metal chequering

santos

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I had a request for chequering a hammer by a friend armourer . He was restoring a German shotgun from the early 20th century with a broken spur on one hammer, and he welded a new one. The original left hammer had small squares 0,4mm large.
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I do have two liners with 6 and 10 lines that are too close , so I had to grind one with two teeth at 0,4mm. I used my lathe for grinding it with accuracy . The diamond disc for grinding is mounted on the lathe chuck and the carbide graver is held on a special fixture with a micrometric screw for adjusting the depth of the grinding .
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The geometry I was looking for is a double “onglette” , but after a few tries I couldn’t grind two onglettes so close : My diamond disc has a thickness of 0,6mm

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I find another solution, grinding my double onglette at 0,8mm and cutting grooves forming squares of 0,8mm .

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Then I cut another series of grooves with the same tool , cutting 4 squares( 0,4mm large) on the primary ones ….
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I don’t know how the German engraver did it. With a single onglette is quite difficult to obtain a lot of parallel grooves and his job was quite neat with very deep cuts. Mine is on the left of course ;)
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I had to cut ant cut again many times and my grooves never come out as neat as his. The hammer is not flat , that increases difficulty ….


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I found some examples on the web of G. Young chequering , and it seems he was using a single tool as all the grooves aren’t parallel.

http://rockislandauction.blogspot.com/2013/07/gustave-young-iconic-engraver.html

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If you look closely to the engraving of the German shotgun you’ll see a parallel border with 2 lines , I measured it and they are distant of 0,4mmn the engraver has certainly used the same tool for cutting the fine parallel line.



How do you manage this kind of work ? Thank you for sharing some ideas here .:)
 
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mitch

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i've been doing it with a single point (square) graver and a pair of dividers, then bringing the diamonds to full depth with a 4-sq needle file, for nearly forty years. over small, tightly curved surfaces, i think checkering files are worse than worthless. with a graver & dividers, one can carefully 'fudge' the line spacing over a curve, so they stay more or less normal/perpendicular to the central plane of the sphere. done properly, the line spacing only appears to be fairly parallel, when there's actually a slight convergence toward the edges of the pattern.
 

mitch

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"'fudge' the line spacing over a curve, so they stay more or less normal/perpendicular to the central plane of the sphere. done properly, the line spacing only appears to be fairly parallel, when there's actually a slight convergence toward the edges of the pattern."

to clarify, you want the lines more like the meridians of longitude on a globe, not the parallel latitude lines. (did i get that right? or do i have it backwards? my brain is getting old)
 

santos

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Merci Messieurs, thank you for sharing:)

JJ, I have two Swiss(glardon vallorbe) checkering files but they are not that small, and I’m with Mitch : These files are not easy to use , specially for working around the borders.

However , they work fine for jobs with no border as Dave show.

I have to purchase one of this rifflers(#31904) : https://www.ishor.com/files/swiss-and-die-sinkers-riffler-files And have a try at Mitch’s method

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My checkering files are mainly used to make …my wood checkering tools, forged with HSS steel. I grind the rows of those with the biggest file(18 LPI) and the teeth with the smaller( 30LPI) . One tool has a chequered handle;)
 

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