S-s-stutterin!

Lorien

Lorien

Nose to the Grindstone
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Knifemaker / Craftsman / Service Provider
Joined
Dec 5, 2005
Messages
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hey shoptalkers, I'm having a really hard time with something and I'm hoping someone might have some magic beans of wisdom which will help me identify and solve my problem.

two knives I'm working on, S30V and A2- same problem. I'm hand sanding with 1500 grit paper, and the scratches are nice and parallel, not much in the way of fish hooks and the surface looks even. But under a certain light, there are these stutters- it's like the light breaks up into bars perpendicular to the scratches. It doesn't feel like the paper is catching on anything but it's been a couple of days trying to get the perfect finish and I'm at wit's end.

the crappy thing is I'm trying to repair the finish AFTER I've stuck the handles on🤦‍♂️. I don't wanna go too coarse because it's going to be WAY trickier to fix the ricasso area.

any ideas on how I should proceed?
 
I assume you have seen the Nick Wheeler YouTube video on hand sanding.
One quick tip that works for me is related to the backing. I use a bare rectangle of 416 steel as a backing until I get beyond 800 grit. Then I put a layer of duct tape over the backing to make it just a tiny bit softer for the higher grits.
You left out a lot of details like what kind of surface you are sanding FFG or convex, what type of paper you have, wet or dry, your grit progression.
 
Are you sanding with a leather or rubber backing on a hard surface?

If so, tilt the sanding stick so the one edge is in contact as you make the final pull.

Also use a brand new strip of paper with the final pull.
 
Can you take a picture and share it? A cellphone pic will show all kinds of detail that even your eyes will have trouble seeing. You need good lighting with no glare.
 
This may sound like a really random question… but what happens if you drastically change the light you use .. especially if you go outside in the sun ?
 
Are there any liquids, oils ,fingerprints, or substances that you may have inadvertently gotten on there?oily smudges can wreak havoc with optics.
 
Nick who?🤣
Definitely going to watch Nick's videos again.
Has anyone encountered what I described?
I cleaned the shop up today, that will help with the frustration level at least
 
I get this when I go to 1200 - 2000. Then I put cloth between my sanding block and the sandpaper. I change the sandpaper very often for the last few strokes and I try to make them with only one move covering all the blade.
 
Could be some magnetism in your steel. I worked one recently that had 1/2 inch alternating polarity along the length of the blade. It would hold swarf unevenly, but eventually submitted to copious application of elbow grease.

I have one now which had a spot of decarb near the spine and it will not finish evenly. The decarb goes all the way through. No biggie for me, it just became my knife and the defect is in a spot that won't hurt anything.
 
Justin W said:
Could be some magnetism in your steel. I worked one recently that had 1/2 inch alternating polarity along the length of the blade. It would hold swarf unevenly, but eventually submitted to copious application of elbow grease.
Click to expand...
Could that be from surface grinding with a mag chuck?
 
What kind of sandpaper are you using?
Larrin Larrin describes in his book how if the abrasive your using is softer then the carbides in the steel (also depends on how big they are as well) then it will create a kind of orange peel texture, I wonder if that’s what you are experiencing to some degree.
 
I think i've seen what your talking about in the same steels you're talking about plus s35vn and cpm154 at higher grits above 800. Do they look like irregular shaped very slightly raised areas that just aren't sanding down as fast as the rest of blade under certain light? If so I think it's in the steel and may be caused by heat treating, maybe for some reason the blade got a little harder in that area and wears down slightly slower than the rest of the blade during hand sanding. I have had very poor luck eliminating them, if you find a solution please share it I would to get rid of them myself.

 
Lorien said:
But under a certain light, there are these stutters- it's like the light breaks up into bars perpendicular to the scratches.
It doesn't feel like the paper is catching on anything but it's been a couple of days trying to get the perfect finish and I'm at wit's end.

the crappy thing is I'm trying to repair the finish AFTER I've stuck the handles on🤦‍♂️. I don't wanna go too coarse because it's going to be WAY trickier to fix the ricasso area.

any ideas on how I should proceed?
Click to expand...

Is there a liquid layer on like oil, or windex ?

Is it like the effect you get with you use an optical flat prism on a flat surface ?

If you degrease it perfectly clean and dry is it still there ?
 
cleaned up the finishing area and set things up so my work is better supported- I think that's where my problems lie. Made some sanding tools and I guess I'll get back in there with 1200 or 1000 grit until I get the perfect finish I'm trying for
WGdFgyL.jpg
 
Lorien said:
cleaned up the finishing area and set things up so my work is better supported- I think that's where my problems lie. Made some sanding tools and I guess I'll get back in there with 1200 or 1000 grit until I get the perfect finish I'm trying for
WGdFgyL.jpg
Click to expand...
Can you post a pic and show us the problem?
 
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