To make that with the DRO but no rotary table, I am assuming you have a cutter of the correct diameter to cut the curved faces of the jaws. To make it you then do the requisite (3?) number of plunge cuts on the appropriate pitch circle to get the shape you need. a rough sketch something like this.

After centring the part, use the DRO pitch circle function to position the cutter for the requisite plunge cuts.

I’d buy a coupling with 10mm holes both ends. Make a bush 10mm OD and M8 internally and press/loctite that into the couplings 10mm hole.  The other end will be the correct size so nothing to do there. All simple lathe work.

If 90 degree increments are OK, then size the pitch circle of the “hole” locations outside the diameter of the part, by enough to clear the cutter. If you place the first hole on the X  axis, then traverse across in X. Go back to your start point and repeat with the next hole ( 4 holes) which will be on Y, then traverse Y across.

120 degrees is a lot harder as you end up needing to traverse diagonally.

I’m with JasonB. However if you want a flywheel effect you could make the fleywheed with a short 10mm locating spigot then machine boss off the coupling half and attach to the flywheel with small countersunk fasteners between the “jaws”.

Robert.

I can confirm that the cutting methods suggested by Peter and Jason are practical and effective when using DRO functions to generate shapes and offsets of the sort desired which, at the core, are just refined versions of the simple dog clutch.

My work involved somewhat different shapes but the geometric cutting principles were sufficiently similar to prove the methods.

A heck of a lot easier with CNC of course.

Some CAD work will be needed to get the correct shape and offsets. Peters post is a particularly good illustration of the sort of thing you will need to figure out. I’d not care to do it on a drawing board with pencil’n paper or calculator maths in support. Despite, allegedly, once having the skills to do so.

Clive

Can you give some more details of the engine and it’s shaft.

Paul

Concerning clocking a vice into alignment on replacement I’ve always found pulling back, or pushing forward against lightly nipped up bolts or studs to be sufficiently repeatable for all general work. Typically better than ± 0.002″, 0.05 mm over 4″, 100 mm.

As I drive a Bridgeport I have the vertical space to leave the swivel base on my vices which makes it far easier to set up with a “good enuf for general jobs” setting by simple pull back leaving the frustrating tapping to get under a tenth thou error for the really special jobs.

If you don’t use a swivel base and if the slots in your bolting lugs aren’t already sufficiently accurate, my experience is that ex-factory they are pretty good for non machined surfaces but not quite good enough there are a number of ways to get decent eatability.

All of which start by inverting the vice to grip an accurately aligned block so you can operate on the underside.

My preference is for quick, dirty and effective by recutting the sides of the lugs so they are true and making atop hat shaped washer-spacer to slide over to slide over the hold down bolts or studs so the pull back method becomes accurate. For dead nuts adjustment you could make a third one with a bit of eccentricity in the stem and a hex shape to fit a spanner rather than a plain washer on top. Turning the hex would shit one side a bit to get it just so. Did the enlarge lug slots thing ages ago for a different machine and found it to work well enough.

The official approach is to cut a keyway so a key that securely fits the table Tee slots can be fixed to the bottom. Effective but the key fit needs to be close and a keyed vice cannot be rotated without removing the key. If the table Tee slots re less than perfect the key can jam making the vice a devil to remove.

A pair of simple round bobbins just inside the mounting lugs works almost as well as a full length key and is generally considered a more Model Engineer friendly approach.

No experience with the type of vice that has a slot for clamps rather than slotted bolting lugs so I can’t advice on easy alignment methods. There may be something in the Geraldi catalogue that could be used as a basis.

Clive

No reason a nut should not work, after all that is all that holds on a prop and an electric starter on the cone is often used for starting.

Flywheel would not need to be too large a diameter if made to a cup shape it could slip on over the driver to keep O/A length small.

Recess the ctr of the coupling so that you can fit the nut without interfering with the middle section.

What you will need to think about is cooling, if a centrifugal fan could also be includes inside a duct to blow air over the head that would work well as per R/C Helicopters.