jean
starting to spend too much on rocks
Member since May 2005
Posts: 127
|
Post by jean on Mar 14, 2010 15:41:21 GMT -5
Can anyone explain the difference between silicon carbide 500 grit and aluminum oxide 500 grit. I had thought that aluminum oxide was a polish and silicon carbide was used for grinding. Please explain when each one would be used in the tumbling process. Thanks much.
|
|
|
|
Post by rockrookie on Mar 14, 2010 16:24:41 GMT -5
i very well may be wrong . i hope that some else also answers that knows for certain . i think that silicon carbide has sharper grit . and that AO is more rounded . i used to use 500 silicon.
now i use sil up to 120/220 then 500 &1000 AO
i hope that i don't steer you in wrong direction . but i am happy with the results that i get .
--paul
|
|
|
|
Post by Hard Rock Cafe on Mar 14, 2010 17:16:55 GMT -5
Paul is correct: SiC is sharper than AO. That makes SiC better for shaping and sanding than AO. SiC also breaks down into sharper pieces than AO.
I personally use SiC through 600 (vibe) then AO 1000 as a pre-polish (or sometimes as the final polish).
Chuck
|
|
revco
starting to spend too much on rocks
Another Victim Of The Rockcycle
Member since February 2010
Posts: 162
|
Post by revco on Mar 14, 2010 18:52:24 GMT -5
The general consensus so far is correct. SiC is much "sharper" and harder than AO. SiC is much more brittle than AO, so it tends to break down quickly...whereas AO is very tough and maintains it's structure better over time.
There was a discussion here awhile back where the two were compared. Somebody posted ultra-magnified images of the two - and indeed, SiC was much "sharper" than AO. SiC looked like broken shards of rock, whereas the AO were little globule looking things. I wish I could find it, but I have troubles with the search here.
The net-net that I took away was that discussion was, from the standpoint of function, the results were basically the same. The SiC quickly breaks down into finer dust, thereby becoming closer to AO's structure. In the end, the results were very comparable and very little difference could be found between the two materials.
I use 500 SiC, for what it's worth...more for price reasons than anything else.
|
|
|
|
Post by rockrookie on Mar 14, 2010 19:51:08 GMT -5
Revco , now that you mention it . i remember the comparrison pixs & post . the was i while ago .
you must have been lurking for a while . huh .
--paul
by the way . im glad that i was not to far off.
-paul
|
|
|
|
Post by susand24224 on Mar 14, 2010 20:11:56 GMT -5
Then if there is still a small amount of "shaping" to be done (but not enough on a special rock to do another 60/90) SC might be better? And AO might be better on softer rocks? Or are they so similar that the difference would be miniscule, if any?
I have both--had no idea the differences. This is most helpful, and thank you, Jean, for asking the question.
Susan
|
|
|
|
Post by deb193redux on Mar 15, 2010 9:07:43 GMT -5
Your idea about that extra bit of shaping, and also about softer rocks, may be correct. You may also be correct that the difference would be too small to notice. I do not think it has been systematically studied.
I think AO grits are more commonly used on metals. SiC is more brittle and breaks faster, but it is also harder and will etch agate and jasper better.
THis only considers time efficiency. There is also cost efficiency. If you already have som AO grits, then using them on the softer rocks instead of buying more SiC grit could be a very sensible thing.
The AO polish you mention is about a 50,000 grit. The basic difference between grit and polish is grit size.
|
|
revco
starting to spend too much on rocks
Another Victim Of The Rockcycle
Member since February 2010
Posts: 162
|
Post by revco on Mar 15, 2010 14:36:42 GMT -5
I think any shaping that you would see from 500 grit would be minimal at best. The point of pre-polish (500 grit & above) is to create very fine scratches in the material that reflects light better and such, is perceived as having a "shinier" appearance. The fact that it's "sharp" merely refers to it's ability to make those very fine cuts. AO works on a similar principle, except it relies on it's tough chemical composition to "beat" the cuts into the rock.
I work with some 1000AO pre-polish and I have noticed that it's much better at taking softer rocks to full shine. I would be inclined to agree that 500AO would have similar properties...but haven't tested it.
The 120/220 stage is better for the "finishing touch" type of work. Even that does very little in the way of shaping, but it'll occasionally take out the small hairline fracture or very minor blemish. I don't rely on 120/220 for any shaping...and some skip the step entirely, going straight to 500+.
Edit: Paul - I've been lurking here since the latter end of last year. I've been getting into the hobby more now that I'm living in Montana and awesome rocks are abundant! Been tumbling since '98, though!
|
|
murph
off to a rocking start
Member since March 2010
Posts: 1
|
Post by murph on Mar 20, 2010 21:36:10 GMT -5
I see on the photo gallery many people using Tin oxide for their finishing polish. I had never heard of this, have only used cerium oxide without pellets. Does the tin and the pellets lessen the tumbling time?
|
|
|
|
Post by susand24224 on Mar 21, 2010 20:52:17 GMT -5
The pellets might lessen your time if they help to balance your load. I use tin oxide occasionally, and it doesn't seem any faster--I use it as a "last" choice when AO and cerium haven't given me as good a shine as I would like.
|
|
revco
starting to spend too much on rocks
Another Victim Of The Rockcycle
Member since February 2010
Posts: 162
|
Post by revco on Mar 22, 2010 9:32:00 GMT -5
One of these days, I want to pick up some TO to test out on some of my problem rocks. Here's a link that shows what polishes are best for different kinds of rocks: www.utahrockhounds.com/tooelegem/tips/stonepolish.htmlI use AO1000 and CO, for the most part. Mainly because CO is half the price of TO. |
|
