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View Full Version : What I made today, boring small holes in ductile iron



MTNGUN
02-24-2010, 04:36 PM
This turned out well and there have been several recent threads on boring small holes and ductile iron in particular, so I snapped a few pics.

Not quite a mirror finish, but as good as I've ever done on ductile iron. The blocks are 1.5" high by 1.75" long.

65-45-12 durabar. The manufacturer claims it machines better than brass, but that is BS. I find it machines about 25% easier than 1018, which is to say, not that great. Tool life is much, much shorter on ductile iron compared to brass or aluminum.
http://i487.photobucket.com/albums/rr235/mountainmolds/duciron2.jpg

Final pass is typically 0.0005" (yes Lane, I work in tenths :) ) Solid carbide bar. Sharp cornered, no radius. Radiused edge does not work at all on small, flexible boring bars, will cause bar to deflect.

The tip on this bar has been resharpened several times and today it was only 0.029" thick. It's very fragile and will probably break in the near future.
http://i487.photobucket.com/albums/rr235/mountainmolds/duciron3.jpg

knudsen
02-24-2010, 04:39 PM
Makin' bullets? Looks like a nice finish ya gots.

tdmidget
02-24-2010, 07:17 PM
Nice finish in the cavities but what's up with that parting line finish?

Bguns
02-24-2010, 07:30 PM
Face finish is a micro vent system...

Finely ground surfaces don't allow cavity to fill well.

All commercial iron molds look like that...

Carld
02-24-2010, 08:08 PM
I'd say that was a DAMN good job if you bored all the angles and lands and grooves with that boring bar. You had to make some tricky moves to do that.

lazlo
02-24-2010, 08:08 PM
How did you bore the conical section of the bullet? Did you have a tracer template?

Gray DuraBar machines like a dream. Not as easy as brass, and it's dirty as hell, but it shears like butter. Haven't machined the ductile DuraBar.

MTNGUN
02-24-2010, 10:22 PM
How did you bore the conical section of the bullet? Did you have a tracer template?

Gray DuraBar machines like a dream. Not as easy as brass, and it's dirty as hell, but it shears like butter. Haven't machined the ductile DuraBar.
Homebrew CNC lathe.

A couple of people are still using tracers to bore bullet molds.

Ductile durabar should be easy enough to outside turn, but it's pretty hard to bore with bars that flex like a fly rod and break like glass.

It dulls carbide quickly, have to resharpen at least once a day, sometimes once for every cavity. Whereas the same bars will go a month without resharpening on brass or aluminum.

I broke a carbide bar yesterday while boring durabar. Ouch.