Help me learn to finish better on the grinder...

[aarongough]

Hey guys!
It became clear recently by way of discussion in other threads that I clearly do not know how to finish on the grinder as well as many others can. I'm comfortable with my proficiency when finishing by hand, but that obviously takes a lot longer than finishing on the grinder.

My goal is to minimize the amount of hand-sanding I have to do in order to produce a tail-to-tip satin finish. If I could go straight to 800 grit when hand sanding and have 15-20 minutes or less of hand sanding on a blade that would be ideal.

The big issue that I tend to run into is that on the grinder all the grit marks are going in the same direction, so I really have no way of telling when I've eliminated the marks from the previous belt. That means I can finish all the way to 600-800 grit on the grinder, then start hand sanding only to find out I have some 220 belt marks still left in the blade... How do you guys deal with that?

Also, when finishing on the grinder what's your general progression of belts? I've personally found that the trizact belts tend to cut very slowly so I often use A/O or silicon carbide belts instead (bear in mind my blade are always 62HRC+). My latest attempts at finishing on the grinder used the following progression:

120 blaze -> 220 A/O -> 400 A/O
Heat Treat
400 A/O -> 600 S/C -> Hand sand

I rough in my bevels using my grinding jig, then do all the finishing from then on freehand, I find I tend to undercut the plunge line less often that way.

Any and all help greatly appreciated! Looking forward to learning some new things!

-Aaron

 

[Lo/Rez]

Good post. I'm looking forward to the replys. I have some Norax belts up to 600 or 700 grit (can't remember) hoping to alleviate some sanding, but haven't used them yet.

 

[LARRYZ10]

Aaron, I put the same question to some knife makers that I admire and they suggested trying some 2x72 belts that they were having success with. I have been using Trizact belts also and they have some really good qualities but also some downside compared to other belts. I would suggest that you try some Norax belts starting with X65 (or65x..I forget) and go through the progression of 65X, 45X, 30X 20X, 16X, and maybe 5X which is over 1200 grit equivalent I think. When you get to 16X you will see your face in the blade. I have recently bought some Deerfos belts which are felt backed in 1200 grit equivalent and 2000 grit equivalent. I think that I got them from Tru Grit. These are thin and you cannot feel a seam so they finish really nice. You will still have some tiny , tiny grind lines but you can sand them out in a few minutes at most. These are what David Sharp suggested to save on the hand sanding and I like them. Yesterday I got some new trizact belts in A20 which is about 1200 grit and A6 which is about 2500 grit. These also came from Tru Grit but I have not used them yet . These belts do not look like Trizact belts...they look like a sparkly hologram or the back of a DVD only crisscrossed. I am posting a photo of a knife blade that I ground this week showing the finish before hand sanding and just before using the disc to flatten the ricasso and the flat area above the grind. They were finished with the Deerfos belts. Trying these belts may help you as they did me. Larry

 

[Maelstrom78]

Maybe go up to higher grits before HT as well?

 

[AVigil]

There are many ways to get there....

I really suggest you buy Steve Johnsons video on building a subhilt fighter. He will show you in detail how to get it to a high finish on the grinder.

Personally I grind 36 to hog off material.

50 to get the grind almost to where I want.

120 to refine the grind

220 to remove the 120

400 Gator to things smoothed out

400 cork to remove scratches

800 cork to a good polish

Back down to 500 hand sand

Then 800 hand sand.

I do this for blades that essentially are going to be displayed and sit in a case...because they are pretty


For blades that are going to see some use and do not need to be like glass....

I can stop at 220 grit and hit with a 400 cork grit for a satin finish for a hard use blade.

I can stop at 400 grit and hit with a scotch brite belt for a nice satin finish like on a skinner


Aaron the trick to get a nice hand sanded finish for me is to go up in higher grits on the grinder then step back down to a lower grit to hand sand and then work your way back up from there.

