Polishing Chamber

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Jerry Biehler
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Location: Beaverton, OR

Re: Polishing Chamber

Post by Jerry Biehler »

O-rings can take way more heat than 50C and even 100C:

http://www.duniway.com/images/_pg/viton ... orings.pdf

A thread on my vacuum system:

http://bbs.homeshopmachinist.net/thread ... uum-system
David Kunkle
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Joined: Thu Apr 17, 2014 12:43 pm
Real name: David Kunkle

Re: Polishing Chamber

Post by David Kunkle »

Jerry Biehler wrote:O-rings can take way more heat than 50C and even 100C:

http://www.duniway.com/images/_pg/viton ... orings.pdf
Thanks for reminding me- I've actually had that link saved for some time since I will have one big Viton gasket. I probably would've forgotten about it by the time it comes to cooking it.

Started some grinding on my chamber pieces, and came to the realization that one guy on the internet was right about starting with 80 grit on a mill finish. Also talked to the welding shop, and he confirmed that I'll have to start with 80, then 200, 400, and then polishing compounds. Still be lots of work, but now that I finally know what equipment I need, at least I'll be able to really get started soon.

On the plus side, he thinks most all the welds can be done from the inside.
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
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Dennis P Brown
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Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Polishing Chamber

Post by Dennis P Brown »

To cut away weld joints, 80 grit would do it but to grind an already flat, and smooth surface with 80 grit? Most mill worked piece's I've cut are rather smooth. Maybe yours isn't smooth enough but 80 grit is very aggressive. Still, if you want to learn how to grind and polish steel, there is only one way to learn and that is to do it. As such, why not try it on a small test piece of steel to learn what you need to do before trying it on your chamber. That way, you can try anything and not worry about fixing a mistake on your expensive chamber ... .
David Kunkle
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Joined: Thu Apr 17, 2014 12:43 pm
Real name: David Kunkle

Re: Polishing Chamber

Post by David Kunkle »

Hi all,

Working on polishing my chamber pieces. First I thought the SS was painted or had a coating. Tried removing it with acetone, then paint stripper. Nope. It's just the "mill finish". For the record in case anyone wants to accomplish the same thing down the road, here's what I found to work best so far to polish mill finish.

Turns out I did have to start with 80 grit. This still takes a fair amount of time to cut through the mill finish which I would describe as millions of tiny pits that, collectively, give the metal surface a dull, satin, greyish appearance. Flap disc on a grinder seems to work the best and the flap discs last seemingly forever for 10 bucks- unlike a sandpaper disc which is shot in a minute or two. Also, I have newfound respect (fear would probably be a better word for it) for angle grinders. It kicked back on me Sunday, and the 80 grit removed a significant strip/deep chunk of flesh from one finger in an instant. Never injured myself this badly with a power tool before. Nearly went to the ER, but decided to nurse it myself. So far so good- or at least it doesn't seem to be infected and the finger hasn't fallen off. ;)

Then 120 grit flap disc (finest grit anyone makes them in) takes out the 80 grit scratches. Trying to go straight to 240 grit sandpaper discs takes too long and too much $$$. Next, 240 grit sanding discs go fairly quickly to remove the 120 grit scratches.

I'm now looking at 400 grit sanding discs which should go fast since all the deep scratches are now gone by the time the 240 grit is done. After that, coarse polishing compound, followed by 2 finer compounds to get to the finished mirror-like finish.

In the photo, the cylinder on the left is untouched mill finish- except for the bright strip where the weld was factory ground. The head on the right is done with the 240 grit.
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If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
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