Mounting Peg Style Heads: Technical Tips for Success
By Stuller Standard | April 24, 2009
To some, mounting a peg style head is literally like forcing a square peg into a round hole. But it doesn’t have to be that difficult at all. Here’s how we do it at Stuller, so the next time you’re facing this particular task, you’ll have these tips to help you get the best result.
Scenario #1: When working with a square peg, many jewelers will measure the thickness of the peg and drill a hole to match the size. Then, they force the peg into the hole. The emphasis is on “force”: Use of excessive force often results in a distorted or damaged head, and it’s not necessary.
Scenario #2: Another technique is to measure the peg diagonally, corner-to-corner, drill the hole to size and insert the peg. This technique leaves a larger gap between the peg and mounting, which then must be filled with your jewelry solder. The problem is with the excessive amount of space around the head. This allows the head to move, making it difficult to achieve proper alignment.
Resolution Tip: This is the technique we recommend: First file the corners from the peg to shape it into an octagon. Now measure the peg diagonally across the flats in at least two directions, and select the appropriate drill size. This will create a hole that is best suited to match the peg and provides the best fit.
Scenario #3: Now that your hole is drilled, let’s look at your second challenge. In most cases, the surface that the head attaches to it’s convex. When the peg is fit into the hole, there’s a gap between the base of the head and the surface of the mounting. Often you see these heads being soldered into place and supported entirely by the peg. This isn’t a good idea because the peg is simply an indexing aid, not a structural element, and shouldn’t be used as such.
Resolution Tip: After the hole is drilled, try this quick technique for creating minimal disruption to the surface of the mounting: Use a 45° bearing bur, and lightly chamfer the hole where the head will set. The diameter of the chamfer will need to be almost as large as the base of the head. This will allow the head to set into a pocket and let the prongs contact the surface of the mounting. This becomes an important point when soldering the head into place. After the head is aligned, turn the piece over and solder it into place from the back. Flux everything, including the joint, to protect the piece from oxidation during soldering. This takes two small chips (pallions) of solder, about 1mm by 1.5mm in size. A little extra solder is needed to fill in the chamfer and make a smooth fillet at the base of the prongs.
Use a soft large flame if possible, and heat the mounting slowly using an on-off heating technique (one second on, one second off). Heating in this manner will allow the heat to travel through the mounting and into the head. You want to avoid heating the head directly, since it’s very easy to overheat the prongs and damage the head. You also run the risk of forcing the solder to run up the prongs.
It never pays to be complacent when soldering heads into place. Mounting a head securely is a most critical procedure for a bench jeweler, and shouldn’t be treated as routine. Remember: The head usually holds the most valuable part of the piece. Why would you want to risk it?
As always, if you find yourself in a jam, drop us an email, hit us up on Live Chat, or just give us a call (4300). We’re here for you and ready to help.