to machine a hexagonal nut using indexing head on milling machine

To machine a hex nut with an indexing head, you first need to mount your workpiece securely in a three-jaw or four-jaw chuck attached to the index head spindle. Since you're looking for a hexagon shape, you're dealing with 6 sides, so you need to figure out your indexing ratio. Most standard dividing heads have a 40:1 ratio, meaning one full turn of the crank rotates the spindle 1/40th of a turn. To get 6 divisions, you divide 40 by 6, which gives you 6 full turns and 4/6 of a turn, or 2/3 of a turn on the index plate.

Set your sector arms on the index plate to cover the right number of holes based on your plate's hole circle. If you have a 18-hole circle, for example, 2/3 of that is 12 holes. So, you'll do 6 full rotations plus 12 holes to reach each face. Make sure your workpiece is centered perfectly, otherwise the nut will come out lopsided and look pretty bad. I usually take a light pass on the first side just to verify the positioning before committing to the full depth.

When you're milling, try to use a sharp end mill and keep your feed rate steady so you don't get chatter marks on the flats. After finishing each face, just index to the next position and lock the head before starting the next cut. It’s pretty straightforward once you’ve done it a few times, just watch your fingers around the cutters and keep the chips cleared away so you can see your scribe lines clearly.