Help make it shine

[Archer Here]

Some of you may know, I am a new knife maker and I need some advice before I pull my hair out. How do you sand and polish a blade and not get the lines, like the picture below. This is how I’m doing it: I’m starting out at 60 grit flap disk, for on my 4 inch grinder and working my way down to a 160 grit, and that’s what is leaving these lines. I thought I could get rid of this by using wet dry sand paper, and I started at 320 grit to 400 grit and ended with 600 grit and it just left a dull finish. So I went back with my flap discs to at least get that shine, but it leaves those lines. Help please.

 

[SteelSlaver]

Clamp the blade down flat. The take a piece of 1 1/2 wide or 2" wide 1/4" thick steel flat bar. Wrap a strip of your sand paper around it and go to scrubbing. If your surface is not flat but convex glue a matching piece of thick leather or hard rubber to one side of your flat bar and wrap sand paper around that. Start at the lower grits and work up. 60, 120, 180, 240, 320, 400, 600, 1200 2000, how shiny you want it. Get all the scratches out at each step. I have 2 belt grinders and a flat disk. I get them as good as I can on those and usuallt can start by hand at 120 or so. Ihave belts to 600 and cork belts too, but, as yet the only way I can get a true. scratch free finish is by hand. Thw better I do with the belts the less I do by hand but ig I finish by machine at 400, I usually need to start at 220 hand sanding. The better I am with the machines the quicker I can finish by hand. Once you get a good 220 hand job:jerkit:, it won't take long to go up thru the rest. Jim

 

[J.S. Carter]

The better I am with the machines the quicker I can finish by hand. Once you get a good 220 hand job:jerkit:, it won't take long to go up thru the rest. Jim

Said Dr McCoy! LMAO! :foot:

No seriously What Jim said is Right Go through the steps by hand. After you get the basic shape and bevels filed in, it's time to do the eternal back and forth dance.

 

[Will Leavitt]

Welcome to the makers section of BF

I hand polish my blades so it may not be quite the shine you want (not like some mirror finish) but one of my 1500 or 2000 grit finishes comes pretty close. A mirror polish requires the use of a buffer... that's the most dangerous machine in a maker's shop and to be honest, I'm afraid of buffing blades.

The secret to a good metal polish is the same as on your bows, a good foundation. Can't get a pretty shine on rough wood, same applies to metal. You want to make sure your metal is flat or uniformly curved if it's a hollow or convex grind.

You have to make sure every scratch from the previous grit is gone before moving to a higher grit. A 60x scratch will always wait until 1000x to show itself I use dykem or magic markers to color the blade so I can see where I'm removing metal and make sure that I change directions when I change grit. So all the coarser scratches should, I say "should" be gone when the dykem/marker is gone and all the scratches from the different direction are erased.

I usually hand sand from 220 or 400 to 600-2000 depending on how the knife is to be used or customer preference. I finish on my grinder with a 400x cork belt loaded with green polishing compound. Usually I can go straight to 400 from there (probably go 600 but I do like to hand polish lol) I use 3m sandpaper with water up to 600x. I don't try to get every single bit of use out of the paper, if I think it's not cutting, I toss it. 600x on up I use baby oil as a lube, there's a saying, "water cuts, oil polishes." Yes, I do a 600x with water and a 600x with oil. It does make a difference.

The last grit is done using a "straight pull" instead of back and forth to prevent j-hooks and to keep the lines straight. The last couple of sanding strokes are done dry, just seems to leave a cleaner finish at the end.

I use some sanding blocks made of 1/4" micarta. I use the 1/4" side to do my polishing, I find it helps keep my sanding cleaner and I get a little more pressure that way. I have a block with leather on it for convex blades.

I hope this helps. By the way, what's your name? If you'd add it your sig line we could call you something other than Archer, unless Archer is your name....

 

[Mark G]

I use dykem or magic markers to color the blade so I can see where I'm removing metal and make sure that I change directions when I change grit. So all the coarser scratches should, I say "should" be gone when the dykem/marker is gone and all the scratches from the different direction are erased.

Will, I thought you were supposed to go in the same direction as you changed grits....wrong? (newbie here too so it is a question and not a statement).

