Model A - clutch spring screws

 Now that the primary chain guard is finished we'll start on some lathe jobs, finishing the clutch dome when it's screws are made. This will need a change from the three-jaw chuck to the ER25 collet which we will do in a while, but first we'll use the chuck to hold the hexagon stock we need to make the clutch spring screws and perhaps the battery strap nuts.

We have four screws but we need six, so here we go. First job is to turn down the bar stock to a 1/4" diameter for threading, copying one of the existing screws.

After a small problem with a blunt die, I was delighted to find that the torque upgrade that we did on the lathe some months ago enabled this 1/4" thread to be cut under power.

Once you're set up it's dead easy to knock these out. In 10 minutes or so I have two of these ready:

The next step, and for this I need the ER25 collet, is to shape the head to that low radius the original has; then we can think about cutting the screwdriver slot and making the washers.

The raised head is formed using a specially ground tool. It's important to keep this sharp and feed it slowly to avoid chatter marks in the work:

Nicely raised heads:

I used the compound slide adapted for vertical operation to put the slots in the screws. They are cut with a 1/16" slitting saw.

Here's the result, with some old screws for comparison:

A nice little job I think. Still need the washers - those standard ones are too small. The originals are special and are quite tight on the screw.