How do you polish a mold?

[Charlie Horse]

I have a Lyman 225415 mold that drops good bullets, but they want to stick in the cavities. Those little 46 grain bullets don't have much weight, so any little burr or whatever wants to keep them from falling out when the mold is opened. I think the process is to coat a bullet with some kind of polish then spin it in the cavity. Anyone have any more detailed instructions? I've been successfully shooting these bullets in my 22 Hornet Contender and want to try them in my bolt action 223. Shooting cast 22's is fun.
Thanks in advance.

Also, how do you polish the top of the blocks and the bottom of the sprue cutter? Thank you.

[vagrantviking]

The usual term is Lee-menting or something like that for search purposes.

I have polished aluminum molds and the occasional steel one with toothpaste or something like Flitz metal polish.

Cast several bullets, drive a screw in the center of the sprue mark and slowly spin it with a drill or similar. Go slow to start and reapply the polish as you go. Replace the bullet when the blocks will close on the bullet easily.
Great care will be required to keep the screw from poking out such a small bullet and scratching the mold.

[JonB_in_Glencoe]

I have posted my technique:
http://castboolits.gunloads.com/showthread.php?358488-Lee-menting-The-Spinning-of-boolits


how do you polish the top of the blocks and the bottom of the sprue cutter?
I wouldn't polish those, unless you are aware of a specific problem with them (like a warp). Machining marks, even microscopic marks will help vent your mold to give better base fillout. Some mold makers purposely cut venting on the top of the mold and at least one mold maker (LBT, I think?) has a sprue plate designed with venting in mind.

[country gent]

The tops of the blocks and sprue plate probably arnt causing the sticking bullets as there shouldn't be anything in that gap. Its more than likely a rough surface, burr or off center cavity causing it. If its burrs or rough finish lapping or polishing may help. On these small light bullets even square shoulders can lock the bullet in the cavity.
I would first look the blocks and cavities over good under magnification. Looking at the surfaces finish and edges closely. Also the grease grooves as 2 square edges may form a lock or if one is slightly under cut. Next would be a q-tip lightly ran thru the cavities and along the edges. Any pulled fibers indicate burrs or rough surface.

If you decide it needs polished.
cast several bullets id to cavity and drill the base for a stem do not break thru the nose body of the bullet.
These bullets are you laps to polish the cavities.
use 2 pieces of flat stock steel to impregnate the lap with compound. very lightly coat one plate with compound and roll bullet between the 2 plates under light to medium pressure. this impregnates the compound into the surface of the lapp.
Carefully and gently insert into cavity and close blocks .
Using a back and forth motion by hand do 4-5 1/3 turns back and forth rotate 1/4 turn and repeat thru 2-3 full rotations.
This will clean and smooth burrs and rough surfaces remember a .001 removed is .002 on the bullet.
Compounds need to be fine for this Flitz, simichrome, red rouge, or tooth paste will work here. All you need to do is smooth edges and cavity surfaces not any real metal removal.

This is a slow process and patience is required. lapp polish and test the cavities as you go. With the flitz, simichrome, or tooth paste water can be used to thin it and lubricate, when using red rouge I use a very light oil for this as it also tends to make it cut finer.

The off center cavities can be hard to trouble shoot as its hard to measure the round half cavities depth, I have done it with a indicator and height gage or CMM and small ball shaped probe. One way too get an idea of this is after the polish if bullets still stick in the same cavity and same side every time its a indication of this.

[Grmps]

New molds occasionally have burs on the edge of the cavities. Get a piece of hardwood or a #2 pencil and rub the edges of all the cavities and see it that helps.

IF you do decide you need to polish them, use the hardest alloy you have to cast the "slugs", a super fine compound (like Fitz or toothpaste) and only polish for 15 - 30 seconds using equal time, speed and pressure in each cavity

[LUCKYDAWG13]

Did you try smoking the mold to see if that helps you i have done this on lee molds and it worked great

[Charlie Horse]

Thanks. Considering that this is a 22 caliber mold I think I'm going to rig a steel wool brush for my Dremel and try that first. And I'll leave the top surfaces alone for now.

[toallmy]

No don't !

[toallmy]

By hand if you Must, steal wool will probably damage the cavity rounding the edge of the cavity , just take a couple cast slugs from the mold - remove them drill a tiny hole in the base wile not in the mold screw a very short 1/4 in headed screw in the boolits then use a 1/4 in nut driver by hand to slightly polish the cavity with toothpaste . Slowly close the mold wile turning the lap by hand + take time to open the mold and clean up the face wile lapping so you don't wobble out the cavity . You could have polished a cavity in a steel mold wile I typed this post by hand with a cast slug . I type with one finger:groner:

[country gent]

Steel wool will round corners and change angles. in this case the slug and polish is the best way it will maintain shape and edges. Steel wool even at the dremils lower speeds will cut and round corners. At upper end speeds balance and wobble become an issue of control and safety.

