Bolthead checking/truing

[allan1066]

Hi
I'm building a new rifle based on a new mod 12 target action. I want to check to see how true the boltface is - What do I use as my datum point? Do I need to check the face is true to the rear of the boltlugs or true to the shank of the bolthead or some other place.
Thanks

[BillPa]

When I do one I'll index off the shaft since the rest ( lugs-face) are going to follow it anyway. I put the shaft in the chuck allow about 3/4" or so of the shaft out past the jaws, use a center in the pin hole then indicate on the shaft. In my thinking its to short to do it any other way.

After setting it up I can take cut on the junction of the shaft and lug to recut the radius to relocate the baffle spring washer and take a LIGHT cut across the lugs. Be careful dong that however. There is only about .010" meat between the bottom of the extractor spring bore and the lug face. Get carried away you'll be buying a new bolthead. After that I'll remove the center, change tools and take a light cut across the face.

Bill

[PEI Rob]

I use a 5C collet. I haven't put too much effort into determining if they are dead true but I can tell you they certainly are not out by much if any. All the ones I've done seem to have almost no misalignment at all, a 1-2 thou cut off the lugs trues them up every time. The face is dished from the tumbling process and gets trued to the lugs with the same set up, its the only reason I machine the head in the first place. I remove the rad, tune the ejector depth, debur and install a new extractor detent ball.

[allan1066]

Thanks guys - Thats just the information I was looking for.