Polishing tutorial

[kcstott]

I was asked to put together a polishing tutorial I will add to this over time. Hopefully this one gets enough sticky vote to become a standard tutorial.

In this first one I'll be polishing a set of scope bases for a high end rifle. I do sell these bases but please don't take it as a plug. These bases are not intended to be put on anything but the highest end rifles. What I'm getting at is these bases because they do cost so much have to be perfect. Perfect in fit, finish, and over all looks and style.

Now some of you may not like them but thats not the point. The point is to purely demonstrate how to attain a high level of polish on a part while keeping all the edges perfectly flat and square. This is what I'm working on at the time. The second installment will be a set of scope rings. And the third will be cleaning up a weld. I'll show you how to make a part look like it was never welded.

Please give me feed back. Tell me what you think I missed. Different pictures, specific techniques, what ever.

So Here we go

Here are the bases notice how rough they ar after the milling machine is done with them








The first thing you will need is some wet or dry paper (320 grit here) and a flat surface. I use my surface plate any flat surface with no dents dings or otherwise rough surface will be fine. A thick piece of glass works well.




Start off by laying the part flat on the paper with a little oil (WD 40 works great) and rub with some pressure in a figure eight pattern. This produces a unidirectional finish. You can also just push the part in a straight line. This produces a directional finish.
When you have a directional finish ( polishing in a straight line) and change to a finer grit rotate the part 90 degrees to the direction you were originally polishing. This will allow you to attain a higher finish.




This is after just a minute or two of work




Now notice this edge. See the machine marks in it.

[kcstott]

Hold it down polish the edge be sure to hold it flat and don't let it roll



Again after just a few short minutes look at how well it came out



For the radius on the sides it is fine to get something that fits the radius and use it as a backer to polish out the surface. On a part I had made that had a 1 inch radius I used a piece to 2" round stock wrapped in sand paper to get the surface smooth. On this part I used a Cratex wheel and a dremel.
Now for those of you with little or no experience with a dremal DON"T USE ONE. it is by far the fastest way to foul up a part. I've been polishing parts for molds that cost more then the house I live in so I have a little bit of experience do this.



Now it's time to move on to the sticks. I use these to polish all the surfaces to a perfect 600 grit finish. These sticks don't break down easy so they don't loose their shape. This allows me to polish everything to a nice high polish and keep all edges sharp and square. They are soaked in cutting fluid which can be Kerosine, mineral spirits, or the like. Stoning oil also work but it is pricey




Here is the finished product. This is the way I supply my bases to the customer as a regular finish. The customer is free to ask for a higher degree of finish and I can take it right up to a mirror if they want.





Now you will notice that there was no buffer involved. No cloth wheel and polishing compound. Nope. That stuff is reserved for very large parts that have little to no detail. If you tried to use a buffer on these scope bases all the edges would be gone and rounded off. the holes would be dished out.

If you need a higher degree of finish you just repeat the above steps with finer sandpaper. Now heres a tip. When changing grades of paper or stones. Polish your part 90 degrees or about to the direction you were on the last grit. This will do two things. One it will allow you to see the previous grit lines as you polish them away. This is huge when you are working toward a mirror finish. You can not advance to the next grit until the last grit lines are gone. The second thing is if you polish in the same direction as the last grit you will just deepen the grooves you cut in the part. Essentially polishing your scratches. You will never reach a high polish and you will end up with a part that has ripples in it so change the direction you polish each grit.

[kcstott]

reserved for scope rings

[kcstott]

reserved for Weld clean up

[kcstott]

Reserved

[Rusty Scabbard]

Nice-thanks for the post KC !

[bigcalidave]

Thank you, can't wait for the rest. I'm not much of a perfectionist with this stuff, I just like to do it myself

[kcstott]

Thank you, can't wait for the rest. I'm not much of a perfectionist with this stuff, I just like to do it myself

The whole idea is to be able to take it to what ever level you need for your application. I learned how to do all this stuff because I never had the money to pay someone else.

[gesundheit]

I have a question. When moving to a finer grit paper to attain a mirror finish, how can we go 90s to the previous paper's marks when we sanded the part in figure 8 pattern?

[Barabas]

[kcstott]

And see there's my first screw up. You can also polish by using just a straight motion. When you do that's when you rotate the part 90 degrees on the fine grit. I'll edit the OP
Sorry for the confusion

[gesundheit]

Thank you both for the explanation. Kerry this is a great thread. Thanks for taking the time to explain this stuff.

[tdaughg]

i plan on doing some nitrebluing soon and the parts should be polished to a mirror finish first. i have a feeling your thread is going to be a huge help.

are the stones just your common arkansas/india stones?

thanks for all the advice.