Lapping a Lyman sizer

[ghh3rd]

I am going to lap my Lyman .431 sizer to .432. I think that would be a good size to accomodate the two molds that I'll be using a lot. I did lap a Lee sizer once and it seemed to come out OK. Is lapping a Lyman sizer more difficult? Are there any good tips available to make it easier?

I will be using a split dowel with #600 paper wound on it until it just fits inside the sizer, and turning slowly until desired diameter is reached.

Also, what's a good way to polish the inside of the sizer? I wonder if the jewelers rouge I have would polish something as hard as this.


Cylinder .432
Barrel .430
Cramer #503 boolit .433
Ranch dog TL boolit .432

[NHlever]

I opened one of my Lyman .44 sizers just like that, and it worked fine. I didn't bother to polish it afterwards as the finish came out pretty good. I do get a bit more lube bypass than I used to, but that's the price you pay I guess.

[JIMinPHX]

If you're going to turn slowly with 600 grit, then I hope you have a lot of time on your hands. I'd use 600 grit in a cordless drill if it were me.

The 600 grit should leave a pretty good finish all by itself. Yes, you can add a little rouge if you want to go a level higher with the shine.

[ghh3rd]

and turning slowly until desired diameter is reached.

Actually I will be using a drill, slowly. It didn't take long to increase the size of my Lee, even going slowly with a drill.


I do get a bit more lube bypass than I used to, but that's the price you pay I guess.
I am trying to visualize why increasing the size of the die would allow lube to bypass. What I mean is what is the difference between a die that would be manufactured as .432 (which Lyman doesn't actually produce), or one that is lapped to .432?

Thanks - Randy

[missionary5155]

Greetings
As you increase die diameter the ejector rod is no longer the same tolerance of fit as before. There now exists that .0005 extra that as you increase lube pressure it will permit a thin measure of "SQUIRT" to slip past.. It does not amount to lots... but it is there. Open a die .003 and it gets goo-eee... But again no bid deal.

[EMC45]

I did a .429 to .430 and I used an electric drill. I did the slow and gentle method first and got nowhere! I then went on to the drill and higher RPMs. It works perfect now. I did make sure to clean it very, very good though. I wanted no grit in there at all!

[ghh3rd]

I just got done lapping. What a difference between the Lee that I did a while back and the Lyman. I thought I had 600 paper, but good thing that I only had 400 because I kept having to repeat the process several times, and get agressive with speed and pressure.

[JIMinPHX]

I've found that when I make Lyman style dies, & the rod that goes inside them, a clearance space of about .001" - .002" on diameter seems about Ideal. .003" will work well in many cases, .004" will work OK if you don't use too much heat on the lube & you don't have a real soft lube, .005" is about where it starts to get difficult to keep good control of the lube & bigger than that tends to be a lot of trouble. When I make the rods, I like to make them about 1/8" longer than stock, so that they push the boolit up clear of the die completely.