ArtfulBodger.net

This is how the clapper and box were when I bought the machine. Depending on several factors and especially on the angle of the tool slide, the clapper did not always manage to be closed at the beginning of a stroke. Sometimes it would bounce open, other times it would never swing shut in the first place. Either way, the result was a buggered cut. Big...

The tool holder assembly showing the nonskid tool pad and the clapper return spring. Big...

The return spring assembly from above, in the closed position. Big...

The spring assembly from above, rotated to the open position. In this position, the flat on the bottom spring retainer allows the clapper to be lifted up (to remove the tool post, for example). Big...

The assembly from below, in the closed position. The flat on the spring retainer is even with the bottom of the clapper box. Nothing projects below the box, so there's no interference during close work when the tool slide is angled to the right. Big...

The tool pad and the return spring assembly, removed from the clapper and box. Big...

The same items, with the return spring disassembled, showing its components. The spring is ten turns of .065" piano wire, wound on a 5/16" mandrel and then stress relieved for an hour at 500 degrees F. It's about right. The bolt is about 1-3/4" long, threaded 1/4-20. Its head is 7/16" square, allowing it to be turned with the same wrench as is used on the tool post. This also allows the bolt to be turned from 1/2" stock. The small top collar turns out to be unnecessary, since there's a collar turned right into the bolt head. Still, if the spring had turned out to be a little wider, it would need that top collar to retain it. The bottom collar is wider than the top one, to make sure it catches the edge of the clapper (or in this case, the nonskid tool pad). It has a flat turned on it to clear the clapper without having to remove the whole spring assembly. Top and bottom collars are a sliding fit on the bolt. I suppose they could also have been made a close fit on the inside of the spring, too, but I made them before making the spring. It's tough to predict what the final diameter of a spring is going to be. Big...

The return spring assembly from the lower end, showing the shoulder turned on the bottom spring retaining collar. This shoulder is .020" thinner than the tool pad. It's there for convenience: when closed, the broad part of the collar bears with full spring pressure on the tool pad (with a .020" gap between the shoulder and the clapper box). When opened, the shoulder holds the broad part of the collar about 1/8" away from the clapper box. This just makes it easier to grab the coller with your fingers, as opposed to having it held tight agains the clapper box by the spring. (You know how hard it can be to pick up a dime off a smooth surface? Picture a dime held down by a strong spring.) Big...