Sanding. Any tips, techniques, and advice is welcome!

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Smithoncorner

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Aug 3, 2012
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I have only just started making knives, and i have had a bit of trouble making evenly shaped bevels with my table sander. Not to mention the finish on my blade isn't very fine, even though i have gone down to 400 grit (then polished with emery cloth). Is there a sanding belt made specifically for metal work? Any help would be great!
 
What exactly do you mean by table sander? If you're talking about a benchtop 4x36, these are not normally used for knife making. They will take off metal but are not setup so that you can get right to the edge of the belt, to do nice plunge lines. Also the platens (backing plate) are not very flat. Also the range of belt grits and types is more limited.

However that is probably not the main issue with your uneven grinds. If you're freehanding then it's probably that you're not keeping a consistent angle, or are lingering too long in one area. It's easy to get into a vicious cycle where you take a little too much off of one spot, try to correct it by taking off more in another area, then screw that up and have to take off even more in first spot. I just try to keep taking very even passes from heel to tip, never stopping in one area. A very fast belt speed on the sander makes all of this more difficult. To keep the angle in check, start with very high angles (like a machete grind) and gradually lay them back to achieve the height that you want. It's easier to control this way than going for your final grind angle from the start.

For the finish, what are you trying to go for? 400 grit would be a fairly coarse finish for many custom knives, but if done neatly (aligning all of the scratch lines) it can make a decent satin finish. What grit emery cloth are you finishing with? I don't think I have seen emery cloth that was very fine grit (compared to what you can get with sandpaper). When hand finishing you need a good flat surface to back the paper, and take long even strokes. To avoid swirl scratch lines do all of the strokes in one direction and lift off the paper before you stop each stroke. If you are going for a mirror polish you will need to go through all the grits up to 2500 or higher, and then buff it most likely. The fine hand-rubbed satin finishes might stop at 1200 grit or so. But even 120 grit can look good if done carefully.
 
I had the same issues with the bevel when I first started. I designed a jig and it changed everything for me. PM me and I can send photos or explain further and even build you one if you like. The jig is very simple.

As far as your sander and frustration, it all comes down to paper quality and grit. If you are using a high carbon you are going to eat up paper it’s just how it is. That being said, grit and paper quality mean everything. Only using one grit of paper will probably never give you the results you are looking for. I prefer to use something in the 30 grit range for stock removal and usually work up to around 400 grit for finishing.
 
Robs92XJ - My sander is actually a regular belt sander flipped upside-down. Not the most professional setup :p but it's what i have to work with at this point. I am hoping to get a bit of a finer finish. So would moving up from a 400 to say a 600 grit help fix that issue? As long as i proceed carefully. The emery cloth i used was 1000 grit i think. I also have seen some people use steel wool. Thoughts on that?

tyecop15- I am Pm'ing you right now! lol
 
Hey you have to start somewhere. And like I said it's probably not the sander setup, crude as it is, that's holding you back. You need to develop a feel for controlling the grinding angle, and just be smooth.

The finer grit you go, the better your finish. To make it look really good you need to get everything flat and even to start, with your coarse grits; get rid of any bumps or divots. Your grind lines need to be crisp. Then go up in the grits, but don't skip any. With every grit, you need to remove all of the coarse scratches from the previous grit before you go to the finer one. Keep all of the scratch lines going the same.

The difference between 400 and 600 grit is not huge for a final finish, but if you're going to finish at 1000 grit you need to go through the 600 grit.

If you're having trouble with the belt sander, do the finishing by hand. Much harder to screw it up. Try doig a search in this forum for hand finishing, I believe there are several good tutorials with photos.
 
Okay, thanks for the help! Do you usually use the belt sander to put the first edge on your blade? then move to files and wet stones? Also, do you use angle grinders for any of the bevel grinding/sharpening/anything else? haha
 
I suppose you could use just about anything for sharpening, but if you've got a belt sander I see no reason to use an angle grinder. Those are more useful for cutting out the shape initially.

Is the blade heat treated yet? If not you don't want to take it all the way to an edge yet. Leave a bit of thickness there to prevent warping.

If it's already been treated, then you can use the sander but be very careful with the heat you create. If you want to play it safe then do not take the edge all the way on the sander; get to where there is just a tiny bit of flat metal still visible. Then apex and sharpen with stones/files.
 
I see no need to use every available grit of sandpaper. personaly I go from 60x for hogging to 220x then to 400x then I do some pre HT hand sanding to refine my grindlines going back down to 220x then straight back to 400x before HT. once back from HT I go 400x ,800x (I stop at 800x for a satin finish) 1500x, 2000x, and finaly 2500x if i'm taking it that high.
 
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