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Old 09-23-2009, 12:29 AM
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Default Re: Gold inlay script and block lettering on a custom rifle

Hi Jim,

An excellent question which I am glad you brought up.

Under the microscope, the raised "bumps" tend to look a little higher than they actually are. Probably due to the scope's ring light and halogen lighting around it.

To recap .... The undercutting tool is used to make an indentation under the top edge and provide a place for the gold to "grab" as it is expanded into the channel. The force of the undercutting tool will move/displace metal in the only direction it can go ... which is up. Pushing the undercutting tool in just enough to give the gold an anchor point will raise some material but not too much to compromise the edge.

To answer your question .... The tool is plunged in and under the raised areas only. I stagger these undercuts, on each side, so that the gold does not slide through (and out the ends of) the channel as it expands - but rather force it to continue to expand wider and deeper into the undercuts. For the ends of the small flourishes and small ends of of each of the script letters, this is particularly helpful as those areas are the weakest points of the inlays. Time is also an issue, on real small inlay channels, I want to use enough anchor points. I could run the undercutting tool along the length but on a shallow channel (or "V" cut channel), there's the risk of the tool jumping the edge and marring the surface.

Because the stones remove metals of dissimilar hardness and density at the same rate, the raised areas disappear along with the excess gold leaving a perfectly planed steel and gold surface.

When you're undercutting a small inlay and you've got the microscope turned up to full magnification, you really see and get a feel at far you can push the tool in without distorting the top edge in such a way that it will compromise the inlay after stoning. Again, I may be over-engineering this procedure but if I can help it, I don't want work that passes through here to have to come back and be re-done in my lifetime.

Here's an illustration which I think will help ....

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