Marking out gun screw and pin heads for engraving

[JRFrankin]

Hi all.

I have a question regarding marking out circles over screw heads where you don't have a centre for using a par of dividers. This is most troublesome over a screw that is domed. Does anyone know of an effective may to avoid this issue. I have tried things like filling the centre of the screw slit with a soft metal to give me a centre to work with but that appears not to be very effective and can also be damaging to the screw head itself.

I have attached an image of the kind of screw. This was one of the better attempts. but its regarding the centre circles and marking internal guidelines for petal sizes.

Many thanks

 

[Dave London]

Bend one leg of divider, run around out side of screw to scribe line in a circle, or buy a hermaphrodite divider to do the same thing

 

[John B.]

Nice job. Keep doing it.

 

[monk]

looks great. have you learned to align all the screw slots so they all point in the same direction? i tried that on one gun i did. drove me nuts !

 

[horologist]

A small lathe? This jumps to mind first although I have been accused of being lathe obsessed.
Something similar might be accomplished with a fixture to hold the screw on the center of rotation of your ball vise. Then you can use the hermaphrodite divider as Dave mentioned. I think it would be much easier to get a clean, consistent circle by rotating the screw and holding the divider steady than the other way around.

 

[Leland Davis]

What ever you did on that it worked very nice. Chuck the screw in your drill turn it slow and use a scribe dragging on the screw works for me.

 

[oniemarc]

If you need to repeat the same pattern on mutiple screws...you could use a drillpress. If you put the screw in the chuck, you can put a scribe in the vise. Don't move the vise to a new position, untill all screws you need have gotten the first scribeline. Then move onto the next measurement you need, and so on. You might have to file all the screws a slight amount though, so they run centrered and are the same size. Most screws tend to have a slight "wobble" to them.

Marc