Simple tool for diamond knurling?

It's all well and good to figure out how a knurling tool works - or not as the case may be. But if you want an example that actually works as you'd hope, you'd want to come up with something better.

It seems to me that the "correct" way to make a properly cut diamond knurl pattern would be to cut one set of slanted grooves, then move the tool and/or work and cut a second set at the appropriate angle to the first. As opposed to cutting one set and forming the second.

Thinking that I've come up with a bit of a smartarse concept, here's what I've modelled in Fusion:

• Reuses the Böni wheel / bearing / carrier aassembly.
• Mounted on a simple length of hex stock.
• Presents the knurl at 30 degrees to the workpiece (lathe axis).
• Can be rotated 60 degrees to present the knurl wheel at "-30 degrees", to create a diamond pattern.
• Spindle rotation will be reversed to cut the "other" groove.
• Single piece body with simple machined features.
• The knurl wheel contacts the (cylindrical) workpiece at the centre line of the hex toolholder body.
• Wheel is angled slightly (at 10 degrees) to provide a rake (clearance) angle with the cut groove, to avoid friction.
• I'd have a fixed stop in the toolpost to position the back of the tool against, to ensure the radial position is retained between the 2 operations.

Hmm. Very clever. I can rotate the toolholder by 60 degrees to change the angle of the knurl without having to reset the height of the tool and the angles are taken care of by the hex section of the toolholder body. 

Yes, but there is no feature for retaining the bearing in its bore. And there's very little meat left where the bearing is supported. I'll probably have to involve an additional component. So - nice try but no cigar etc - try again, Fatty.

Here's another approach. The point of contact of the wheel with the work is on the axis of the hexagonal toolholder body, so I can rotate the tool in the toolpost without creating any offsets. This constraint is a sliding joint, so I can move the wheel assembly along the toolholder axis without screwing that up.

I need to align the parts and join them in a manner that wouldn't require a mammoth fabrication / machining / welding event. Something like this:

A simple turned part, welded to a length of hex stock with a short joining connector. Alignments are fairly simple, so setup for boring the bearing hole should be easy to set up. Hell, I could even use that connector as a stop, to ensure a consistent position in the toolpost without the need for an additional, external stop.

I've got a nagging feeling that the length of 19mm (3/4") hex bar stock I have may be EN1B (leaded) which is wonderful to machine but doesn't like to be welded. That's a good reason to do the welding early on - if it's not weldable, I will need to get some alternative material.

Let's get going!