doublegunshop.com - home Forums General Discussion Classic & Custom Single Barreled Sporting Rifles @ doublegunshop.com unusual bolt treatment

Hi Brent,

With everyone saying it was scraping, I've lost a bit of confidence in
my explanation. I had hoped to do an experiment today, but instead
the day was spent doing home and car repair.

Ok, when I look at the pictures of the bolt, I sometimes think I see dots
and that some of the lines look like overlapping dots. I have a copy of
Clyde Baker's book "Modern Gunsmithing", my edition is copyrighted 1928.
Near the very end of Chapter 19, Engraving and Ornamentation, he talks about using
an "Ark-O-Graph", basically an electropencil and even tells how to make one.
He writes "that by moving the point rapidly over any metal surface it is matted
quickly and without fuss". I hope to try to reproduce this stuff sometime soon.

Fred,
I think what Clyde Baker is talking about will give you a much different surface.
Mike

this is the type of scraping I was referring to.

Steve, that appears to have the tooling marks of scraping, while the original bolt picture looks to be a rotary bit, maybe like rm bill said, a pointed stone.

Can I ask, did you do that? Do you know the whys and what fors of that amount of coverage? Just curious. The machine way scraping I was thinking about just skims high spots on ways and doesn't really show as tooling marks.

Craig,
I did not do that treatment to the metal. It is very common on Bridgeport mills. I believe that surface is done by hand and that the reason is that it reduces friction and gives the lubricant a place to go.
Steve

Thanks Steve. I notice they didn't want to do the dovetails. I suppose, a tiny scraper, good magnification and a really practiced hand could create an interesting effect on a gun part, but I'm not so sure about sort of random looking squiggles. It's probably just me.

The visible pattern on the Bridgeport knee is flaking, not scraping. It is done on the finished surface to aid lubrication and reduce stick/slip. The actual scraping can be seen beneath the flaking, it appears as wider, straight marking.

Scraping is an iterative process on machine tools to produce precision surfaces. Flaking is a secondary operation.

The finish on the bolt in the OP appears to have been done as RM Bill described, for purposes unknown.