Is there an easier way to mirror finish?

J

JDW

Well-Known Member
I have been doing mirror finishes for sometime now, and do it all by hand sanding from 320 grit up to 2000 grit then lightly buff. It looks good, but it sure is slow going. Is there something that I am missing, that would make it faster, easier? I guess it doesn't take all that long, 2-4 hrs, usually covers it, but my arms are about to fall off, seems every order lately is for a mirror finish.
 
It depends who you ask, and how you define "mirror". A lot of guys go to 800, buff and call it good.

If you prefer to actually get all the scratches out, rather than just make them shiny, do as much hand-sanding as you can before HT, at least to a clean 600. If you're using a vacuum furnace or well-wrapped stainless in a regular kiln, this saves a lot of time. If you're using oil-hardening steel and HT'ing in an open forge, I'm not sure it would be worth the effort, there will be scale to grind off anyway.
 
Do you use a belt grinder for any of it? If so, how high up in grit size do you go on the belt grinder?

What are the particulars on buffing?
Which wheels and compounds?
What is the speed of your buffer?
 
I don't do a lot of mirror finishing, but I do use some finer belts.
Trizact cf belts go up to a30, which is quite fine, and norton goes x16 and x6.
My recommendation is to buy a few more belts and after the a30 you can start with 800 grit for hand sanding, which should save you an hour at least.
Del
 
rob45, I use belts upto 320 grit, sometimes 400, I have problems with belt bumping with finer grits, so 400 is as far as I go for finishing, then go to hand sanding. My buffer is 3450 rpm, I know a little to fast, but it is what I have. I use a sewn wheel with green compound, and then a loose wheel with pink compound. I do sand upto 400 before HT on all my stainless steels, and A2. I have went higher, but it seems that I still have to go back to 400 after HT anyway. On a mirror finish, I want all scratches out, and my wife could use it as a mirror to put her makeup on with. Sometimes I miss a few scratches, and they sure look bad in a mirror finish.
Thanks for the help dogs.
Dale
 
I dont do a lot of mirror ploishing, but in the past have belt sanded to 600 grit then go to a scotch bright belts green , red then grey, then to a cork belt with compounds, then buff.
 
Dale, the only other thing I can add for your technique (which is basically the same as mine), is try sanding wet with Mobil 1 for "lube" after you get your 400 nice and clean. I found things go faster and less fishhooks that way, than with water, windex or WD-40. 400 is where the rubber meets the road, if i get that nice and even by hand it seems like the rest goes pretty smoothly.

Ed's modified palm-sander and the use of Scotch-brite and cork belts sound really interesting, thanks guys.
 
JDW said:
rob45, I use belts upto 320 grit, sometimes 400, I have problems with belt bumping with finer grits, so 400 is as far as I go for finishing, then go to hand sanding.
Yep, the finer-grit belts can cause this to happen. The dreaded belt splice gives a similar problem for those using the really small contact wheels.
For that problem, the best solution I have found so far is to either use it as a slack belt, or a soft contact wheel (40 Duro).
I realize this may go against the conventional wisdom of having a very stiff backing to maintain crisp lines and edges, but, for me anyways, the higher grits don't mess things up as long as I keep the pressure light. I like to slow belt speed down, too.

If you can't find a way to make belts work for you, the link to Ed Caffrey's post provided by Uncle Billy is worth checking into, if you haven't already.

My buffer is 3450 rpm, I know a little to fast, but it is what I have.
Please see my comments about this below.

On a mirror finish, I want all scratches out...
Sometimes I miss a few scratches, and they sure look bad in a mirror finish.
Absolutely. I am very "old school" concerning that concept.
Shortcuts usually don't pan out the way we want them to.
I suppose the best we can do is adhere to the normal grit progressions and use the machines to make it quicker and easier.
The one exception to this may be a tip that Ed Caffrey presented in a thread recently: post #6 in this thread http://knifedogs.com/showthread.php?18445-Blaze-v.-977s
I have not yet tried the suggestion, but am interested and plan to see how it pans out for me. Like any other technology, the field of abrasives is ever-improving, so perhaps I'm a little "behind the times".
Click to expand...

You mentioned the speed of your buffer (3450 RPM) as "being a little too fast". Maybe, maybe not. It really depends on the material you're working, and the wheel size.
I suppose I should have provided more clarity when I asked you about speeds.

Concerning "speed", the real objective is to obtain a desired SFPM (surface feet per minute).
All material removal will be based upon pressure in combination with speed (with the proper removal agent). It doesn't matter what material- wood, plastic, various metals, etc. This concept also applies to differing types of removal, be it cutting, drilling, grinding, sanding, or buffing.
Whatever it be, there will be general guidelines as to what combinations have been proven to work best.

