I would like to discuss mirror finish on a buffer

B

Black cat

Well-Known Member
Just a random thought really.
I spent about four hours yesterday trying to buff out a small imperfection about the size of a speck of dust.

I can get a pretty decent mirror finish these days. I'm picky so it has to be free of distortion, imperfections and haze or small scratches.

I know what I can do to improve my buffing game, which is far from perfect (especially since my last buffing wheel burst into flames and is no more :p )

One thing I notice is sometimes very small imperfections (not scratches) show up.
Usually when you are near the end and at a very high luster.

If i'm lucky a little buffing can get rid of any that show up. If i'm not lucky, more appear while i'm working on the first one.

Too me it looks like imbedded grit or idk carbon? I also noticed if you comstantly buff in one direction it makes them worse by cutting around them. If you ever over buff a soft handle material around a steel pin and you notice it makes a groove around the pin. That's what these marks do. That tells me that it could be something hard deposited in the blade.

I wonder if its carbon from the blade itself or it could be grit from my wheel or buffing compound. Those are my best guess.

It doesnt really bother me but I havent found much info on it and i'm a little curious what these are.

I do have to get some new wheels/compound, slower buffer speed, dust covers for the wheels, and baggies to keep the compound clean. I'm sure that will help.

I have seen a few blades from a vetran knofe maker in my area who (sadly) passed away before I could ever meet him. His grinds and polishing imo were perfect! I want to achieve the same skill someday. I think i'm getting pretty close now (practice)

Anyway, back out to the shop... I have a stack of unfinished blades to work my way through in the next few weeks.
 
The 'secret' to a really beautiful imperfection free mirror polish is not the result of high-quality buffing.
A good mirror polish is the result of effective sanding.
You don't remove imperfections in your work piece by buffing.
You need everything perfect at 2000 grit, or 3000 grit. Then buffing only takes a few seconds and your work piece surface is defect-free and consistently smooth and flat.
If you attempt to remove imperfections with the buffer, you will remove areas of material that end up showing in the mirror finish.
Go back to sanding.
ON another note - a nicely done hand-sanded knife blade is not the result of a lot of good hand-sanding.
It's the result of effective and accurate grinding.
 
^ that.

It took me about a year to realize on my own what Karl just shared in one paragraph.

It comes down to this: You cannot sand/buff out a scratch. You have to remove everything that ISN'T the scratch. You are removing an entire layer of blade until the whole blade is now removed down the the lowest level of the bottom of the scratch. Think about it. Sure, you can blend an area- but all that means is you just made a big, gradual divot. That's called a dip or a wave. And it will show, especially in a mirror finish where the light is going to show it off like a dent in a brand new black paint job on a truck. Everything looks good under bad shop lighting. Take that sucker out into the sunlight. It's like meeting a hot woman in the dark bar and then walking out into the light and getting the fright of your life. All of a sudden you have that thing you gotta do early tomorrow and uh, yeah...gotta go! See ya!

Getting things as darn near perfect as you can on the grinder is the holy grail. That's not going to happen in the beginning. But sooner or later you'll come to the conclusion that hand sanding for 4 hours is for the birds and maybe you should just slow down and be more patient and deliberate on the grinder. At least on the grinder - the grinder does the work! It's not a race. Now, I don't mean to infer that you can do everything on your grinder. I'm the world's biggest proponent of hand sanding. But just as Karl says, hand sanding is to get the *finish* you desire, not to remove gouges and dips and waves left over from grinding. It'll be that way for a while. In the beginning, work towards FLAT and EVEN on the grinder. When you are doing that consistently, work towards NO STRAY SCRATCHES on the grinder. You'll find with each step that hand sanding time is reduced a by a lot. A lot of that time savings is that with each improvement on the grinder, you can begin hand sanding at a higher grit.
 
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I've been "preaching" your point for years - thanks for saying it.

My quote has always been, "When you're sanding out scratches - you're not sanding the scratches. You're sanding everything that's NOT a scratch."
You need to take everything down equal to the bottom of the scratches.
Which means going BACK! to the grinder.
Not more hand sanding.

And for some reason, it seems to takes years to figure that out.
It sure did for me.



John Wilson said:
^ that.

It took me about a year to realize on my own what Karl just shared in one paragraph.

It comes down to this: You cannot sand/buff out a scratch. You have to remove everything that ISN'T the scratch.
Click to expand...
 
I always use this concept when teaching nearly any aspect of Bladesmithing/Knifemaking. I call it the Lowest Common Denominator. It applies from forging a blade (if you leave a hammer mark/divot that is the "lowest common denominator" at that time), when grinding if there is a mark/divot anywhere, then the is the "lowest common denominator", and so on. The concept carries through the entire process of a knife, including the finishing work. Sometimes its a tough concept to wrap your head around, but once you do, it changes you're outlook on how to approach a given issue, and allows you address it more appropriately.
 
That's all interesting to consider. Some of that I will have to think about a bit...

Like I rough grind by belt then take it too a wheel. On the wheel I go through rits 320,400,600,800 then I hand sand and buff. I find the wheel does a much finer grind/sand but the marks go in all various directions. Especially with the bevelled disk which actually drives me a bit crazy because I find that small bevel makes a HUGE difference in the shape of the blade imo. I've used flat disks for years and when I went to the bevelled disk... I'm just not getting a feel for it.

By the time I complete hand sanding and take it to the buffing wheel I can get a good mirror pretty quick.
No divits in the sunlight but thats technique. I don't buff a scratch I buff the whole blade till the scratch is gone.

Unless there is a huge scratch or flaw I can have it buffed in a few minutes... However I often have a scratch or two that takes me hours.

More often than scratches though I tend to find super fine... Idk like pin marks that look like this "." If I buff too long in one direction they turn into this "<" to get rid of those I buff, constantly changing directions.

I have no idea what those little pin marks are. Too me they seem like fine imbedded grit or something.

I hand sand quite a bit and really dislike it these days lol, but the whole process is practice. The more I do this the more I learn how to make small adjustments to my technique that makes it easier.
 
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