Mark

 

[scottickes]

Will, I thought you were supposed to go in the same direction as you changed grits....wrong? (newbie here too so it is a question and not a statement).

Mark

I change directions with each grit change. If you're sanding down the length of the blade and see scratches running from the edge up to the spine, then you need to stay at that grit until they're gone.

Once their gone, move to a finer grit and go from the edge to the spine. Sand this way, until you get rid of all the scratches running the length of the blade.

I use the dykem sometimes too, to help me see what I'm removing. I also have poor eyesight up close, so I use 3.5X reading glasses while hand sanding to see better. I'll even take a magnifying glass and check it out to make sure, before I move to a finer grit.

I've found that any sanding done with a finer grit before you should have moved to a finer grit is completely wasted time and effort. Because you'll just have to go back to a coarser grit to fix the stuff you missed and that will ruin all the finer grit hand sanding.

"My motto is: "Never move to a finer grit before it's time."

 

[SteelSlaver]

Another thing is good light. You need to see the scratches. I wear an optivisor as I am getting up a bit (57) and I also have a small flash light near my sanding area. before I quit with each grit I give the blade a pass with the flashlight from different angles. Amazing what you see when the light hits from a different angle.

 

[Will Leavitt]

I have a magnifying lens light thingy and wear an optivisor when I hand sand. Light is important, different lights at different angles really helps to inspect the finish.

 

[Archer Here]

Thanks for all the great advice. Now I will apply it to my methods, which is pretty rough right now; but will be better soon.

One problem I have: Home Depot and Lowe’s does not carry anything over 600 grit wet dry paper. Where does one go to get up to 2000?

Will, I added my name to my signature. It’s Chris. Archer is from Star Trek Enterprise, and also I’m a Bow Archer.

 

[Will Leavitt]

Thanks for all the great advice. Now I will apply it to my methods, which is pretty rough right now; but will be better soon.

One problem I have: Home Depot and Lowe’s does not carry anything over 600 grit wet dry paper. Where does one go to get up to 2000?

Will, I added my name to my signature. It’s Chris. Archer is from Star Trek Enterprise, and also I’m a Bow Archer.

Cool, nice to meet you Chris I'm an archer too... mainly shoot a wheel bow but have taken deer with a flat bow I made.

Check your local auto body supply store, they'll have QUALITY sandpaper up to about 2500 or so. A good 600x finish is a very good working knife finish. Course a good 600x finish is better than a half ass 2000x finish. You'll need more of the lower grits than the finer grits.

 

[Archer Here]

Great. Easy enough. My wife works as a programmer for O’Reilly Auto Parts. I should be able to get it pretty cheap. One other question. How do you put pictures in the post themselves on this forum. When I pick the “attach” option, you have to point your mouse on the picture to enlarge it. Is there some kind of code I can use to “embed” it into the post itself? Sorry … not real computer literate…

 

[Rusty McDonald]

Do you use photobucket if not google it and make an account upload your pic that you have on your pc to the img site using the blue button that says choose files, (hold ctrl down to choose multiple files) then all you have to do is select the IMG code under the pic it will copy automaticly for you, then paste on the site and there you have it.
remember you need to have the [/img] thing in it should kind of look like this

 

[silver_pilate]

All good information on here.... Another tip would be the following: when you're switching from a machine to a hand finishing, I at the least start with the same grit by hand that I finished on the machine with. Often, I start with a rougher grit. For instance, if I finish at 400 on the grinder, I'll usually start with a 320 paper and work up from there. When you're using powered abrasives, there are often high spots or large grains that you'll get in a new belt/flap wheel and they can create scratches that run pretty deep....deeper than you want to spend the time on to get out using a high grit paper. If I finish at 400 on the machine and notice some big scratches as I'm working with 320, I'll sometimes even jump down to a 220 hand paper to quickly work them out. The scratches made by hand are just so much less severe than a powered abrasive that it doesn't take that much longer to start at a lower grit and work up. Once that initial hand finish grit is well established (for instance, the 320 sandpaper), the following grits will go a lot faster. The toughest part of hand finishing is to remove those stubborn deep grinder scratches.

--nathan