metal chequering

[santos]

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.


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 .


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


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



Then I cut another series of grooves with the same tool , cutting 4 squares( 0,4mm large) on the primary ones ….



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

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 ….



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





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 .

 

[JJ Roberts]

Santo,We use checking files for that restoration work on hammers and other gun parts,you can find the files at Brownells gunsmithing supplies at brownells.com.You did good work. J.J.

 

[Brant]

Another option would be to use a 'thread restore' file. They can be had in both SAE and Metric.

 

[mitch]

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.

 

[Dave London]

Good Job , checkering is a PITA. I have used checkering files and 60 degree very fine riffers

 

[mitch]

"'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]

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



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