_sha1]

Can’t tell what’s in the picture.
But when I thin, I tend to thin it all the way until the two plains meet, but the two plains are convex not flat, then do 12-15 degree sharpening gives it micro bevel if the zero edge is too thin, not strong enough.

 

[Benuser]

Rule of thumb for general purpose chef's knives once finished:
Thickness immediately behind the bevel 0.2mm; at 5mm from there 0.5mm; at 1cm 1mm.

 

[The Edge]

Welcome to the fun of knife making! Most makers test different grinds to see what they like. My advice would be to start testing it out for yourself. You can also compare other knives with calipers to see what they've done. Making a great knife is hard work. Grinding metal isn't easy or fast, especially when you're dealing with hardened steel.

So the answer is: it depends. What is the knife meant for/what will you be cutting? Are you designing for ease of cutting, food release, or some combination thereof. What can the steel handle? Who's going to be using it?

Every maker has a slightly different view, and none of them are wrong.

Sorry for not giving you numbers, but you'll learn more making and testing. My advice would be to go much thinner though if the steel has already been heat treated. You can always put an edge on, test, thin, test, thin, etc.

 

[Ploppy Blobby]

Can’t tell what’s in the picture.

Ah, that's the top edge of this

 

[Ploppy Blobby]

Welcome to the fun of knife making!

Quite should have put a lot more info into the OP.
Am attempting a Santoku, of hardened carbon steel (HRC~61, 105WCr6 /1.2419) another practice piece for veg etc.
Thanks for the help folks, deffo need to reduce the thickness, back to the grind.............

 

[milkbaby]

For heat treated steel, I prefer to grind my kitchen knives to zero before sharpening then put the edge bevel on by sharpening. So the knife will cut food decently before sharpening, but it won't be that crazy serial killer sharp that you want for the finished product. Carrot cut of by not yet sharpened knife here: https://www.instagram.com/p/BePSSd2HfVq

Before heat treating, for carbon steel you want to leave around 0.5 to 1 mm or more edge thickness to avoid "bacon edge" when heat treating. The thinner you go, the less hard steel you have to grind away post-HT but the more likely you'll get bacon edge... Some people prefer to do all grinding post-HT (also depending on steel) to avoid warping issues.

 

[Ploppy Blobby]

As an aside, how do you respond when your partner complains that your knife is TOO sharp!?

 

[John N]

I am usually about .2 - .3 mm off the (water cooled) grinding wheel at the very edge. Stone finishing (or paper sanding) brings it a bit thinner before sharpening.

You have to be very careful not to toast a thin edge with heat when grinding, and be aware you have *no* margin for error.

It is beneficial to stop grinding, and give the blade a few sharpening strokes on a stone to verify edge is true before continuing. A flat stone does not lie.

 

[John N]

This is the last one I finished, Bit thinner behind edge than I normally go - this was about .1mm , not sharpened in the photo, quite a flat profile to the grind.

Daft as it sounds, when you are taking a choil shot, turn your phone upside down, so the carmea lense is closest to the handle. You can then flip the image! - white background helps.

 

[Ploppy Blobby]

this was about .1mm , not sharpened in the photo

In my dreams! Already binned one blank after leaning on the belt too hard.

 

[Ploppy Blobby]

This is the last one I finished, Bit thinner behind edge than I normally go - this was about .1mm , not sharpened in the photo, quite a flat profile to the grind.

Daft as it sounds, when you are taking a choil shot, turn your phone upside down, so the carmea lense is closest to the handle. You can then flip the image! - white background helps.

Sweet blade

 

[Ploppy Blobby]

Tried to emulate your shot when I saw what thought was a warp in the blade and turned out to be an overground in the middle. Dunno which is worse