sandblasted mold?

[Walter Laich]

saw some molds that look like they were sandblasted--guess to remove rust or whatever

any thoughts on these molds?

thanks

[Mica_Hiebert]

I would guess the bullets they cast would look sand blasted as well not to mention would drop like **** maybe you could polish them back out good enough to drop decent and powder coat the bullets

[dragonrider]

May not have any sharp edges on the rings and base.

[Reg]

Great way to ruin a good mold.

[brassrat]

This is an upsetting post and may cause nightmares and hangovers

[Doc Highwall]

It depends some on the grit used and for how long they were blasted. I have done it with a very fine abrasive using water in a vapor blast that removes almost nothing. I then polish the cavities making sure the edge breaks are even all around. After cleaning the mould I heat it up with a propane torch and use gun bluing to protect the finish and add the oxide finish to help the bullets release.

[country gent]

There are many mediums for "sand" blasting. I have seen fine sands, very coarse sands, baking soda, rice, corn cobs, walnut hulls used. All have thpluses and minuses. sands fine and coarse can be very abrasive. The medium pressure used to blast and angle of blast all affect the severity. A light polish with bullets cast from the mould with flitz or shimichrome polish might help remove the "roughness" to get bullets to drop good. It may have been done to remove rust or someones Idea to help tumble lubes to adhere better. Or an effort to correct a mould that wasnt dropping good. First thing to do would be make a test cast with mould and see what it does. Then go from there. A coat of soot or mould release may fill in the blasted roughness also.

[gwpercle]

Thoughts...not good. About like the folks who take a powered wire brush to the cavities !
I saw one that had the cavities blasted and it cast "frosted" boolits every time....the surface just wasn't smooth, thus they came out looking frosty.
Gary

[sparky45]

Thoughts...not good. About like the folks who take a powered wire brush to the cavities !
I saw one that had the cavities blasted and it cast "frosted" boolits every time....the surface just wasn't smooth, thus they came out looking frosty.
Gary
Wouldn't that be beneficial to those who Powder Coat?

[Dragonheart]

Wouldn't that be beneficial to those who Powder Coat?

PC chemically bonds to metal, so it doesn't depend of a rough surface to stick. I can see absolutely no benefit in sand blasting a mold. If rust has damaged the cavities then there are better ways to get rid of the rust, Kroil Oil for one. If the cavities are damaged then sand blasting is only going to make it worse. If I came across a mold like that I would try brushing it with Kroil Oil then heating in a toaster oven to about 400 degrees, let cool and continue to repeat the process until I had created a seasoning in the cavities, like seasoning a cast iron skillet. It wouldn't fix bad pitting.

[leadman]

I haven't use glass bead on a mold but I do have some 1500 grit glass bead that removes very little when used at a low pressure.

[rbuck351]

Fine glass beads probably wouldn't hurt much especially at low pressure, actual sand would not do the mold any favors. You could probably leement it and then just size it to what you want unless it was a nose rider. Most metal removed during sand blasting will be smoothed out in a sizing die and brought back to proper size.

[longbow]

There's far better ways to remove rust from moulds than sand or bead blasting.

However, even if something like phosphoric acid (Naval jelly) is used to remove the rust, if the surface is pitted it will have a sand blasted look to it.

If a mould had light rust I would use Naval jelly or just lap the mould. If it has heavy rust it is likely pitted. Could still cast usable boolits though. A guy would have to try it.

Longbow

[P Flados]

saw some molds that look like they were sandblasted--guess to remove rust or whatever

any thoughts on these molds?

thanks

Restoring a mold that has been blasted to useful might be possible, but only if it is OK to end up with larger than original size. Lapping can restore the mold surface and make it "round" again. Any sharp edges for holding grease in will be rounded off. This will not matter if you tumble lube or PC. If the base will not cast right, or if the surface under the sprue cutter is messed up, milling down the blocks might be needed.

The above sounds like a lot of work to get something that may not end up good enough for your trouble.

[rbuck351]

If one was a mold I wanted and the price was right, I would take a chance. I have a Swag-O-Matic that will cure a lot of cast boolit issues.