hi,
i am not a mass finishing expert.
this post is just about barrel size and shot weight really…
i did investigate and attempt the processes awhile ago…
i read Judy Hoch’s excellent book first thing!
i also watched a video , about barrel tumbling with steel shot that was very instructive…
(i have not been able to locate that video again, so if any one knows of it and can send the link, that would be awesome!)
(i think it was an embedded link on a tumber manufacturers website…)
it showed the desired “action” of the media for optimum results and least part on part impingement.
they described it as the “S” motion…where the shot is rotated/ rides up the sides on the barrel to the optimum height and then gently slides back down the sides…rather than rolling too high up and then raining down…
i recall that barrel speed was said to be a factor too (in addition to other factors too of course) but more importantly the ratio of steel shot to barrel size was critical in achieving the right S flow action to reduce impingement potential…(i was attempting flat discs at the time, so i had a specific focus…)
i believe it wad 50% shot to barrel size…ie: fill the barrel up halfway…
what i discovered with a few small barrel tumblers that i bought, was that the motor rating was lower than the weight on the shot needed to fill the barrel halfway…
ie: motor rated for 3lbs maximum, but half a barrel of shot was 5lbs…
not sure how closely that needed to be followed…so i returned the smaller tumblers and continued my tumbler search…
i was trying to do multiple pieces, as opposed to single pieces…
somewhere along the way i got the idea that i needed a minimum of 50lbs of shot
which lead me to search for a barrel tumbling system that could accomodate the weight…and a barrel size that would be half full at 50lbs…
(i should preface all this with the declaration that i am an avowed tool junkie, and often go into “overkill” mode relative to my needs…)
anyway, i am just rambling on here…the main point being that be sure to look at the motor max weight rating, and barrel sizes. and weight of shot desired…
if i ever come across that lovely video again i will post it here!
julie