Hi Everyone, I’ve been making some handmade basket settings for large
faceted stones lately and I’m having a difficult time keeping the
prongs symetrically spaced around the bearing wire. When I mark the
upper bearing wire for the prong notches I lay it on a piece of graph
paper, and mark it with a scribe. I make initial notches about 1/3rd
of the way through with a sawblade and then use a cylinder diamond
bur about half the size and then another the same diameter as the
prong wires. I often stop to check the spacing but somewhere in the
process sometimes they just end up in the wrong place. Is it the bur
wandering or is there some trick to this that I don’t know about?
It’s quite annoying to discover that the prongs are asymmetrically
spaced after going through all that. Your help is appreciated…
Douglas, try cutting the slots with a joint file rather than a burr.
A burr will always try to wander in the direction of rotation. If
most of the material is removed with a file and a burr used just for
the final fit, the wandering effect will be greatly minimized. It is
surprising how a minor difference in the spacing becomes very
apparent in a prong setting. In the case of building something like a
three stone ring those minor variations become major as the piece is
constructed causing the entire ring to look crooked. Frei and Borrel
will have joint files as will most of the other tool suppliers. for a
broader selection of sizes you can find them at the Luthier supplier
Stewart MacDonald Everything for building and repairing stringed instruments! - StewMac
Try using the tip of a rat tail file instead of a bur. It’s much
easier to keep it in the right place if you are filing perpendicular
to the gallery as opposed to using a bur that is cutting (rotating)
parallel to the gallery. The bur can wander almost imperceptibly
while cutting and as you already know, a little bit off can be a huge
amount when you start adding prongs. A file is a lot less likely to
slip out of the kerf and cause damage too.
Not a trick so much as a hand work approach instead of mechanized
one. If you want to keep the locations precise and symmetrical put
down the flex shaft and pick up a file.
Try this: Layout positions, mark centers with scribe, incise scribe
marks with an upwards push stroke of saw blade to make a notch. Saw
the notch mark deep enough to use as guide for a file. Use a small
round file (needle or escapement, depending on the size of wire and
notches) or either a joint edge or crochet file clamped in a saw
frame to keep the grooves perfectly centered and aligned.
In this type of work requiring precision, the expediency of a couple
seconds with the flexshaft is not an adequate replacement for a
minute or two of proper hand work with a file. Once you have the
center locations marked there is no need for them to end up off
center.
Hi Douglas, However you lay out the spacing for your prongs, don’t
make one line, make two; one on each side of the place you want a
prong. This way you can avoid bur drift.
I have a jig it is a piece of round stock that is tapered on the ends
with grooves milled longways down the rod. The idea is the grooves
are evenly spaced at 45 degrees so you can lay a piece of wire in 4
or all 8 grooves tie them in place with tie wire then put your
bearing wire in place and solder the joints for a round basket the
other end is done 15 - 30 degrees apart for odd numbered prong
baskets - goo
Douglas- If you are marking and sawing accurately it sounds like a
wandering burr. Try flipping your work over. Burr from the top as
well as the bottom. We all have a tendency to lean one way of the
other. When ever I am removing metal by burr, file or drill or
whatever I constantly rotate my work. Three or four file strokes,
spin 45%, 3 or 4 file strokes rotate again and so on. Drilling the
same. If I’m trying to keep a prong notch straight I flip it over as
well. That way the tendency to lean one way or the other will self
correct.
Remember “Absolute Straight” is somewhere in between measured
straight and eye ball straight.
One additional layout and marking tip; 3 registration marks instead
of only 1. After marking the prong centers and notching with a saw
blade, set divders at half the prong diameter and scribe parallel
lines from the centers to mark the outer sides of each prong.
I don’t know if this will help, but I will be teaching this very
technique during my CUSTOM SETTING FOR FACETED STONES workshop at
the Mendocino Arts Center August 6th - 8th.
Many of the tips that the members of this forum have put forward are
part of my lesson plan for the workshop. I also cover slot-in-slot
head building for oval and cushion cuts.
Hi everyone, Thanks for the tips on files etc. I guess I probably
would have used a file for notching except I did not have a round
file that small, but I did have a diamond cylinder bur the exact
size for my prongs. Thanks Tim for the luthier supply tip, here’s a
link to some really cool files they have for notching guitar nuts: