sand / shot bags for metal forming

[Mike Sal]

Are any of you (besides Gary) into making repair panels from sheet metal? I've finally made room to actually work in the shop now and ran across a leather sand bag for pounding on panels. Right now I have about 30 lbs of lead shot in the bat which makes it about 2/3 full. Just how full should the bag be? Should I stick with lead shot, or can I finish it off with sand?
Mike Sal

[tsenecal]

I'm not sure how the two would work together. I googled the bags on eastwood, and they say to fill theirs with dry sand. Hopefully folks with more knowledge than I, will respond. I have not used one, but would think that they couldn't be too full, although 2/3 may be too little.

[garyash]

Did I hear my name called, LOL? Kent White, who teaches metal forming near Grass Valley, CA, sells both canvas and leather bags as well as lead shot. Lead is expensive to buy and ship, but steel shot abrasive is much cheaper and usually available locally. Lead has a density of 11.3, steel about 8, and sand about 1.6, so a bag full of sand is typically too light for most forming jobs. Kent recommends 18 lbs of #8 lead shot in an 8"x8" bag, so that's maybe 13 lbs of steel but only 2.5 lbs of sand. The size of #8 shot is about 0.090" diameter. Smaller shot makes a smoother bag, but very small shot will run out the seams. Though you can't use it to hunt ducks, lead shot is still available for about $40 for a 25 lb bag.

See https://tinmantech.com/products/hand.../forming-bags/

Mike, I think the 30 lbs of lead shot in your bag is probably enough. Any heavier and it's too tough to move it around.

You can probably also use a stump or "shrinking facilitator" with a depression in it for rough forming and shrinking.
Here's Wray Schelin at Pro Shaper showing how to shrink metal: https://youtu.be/u4sKwu3jDHo

[Mike Sal]

I bought this bag from Harbor Freight 15 years ago but never used it. It's about 12 inches in diameter. It was made in india instead of china & has very tight seams. I've been accumulating lead shot for a while (I re-load shot gun shells into blank cartridges for our ww2 reenacting weapons) so will eventually gather up more to add to the bag. I have the bag on a 13 x 13 x 30 old beam that I can scoot out to use when needed. I've got a stump with a depression in it from when I was doing a lot of blacksmithing.
I have a man crush on Lazze & his videos on metal shaping. I've watched a lot of Wray's also (although I'm not too interested in working in aluminum). I have 10 more working days before I retire & am looking forward to getting a little deeper into panel making.
Mike Sal

[Mike Van Veghten]

One thing about lead, eventually it will break up and be mostly unusable (become too soft), starting from the first hit.
Sand will actually last longer, with steel lasting nearly for ever. Just remember to use small diameter balls. After using a sand bag, #8 steel balls seems rather large.

Personally, I'd use sand. I've shaped a couple small pieces for myself and a few pieces for a friend years ago. The bags I used were...OLD...purpose built, round leather bags. As I recall, it seemed to be filled with sand to about 75% in volume. I didn't use any fancy shaped plastic hammers, just an old ball peen.

The most difficult part if you don't have a planishing hammer, or roller is getting a smooth surface out of your hammered surface. I didn't have either of those "fancy" tools either... Just takes a lot of work (depending on your shape) in progressively lighter and lighter hammer blows, finally finishing with plain ol body dollies to smooth the surface.

One thing, depending on what you are doing, prepare to have one "hard" forearm muscle..!

Mike