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Thread: Best/safest media blast?

  1. #1
    CT70sKid's Avatar
    CT70sKid is offline 90cc
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    Best/safest media blast?

    I'm going to order some media blast from Harbor Freight for my ST90 project. I have no experience with this, but I've heard that sand is very harsh on the parts. Harbor Freight has Soda Blast, 80 grit Glass Beads, 40/70 grit ground Glass, fine Walnut and coarse Walnut. What should I get that would be effective but won't damage the parts resulting in unnecessary work? Thanks!

  2. #2
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    80 grit glass is all I use and the ST90 frame will not fit that cabinet. But I did all of my other parts in it. I paid somebody to sand blast my last ST90 frame.

    Rick

    Two CT90 and two ST90 bikes
    1973 Mighty Green ST90 K0
    1974 Mars Orange CT90 K5
    1975 Topaz Orange ST90 K2
    1976 Shiny Orange CT90
    2006 Honda Foreman 500 (restored)

  3. #3
    racerx's Avatar
    racerx is offline Super Moderator
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    Forget about using sand, it's only suitable for outdoor use...cleaning old buildings, etching headstones, etc. Never use it in a cabinet, it's crystalline silica and will shred lung tissue.

    Soda has some interesting properties...and potential problems. It leaves a nicely smooth surface, with minimal material removal...good for use on sheetmetal. Wet soda blasting is especially gentle on sheetmetal. However, there's some question as to its alkaline properties. No paint manufacturer will warranty their materials when used on a soda-blasted surface. That may be why its popularity seems to be fading. Soda is single-pass only, it cannot be recycled (run through the gun a second, third, etc time) making it pricey for the coverage.

    Glass bead is probably the best general purpose media. Its amorphous molecular structure makes it safe for use in cabinets. It will also survive at least three passes through the gun, though it does break down with each pass, becoming progressively finer. I would advise against using glass bead on any internal engine part surfaces, carburetor parts or non-metallic items.

    Walnut shells can be used on engine cases and internal pieces, since it's softer than metal. I wouldn't use it on engine internals except in rare cases where staining cannot be scrubbed away in a parts washer. That said, it works well to clean piston crowns, head castings and external surfaces of engine case castings...it won't "profile" (etch) the as-cast surfaces. The limitation of walnut shells is that they're also softer than iron oxide, meaning ineffective for rust removal.

    It's possible to change-out abrasives in the same cabinet, for specialized jobs. That quickly becomes a pain in the arse...and the primary reason most guys settle on glass bead.
    I am not a pessimist...I'm an optimist with real-world experience.

  4. #4
    CT70sKid's Avatar
    CT70sKid is offline 90cc
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    Thanks so much guys! I'm so glad I asked. I was going to go with walnut, but glass it is.

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