Gunsmithing What size media for bead blasting?

[ridgeway]

What size glass bead media to get for a nice smooth bead finish on barrels and other parts including aluminum? There is a local supplier that carries all kinds of media in 50 pound bags. He said there is about 10 different ones and could not tell me grit equivalent since the manufacturer uses a mesh number of some sort. I'm guessing I would need something on the finer side of the spectrum?

They specify sizes as: Sizes: 20-325 mesh, 20-325 mesh MIL SPEC

 

[STR]

320 grit glass beads will give you what you described.

 

[STR]

I have never heard the word mesh to describe the grit on blasting media, sorry. Go somewhere else if they can't tell you what's equal to the grit you want.

 

[ridgeway]

With a little intardnet searching, I think I found an explanation to grit and mesh...

The terms Mesh and Grit are often misunderstood and confused. When it comes to discussing these terms in regard to abrasive blasting or similar, the terms are used interchangeably. A 60 mesh Aluminum Oxide can also correctly be termed a 60 grit Aluminum Oxide.

The differences arise when trying to determine the exact particle size of a 60 grit (or mesh) product. Each of the terms would be more correctly defined as follows:

Mesh is a count of the number of evenly spaced openings in one square inch of a screen (i.e., screen size). Mesh is basically a specific size or dimension (see Mesh and Micron).

Grit is generally defined as an angular media used to abrade or cut a work piece. Grit is a specified range of particles for a given product.

In practical terms, identifying a specific abrasive product with the term 60 Mesh would normally indicate that the product has an median size of the openings on a 60 mesh screen. The term 60 Grit more accurately identifies the particle size distribution of the product.

 

[forrestgump01]

What size glass bead media to get for a nice smooth bead finish on barrels and other parts including aluminum? There is a local supplier that carries all kinds of media in 50 pound bags. He said there is about 10 different ones and could not tell me grit equivalent since the manufacturer uses a mesh number of some sort. I'm guessing I would need something on the finer side of the spectrum?

They specify sizes as: Sizes: 20-325 mesh, 20-325 mesh MIL SPEC

Go to mcmaster carr website and pull up the type media you want and it will list the grit and mesh size for that particular type media. Example - 120 grit alum oxide media has a mesh size of 70 - 270. Hope this helps.

 

[bhoges]

My glass beads are called #10. Its makes for a nice smooth flat finish. Most places that sell it have samples of parts blasted with media you can check out.

 

[Geno C.]

The way I've been taught is that the numbers like 20-230 stand for 20% is retained in a 230 mesh. So 80% is finer than the 230 mesh holes. That's how it works when you order silica sand anyway.

 

[ridgeway]

Cool, very helpful guys. I'll see what I come up with...