I’m finally getting to start work on my Form 1 can.  It’s going to be filled primarily with freeze plug baffles.

Is it better to center punch a freeze plug then form it, or is it better to drill a starter hole before forming?

This is a .22 LR caliber can, and I don’t want to wind up pressing the baffles with oversized holes.  I don’t want to waste a bunch of freeze plugs finding out the hard way, so if someone can share their experiences with this sort of thing, I’d appreciate it.

Are you using a jig or the Torx bit technique?

TBH, I don't understand why no one forms the cone and cuts bore to size by plunging an end mill into cone tip or running a slotting saw across.

I seem to recall from the very long thread on cheap F1 builds...

That one of the best methods involved using a 90° forming point to a limited depth, then switching to a 60° (like a lathe center) to extend the cone.

Even using a 1/16" center spotting hole the material will open up as it is stretched.

Ideally the builder will bribe someone for the use of a lathe to bore the holes true to actual center with a 1/4" or 9/32" End mill or solid boring bar.

I'm using a steel plumb bob with (I think) a 60 degree point.  I've set up my own fixture to center the bob and the freeze plug.  I went this way because I could never find the correct, tapered Torx bits, and buying a bearing puller just for the centering part didn't make sense.

And while it would be really nice if I had a lathe and a bunch of other metal working tools, I don't.  So I'm doing things with less advanced tools.  I have built a fixture to accurately center the plugs, and I have a small lathe chuck to hold parts on my drill press's table, but I don't have the money or the room for even a small metal lathe.

No lathe needed, provided you get a reasonably centered cone and allow for a generous bore to bullet clearance.

Form cone. Center fixture in drill press w/ cone pointing up. Use a decent size end mill ( ⋝  1/2") and plunge down on cone until desired bore size has been achieved.

With a large enough end mill, the fixture need not be centered at all. HSS cutters should be fine for FP's (they'll keep tooling costs down)

.

1. A pilot hole 9/10 of final I.D.
2. Form with ball bearing slightly larger than hole.
3. Ream to final size, coming in from convex side.

Clamp everything TIGHT and perfectly centered, Lathe is best.

I'll have to look into getting the right size ball bearing to try this.  For a .22LR diameter, a 0.250" ball bearing would probably be "slightly larger" enough to do the job.

And also thanks for confirming reaming is done from the convex side.

I should point out that I'm not using a large vise.  I'm using a 6-ton hydraulic press.  That might alter how I would use a ball bearing, but probably not much.

I used a Fostner wood drilling bit for center punching. Just found one close and wrapped tape around it to get the right size. Place it squarely in the FP and tap it. I made a 30 cal can. I started with a 3/32 inch hole and formed them in the vise. The 45* cone first and followed with the plumb Bob until the hole was the right size (23/64). I didn't drill the holes out. I found that I could "move" the hole as I formed it to keep it centered, checking by spinning the baffle on a socket. I had a few failures that had to be deformed and thrown away, but they were only 69 cents each.