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

Try close spacing between belt grits around 120 grit or even a redundant stage at that point... 120 ceramic to 100 gator belt (180 grit) or even 120 ceramic to 300 gator belt (120 grit IIRC).

I find most scratches lie within that area and the close spacing between grits really helps. I learned this when I did lapidary for living, I'd go from a 220 hard diamond wheel to a 280 backed wheel and the small jump in grits really removed those scratches I'd see pop up later at around 600 grit... which is another trick... after your last ceramic belt go straight to 600 or so (just a pass or two) and you will really see those deeper scratches "pop up."

Once your base is super clean you can sometimes skip grits, etc...

Also pay attention to your last few passes and do them lightly. You should be able to see the difference between a light pass and a heavy one.
 
Daniel Fairly Knives said:
Try close spacing between belt grits around 120 grit or even a redundant stage at that point... 120 ceramic to 100 gator belt (180 grit) or even 120 ceramic to 300 gator belt (120 grit IIRC).

I find most scratches lie within that area and the close spacing between grits really helps. I learned this when I did lapidary for living, I'd go from a 220 hard diamond wheel to a 280 backed wheel and the small jump in grits really removed those scratches I'd see pop up later at around 600 grit... which is another trick... after your last ceramic belt go straight to 600 or so (just a pass or two) and you will really see those deeper scratches "pop up."

Once your base is super clean you can sometimes skip grits, etc...

Also pay attention to your last few passes and do them lightly. You should be able to see the difference between a light pass and a heavy one.
Click to expand...


Great tips all around. I grind 50 grit, 120, grit, then 320 or 400 on a disc then hand sand. Sometimes I might come back to the disc and add a soft backing with 220 grit paper to get the party started early. Total time hand sanding lately is less than 30 minutes. Used to spend hours! Now on average its about 15 minutes total. The key to using the 2x72 or whatever grinder is to grind the 50 grit like this |||||| then the 120 grit like this \\\\\\\ that way you see the overlapping scratches. You can also put some graphite tape on your platen or leather, something firm but slightly forgiving and go back to the 120 to blend it. Not sure if this is ideal for tactical nightmare spooky grinds but it works well for full flat.

At least this is what I do until I find a better way to shave steps or time off.
 
Has anyone made a really good knife making video, which focusing on highlighting how to use a disc grinder? I have the TG-92 grinder from Tru-Grit, but I honestly struggle using it on flattening grinds. I really only use it for squaring up knife scales, making a few home made tools, etc.
 
I start with 80 grit to get the pre ht grind in there. After ht I begin again with the 80 grit and clean up the steel. Then on to 120 grit to refine the grind. When the shape of the grind is close to what I want I drop the tip and change the angle the 120 grit belt runs. This really highlights the missed 80 grit scratches. I get all the scratches (especially at the tip area) in the new direction and leave them like that. Then I go to Trizac Gator belts from there. The key with getting the scratches out is to go across the old scratches in a new direction. It is very fast to know whether the 80 grit stuff is still there or is truly gone.
 
stereo.pete said:
Has anyone made a really good knife making video, which focusing on highlighting how to use a disc grinder? I have the TG-92 grinder from Tru-Grit, but I honestly struggle using it on flattening grinds. I really only use it for squaring up knife scales, making a few home made tools, etc.
Click to expand...

Yea, somebody should really do that. ;) :foot:

While the TG-92 is a super nice unit, it's not suited to blade grinding because you don't want a table on the disc while blade grinding.
 
Aaron,
Does it matter if the blade rusts mid-way through finishing? I have always accepted that when wet hand sanding O1, the bottom side of the blade would start to rust. I just leave it alone until I start getting to the fine grits, 800+. At that point the steel seems less prone to rust anyway. I don't think it has ever made a difference in the final finish, but maybe I have just been lucky....???

I use the EDM stones in 220g and 400g in the middle of the finishing sequence, lengthways down the blade to show up deep scratches and to take them out. Then back on the grinder with 400 Norax or cork to take out the EDM scratches. Do it at 400 and I know there are no deeper scratches left. Only using O1, RWL34 and 12C27, so might not work so well on high carbide steels.
 
Making a 9" grinder is very easy. Something like a 1hp 3ph motor with a 5/8" shaft. Your choice of flat or beveled disc, or maybe Nielsen's disc system with the interchangeable discs. Power it with something like a KBAC-24D, so even if you don't have 220 you can run the motor off 110v. Mount it to a plate or even 3/4" plywood, or directly to a bench. Wayne Coe has a video where he shows one with a plywood base, and an attached piece the same size at the back so it can be used in either vertical or horizontal orientation.

Pretty east to source parts and put together and save some money. If you think you may want to ad the Beaumont adjustable workmrest some time make sure you get a 56C motor. They are mostly used for pumps and have four threaded holes on the face, which is where that particular rest bolts up.
 
C_Claycomb said:
Aaron,
Does it matter if the blade rusts mid-way through finishing?
Click to expand...

WD40 the blade, I even use it to wet sand....and I use windex as well.

If you are gettting rust in the time period of sanding then you might want to take it off at the 1/2 way mark, clean and hit with WD40.
 
