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Post by liveoak on Oct 6, 2022 12:04:16 GMT -5
I read this in Rock & Gem a couple of months ago but thought I'd post the link I got today via e-mail as I thought Bob Rush explained it quite nicely
Patty
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Post by jasoninsd on Oct 6, 2022 12:58:28 GMT -5
That's an interesting read. Thanks for posting that.
I do mine differently. I don't do the dome in a vertical position...only when I'm shaping the preform do I hold it vertically.
I have the cab at a 45 degree angle to the wheel. This allows the curvature of the wheel to fall perfectly into the curvature of the inside swoop...
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realrockhound
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Chucking leaverite at tweekers
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Post by realrockhound on Oct 6, 2022 14:06:06 GMT -5
That's an interesting read. Thanks for posting that. I do mine differently. I don't do the dome in a vertical position...only when I'm shaping the preform do I hold the it vertically. I have the cab at a 45 degree angle to the wheel. This allows the curvature of the wheel to fall perfectly into the curvature of the inside swoop... Interesting approach. I personally prefer swearing at my stone when I’m doing the inside curve. It lets the stone know who’s boss and keeps a crisp even girdle. |
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Post by jasoninsd on Oct 6, 2022 15:11:57 GMT -5
That's an interesting read. Thanks for posting that. I do mine differently. I don't do the dome in a vertical position...only when I'm shaping the preform do I hold the it vertically. I have the cab at a 45 degree angle to the wheel. This allows the curvature of the wheel to fall perfectly into the curvature of the inside swoop... Interesting approach. I personally prefer swearing at my stone when I’m doing the inside curve. It lets the stone know who’s boss and keeps a crisp even girdle. I've tried that approach...but I must have deaf rough as mine doesn't listen! LOL *Deaf Ruff - Sounds like a really bad 80s band! LOL |
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rockbrain
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Post by rockbrain on Oct 6, 2022 16:05:19 GMT -5
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Post by liveoak on Oct 6, 2022 17:02:17 GMT -5
Well, to each his/her own.
Personally, I think it depends on the curve you're trying to grind, but Bob's way, in my opinion, gets you the most bang for the buck, on whatever wheel size you have.
And once you get the curve ground, it's only a matter of rolling the cab over, to get a nice curved top, on that inside curve
Works for me.
Patty
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Post by jasoninsd on Oct 6, 2022 21:01:40 GMT -5
Here's why I don't think the vertical position is the "best" way to do it. When you start rotating the cab to start shaping the dome, the contact area on the surface is minimalized to a very small area when in the vertical position. This can cause "waves" when shaping the dome on the inside curve. When you keep the cab at a 45 degree angle, the contact area starts out minimal, but as you grind down to the girdle line, your surface contact area stretches the entire length of the inside curve...completely eliminating any possibility of "waves" happening on the dome.
Unless a person is using the edge of the wheel...and is beyond uber talented...the maximum amount of inside curve can only be the same curvature of the wheel you're using. A 6" wheel gives a more pronounced curve than an 8" wheel...and a 4" is more than a 6". If a person wants to curve LESS than the maximum, then when doming they would need to keep their cab at something less than 45 degrees...like maybe 30 degrees, or whatever. Working the inside curve at a diagonal (versus vertical) allows the maximum amount of surface contact with the wheel - which should give a person the "smoothest" surface.
I don't think the way you or Bob are doing it is "wrong"...not at all, as the results are there. I just think the diagonal method gives a more consistent surface with the least amount of variable...
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Post by stardiamond on Oct 7, 2022 17:05:54 GMT -5
A template for the curve, tweet, 15 yard penalty. The curve is part of a freeform and that needs to have the entire shape be pleasing to the eye. When making the preform, the bottom edge is pushed into the wheel and then the girdle is marked. As the cab is domed the shape and pattern change. the shape can be adjusted to get the best appearance.
I only make freeforms when no template shape best frames the material. This is usually done with scraps from trimming another cab. I don't know how long Paul has been swooping, but Silverhawk was a big time swooper. My wife collected cabs and I have some of his. If one of his shapes framed a piece of my material, I would put a loop of painter's tape on the back and trace it on to the bottom of the trimmed slab. I usually start with a wedge shape with the trim saw, trace the cab and then trim again before grinding.
It took me a long time to figure this out and the best doming technique is the same no matter the shape. It is what is taught in cabbing pamphlets for circles and ovals.
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realrockhound
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Post by realrockhound on Oct 8, 2022 15:52:00 GMT -5
I’ve tried both techniques. As many of you will find, it really comes down to the shape, size and depth of the curve. I guess you could say I don’t have a set way of doing it, just use whatever works best in the moment. You know what I actually find more difficult than inside curves? Small oval cabs. Things are an absolute pain to keep symmetrical
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