Post by herchenx on Jan 24, 2012 23:33:07 GMT -5
Third day of this my fifth cab overall, day #3 of my "Cab a day" experiment - picture Jasper - I trimmed this piece that had a nice little scene from a larger slab that I bought as a batch from eBay.
So the first thing I was hopeful for was that since I opted to use some harder material with a more uniform hardness that some of the challenges I was discovering would be remedied.
Secondly, I bought a batch of pre slabbed stuff so this would be the first cab I had attempted with a uniform thickness, the ones I was cutting from local rocks were strictly freehand so they ended up as a slight wedge. I thought this might remedy some problems.
Wrong on both counts.
My issue is that the top surface of the cab seems to be incapable of being smoothed like the rest of the stone. I didn't grind the top, I just shaped the stone on the grinder, rounded the edges and did not scuff up the top (table?) with the coarse grind. I spite of this fact, somehow it seems that the very top center is unreachable by my expando with 220 or higher grit.
See the attached photo and it appears that all the surfaces have taken a nice sheen except for this area on top.
I noticed this on another recent thread as well, another new person had actually developed pronounced ridges around the border of the top of the stone and had a depression in the center.
I am perplexed and somewhat lost. I have tried limiting the water on the wheel, changing coarseness of the SiC belts, but this area seems to persist.
As I type this out, it occurs to me that perhaps as the expando is pressing on the edges, it is creating an area of lower pressure in the middle of the stone that warps the belt so that it removed material faster in the middle?
As I said, I am now lost. Anybody else more experienced know what I am doing wrong? For now I only went up to 400 grit because the problem is not getting lessened as I increase the grit (reduce the coarseness)
Thanks all for any help.
UPDATE*****************************************
I didn't make clear that I am using a vertical wheel, not a flat lap. From what I am reading, true flat tops can't be properly polished unless you are using a flat lap, or it is possible that I am misunderstanding and it is the flexibility of my expando that is preventing the surface from polishing correctly. If I had a hard wheel it might work, or a flat lap. I am OK with this since I can vibe polish in the vibratory when I get that going - and in the interim I can put a slight dome on my cabs in order to finish them on the vertical wheel. Thanks all for helping me out.
So the first thing I was hopeful for was that since I opted to use some harder material with a more uniform hardness that some of the challenges I was discovering would be remedied.
Secondly, I bought a batch of pre slabbed stuff so this would be the first cab I had attempted with a uniform thickness, the ones I was cutting from local rocks were strictly freehand so they ended up as a slight wedge. I thought this might remedy some problems.
Wrong on both counts.
My issue is that the top surface of the cab seems to be incapable of being smoothed like the rest of the stone. I didn't grind the top, I just shaped the stone on the grinder, rounded the edges and did not scuff up the top (table?) with the coarse grind. I spite of this fact, somehow it seems that the very top center is unreachable by my expando with 220 or higher grit.
See the attached photo and it appears that all the surfaces have taken a nice sheen except for this area on top.
I noticed this on another recent thread as well, another new person had actually developed pronounced ridges around the border of the top of the stone and had a depression in the center.
I am perplexed and somewhat lost. I have tried limiting the water on the wheel, changing coarseness of the SiC belts, but this area seems to persist.
As I type this out, it occurs to me that perhaps as the expando is pressing on the edges, it is creating an area of lower pressure in the middle of the stone that warps the belt so that it removed material faster in the middle?
As I said, I am now lost. Anybody else more experienced know what I am doing wrong? For now I only went up to 400 grit because the problem is not getting lessened as I increase the grit (reduce the coarseness)
Thanks all for any help.
UPDATE*****************************************
I didn't make clear that I am using a vertical wheel, not a flat lap. From what I am reading, true flat tops can't be properly polished unless you are using a flat lap, or it is possible that I am misunderstanding and it is the flexibility of my expando that is preventing the surface from polishing correctly. If I had a hard wheel it might work, or a flat lap. I am OK with this since I can vibe polish in the vibratory when I get that going - and in the interim I can put a slight dome on my cabs in order to finish them on the vertical wheel. Thanks all for helping me out.