? Polishing iron mold ?

[minmax]

I was thinking about beagling/lee-menting an old Lyman mold. I was also going to increase the diameter by placing aluminum tape between the molds. I have some straight lynotype. I was wondering if that is hard enough? I also have a little bit of tin soldier that I could add. I don't have any lapping compound or valve grinding paste. What grit should I start with a should I just use coww or another alloy? I guess that is my real question.
Thanks Kevin

 

[Brad]

I would think soft would be better. You want to hold the grit. Might add a bit of Linotype to pure to increase as cast diameter but not much.
I would use 320 grit Clover brand grease type compound.
Personally I prefer the Beagling to lapping. I haven't had great results removing much with lapping. It will polish out some rust but I don't get much metal removal.

 

[fiver]

you have to be patient when lapping a mold out.
i just bought valve lapping compound from the NAPA store and used it.
i needed to lap out a lyman [surprise] 4 cavity mold from 428 up to a tick over 430 it took me 5 days of casting cleaning and lapping
a little here and a little there.
i would lap the mold hot then clean it and then cast some boolits from it.
I'd use them to lap the next go round.
taking the blue color out of each cavity fully before cleaning and casting with it again.

when i got it where i wanted it, i done one final polish with colgate whitening tooth past and a little baking soda mixed together.
i shoot this mold a lot now.

 

[Brad]

I have a Lyman 429421 that doesn't cast near large enough to stop leading in my 44 Mag. I am leaning towards seeing if I can indicate a cavity well enough in the lathe to use a small boring bar to open up the bands a bit.
The mould isn't worth a damn now so if it gets screwed up I'm not really out anything.

Should be a good learning experience too.

 

[JonB]

Have you read the sticky on the other forum ...expanding a mold the WEET method ?
It should pop up first via a google search.
besides being extremely detailed, it exposes a neat simple trick...so simple, you'll think, "I shoulda thought of that"
which is...
stippling the driving bands (the only part that needs to be honed).
the stippling does two things, it enlarges the bullet as well as grips the abrasive paste.

 

[Brad]

I never read that thread but stippling makes sense. I wonder if even a roll on a steel plate with a file would work.

 

[JonB]

Oh, I should have clarified...that is exactly what the poster did, was to roll the bullet using a coarse file.

 

[Brad]

A poor mans knurling tool. I like it

 

[Brad]

I will need to do some casting with this one. Just opened the bands up .004 on the lathe.
I need to grind a better tool for this kind of stuff but that can wait for a bit.
Boy does the photo make the cavities look rough.

 

[fiver]

you run out of cutting fluid?

 

[Brad]

no, not out. I just cut this one dry.
Problem was that I used a tool ground to a very fine point, I need one ground to a radius. That would give a far smoother cut.

If the mould doesn't drop bullet well then a quick polish will smooth things up. This was more of a learning thing that anything else.

I did learn that the cavities are .003 out of round. The indicator told me! Drove me nuts for a bit too.

 

[fiver]

I wonder if lyman even pushes their molds closed all the way when cutting them any more.
or If it's cut box cut box cut box.
hmm we should measure one of these maybe???
nope, you just keep on cutting, we got a schedule to keep.

 

[smokeywolf]

Brad, you'll be grinding a lot of boring and probably a few trepanning tools. A trepanning tool is used to bore a shape (usually a groove) into the face of a part or the bottom of a hole that has been bored into the part.

For steels that have a tendency to tear instead of cut cleanly when the edge of a cutter is applied, Castrol's Moly-Dee cutting oil can make it a little easier to produce a better finish. Another cutting oil that works pretty well on low carbon steels is purified lard oil.

 

[Brad]

Never even thought of the mould as low carbon steel, duh. No wonder it tore a bit.
I have gotten much better at grinding tools lately. Takes a bit of thought to determine what needs to be removed and from where on the blank. Frequent stoning helps too, gotta have em sharp.

Fiver, I doubt Lyman measures much of anything. If they do then they have some pretty generous tolerances. My guess is that they figure on cutting a set number of moulds with a a cherry and don't stop til they hit that number. Imagine the range of diameters those moulds cast! Despite what some say Lyman does make some pretty undersized moulds.

 

[smokeywolf]

Not counting inserts of course, I stone all my bits. Not only does it produce a better finish, your bits stay sharper longer. It becomes even more important after you've spent an hour or two grinding a form tool.