Problems with finish

J

Jellis11

Well-Known Member
Hey guys, you have all been helpful so far....I got another issue hopefully some of you may have an answer for. I hand sanded this knife from 150g to 800g grit for two days, heat treated last night then began sanding with 320 and worked my way up to 2000g.

So, problem number one: I have sanded till my fingers were bloody and I cant get rid of these sanding marks. I cross each grit and sand until the previous marks are gone, but even at 2000 I am getting these "scratches"? What am I doing wrong? I think these were left by the 2000g
IMG_2244.JPG

Problem two: I got the bright idea that all I needed to do was buff these out, so I went to Harbor Freight and bought a buffer that came with a "buffing wheel", Picked up some green compound as well.

I turned it on and I thought it was gonna rattle the bolts loose. After it got to full speed and settled down a bit I loaded the wheel up with the green compound and reluctantly began to try and buff the scratch marks out...well, it made things worse..it is a cloth wheel and seemed rather hard...does this buffer suck? Did I use the wrong type of wheel? How do I fix this?
IMG_2245.JPG

Thanks for any help you guys can offer....
 
1. that looks like about a 600 grit finish to me. what kind of sandpaper are you using? what kind of lubricant? are you switching to a new clean paper towel with each grit?

2. the cotton wheels can vary depending on quality and construction. if they are very stiff, cut into the fluffy side to sever the threads. if you look at the side of the wheel the reinforcement threads are concentric circles. You want to cut the outer 2 or 3 to soften the wheel for light buffing. leave the threads alone for scratch removal.

Does the buffer shake if you run it with no wheels on it? if not I'd say your wheels are off center.


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Thanks for the reply John, it is respectively: 150,220,320,400 (3M wet or dry-red); 600,800,1200,2000 (3M wet or dry-black), I'm using windex as a lubricant and clean cotton t-shirt rags to wipe down after each piece of paper I go through. The picture makes it look worse than it is, but still bad enough for this perfectionist to accept. I know its not, but it almost looks like a scratchy haze right under the surface.

That makes sense about the wheel. Ill cut through a few circles and try it out. As a side note, when I was putting the compound on the wheel and when I was running the blade over it, it was throwing threads and shards of cloth all over the place. I'll try taking the wheels off and running it tomorrow...

Thanks again for your reply!
 
I'm not a great knife maker. May never be, but I am a pretty good hand sander! Lot's of practice! John's heading where I would, what kind of sandpaper? I've been using wet/dry type with a lubricant. I've been back and forth with wd40, windex, and even just water. I can't tell a huge difference between the 3, but you need something. I also do my sanding on a 45 degree angle to the edge, then next grit is a 45 in the other direction. For most of the grits I use a hard, very flat tool steel bar as a sanding block. On my last grit I switch to a rubber backed block and finish in the direction of the blade. I have two light sources when sanding, one general light and one at a low raking angle to highlight scratches. My guess is that you're just leaving scratches behind without realizing it. When you think you're done with a grit, keep going a little while longer. Wipe it down, and look at it with some magnification before moving up. Buffers are ok, but if there are scratches in there I haven't had any luck buffing them out either. I sound like a stuck record, I've repeated this to many, but get on YouTube and find Nick Wheelers videos on hand finishing. They helped me the most.
 
When hand sanding I look at the blade under 3 different lights before moving on to the next grit. It is amazing what you see under different light conditions. You might be over using your sand paper. The grit plugs up and it will start ball up and cause deeper scratches. Change your paper often it will cut down time and save paper in the long run. The higher grits are the worst. Also use some kind of a backer on the blade.

IMG_20170319_041120051.jpg

I use a 1X2 clamped in my vise. This also cuts down on how long it takes to hand sand. The blue painter's tape gets pulled off and replaced before flipping the knife over. Some of the scratches look like the ones I get from laying the knife down on the bench unprotected. Try setting on a towel or a clean rag. And Nick's video is the one to watch. The knife is looking good I am looking forward to seeing it when it's done.

ETA; wipe off the blade and reapply new oil when you rotate the sand paper.
 
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Problem #1....right off the bat.....you're spending WAY too much time hand sanding. Hand sanding prior to heat treating is fairly pointless (in most cases, there may be some exceptions but not for our purposes here so I digress), hand sanding to 800 grit prior to heat treating especially is a waste of time. I'm not at all belittling you or making fun...just seems you may have been misinformed. A good 220 grit belt finish prior to heat treating should be more than adequate.

