blasting/tumbling question.

[jdm61]

How fine of a finish would you need in order for blasting or tumbling to remove tool marks, abrasive scratches, etc? The instructions on the bottle of rust eluding solution that I have had for years says that the process will "hide" 400 grit scratches. Is this about the same with blasting or tumbling? Also, can you do some blasting or tumbling before HT on areas that are not going to be ground afterwards and then go back and clean them up after HT?

 

[kuraki]

It depends on the type of abrasive being used, what velocity it's being delivered at, among other things. I've used 40 grit aluminum oxide at 90 psi and have had good results with the resulting blast profile hiding 320 grit sanding scratches. This blade was done that way, then parkerized.

40 grit AO may leave too much of a profile for some people. I have a bucket of 80 grit garnet that I haven't yet been able to try, but I think it would be safe to say it will hide 400 grit scratches.

I can't speak to tumbling other than my experience using a vibratory tumbler with corn cob or walnut media leads me to believe it won't remove any scratches. I'm sure ceramic media would, but that blasting does a much better job of it than tumbling would. But I've never tumbled blades, only rusty tools and shell casings.

 

[jdm61]

Thanks. The looks like it did the job for sure. I was thinking about ceramic media like what some folks use for the "stone washed" finish.

It depends on the type of abrasive being used, what velocity it's being delivered at, among other things. I've used 40 grit aluminum oxide at 90 psi and have had good results with the resulting blast profile hiding 320 grit sanding scratches. This blade was done that way, then parkerized.

40 grit AO may leave too much of a profile for some people. I have a bucket of 80 grit garnet that I haven't yet been able to try, but I think it would be safe to say it will hide 400 grit scratches.

I can't speak to tumbling other than my experience using a vibratory tumbler with corn cob or walnut media leads me to believe it won't remove any scratches. I'm sure ceramic media would, but that blasting does a much better job of it than tumbling would. But I've never tumbled blades, only rusty tools and shell casings.