Star lube die question...

[mattw]

I have a Star .400 die that I really need to open up just a tiny bit, would like .4015 or so. I do not have a lathe, but could chuck fine paper up and hone it out. But, would removing that much take forever and would I have a chance of having a true die afterwords? I am also concerned about removing the hardened layer of steel... I have papers from 400 grit to around 4000 grit to work with.

[bosterr]

A lot of guys use wood dowels. I much prefer steel round stock of different diameters for different calibers. I cut 400 or 600 wet/dry into 1" strips and wrap in the direction that will tighten rather than unwind. Start wrapping with tape to the rod and wind until you push it into the die with resistance. The end will wear quickly. Cut some of that end off and insert a short piece under the end of the wrapped enough so it will stay wrapped. Increase the length of the new piece each time to lap out to the diameter you need. Go slowly and try sizing a boolit after every round of lapping. Boolits that are cast long ago with antimony and have had time to harden will spring back, so pure lead is better to size and measure. When you start getting close to the target size switch to 600 or 1000 paper. A word of caution: every time you lap and want to try sizing a boolit to check your progress, lube to boolit first with lube of some kind. I always stick the boolit in the die then have to beat it out with a punch and hammer if I don't lube it first.

[Valley-Shooter]

I just did this last week.
I honed out my .401 die to .4022

I used 400 grit wet/dry cut into 1 1/2" strips cut to 4".
I used a hardwood pencil that I had sitting around.
I taped the wet/dry on to the pencil with a strip of packing tape and rolled the die back on a piece of plywood on my lap.
It takes awhile, I think I went through 4 pieces of wet/dry.

[Mal Paso]

The die is tapered so keep that in mind. The one I lapped went fast, split dowel/600 wet or dry. I used pin gauges to check. Hard bullet alloy will spring back after sizing, how much depends...

[sigep1764]

I did this a couple of months ago to open up a .278 die to .2795. Took about an hour or so with wet/dry 600 grit wrapped around a screwdriver shaft. Don't worry about the hardness layer, won't make one bit of difference in my experience.

[wv109323]

I opened up a .358 die. I used a drill with a wood dowel. It took longer than I expected but turned out ok. I used dry paper but the wet may be the ticket.
I checked my progress several times by sizing a bullet then miking diameter.