 

[aarongough]

Aaron, I put the same question to some knife makers that I admire and they suggested trying some 2x72 belts that they were having success with. I have been using Trizact belts also and they have some really good qualities but also some downside compared to other belts. I would suggest that you try some Norax belts starting with X65 (or65x..I forget) and go through the progression of 65X, 45X, 30X 20X, 16X, and maybe 5X which is over 1200 grit equivalent I think. When you get to 16X you will see your face in the blade. I have recently bought some Deerfos belts which are felt backed in 1200 grit equivalent and 2000 grit equivalent. I think that I got them from Tru Grit. These are thin and you cannot feel a seam so they finish really nice. You will still have some tiny , tiny grind lines but you can sand them out in a few minutes at most. These are what David Sharp suggested to save on the hand sanding and I like them. Yesterday I got some new trizact belts in A20 which is about 1200 grit and A6 which is about 2500 grit. These also came from Tru Grit but I have not used them yet . These belts do not look like Trizact belts...they look like a sparkly hologram or the back of a DVD only crisscrossed. I am posting a photo of a knife blade that I ground this week showing the finish before hand sanding and just before using the disc to flatten the ricasso and the flat area above the grind. They were finished with the Deerfos belts. Trying these belts may help you as they did me. Larry

Thanks Larry, I will have a look at the different belts on the Tru Grit site.

 

[aarongough]

Maybe go up to higher grits before HT as well?

Yes I agree, I had meant to do that on the most recent batch but I forgot.

There are many ways to get there....

I really suggest you buy Steve Johnsons video on building a subhilt fighter. He will show you in detail how to get it to a high finish on the grinder.

Personally I grind 36 to hog off material.

50 to get the grind almost to where I want.

120 to refine the grind

220 to remove the 120

400 Gator to things smoothed out

400 cork to remove scratches

800 cork to a good polish

Back down to 500 hand sand

Then 800 hand sand.

I do this for blades that essentially are going to be displayed and sit in a case...because they are pretty


For blades that are going to see some use and do not need to be like glass....

I can stop at 220 grit and hit with a 400 cork grit for a satin finish for a hard use blade.

I can stop at 400 grit and hit with a scotch brite belt for a nice satin finish like on a skinner


Aaron the trick to get a nice hand sanded finish for me is to go up in higher grits on the grinder then step back down to a lower grit to hand sand and then work your way back up from there.

Thanks Adam,
I know you really like the Cork belts, I will make sure to order some of those next time!

How do you tell when you've eliminated all the previous grinding marks with each new belt? That's one of the big things that causes me grief...

I agree that I should be going higher on the grinder, then dropping back down. Makes sense, I just have to get some finer belts.

-Aaron

 

[Salolan]

To help me see the previous grit scratches, I use a wide sharpie marker. The bigger scratches should still show black after you've sanded the rest of the marker away, I'm sure dyechem would do the same.

Chris

 

[AVigil]

To find scratches I use light and optivisor

 

[Nathan the Machinist]

We use Dykem blue here to help see deep scratches and spots between belt progressions. You can still remove the blue from the bottom of deep scratches with grinding dust so it's not 100% perfect, but it will help you catch most of them.

For flat grinds you can change grinding direction. Not so much with a hollow grind.

Try grinding lengthwise for flat grinds. Way under utilized IMO.

I think it's worth learning to use EDM stones for hand work (Falcon tool, N grade). They cut faster and don't wash out like paper. You still finish with paper, but the stones do a better job for most of it. We all have a lot to learn from mold makers.

 

[Lu1967]

Vari-speed disk grinder in higher grits has helped me with this same problem.

 

[PEU]

Nathan, the EDM stones catched my attention, how do you keep them flat so they properly replace sandpaper+block ?


Pablo

 

[JG Custom Metal Works]

One thing I'll add is make sure your platen is flat and doesn't have any gouges in it. I usually scrape black buildup off with a razor but I was having an issue with my grinding lines the other day and inspected it and found it to be shot to shit with a bunch of gouges. It's just a standard KMG platen so I was able to flip it over and use the other side. I did flatten it out a little bit first on my surface plate because the surface was a little rough. I'll probably buy a reserve for once this one goes out. Once I get the new one I'll just put it on and then surface grind the old one with the new one. Eventually I'll just buck up and buy one of Nathan's hardened D2 platens with the radiused tops.

