Crazy lace, Montana, Amy Sage and a Sintered Wheel Story
Jan 26, 2022 16:08:42 GMT -5
catskillrocks, RickB, and 8 more like this
Post by holajonathan on Jan 26, 2022 16:08:42 GMT -5
If you're not interested in my recent experience regarding heavy-handed grinding with sintered wheels, skip this section.
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For the past few months, I've been grinding my cabs on a Covington 8" grinder with 80 and 220 grit sintered wheels. Then I move to the Genie -- currently setup with all resin wheels: 140, 220, 280, 600, 1200, 3000. This approach works well, except the 80 grit sintered wheel grinds slowly, especially with hard agates. Not only does it grind slowly, but it feels very smooth when doing so. I have dressed the wheel repeatedly, which helps only a little. The wheel isn't "dull." 80 grit sintered wheels just don't grind like 80 grit plated wheels... or so I thought.
Last night I was frustrated with the slow grinding action when working a Montana agate cab. I decided to break all the rules and apply a lot of pressure. I normally use a light-to-medium amount of pressure with the hard wheels. I have always assumed that the harder I press, the deeper the scratches and the greater the risk of subsurface damage. But in this case, the harder I pressed, the smoother the grinding action felt, and it actually started to grind fast! The grinding action was similar to a brand new plated 220 grit wheel -- aggressive but smooth. After spending at least 10 minutes just grinding the first bevel of the dome (with a light touch), I finished roughing out the dome of the Montana agate cab in about 2 minutes with the heavy-handed technique. I didn't totally smooth out the ridges with the 80 grit wheel, since I wanted extra time on the 220 to remove any deep scratches I had created.
I took a look at the cab after really muscling it against the 80 grit wheel, and surprisingly, I couldn't see any particularly deep scratches.
I moved on to the 220 sintered wheel. Still feeling impatient, I pressed hard on that wheel as well. I rounded off the dome and fixed up the girdle in about 5 minute.
There were still no obvious signs of deep scratches or subsurface damage, but those things don't usually show up until working the resin wheels.
I ground three more cabs with a very heavy hand onthe sintered wheels. The Covington grinder is powerful, and I was pressing so hard that my arms actually got tired. I make no claims of having great physical strength, but I've never had tired arms from cabbing. In less than a half hour I ground the domes on the other three cabs with both the 80 grit and 220 grit sintered wheels.
When I moved to the Genie, I gave all 4 of the cabs a quick pass over the 140 resin wheel. I normally use that for hard agates like Montana agates, but not for most other materials.
I might have spent a little more time on the 220 resin wheel than normal. Not so much because the cabs needed it, but because I was convinced that there had to be some deep scratches or subsurface damage my the abuse I put the cabs through with the sintered wheels. Much to my surprise, I did not find any deep scratches or subsurface damage on any of the four cabs.
My tentative conclusion is that the 80 grit sintered wheel is not as slow as I've alawys thought. I've just got to press hard. I still feel like I'm doing something bad by pressing that hard on the sintered wheels, but the results speak for themselves. The four cabs are shown below. There are absolutely no lingering scratches or subsurface damage. They look just like my other cabs; they just took a lot less time to make.
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1. Crazy Lace Agate from Mexico
2. Amethyst Sage Agate. Looks like I've got a little cerium stuck in the druzy vug.
3. Amethyst Sage Agate with no Amethyst = Sage Agate? There is some very sparkly micro-druze in those vugs.
4. Montana Moss Agate. Unfortunately, you can see the dop screw through the face of the cab.
How's the polish? Good enough to see my house (and a lot of snow) in the reflection.
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For the past few months, I've been grinding my cabs on a Covington 8" grinder with 80 and 220 grit sintered wheels. Then I move to the Genie -- currently setup with all resin wheels: 140, 220, 280, 600, 1200, 3000. This approach works well, except the 80 grit sintered wheel grinds slowly, especially with hard agates. Not only does it grind slowly, but it feels very smooth when doing so. I have dressed the wheel repeatedly, which helps only a little. The wheel isn't "dull." 80 grit sintered wheels just don't grind like 80 grit plated wheels... or so I thought.
Last night I was frustrated with the slow grinding action when working a Montana agate cab. I decided to break all the rules and apply a lot of pressure. I normally use a light-to-medium amount of pressure with the hard wheels. I have always assumed that the harder I press, the deeper the scratches and the greater the risk of subsurface damage. But in this case, the harder I pressed, the smoother the grinding action felt, and it actually started to grind fast! The grinding action was similar to a brand new plated 220 grit wheel -- aggressive but smooth. After spending at least 10 minutes just grinding the first bevel of the dome (with a light touch), I finished roughing out the dome of the Montana agate cab in about 2 minutes with the heavy-handed technique. I didn't totally smooth out the ridges with the 80 grit wheel, since I wanted extra time on the 220 to remove any deep scratches I had created.
I took a look at the cab after really muscling it against the 80 grit wheel, and surprisingly, I couldn't see any particularly deep scratches.
I moved on to the 220 sintered wheel. Still feeling impatient, I pressed hard on that wheel as well. I rounded off the dome and fixed up the girdle in about 5 minute.
There were still no obvious signs of deep scratches or subsurface damage, but those things don't usually show up until working the resin wheels.
I ground three more cabs with a very heavy hand onthe sintered wheels. The Covington grinder is powerful, and I was pressing so hard that my arms actually got tired. I make no claims of having great physical strength, but I've never had tired arms from cabbing. In less than a half hour I ground the domes on the other three cabs with both the 80 grit and 220 grit sintered wheels.
When I moved to the Genie, I gave all 4 of the cabs a quick pass over the 140 resin wheel. I normally use that for hard agates like Montana agates, but not for most other materials.
I might have spent a little more time on the 220 resin wheel than normal. Not so much because the cabs needed it, but because I was convinced that there had to be some deep scratches or subsurface damage my the abuse I put the cabs through with the sintered wheels. Much to my surprise, I did not find any deep scratches or subsurface damage on any of the four cabs.
My tentative conclusion is that the 80 grit sintered wheel is not as slow as I've alawys thought. I've just got to press hard. I still feel like I'm doing something bad by pressing that hard on the sintered wheels, but the results speak for themselves. The four cabs are shown below. There are absolutely no lingering scratches or subsurface damage. They look just like my other cabs; they just took a lot less time to make.
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1. Crazy Lace Agate from Mexico
2. Amethyst Sage Agate. Looks like I've got a little cerium stuck in the druzy vug.
3. Amethyst Sage Agate with no Amethyst = Sage Agate? There is some very sparkly micro-druze in those vugs.
4. Montana Moss Agate. Unfortunately, you can see the dop screw through the face of the cab.
How's the polish? Good enough to see my house (and a lot of snow) in the reflection.
The dendrites don't pop until everything around them is crystal clear, as you know. 