Secondly, if it takes you two days to hand sand an unhardened blade to 800 grit, something is way wrong. I can hand sand 3 blades after heat treat to 1200 grit in a day, and I am certainly not a fast knifemaker. Remember this about hand sanding: You're not trying to sand out a scratch...you're trying to remove ALL THE METAL around the scratch down to the bottom of the deepest scratch. If it takes you two days to do that, hand sanding isn't your problem....good grinding is your problem. You need to make sure your grinds are flat and even, once they are, you should be able to sand a hardened hunter sized blade to 800 grit in 20 minutes per side.

Third....USE GOOD PAPER!!!! if you're not already. Good paper is a must. It seems more expensive at first but in the long run, you'll be hours and hours ahead of the game and time is money. Good paper or bad, once the paper 'slips' on the steel and loses it's bite, toss it and get a new strip. It is totally pointless to scrub and scrub on steel with a piece of worn out paper. As soon as it stops cutting....ditch it. You have to use it like it's free, as hard as that may seem to do. I'd stick with Norton Black Ice paper or RhynoWet Red paper and not even mess around with anything else.

Lastly, are you alternating directions when you sand so you can be sure all the scratches from previous grits are out? I would if you're not. It looks like your picture is a 600 grit finish with some 2000 grit passes over top of it. You should sand plunge line to tip of blade with one grit and go perpendicular or diagonal to that on the next grit, then back to plunge to tip on the following grit and so on and so on. That way you can make sure you have all the scratches from the previous grit out. A GOOD 400 grit finish looks much better than a not so good 1500 grit finish. I've seen many a handed sanded blade that look BEAUTIFUL with a nice even 400 grit hand finish.

Good strong lighting is important...you can't have too much. I like a mix of florescent and incandescent light. Look at your blade from multiple directions carefully to see if you missed anything.

Hope this helps you out.
 
Based on what I see in the 1st photo, there are still marks left over from heavier grits. What that tells me is you did not clean out all the previous grit marks before jumping to the next finer grit. If ANY 150grit marks are missed being COMPLETELY cleaned up with 220 grit, then they will boldly show up when you move to 320 or 400, and so on. You have to train your eyes to pick up on any "missed" heavier grit marks, and get then completely out, before moving on to the next finer grit.....otherwise you end up with what the picture shows.
Good lighting, and looking at the blade as you sand, from different angles, will help reveal anything you missed.

I also echo what John said about using "good" paper.... ANY of the cheaper brands of sanding paper (the stuff you generally buy at hardware stores or home improvement stores) often have "stray" grits of other sizes in them, and it's more of less self-defeating to use them. Personally, I would suggest using ONLY premium grade sandpaper...... such as Norton Black Ice, or Rynowet Redline.

When it comes to buffing, you simply cannot "buff out" scratches, particularly on steel. Trying to do so will generally only get you "buffed over" scratches that show more so then they did prior to buffing.
 
J. Doyle said:
...you're spending WAY too much time hand sanding. Hand sanding prior to heat treating is fairly pointless....
Click to expand...

John, I can't speak for the original poster, but for "me" I often do some hand sanding prior to heat treat. I don't go up to a high grit, but I do use it to check for flatness and to point out any really deep scratches. I often have a little grinding error to two that I can fix with a little preheat treat hand finishing. It so much easier to make those fixes before it's hardened. I've also recently starting using the scrotchbrite belts and they shave off a lot the time I spent hand sanding. Also, he didn't say what steel he was using, but if it's stainless I hand sand to almost finished before ht. I usually don't put my SS blade bevels back on the grinder after ht, not sure if that's how everybody else does it though.
 
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Anthony, I get what you are saying. That is why I said in parentheses that there are some exceptions, like using some stainless steels and for some heat treating applications but generally speaking, if you're gonna grind it again after heat treat, you might as well not hand sand it before.

But....if that's what someone needs to do to make sure they got all the deep scratches out....by all means, I'm all for it.

Sorry for any confusion.
 
Thanks guys, all great information. I have watched Nick Wheelers video and it made a lot of sense. Few things I'm gonna change up: Ive been using the 3M wet/dry red sandpaper from Lowes, I'll be ordering some higher quality paper tomorrow. Also, Ive been using a small homemade 1-1/2" by 2" sanding block made from an old phenolic cutting board....threw it in the trash and made a longer more rigid sanding "bar" out of some scrap 3/16" D2 like the one in Wheelers video. Most likely, as Ed and others pointed out, I am not being thorough enough in getting prior grit sanding marks out. I have taken my lumps and will start over at 150g using what Ive learned here...hopefully I can recover this like a champ.

All the comments are appreciated!
 
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