SGA Finishing

[Sando]

I don't know about you guys, but any vanadium steel is a nightmare to finish. It takes me forever, no matter what method.

So I tried using my SGA (surface grinding attachment) to do the flats, before I grind the bevels. I've gotten good enough with it, that I'm selling knives with that finish. Saves me a ton of time and I can pass a savings on.

So, I thought I'd pass on my recipe:

* Flatten everything with an A300 Trizact (green gator) belt
* Then A160 Trizact
* Then A65 Trizact
* 220 grit cork belt loaded with coarse compound (an A40 belt works too, but I found I liked the cork finish better)
* Medium scotch-brite belt

Tip #1 - in between each belt, cover the blade with a Sharpe and let it dry. Grind until the black is gone, and then a little more.
Tip #2 - move the belt left and right a little, all the time (keeps from making parallel lines in the finish)
Tip #3 - keep the spine to the left (or right) when you change sides. In other words, one side the blade is always point down and the other is point up. This compensates for any unevenness in your chuck.
Tip #4 - after the A160 belt, put tape down on the chuck so you don't scratch the finish.
Tip #5 - I tried using regular, non-trizact belts and I didn't like it at all.

If you've ever tried this you probably noticed some wash-boarding effect caused by the seam in the belt. I can never get rid of it completely, but here's some ways I found to minimize it:

* Before using the belt scrape the grit off the seam area with a coarse stone of some sort.
* Use the absolute minimum pressure will grinding.
* After you finish with one grit, back off the chuck just a tad and make several more passes. Then back it off a tad more and do it again. This seems to knock-down the high spots.

The end product does not look like a normal machine finish from a flat platen and certainly doesn't look like a hand finish. But, it is consistent, smooth, and doesn't take me 3 hours to do a MagnaCut blade.

 

[pafka]

I am avoiding using Trizact/Gator belts on the SGA because I am worried it would wear out in the center and not on edges (since the abrasive is so three dimensional). When you say moving the belt left and right all the time, what do you mean? Do you do it between passes or even during each pass? Ideally if there was a gimmick that would move the belt by itself, that would be nice... Also it would help grinding blades wider than the belt... I do not want to steal the thread, but are there any solutions for that?

 

[Sando]

I am avoiding using Trizact/Gator belts on the SGA because I am worried it would wear out in the center and not on edges (since the abrasive is so three dimensional). When you say moving the belt left and right all the time, what do you mean? Do you do it between passes or even during each pass? Ideally if there was a gimmick that would move the belt by itself, that would be nice... Also it would help grinding blades wider than the belt... I do not want to steal the thread, but are there any solutions for that?

I know what you mean!

I move the belt all the way to the right and make a dozen passes (varies), then all the way to the left. Then a little left and a little right. In other words, I try to use the belt as evenly as possible.

Once in a while I hit it with a coarse square grinding stone (1x1x6), to clean up the belt and level it out.

 

[Scaniaman]

I have done a few Magnacut 63 Hrc. I use 120 ceramic to flatten. Then compact grain VSM KK712X 120 grit to remove scratches from the ceramic belt. Then a couple of minutes with 220 paper handsanding.
The light here makes it look a little more shiny than it is:

 

[Sando]

S Scaniaman that looks great. Did you use a flat platen or SGA?

I swear when I try hand-sanding MagnaCut it just looks worse.

 

[Scaniaman]

S Scaniaman that looks great. Did you use a flat platen or SGA?

I swear when I try hand-sanding MagnaCut it just looks worse.

I use an SGA. The compact grain leaves a really soft scratch pattern, så only brief hand sanding is needed afterwards. On this blade I used maybe 10x10cm paper per side.