I might also try out a glass platen but when I'm profile grinding I really push the side of the steel into the platen and I'm not sure if the glass would hold up...

 

[aarongough]

I have tried EDM stones and I really like them, you definitely need a diamond plate to keep them flat though... My waterstone lapping stone won't even touch the EDM stones as the bond is too hard. I'm using the Orange EDM stones from MoldShopTools.com

The difficult part for me when using the EDM stones is rust prevention. I'm used to using a little WD40 on the opposite side of the blade when sanding to keep it from rusting, but that oil instantly soaks into the EDM stones and makes them load up like crazy. Once they get oil on the it seems there's no way to fix that.

I will make sure to use dykem or sharpie on my blades more often!

Thanks for the tips so far guys!

 

[Patrice Lemée]

Subscribed, always looking to improve in that area too. Thanks.

 

[Frank Niro]

I've been at this for more years than most and still am have to do too much hand sanding. I do as much as necessary but I don't think it helps the grind lines. Most of this is hollow grinding.I too have that problem of not been able to recognize the scratch problem as being good or incomplete as I go along from one grit to another. I believe LarryZ10 has said it all as one way to get there and so has AVigil. I expect I'm over using the belts. I'm going to try the sharpie and or the Dykem blue that I think I have some of. Yes, once in a while I do see results that I'm pleased with so I know it can be done.
Frank

 

[PEU]

I don't know the english name for this wheel:

It helps a lot when you are around 150/180 grit to fast forward to a nice finish, not satin, but nice nevertheless, ideal for users not shelf queens. I use it with yellow paste, a very fine polishing compound for stainless. If you use lenghtwise the only drawback is that you cannot polish very near to the ricaso

Also when I use sandpaper I have an aluminum stick with firm leather attached to one side, sometimes using this side down helps with rebel lines
To remove lines near the ricaso I use different tools, a chisel shaped piece of acrilyc, also use 280 grit SIA pads and other times a scrap piece of wet thick soft leather.


Pablo

 

[kc custom]

Aaron I grind both on a disc and hollow grind. A disc is simple because you just keep going up in grit as high as you
want. Hollow grinding (granted they are folders so the blades are smaller but the mechanics should remain the same)
I start on heat treated blades with 60 Zirconia, go to 180 ceramic, then 320 grit "J Flex". I start hand sanding with
320 SC and just go up in the grits from there. Not much more than 5 min. per side of a blade. I know this works on
bigger blades because I've done it on hunters with 5" blades up to 7" bladed fighters. Possibly a bit longer on the bigger
blades. If the grind is right hand finishing is'nt all that big of a deal. I can't remember the last time I ground flat on a
platen at least not in the finishing grits.
Ken.

 

[Frank Niro]

I'm saying thank you Ken, and I haven't tried your way yet. I do know it works . I see the super finish you have on your blades. I will be trying this for sure. Frank

 

[aarongough]

Aaron I grind both on a disc and hollow grind. A disc is simple because you just keep going up in grit as high as you
want. Hollow grinding (granted they are folders so the blades are smaller but the mechanics should remain the same)
I start on heat treated blades with 60 Zirconia, go to 180 ceramic, then 320 grit "J Flex". I start hand sanding with
320 SC and just go up in the grits from there. Not much more than 5 min. per side of a blade. I know this works on
bigger blades because I've done it on hunters with 5" blades up to 7" bladed fighters. Possibly a bit longer on the bigger
blades. If the grind is right hand finishing is'nt all that big of a deal. I can't remember the last time I ground flat on a
platen at least not in the finishing grits.
Ken.

Interesting! I keep seeing people use discs but have never tried it. Guess I'll have to get one at some point soon!