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View Full Version : Opening up a Lyman sizer die



Johnch
01-23-2006, 09:03 PM
I have 2 .357 sizer dies for my Lyman , 1 says .358 , but both size to the same diamiter.

I want to open 1 to size .3595 or .360
I was thinking laping compound on a wool mop and polishing out the .0015 a side .
Is there a better way ?

Also how much can I inlarge a die before I need another push rod ?

Johnch

Buckshot
01-23-2006, 10:09 PM
................Assuming no lathe, or drill press, or access to one:

You can open a sizer die a couple thou fairly easily. I have a method posted at www.castpics.net you can check out. Another way is to use a split rod with abrasive wet or dry paper spun by a drillmotor. For a .358" die about the closest wood dowel will be 5/16 (.312"). Split the end for about 1" or so. Put a couple wraps of masking tape around the end of the rod to fatten it up a bit. Use a razor blade to slit the tape over the slot.

Cut a strip of 220 grit paper, start the end in the slot and then make one complete revolution around the dowel and try the fit in the die. Ideally it will be snug so the paper will cut. If not, then put on another wrap or 2 of tape. No sense wrapping on more wet or dry paper as the outside is the only part that's gonna be working!

You should have 3-4 lubed lead slugs standing by to use for checking the progress. Hold the die in one hand and the drillmotor in the other or clamp it in the benchvise. Put a couple drops of oil on the paper and with the dowel spinning fairly slowly work the die down over the paper. It should be that snug. Speed the drill up some. The paper will cut well and it will guide well and not be all floppy, so snug is the word.

You'll feel the torque against the die lessen as the paper cuts but also as the abrasive breaks down after a few minutes. Stop and rinse the die in some solvent of some kind and push an oiled patch through it. Then drive a slug through and mike it. How much was removed in how long a time will be a good indicator about how much longer you have to go.

When you reach the point where you're less then a thou away, switch to 400 grit. Also while the dowel is spinning you should be moving the die back and forth, and then swap it end for end about once a minute.

The last few fractions of a thousandth will go fairly fast as most of what you're doing is knocking down the course 220 grit surface.

You can usually go a couple thou over without needing a new ejector pin. Watch your lube pressure and remember that when the temp goes up it'll flow a bunch better, so back off the pressure.

.................Buckshot

woody1
01-24-2006, 12:01 AM
Also how much can I inlarge a die before I need another push rod ?

Johnch

My .360 sizer started life as a .358. Opened up pretty much as per Buckshot's description. I have no problem with leakage using the original ejector pin. Regards, Woody