By Guy Hanson
Thread milling is addictive. The cutters are on the expensive side for a hobbyist like myself, so I wondered if there was another source of multipoint cutters that could be adapted for thread milling and more conventional threading on a lathe. I picked up a box of about 30 inserts for a die head on eBay and started playing with them.
Photo 1 illustrates one common style and the holder I made for it to use for internal threading. I measured the angle on the cutter base and set a piece of bar stock to that angle in a swivel vise on the mill. The insert sits on the grooves and is secured by a top plate (Photo 2). The only significant tolerances to maintain are ensuring the correct angle and that the insert is flush or slightly proud of the bar stock so the plate will secure it. You’ll have to adapt to however your inserts are designed to be held.
Feed gently as there is a lot of surface area. You’ll find it’s easier to visually pick up a thread compared to a single point tool when you have to redo or clean one up. The inserts are also far more precise than the single point tools I grind freehand. I’ve been paying about $3.00 for a set of four and they have been working great, give it a try!
Thanks, Guy, your subscription has been extended by an issue!