For our applications, the pressure is variable, as we apply the pressure with our own hands. Finding the correct pressure is what elevates our finishing procedures to an "art form". But we can certainly narrow down the variables if we know speeds.

Everyone has their own methods, but here is what works for me.
I like to run as fast as the material allows- I'm using a machine to speed the process up, and it only makes sense to me to take full advantage of it.
This doesn't matter whether I'm grinding, sanding, or polishing- my speeds stay the same, but the abrasives, backings, and pressures change.

For carbon steels, 5000-7000 SFPM gets the job done for me.
The stainless steels seem to prefer slower speeds, so I slow it to anywhere between 3000-5000 SFPM.

You can experiment with different circumstances to see what works best for you. Don't be too concerned about exact speeds; you're simply trying to find a range that works for you.

Assuming your buffer is a direct-drive unit, here are the surface speeds that 3450 RPM will give you with common wheel diameters:
4"...3613 SFPM
6"...5419 SFPM
8"...7226 SFPM

So if you want to change the amount of time you spend on your operations, simply adjust your equipment to do the work in less time.
But there are limits. For example, I have found no difference in speeds of, say 7000 versus 8000. Materials don't like it, equipment doesn't like it, and application becomes considerably more critical.
So it will do you no good to run a 10" wheel on your particular machine.

How much ground do you cover by hand?
Well, the "average" human can sand 50 feet per minute with a slow, steady pace, and get up around 125 with "fast" sanding.

This brings up a special consideration in regards to the orbital sander modification mentioned by Ed.
I have had several look at all of this "speed of removal" concept and give retort similar to this:
"Well, if the average orbital sander gives about 14,000 orbits per minute, and has a 1/16" orbit, then that only equates to about 75 feet per minute! I can do it by hand quicker than that!"
Indeed, they are correct. But a human will quickly tire out, and, more importantly, the applied pressure will be much more inconsistent. In the end, the "lowly" orbital hand sander will get the job done quicker.

Don't let my illustrations about buffers throw you off, as these concepts apply just as much to grinding and sanding as well.
What it all comes down to is that if doing it by hand is not fast enough for our needs, we need to rely on the machines, tailoring them to our individual satisfactions.

Best of Luck,
Rob
 
Thanks to all for the help.
James, I will try the Mobil 1, I use WD40 now. And I agree with you on the 400 grit being the most important step, then 600 I think is next important, from there it goes prety good.
Rob, thanks for the buffing info. I am running an 8 inch wheel, so it is a little fast for stainless. I have an old grinder arbor, and a 1725 rpm motor, that I have been wanting to setup for buffing, now I have a good reason to take the time to do it, may help on other buffing as well.
Thanks again for all the good information.

Dale
 
Just wanted to say I wholeheartedly agree with JDW and Rob45, being picky about getting the coarse scratches out is the right way. Even on a super-basic 400 grit finish, it will look much better if you go at least to 600 and then come back down to 400. I'm refering to hand-sanding; I've never been happy with a perpendicular belt finish... every time I think I have a blade nice and clean with a 400 belt, just a few parallel strokes by hand shows lots of coarser scratches that were "hidden". A magnifying glass, jeweler's loupe, opti-visor etc don't lie :biggrin:

What folks are saying about using progressively finer scotch-brite and/or cork/compound belts sounds like it would help that, though... I'll have to try it and find out :)
 
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With all sincerity I say this. If you are getting a fine mirror finish you are doing it right !!!Usally I don't do mirror finishes but do go to say 2000 or a size or two under after I've used a Norton 16 on thre machine. The truth is most of my blades are under 4" since they are folder blades. I've got a few years on this body, so what I often do is break up the hand sanding by doing something else in between like more belt grinding of one sort or another. Frank
 
Have you tried the Norax belts from boss's shop? I do something like a 45x, 24x, 16x, and 5x if I remember correctly (the backs of the belts are so dirty I can't see the numbers anymore) I think tracy recommends which 4 or 5 he uses for a mirror finish. I don't recall ever having issues with belt bump and I really only takes a couple of minutes per belt with the proper prep.
 
After HT, 220 grit, then 3M Trizac belts A30,A16, and sometimes I will use an A6. It will only take a few minutes on the buffer to get every scratch out and have a mirror polish.

I have tried the cork belt with compound but don't see where it helps. Just use the Trizac belts and make sure all the scratches from the previous grit are gone before going to the next grit.
 
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