After uploading the videos, realized that the audio on most did not pick up my voice. So will type out as best I can a description of what is going on in each video. I can hear them much better using my headphones.
I think could have slowed down a bit too and explained better and in more detail.. So parts of this may just be difficult to make heads or tails out of..
As always, what works best for me can be different for someone else. So please critique, add too, point out, or anything else that you find works for you so it can be added here for others to take in.
A lot of this really applies to most any cabbing.
One of the first things I like to take the rough edge off the perimeter of the preform.. I take it down through the 400 diamond bonded wheel. I don't want to be grinding on it later after I have my doming complete because it will result in changing the girdle height. So all I really want to have to do is touch it up with the silicon carbide stages.
Ok here we go.... ! :)
This first clip shows the grinding down of a bevel. Not a finish bevel. A bevel that will determine the girdle height and also the outside/lowest part of the low dome. Depending on the size of the cab or rather the surface area will depend on how little you will need to bevel. You can get away with a lot less of a bevel because no need for as much doming. A larger surface area will require more.. Make sense ??
No need to actually go though any additional beveling steps for the corners. The bevel from doing the sides will join nicely at the corners.
Here are a couple of pics showing the results. I leave the corners sharp cornered until the very end of the cabbing. Then I will round them off. If for some reason I want the cab to wind up with sharp corners, then I have to pay extra close attention to them as shown a bit later.
This next clip try's to show how to begin getting the contour of the dome uniform across the entire surface.
A while back someone mentioned how they listened to the grinding. As what ever grit your working progressively removes bumps and ridges the grinding sound will subside into a smooth almost quiet grinding action. Meaning the surface is uniform so to speak with the flat surface of the grinding wheel. So I work each wheel until I can go around the entire surface of the stone to the point where there is really no grinding going on. Hard to explain. Just think about it while your working the surface of the cab. It will come to you !
I noticed that it appears in the clip that I am pressing harder than I actually am.. I am hardly pressing at all and the wheels are running a lot faster than these videos depict.. Just a video thing I guess..
I have come off the initial 80 grit and this step is on the 220, then moving on to a somewhat worn 220.
Again, mostly working the outer part of the surface of the cab and spending little time hitting the inner part or highest part of the dome. Don't want to grind down what little dome we are working to have in the end. Although I do have to spend a bit of time on the center just so as to include it in the grit processes. Most of the grinding is needed around the outer part of the cab. That is where the ridges were left which is more covered in the adjacent clip..
I notice too that my camera crew did not do a great job of showing a lot of the cabbing action.. Hopefully you will get the idea.
This next clip starts out going through the same process except on a 400 grit. Again, listening to the sound of the grinding.. Just like any other progressive grinding or sanding steps.. Need to work it until the previous abrasives grit marks are removed. Pressing fairly lightly.
The pic below shows a close up of the problem I run into on the corners.. The accidental excess grinding on them.
This next one shows how sometimes I have to go back over the girdle so as to keep it uniform. Sometimes as a result of going through the grinding process the girdle will become thicker in the center and have to re-bevel and then smooth out the surface a bit. Again.. A bit hard to explain.. Sorry. !
Next I move on to some silicon carbide papers. I start off on the 80 with this agate. Running up through the 220, 400, 600 and finally a worn 600 just like any other hard mineral cab. Other softer minerals, I may skip the 80 and start off with the 220.
I listen to the sanding just like I do the grinding..
You can see I have not tried Old Hickory's belt slipping trick
This next one shows rounding the corners.
Finally..., Lets try beveling !
After going through all the silicon carbide grits for the bevel and girdle, here are the results ! :)