[Grmps]

Brass brush maybe if done By hand using a brush with a wooden handle, (thanks JonB for pointing out my omission) try the hardwood first. Brass (any ) brush in a power tool had a steel shaft that can harm your mold.

[Traffer]

Steel wool is a big mistake! You will be taking off far more material than you realize.
One "trick" I have learned for cleaning/polishing stuff in a cylinder type situation is to use a "Q" tip in a dremel. cut one head off and stick it in in the dremel and use the other end as the polishing head. But if it is not used inside of some type of round hole it will spin itself off right away.
EVEN with this method, I would be very careful as to what I would use for a polishing paste. Something very very fine and hardly abrasive...maybe talc or chalk or something. Jewelers rouge would work but again CAREFUL you will expand the size of your mold before you realize it.

[Walter Laich]

variation on screw in bottom of cast bullet:

I close the mold, move the sprue plate out of the way

put a 3/8 or 1/2" nut more or less centered over the cavities (usually have to skip one due to lack of room between cavities). I make about twice the number of these are there are cavities.

pour lead through nut and fill cavity and nut to top. now you have a bullet that can be turned with a socket or box wrench. YOU DON'T HAVE TO WORRY ABOUT A SCREW COMING THROUGH A BULLET AND RUINING A CAVITY!

when you put polishing compound on don't get any on bottom of nut --some usually gets on it anyway and while making shiny circles aroud top of cavity never seems to hurt the mold.

I have an air powdered socket wrench that I use to turn these. As I'm running it I push the socket/bullet against the cavity walls all around the mold--not sure if it helps but hasn't hurt.

I usually use two per cavity 'just because' and 600 grit Clover grinding compound.

As mentioned above--plan to spend some time doing this but it is time well spent in the long run.

[JonB_in_Glencoe]

don't use steel wool.
don't use a brass brush.

[Traffer]

I have used several molded bullets with stems of various sorts to polish both molds and swaging dies. One of the problems to work out is getting whatever stem you decide on to be centered. You can do a slug with some type of polishing compound on it with a stem to stick in a dremel, (which I have done many times). BUT if the stem is not PERFECTLY CENTERED in the bullet, It is going to spin eccentrically and that will BEAT THE LIVING STUFFING OUT OF YOUR MOLD when you put it on a dremel. If you are going to go with a bullet on a stick, I strongly suggest you spin it by hand to avoid destroying your mold.

[Dieselhorses]

Smoke it with a match or lighter like luckydog mentioned. Get a good enough carbon build up in cavities bullets fall right out.

[Traffer]

Smoking works! AND, Usually after you smoke them a couple of times they don't need it anymore.
I use a butane lighter. stick the flame right on the mold and it will soot up real fast.

[Rattlesnake Charlie]

I have found that many molds from different manufacturers have a slight "burr" where the cherry came out of that half of the mold. You can usually find this with a cotton tip as the cotton will "catch" where you cannot even feel an imperfection. I usually run a needle file around the edges of the cavity on any new mold I buy, applying very light pressure. This usually takes off that very fine "burrs" from the machining. Use a round or half-round for the curved areas and a flat for the straight areas. Easy Does It applies here. And, every mold has a "personality" unto itself. Some like the alloy hot, some cooler, some a fast pour, some slower. Experiment. Breaking in and learning a new mold is not something to undertake if you are under pressure. Kinda like getting to know a new woman. Please post your progress with this new mold here so we can all learn.

[Charlie Horse]

Thanks. You all have given me much to work with. I'll let you know what I find out.

[JSnover]

Every method I've used was slow and I'm ok with that. A $100+ mold can be ruined in under a minute.

[dragon813gt]

Also, how do you polish the top of the blocks and the bottom of the sprue cutter? Thank you.

You don’t want to touch the top of the blocks. But you can stone the bottom of the sprue plate. I do this w/ every mold I buy. Except for the ones made by Miha. Those plates are perfectly flat w/ no burrs. I really like NOE molds but the sprue plates always have burrs which will scratch the top of the blocks if not taken care of. You really see the inconsistency in how flat they are when you start removing the bluing from them. But they work great after being stoned.

[toallmy]

^^^^^ good point about checking the bottom of the sprue plate - even on new molds .

[Traffer]

^^^That there is good advise...gonna do it to mine now.

[Dragonheart]

Here is a simple trick that you may be surprised at how well it works and that is use a #2 pencil and color the cavities with the pencil lead.