Keeping grind lines sharp during hand sanding

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unky_gumbi

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Aug 28, 2009
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I am working on my first non full flat grind and want to keep my grind lines sharp, but they keep rounding out. The swedge stays nice and sharp but it is at a steeper angle than the bevel so that explains that.

I am keeping my paper as tight as possible on my sanding sticks, I have locked my finger to the under side of the blade to keep my angle on the bevel, yet I still get that rounded mushy looking grind line. I have tried with both of my sanding sticks, one is a piece of oak trim about 1" wide by 6" long and the other is a piece of 2oz leather backed brass about .5" wide by 5" long. I get my best results with the piece of oak, but it still isn't what I am looking for. The grind was nice and sharp off of the grinder and it is easy to pull it back with a pass or two with a file, but I can't keep taking away material till I get it right by trial and error so I could use a few pointers and suggestions here

Thanks a lot
George

PS I feel I really need these sharp standout grind lines to make the knife pop visually.
 
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I would use a heavier sanding device, something that won't flex, go slower, maybe glue down the sand paper, and mask off where you don't want to sand. It sounds like you are rocking which is what's making the rounded lines.
 
Leather backed brass... ?????

Once I get down to sharpening up transition lines, I use steel backing with TIGHT paper and a light touch. Think more about staying flat to the surface you are sanding rather than the line itself. If you start focusing on making the line straight and crisp, you may have a tendency to lean into it a bit. Just my .002".
 
Thanks for the suggestions, I have to make a run to the grocery store but I will give both those ideas a try when I get back.

Rick the brass flat stock has a piece of 2oz leather glued to it, I find it makes sanding in the plunge lines easier and give a nice smooth rounded transition from the plunge to the bevel. Normally that is the only place I use that one, it allows me to get a nice finish in that area and move the sanding marks out far enough for me to eliminate most of the fish hooks, if I just try using the oak trim piece I have I don't get in close enough:o. I still have some O-1 scraps that are too small to use for a 3/16" thick knife so I guess that will be another sanding stick for me.
 
Also, try to line up the edge of the paper with the edge that you would like to not round off. Follow up with the swedge edge since it is at a sharper angle; done with great precision as Rick mentions.
 
Are you using your grinder, now George? How fine a grit are you using befor going to hand sanding? I go to 16 and some 6 with the Norton belts.I use micarta blocks. Also, try using Mobil 1 to help avoid the fish hooks if you are not now doing that. Frank
 
I use a square steel tube, no soft backing. I glue strips of paper to it with contact cement. Not that it means much since I've made like 3 knives, but it works pretty good for flat surfaces for me
 
I take the lazy route and sand the bevels then take the blade to the 6x48 grinder and surface the flats, seems to work well. I used to sand the flats then the bevels, just happened to do it backwards one day!
 
I still struggle with that myself. I'd say your best bet is to do as Frank said and go with as high a grit as you can on the grinder. I don't see how you can keep the lines crisp if you have to do a lot of hand sanding with heavier grits.
 
I only have some Zirconia belts with the highest grit being 220 grit, so I start my hand sanding at 320 grit. I have being trying a combination of Rick's piece of steel and gluing the paper to it and it is working pretty good for me. I need to get some good/better contact cement, what I have right now is some 12 year old Canadian Tire spray on stuff. It is working, but it doesn't set up fully and the paper has a tendency to slide off the steel. the old stuff is working better than my other option, Tandy leather cement. It sticks to the paper but not the steel. I apply it let it tack up put the two together and the curl in the paper pulls the glue off the steel:D

I am hoping to get it sanded out to my HT finish tonight and will post a couple of pictures of the results later tonight or early tomorrow.
 
You might try using a fixed backing/block for the sandpaper and move the blade back and forth on it. If you are tilting/rocking your angle, this will eliminate a lot of that. The rest sounds like you need a more rigid backing. It takes very little flex in your sanding stick to mess up a nice flat grind.
 
