I’ve done similar by marking it out and filing it to shape, after first making a hacksaw or Dremel cut for the driving face of the dog. Use a piece of emery tape wrapped around the job to mark out the spiral part. Then hacksaw or Dremel the slot to full depth. Then file with a 10 inch flat file. If they are just those common locking levers etc, spiral does not have to be any kind of perfect.

Same technique used to make special counter boring tools and the like from silver steel. It’s not hard.

You could mill it but its a lot of faff, requiring a dividing head geared to the longitudinal movement of the milling table and a second set-up to mill the sharp corner at the base of the driving dog face. Not worth the hassle for such an application.

isn’t it a job for the rotary table / dividing head which is set at the angle of the slope?  A bit of careful milling as the face of the slope is perpendicular to tilted axis. This is one I made for the start dog of a vintage car.

In a lathe with toolpost milling attachment and lathe in threadcutting mode, turn lathe mandrel by hand.

On 27 July 2024 at 14:08 bernard towers Said:

…lathe in threadcutting mode…

A modern take on the threadcutting aspect, especially if it would be difficult to set the lathe up for the coarse pitch the object requires, would be to 3D print a facsimile of the object and use it as a copy template (like how rifle stocks were duplicated from a hand-made master pattern).

The helix cutting above reminds me of a woodworking contraption, I think called a router lathe, that used a tensioned steel cable over different size pulleys to synchronise rotary and sliding movements. I guess in that situation, some potential slip would not be a disaster, unlike in threadcutting.

I had one made at work ! It was a 3 spiral for an Austin Champ, it was milled, 3 sloping faces – worked fine . Noel.

On 28 July 2024 at 14:12 Phil P Said:

I used a slotting head and geared the dividing head to the table traverse on my milling machine.

If you could accept a bit of filing, you could do the same but with mathematical gearing instead of mechanical gearing between leadscrew and dividing head.

Work out the table advance per degree of revolution and proceed from there.

One degree of revolution is 360 divisions, so you could do the inverse – work out how many divisions of the full circle would result from 0.005″ linear steps of movement and pick a plate and hole circle to suit.

For that sort of use a hacksaw and file should get you close enough

Two sideways saw cuts half way through it at opposite angles and then a final cut to do the vertical face. Bit of file work to smooth the transitions.