# Trying to get a centerline for grinding with distal tapers and warps.



## Don Nguyen (Aug 19, 2013)

This is one of the biggest things I struggle with.

Normally I could just go to a surface plate with a flat blank and scribe it out, but on the big kitchen knives it gets tricky for me.

I usually do the distal taper before heat treat, and they never come out perfectly straight (I can get them straight enough to grind them OK). How would you do the centerline in this situation? I've been eyeballing my knives so far but there has got to be a more efficient method. In other WIP's I have seen, they have surface grinders and some fancy scribe setups, but that's a bit much for myself in this stage.

The issue I'm having, putting it shortly, is that I don't have a straight enough blade to accurately scribe out.


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## CrisAnderson27 (Aug 19, 2013)

Are you on Facebook right now?


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## Zwiefel (Aug 19, 2013)

Im pretty stupid about this stuff but....Ive seen a micrometer used to measure thicknesx, calculate the centerline, then used to scribe it along the spine using the blade itself as the guide.

HTH


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## Don Nguyen (Aug 19, 2013)

Dan the problem I'm having is that I would need a perfect straight blade with uniform thickness to do that. My blades are relatively straight, good enough to grind down, but not enough to do an accurate line. I also have the distal taper so the it gets thinner towards the tip.

I was talking to Cris about this and he gave me some good pointers, but if I'd really like to get a dead-on line I think I'll have to revise something in my methods.

Maybe something I can do is leave the tang a little thicker than normal, grind that as flat and straight as I possibly can, and then go with a height gauge and surface plate. The idea would be to use the tang as the reference point.


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## CrisAnderson27 (Aug 20, 2013)

Don Nguyen said:


> Maybe something I can do is leave the tang a little thicker than normal, grind that as flat and straight as I possibly can, and then go with a height gauge and surface plate. The idea would be to use the tang as the reference point.



That will work great, if you can get the point to line back up with the tang out of the quench . Although, you could use your height gauge to help you get the point in line maybe.

I don't know...it all seems too complicated lol. I like the 'grind the waves out of both sides and see what you've got to work with first' method better...but I know it goes against your engineering student sensibilities =p.


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## DevinT (Aug 20, 2013)

You could find a center point any where along the blade by using your height gage and the surface plate. Scribe two parallel lines even with the sides of the blade and where they intersect is the center point. Do that at the point and the heel and one or more times in between. That should get you close enough and the rest is by eye.

Hoss


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## CrisAnderson27 (Aug 20, 2013)

DevinT said:


> You could find a center point any where along the blade by using your height gage and the surface plate. Scribe two parallel lines even with the sides of the blade and where they intersect is the center point. Do that at the point and the heel and one or more times in between. That should get you close enough and the rest is by eye.
> 
> Hoss



We talked about something similar Devin, only using a scribe that registers on the flat. I made a tool awhile back for that purpose...mark from one flat, then the other...in between the marks is the center. The height gauge would find the accurate center of the existing piece...but until he's ground the warps out, he won't know if the 'center' he found...is actually going to be 'the center' anymore lol.

Honestly though, his current methods are turning out gorgeous knives! I'd almost say leave well enough alone...but I totally understand jiggling the handle of a process to try to make it more efficient.


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## pitonboy (Aug 20, 2013)

Devin, if you do the distal taper AFTER the heat treatment, would that do anything to minimize stress and thereby warpage?


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## DevinT (Aug 20, 2013)

Yes, anytime there is a variance in thickness there are added stresses in the quench.

Hoss


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