scratches on blade

M

Marcel J.B. Morin

Joined
Sep 17, 1999
Messages
602
No matter how careful I seem to be, I just can't seem to eliminate all the sanding scratches. What am I doing wrong? Thanks for the help.

Marcel
 
Howdy There....!
I do mirro polished finishes myself, and the only help I can give you is to keep going to the next finer grit. I go to 600 and a trizac belt before I go to the buffer. Just keep making those scatches smaller and smaller....! Good Luck!
"Possum"

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Thomas Clegg
 
Marcel, I've had many good smiths tell me how they can mirror finish a blade in 30 minutes. Bull%(&*! IT takes work. Make sure you use the next finer grit each time. Too big a jump and it becomes work. I use baby oil as a cutting oil starting at 400 grit. It helps me a lot. I do go to the buffer from time to time to find the scratches but you really need to let the sandpaper do the work.
Now you know why so many blades are beadblasted.
 
Thirty minutes doesn't sound unreasonable ~if~ all the flats are done prior to grinding. Thirty minutes does not sound unreasonable ~if~ it is a hollow ground blade. But most importantly: Thirty minutes doesn't sound unreasonable ~if~ you've been doing it a while.

It can be easily done by hand in about an hour and a half.

Prior to heat treat, take the blade up to at least 400 grit on the grinder. Now here is the important step. Get some 180 or 220 grit sandpaper and a sanding block, place the blade in a vise and get after it. If the blade is hollow ground, make yourself a sanding block with the same contour as your wheel. The easiest way is place the wood on the side of your contact wheel and mark it with a pencil then cut it out with a bandsaw or jigsaw. Glue a piece of leather or neoprene on the face of the sanding block. Even water works OK as a cutting fluid.

The first step with the 180 or 220 grit sandpaper is the most important step. You must get ALL the scratches out at this step. As Mr. Tichbourne expressed, it is easiest to angle each grit to see "where you are". Go up to at least 400 grit, preferably 600 grit prior to heat treat.

Once you get the blade heat treated, step up thru 320, 400, 600, 1000, 1500 then 2000 grit. You will be amazed at how fast it goes ONCE YOU GOT ALL THE SCRATCHES OUT IN THE FIRST STEP!

Many new makers try to take shortcuts by doing more on their grinders than their grinding skills allow. Disappointment is the rule of the day. Not to mention discouragement when they hear that a mirror finish shouldn't take more than 30 minutes.

This is true of some makers but these are the ones that have been grinding for a considerable period of time.

One other thing along these same lines however that you should never forget....

DON'T BELIEVE EVERYTHING YOU SEE ON THE INTERNET!!!

As your grinding skills improve, the less time you will spend getting those initial scratches out.

Once you get it to 1500 or 2000 grit, green chrome buffing compound is good stuff, followed by scratchless pink. Now you can take this to the bank. You will spend less than 10 minutes on the buffer if you take it this far by hand.

A mirror finish takes more patience then skill. Even I can get a mirror finish this way.....

C Wilkins
 
Thank you all. CL, I think I have been trying to rush the finish. I am going to try your method and let you know how it works out for me. Thanks again .

Marcel
 
I came across a good way by mistake.I have felt wheels one I have is curves like the hollow so I can go in with darkgreen compound
and work the beveil with the felt wheel with out messing up my lines,then I go onto anoter felt wheel that is left flat so I can do my flats with very little effert i had sand the flat close to cl but I start with 400 then 600 than buff with pink compound
The felt wheel are expensive but worth it
get the hard kind they do not flex which is were you get your wash out from.there are as many way to do it as there are knife makers
just though I would share from my learning.
 
Although I havent done it in a LONG time, I used to mirror polish all my blades... The KEY to anything is prep.....extra time on EVERY grit as you work up to say a used 800 grit belt....that is really as far as you need to go.....another key ingredient is the lighting.....if you cant see the scratches as you are getting them out you will NEVER have success in a nice mirror polish...Once you have gotten to a nice DULL 800 grit finish....it will look like a mirror finish with lines....and LITE buffing will take all of the lines out.....the polish you use is very important too....the greasy green chrome rouge is junk...get the kind that is light green and non greasy....I dont know what its called but it works way better.
 
Tom, I believe what you may be referring to is green chrome 50....or may be called GC50 by some folks.

C Wilkins
 
One hint that I saw here helped me a lot. Color the blade between every grit. I keep meaning to buy some lay out fluid but I'm still using old 'dry markers' on stainless and gun blueing on carbon steel.
Blind as a bat, Lynn
 
Pawnbroker
Mr. Wilkins has a heck of a lot more experience than I do and I really enjoy and benefit from his posts here on the forum.
He mentioned making a sanding block to the profile of your wheel to sand hollow grinds.
Here is a neat trick taught to me by Joe Arnold. Use a hockey puck ! Place it against your wheel like Mr. Wilkins described and trace out the profile. On your bandsaw cut off the excess then on your grinder take it right down to the line.
It will fit perfectly into the palm of your hand and it is its own cushion.
Jim Ziegler
 
You damn Canadians and your hockey pucks!
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How about you whack one down here so I can try that trick?

I think Craig's advice is great. Even though it will take you longer, I think until you are really proficient with your grinder you're better off to do a lot of hand work.

Nathan was right on when he said there are as many techniques as there are knifemakers.

My biggest catch on mirror finishing advice is this: Can the maker giving you advice put the finish on a knife that you consider a great mirror? Can his method leave you with great/crisp grind lines? Or does it wash everything out? Is the finish clean? or is it orange-peel or streaked?

A maker that mirror polishes slack-belt grinds won't really understand the concerns of a new guy trying to keep crisp lines on his hollow grinds, and this sort of thing.

I don't do them too much anymore now, but every once in awhile I'm asked to or just get a wild idea to do it. And what I've found is that I can do it differently everytime just for kicks and get the same result. So have fun with it
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Nick
 
Well, I read all the posts and then when into the shop and took one of my blades that had visible scratches on it and started with a 120 then to a 220 and so on until I had used every grit up to 1200 and lo and behold, no more scratches. I was skipping grits and was not getting out the previous scratches. Three minutes on the buffer and the blade looked great. Thanks to all for the words of wisdom.

Marcel
 
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