A coat of Dykem between belts will usually highlight any residual scratches from previous grits.
 
Daniel has given me another out. I don't flat grind much so I've been hoping for answers that better suit that styling. You are another maker I see doing terribly good grinding for the time at it. I would love to be able to make a noticeable improvement , at least to me, in my grinding. Frank
 
Since Aarons original question was about finishing better on the grinder, I have something to add. Don't get in a hurry putting the blade back onto the belt. Most of the deeper scratches come from touching one edge of the belt first. If you want to come off the grinder with the best finish possible, be very careful how you introduce the blade to the grinder at all grits. We used to have a saying when teaching Close Quarters Combat/Room Clearing; "Slow is smooth, smooth is fast". Seems to apply to grinding pretty well too.

Bob
 
Aaron, I have had a 9 inch variable speed disc grinder for over four years but I was afraid to use it for much more than dovetailed bolsters or squaring pieces of steel. When I had a finished a blade ( 99%) I was afraid to put it against the disc and sand the flats above my grind lines and the ricasso for fear of spoiling the blade. I wasn't getting the really nice crisp lines that others were getting. I sent e-mails to David Sharp and other fine knife makers asking for advice to get flatter and smoother flats out of my flat platen and they all pretty much said that I would have to learn to use the disc to get things really flat and nicely finished. I slowed the disc speed down and used finer grits of Rhynowet red paper sprayed with a mist of water and a block with magnets in it to hold my blades against the disc. I also put a tiny chamfer on the disc edge to keep from getting edge marks and I am slowly getting better and better results. I now use the disc on every blade. Nick Wheeler has a really good video segment showing finishing a blade with the disc. You have a really nice shop and you need this tool. It will save on hand sanding and give a better finish in my admittedly limited experience. Larry
 
NickWheeler said:
Yea, somebody should really do that. ;) :foot:

While the TG-92 is a super nice unit, it's not suited to blade grinding because you don't want a table on the disc while blade grinding.
Click to expand...


Nick, is this the video you are "referencing?" :D [video=youtube;RwjO3DDf4eE]https://www.youtube.com/watch?v=RwjO3DDf4eE[/video]

Looks like I am going to need to save up and buy another disc grinder, still though I would love to see a more in depth video, which specifically talks and demonstrates the use of a disc grinder in knife making.
 
This has worked well for me.

60 grit ceramic

180 grit gator

Fine scotchbrite belt sprayed with WD40 as its running.

Thats it! I like a satin finish look, and this is a great looking finish for all kinds of knives. Maybe not for everybody, but I really like it.

I recently added a 240 grit gator to this progression, and the finish is even better.

To freshen up the gator belts, take a wire brush lightly across the belt as it's running.
 
Pete--- Nope, I was meant this part of the series I did this year ;)

[video=youtube;ssribfAn8TQ]https://www.youtube.com/watch?v=ssribfAn8TQ[/video]
 
C_Claycomb said:
Aaron,
Does it matter if the blade rusts mid-way through finishing? I have always accepted that when wet hand sanding O1, the bottom side of the blade would start to rust. I just leave it alone until I start getting to the fine grits, 800+. At that point the steel seems less prone to rust anyway. I don't think it has ever made a difference in the final finish, but maybe I have just been lucky....???

I use the EDM stones in 220g and 400g in the middle of the finishing sequence, lengthways down the blade to show up deep scratches and to take them out. Then back on the grinder with 400 Norax or cork to take out the EDM scratches. Do it at 400 and I know there are no deeper scratches left. Only using O1, RWL34 and 12C27, so might not work so well on high carbide steels.
Click to expand...

Hey mate!
In my case the rusting does matter as it happens when I'm close to fine finishing... A friend pointed out an anti-rust additive that's designed for use with waterstones the other day. I believe you can also add borax to your sanding water to stop rust, so there are options that I haven't tried yet.
 
Thanks for all the tips guys! Sounds like I might be skipping grits too much right at the beginning, I will change that and see how it goes. I will also buy a diamond lapping plate so I can start using the EDM stones more.

How do you guys refresh a scotchbrite belt? mine has gotten gunked up on the surface but should still be good underneath that...
 
Great thread!

Also... an 80 grit belt has a much smaller grit size than a 60 grit belt. Try skipping from 60-600 and 80-600 and you will see a massive difference. 80 is much easier to finish from.
 
Josh Mason said:
This has worked well for me.

60 grit ceramic

180 grit gator

Fine scotchbrite belt sprayed with WD40 as its running.

Thats it! I like a satin finish look, and this is a great looking finish for all kinds of knives. Maybe not for everybody, but I really like it.

I recently added a 240 grit gator to this progression, and the finish is even better.

To freshen up the gator belts, take a wire brush lightly across the belt as it's running.
Click to expand...

Josh....you might like trying this... Buy a cork 220 belt, break it in and then run it after the 180 gator...It will give a nice stain finish with a slight polish that makes a nice working finish.

This little blade was finish like that. I think you might like the cork in 220...and it lasts for several years as well, does not get contaminated and you can control the scratch pattern better then you can with the scotch brite belt.
LzPErQe.jpg
 
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