Enlarging Lee 457-405-F

[Rokkit Syinss]

Why Lee puts this mold out at .457 instead of .460 is beyond me but it's cheap so I decided to try it. Using 1:20 alloy. Parting line one cavity drops .455 and the other cavity drops .456, both cavities are .457 at 90 degrees from the parting line. I tried beagling and the major dimension did go to .461 but that of course doesn't help the parting line dimension.

So time to try lapping. I do not have Clover Paste, I do have diamond paste in 3 micron, 1 micron and half micron. Will this work with a drop of oil? It may be too hard for aluminum molds or it may be too fine for this use.

[KenH]

I agree with you 100% - that mold SHOULD be designed to drop at .460 - it can always be sized down. I doubt anybody actually shoots a .457" diameter cast bullet - isn't that about jacketed size?

Lapping should work just fine with the 3 micron size - I just lapped a Lee mold with 8000 grit, which is about 3 micron and worked pretty good. I got an extra thou pretty easy.

[GONRA]

GONRA's suprised ya'll can lap ALUMINUM!
Thought that soft metal would be THE LAP not THE PART!
(Learn something new every day!)

More lapping details guys? Softer Lead Bullet Laps? ???

[KenH]

If you're wanting to lap a mold to enlarge the bullet size that's dropped, you're not cutting with the soft lead bullet, but with the grinding compound. Take a bullet as dropped from mold, drill a hole exactly in the center of base, screw a long screw in. Cut off head. Coat bullet with grinding/polishing compound, clamp bullet in mold and start spinning with a drill motor. If needing to enlarge a good bit, I'd use a pretty large grit compound - perhaps 200 to 300 grit range? BUT - be sure to finish off with a fine grit, like 5,000 or so.

If you've got a mold that's not dropping bullets easy, a good polish with 8,000 grit seems to help. Just a quick polish doesn't seem to enlarge much at all - perhaps <.001" or so. The bullets do drop a good bit better.

[Rokkit Syinss]

Screwed that up....oh well.

[Stephen Cohen]

I have laped several Lee RCBS and Lyman moulds, I pretty much do as KenH said, I do however remove material from the lap in areas where I do not wish to lap. If I find a mould is out of round I use a lap that has been relieved on the larger axis and just lap back and forward in the area where I wish to remove material. A good final polish with tooth past on Lee moulds works a treat. Take your time and all will go well. Regards Stephen

[john.k]

if you need to enlarge more,a simple way to make the lap cut bigger without casting intermediate sizes is to roll the lap bullet between two files......this raises a knurl somewhat over the cast diameter.....Not mine....a very old idea.

[KenH]

Screwed that up....oh well.

Bummer if you screwed something up - care to share what the problem is?

[Stephen Cohen]

Will be trying this idea, and thanks in advance. Regards Stephen

[longbow]

Pretty much all a guy needs for direction:

http://castpics.net/dpl/index.php/th...81-lapping-301
http://castpics.net/dpl/index.php/th...menting-a-mold
http://castboolits.gunloads.com/show...ing-of-boolits
http://castboolits.gunloads.com/show...hod-(In-parts)

I've lapped aluminum moulds by Lee, NOE and Mihec successfully and iron moulds by Lyman successfully.

In my experience enlarging more than about 0.003" is not only work but the tendency is that cavities start to lose sharp edges and start to go oval. Enlarging 0.001" to 0.002" is pretty easy especially with aluminum moulds.

I do not recommend using an electric drill for aluminum moulds if using relatively coarse valve lapping compound (400 grit). Best to lap by hand as aluminum is removed quickley.

Same for simple clean up (Lee-menting). Casting through a nut is easy and works well. Just put the mould in a padded vice and turn the nut back and forth using a wrench.

With iron moulds basic clean up and burr removal lapping by hand goes pretty well but to remove any significant metal a drill is better.

And the advice to go slow is absolutely correct. Take it slow and easy, after a bit of lapping stop, clean up the mould blocks (get all lapping compound off the faces of the blocks), check the new diameter and finish then if required put another lap in and do some more. If you get impatient and go fast there is much more likelihood of ruining a mould.

My experience anyway.

YMMV

Longbow

[Rokkit Syinss]

Bummer if you screwed something up - care to share what the problem is?

It went oval. No biggie, only a $20 mold and a little effort wasted. Meanwhile I think I'll just buy a mold that does what i want from the get go.

[Rokkit Syinss]

Pretty much all a guy needs for direction:

http://castpics.net/dpl/index.php/th...81-lapping-301
http://castpics.net/dpl/index.php/th...menting-a-mold
http://castboolits.gunloads.com/show...ing-of-boolits
http://castboolits.gunloads.com/show...hod-(In-parts)

Snip for brevity.

YMMV

Longbow

I checked all that out before I started. Like I said above, no biggie, just a $20 mold and some effort wasted.

[Bent Ramrod]

If the ovalization occurs at the parting lines (which it generally does for me) you could restore roundness (and even out much of the enlargement) by judicious beagling, then sizing and lubing.

That’s “the Heartbreak of Lapping:” any attempt at serious enlargement (more that 0.0015” or so) of the cavity generally results in slight out-of-roundness. Even clamping the blocks in a four-jaw chuck in the lathe, indicating the cavity to 0.000” and using the lap in the tailstock chuck will induce a thousandths or so ovalness at or beyond 0.002-0.003” enlargement.

The hopeful news is that this condition (for me at least) doesn’t seem to manifest itself at the target, even at considerable distances. The boolit swages back to round in the leade of the chamber as the cartridge is fired.

I wouldn’t judge that mould as “ruined” until I shot a few castings out of it and saw how they did.

[Rokkit Syinss]

Setting it aside for now. No biggie as I learned diamond paste cuts VERY fast on aluminum and one cannot learn without the occasional failure.

[Petander]

I lapped both my Lee 457 molds long time ago,45-70 was the first caliber I learned casting on. I felt stupid when I realised my boolits were undersized.

I've bought bigger "458" molds from other manufacturers ever since. 460 is good.

[Petander]

I tried the old Lee the other day just to see how it is doing.

Works fine,gives good bullets - It has made at least 20 k bullets during the years. I remember casting 1000 bullets the very first day I got it. Open fire and ladle,just starting on this back then.

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