Where to source loose abrasive powder for WEETing a mold?

[BHuij]

I have a Lee mold that needs to be dropping a little larger than it currently is. After much reading around here, I think this thread is what I'm going to try:

http://castboolits.gunloads.com/showthread.php?257858-Expanding-a-boolit-mould-the-quot-WEET-quot-method-(In-parts)

Is there somewhere local I should be able to pick up a small quantity of abrasive powder, in the 180-220 grit range? I figure that will expand and then I can just use toothpaste to polish the cavities back up.

Everywhere I look I can only find paper- or cloth-backed abrasives. AKA sandpaper. We have Lowes, Home Depot, and Ace here.

[Minerat]

Have you tried looking for valve grinding compound? Autozone should have it.

[JSnover]

https://www.mcmaster.com/#4908a44/=1bg0by9
This is what I used.

[Preacher Jim]

That McMaster is what I have used. I have used valve grinding compound also.

[country gent]

Mc Master Carr, MSC, Graingers all have it both wet and dry look under lapping compounds. Also if there is a tool supply house near you that specializes in machining tools they should have it. There is aluminum oxide and silicon carbide available along with some diamond grades. aluminum oxide is harder and dosnt break down as fast so it dulls more. Silicon carbide is softer breaks down better and stays sharp better. also as it breaks down it naturally becomes finer grit. Diamond is very hard ( usually used for polishing carbides and other very hard materials) and very fine it takes along time to remove metal with it but a mirror can be made.

When lapping charge the lapp. every few turns add a drop or 2 of water or oil depending on your compound and a few more turns. The nice thing with dry compound is it can be used with either as you want.

If you have a machine shop local they may be willing to sell you a small amount of what they have on hand. Take a pill bottle with you. A pint can of compound goes a long long ways. LOL. (I have a tube of yellow diamond here that's been in my box for 20 years. also red, purple and white.) It dosnt take much to lapp a mould. maybe a amount the size of a pencil eraser.

[jcren]

If you just end a bit, "barkeepers friend" is a mild abrasive powder in the kitchen cleaning section that is more agressive than polish or tooth paste but milder than grinding compound.

[M-Tecs]

https://www.amazon.com/gp/aw/s/ref=is_s_ss_i_0_7?k=lapping+compound&sprefix=lapping&crid=1ZH7BKEM5JV31

[GhostHawk]

I had a opened can of valve grinding compound I acquired somewhere I used for my first.

Cleaned up and polished with this.

https://www.amazon.com/gp/product/B000BO8Z9I/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I used a bullet cast through a 5/16's nut, poured the lead through the center hole.

I "should" have done some hand filing in the gas check area. And I "should" have cut the nose off.

I did not put any compound or polish in either area but it does migrate into them.

I hand turned mine with a nut driver. Did not take long. Check often.

I use the blue metal polish for many little odd jobs, nice stuff. I also put it on a plastic barber strop.
Does a great job of polishing knife blades, even stainless. In 2 years I may have used half of that little tub. A little on a cotton rag is great for polishing up high carbon knife blades.

Plan ahead, Go slow, check often.

[gwpercle]

Another mild abrasive is automotive Rubbing Compound which is slightly more abrasive than Polishing Compound which is great for a final lapping .
I found things like Comet and tooth paste either too course or the grit was not consistent , rubbing and polishing compounds are ideal for finishing up .

[stubshaft]

Brownells

[MaLar]

Try your local headstone maker they use abrasives of different gritts. I asked the one here and they gave me a large paper cup full just for asking.

[BHuij]

Thanks for the pointers guys, grabbed some at an auto parts store.

Weet mentions in his tutorial using 180 grit equivalent for the coarse end of his cavity expansion; presumably he polished with something finer once he was approaching his target cavity dimensions. This was for a steel mold.

I am expanding cavities on an aluminum mold, and my compound came with a tube of 120 grit equivalent and 220 grit equivalent. Since aluminum is so much softer than steel, am I safe in assuming I should go with the 220 grit for my "rough" expanding and then final polish using something like toothpaste metal polish?

[Traffer]

120 grit is VERY large grit. I wouldn't get that anywhere near my molds. Even 220 is going to take it down quickly, depending on what you use to polish with. Turning it by hand will take a long time. Putting it on a dremel type tool is much quicker but you will have to be careful and do just a little at a time. I put a link to different paste grits on eBay. They are cheap. I find myself using the 320 equivalent for most of the rough work. Working my way down to 1000 grit, But this is my opinion. Others may have something else to say.

[Ballistics in Scotland]

Just about anything is much harder than aluminium or brass. A lapidary store, for gem polishers, will supply most of them, from the same grit you get on sandpapers down to very fine cerium oxide. Oil or turpentine is good for making a paste, for it may give trouble if water dries out. I agree that 120 is too coarse for mould work, and I would start with 20 or 400.

The best material for the lap would be bullet metal, for soft tends to drag embedded grit across hard. If you can't get the rotating rod dead central in the lap, you could run it at electric screwdriver speed, allowing screwdriver and blocks to move a little in your hands, so that the lap runs true in the mould.

[BHuij]

Ended up using the 220 grit. It was pretty quick to expand the cavities, but I was expanding them from about .355 to a target .359, so I had some material to remove. Worked great, my 6 cavity mold now has uniform .359" cavities, and I polished the cavities up with Brasso metal polish on a boolit to finish off. Gave the mold a thorough clean & dry, some graphite, and hit the important parts (sprue plate pivot screw, alignment pins) with some 2-stroke engine oil, and now it feels better than the day I unboxed it.

I'm hoping to find an evening to cast up a big old pile of 9mm boolits this week; will report back on how everything goes.

[Grmps]

If I'm taking a lot off I start with a valve grinding compound

And polish with Flitz Metal, Plastic and Fiberglass Polish Paste in 1.76-Ounce Blister Tube

or just use the Flitz for the whole process

See leementing http://castboolits.gunloads.com/showthread.php?32584-Leementing-Documentation-w-Photos


I've been thinking about cutting the boolit just above the shoulder/bearing surface so I don't enlarge the nose when I enlarge the base.

[BHuij]

I've been thinking about cutting the boolit just above the shoulder/bearing surface so I don't enlarge the nose when I enlarge the base.

I actually did this. I only wanted to expand the driving band area, so for all the abrasive slugs I made, I shaved off enough of the round nose area that it didn't make any contact with the cavities. Worked exactly as expected.