I used screwed-shank collets, Osborne rather than Myford, back in the day when screwed-shank cutters seemed the norm. Nowadays I use only ER collets, which I find perfectly reliable for both screwed and plain shank cutters in low powered hobby machines. I personally wouldn’t bother looking for screwed-shank collets, even if they’re available.

However, I try not to be tempted into holding end-mills / slot-drills in the three-jaw chuck if I’m milling in the lathe.

Chronos sell the Vertex Posilock holder and collet sets in assorted tapers. When used in a Myford lathe (unless it’s the ‘big bore’ version), you may soon find that the MT2 arrangement which fits the standard Myford mandrel is too flexible for larger cutters. It’s fairly simple to take a lump of 2-2.5″ diameter bar and make an adapter which screws on to the 1-1/8″x12tpi  mandrel nose and uses the vertex collet nut. Doing that ends up with a vastly more rigid setup 😀

I’ll try to get a photo to show what I mean tomorrow.

If you are using Clarkson threaded collets you have to be very careful how you tighten them, especially with the smaller end mills and slot drills. This is because there is a centre inside the body of the chuck which engages with the centre drilling at the threaded end of the cutter. If the cutter is screwed into the collet to the end of its thread and the chuck is then tightened, thereby forcing the cutter hard on to the internal centre, it is liable to break the threaded end of the cutter. The procedure to adopt is to place the collet into the holder and then screw the holder into the body of the chuck within a quarter turn of it being tight. Screw the cutter into the collet until it engages with the internal centre in the chuck body. Then just nip up the last quarter turn of the collet holder into the chuck body. Don’t ask me how I know this!

This is for the S Type, I’ve never found instructions for the C Type

Bill