I just can't see using any backing like leather or (?) on a sanding stick. It's like trying to flat grind with a slack belt. I also believe the 320 isn't fine enough on the belts to be used before hand sanding. I am repeating these things because I believe them to be very important in helping to get the results you want. If you start working with Damascus you will find it is even more important to go as far as you can with machine grinding. Frank
 
It was suggested to me back on the first knife I made as a way to limit the amount of fish hooks I was getting and it does work, but up until I had this wash out problem I had never used it for anything other than plunge line areas. The rest of my blades were sanded out with the piece of oak, but everything up until now have been full flat grinds so there was no wash out to be had.

Right now due to finances all I have is some 60g, 120g and 220g belts so I am unable to take things higher on the grinder till WCB and my doctors get off their butts and either clear me to work or start paying my my full wage replacement. I was all set to buy a couple hundred dollars worth of belts before my forced move. I have one more payment to my mother for the move to make then I can start buying supplies again, for now $500 a month doesn't go far:(

The tips are working even though I can only go to a 220 belt finish. I have one side at 400 grit and the other is almost done to 600 grit. I still have a few light scratches from the 400 to clean up before it is done, but that line keeps getting sharper.

This is the side that is almost fully sanded to 600 grit
DSC02549.jpg


and right at the tip the line is sharp as can be
DSC02551.jpg
 
My best to you on the injurie and financial recovery. Good for you to do more of the hand thing to get by with !!! Yes it is looking pretty darn good now !!!! Frank
 
sharpeknives said:
Looking good so far. Try a spray adhesive to attach the sandpaper to the steel.
Click to expand...

I am using a spray on adhesive, its just 12 years old:eek: I had bought it before I moved to Winnipeg to do a custom speaker box for a friends car. It works, barely, it just doesn't set up enough to keep the paper from sliding off the steel. I do a couple of strokes, and slide the paper back to where it is supposed to be. It will do for now and if there is enough money left over from my next check I will pick up some better glue.
 
go to a bike shop and buy some patch glue, few bucks will get you by for this blade, if you're thrifty with it. Goes pretty far. That's what I used on my first knife, then I spent a whole 10 bucks or so and got a jar of contact cement from the hardware store. I tried the spray adhesive and found that it sucked, compared to contact cement, for me at any rate. Besides I love huffin patch glue.
 
Why this need to glue on? For hollow grinds I have an arc cut out of micarta, It is about 1" wide and has an arc for a 9 1/2" circle. I have cut out part of the curve on the inside . I use this on hollow grinds done with a 10" wheel. I simply hold the sand paper on to the arc with my fingers and away I go with a few drops of Mobile 1 on the metal.The sand paper stays there just fine. Frank
 
When I flat grind , I grind on the belt sander to 320 g and then move over to my disc sander with a fresh piece of 400G just to check my flatness and change my scratch pattern to see if I missed a few 220 g scratches. My disc is reversible and variable speed so I do this edge up and fairly slow . I also use a 1/8" semi hard rubber backing between my paper and the steel disc. This makes hand sanding easy .

For hand sanding I glue a piece of G10 to an old 3/4 " wide flat file and slightly radius the corners . I cut silicone carbide sandpaper into 1" X 4 ish" strips and wet sand the blade holding the paper with my hands. I start with 400 g and go up from there . Change out your paper often . It appears to me by looking at your blade that you are using your paper to long and to dry . It looks like you are partly sanding and partly burnishing your blade with the metal that is impregnated into your paper which is why it looks uneven.

Once you get all the scratches out and want a nice uniform finish use fresh sandpaper , keep it wet and only sand in one direction using smooth long strokes . Take only 2 or 3 strokes before moving to a fresh area of your sandpaper.

I use this to clamp my blades to:
I cut a strip of hardwood approx 2" wide 1/2 " thick and 15 or so inches long and spray glue a piece of leather to it . I clamp this to my workbench leaving whatever the length of my blade is overhanging my bench and clamp my blades to this with a simple spring clamp . It will be easy to sand your blades using a contraption such as this as you will have plenty of room for your hands on either side of this blade rest and you wont risk gutting yourself if you stand up or lean over your bench to reach for something . I see to many makers just clamp there blades over the edge of there work bench and have known a few that got hurt pretty bad , so be careful . Hope this helps !!
 
Also, try a wider block. I find that a 1.5" or a 2" wide block will wobble less with the stroke.
 
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