Build it Yourself: "Jam Peg"

Very few of us that are attracted to the hobby of gemstone cutting can afford at first one of the expensive cutting machines that range in price from $2,500 up to $20,000. I am one of those people.

Sitting down and researched the art of gemstone cutting, I found that the oldest and still most common method of cutting stones is with an outfit called a Jam Peg. Here is a detailed list of items you will need to complete this project: 

• (1) 1/2'' copper tubing (approx. 16'' -18'' long)
• (2) 1/2'' copper end caps
• (2) 1/2'' copper pipe holders
• (1) 1/4'' steel rod (approx. 4''-6'' long)
• (1) 32 gear index wheel (adding more or less index teeth for more or less facets)
• (1) 1/4'' locking collar
• (1) 9/32'' copper tubing
• (1) 6''-8'' length of scrap metal used for the gear placement locking leaver.

I have constructed and have been using this jam peg system myself and they are as accurate as anything you can buy through a lapidary retailer and will cost you a lot less. The only drawback is that most facetor’s today use a 96 or 120 Index wheel and because of the nature of Jam Peg, Using a large gear/wheel would make the stylus almost impossible to use. So you are restricted to 32, 40 and 48 index wheels which are readily available from Mr. Gerald Wykoff's YouTube Page. But never fear I have converted a number of cutting diagrams to 32 Index and will provide those later.

The tools you will need to assemble the stylus are a drill with a ¼” metal bit, something to cut the copper tubing with, some files to take the sharp edges off and some Epoxy Steel glue. If you do not like the idea of the glue you may attach the Copper pieces together by way of soldering.

First set the length of the Copper tubing, ideally it should be no more than 5 ½” long with the end caps in place. Next cut the 9/32” Brass or Copper tube so that approximately ¼” of tubing will extend past the end caps when installed. The smaller tubing will be placed inside the larger one.

Next drill ¼” holes in the end caps as close to being center as possible, accuracy here is paramount. The caps are not that expensive so make sure you have two caps drilled with the holes as close to center as possible.

Makes sure the 9/32” tubing will fit through the holes, file them out slightly if needed but keep the tolerances tight without being restrictive. Dry fit the caps on the ½” tubing and slide the 9/32” tubing into the holes. Make sure the inner tube can rotate freely and that the ends protrude the width of the ¼” lock collar which can be purchased at most good hobby stores. Assured everything fits properly, you can now remove the inner tube and glue the end caps in place.

In this instance, I've use Epoxy Steel glue because I found it is the best two part epoxy for the job. It can also be removed with some hot water and persistence if you make a mistake and have to take it apart. Set up for a couple of days and the glue is as good as steel.

Now comes a tricky part, the locking collar has a small screw in the side of it to set or hold it in place. This screw will hold the dop sticks in place and lock the tubing and the dop together. You must cut or file a small opening in the end of the 9/32” tubing just large enough for the screw to slide inside of. You slide the lock collar over the tubing and insert the dop then tighten the screw and all is held in place securely. 

Important: DO NOT GLUE the lock collar in place! Trust me on this one. You may find yourself filing the inside of the lock collar down a bit for it to slide over the tubing with ease. Also, you'll need this fit snug but not tight, the dop stick has to slide in and out easily.

Dry fit all the parts you have been working on and see how they now fit. With these parts in place slip the Index gear over the 9/32” tubing and allow a little bit of play up and down. Mark the tubing where the gear fits correctly. Then place a mark on it as so that the zero on the gear is in line with the nut on the locking collar. You will find that this becomes a very nice marker for centering the dop sticks. I did not do this with my original one but from here on out it is a must for me.

Now remove the inner tube and glue the index gear in place being careful not to smear any glue on the area close to where it will meet the outer tube when assembled. this part is critical make sure that the gear is at right angles to the tubing. You do not want the gear to be lopsided as this will bind when adjusting the gear for the facets to be cut. Allow all glued parts to dry over night.



Edited by: Wizard