Ball bearing dimples
In my haste I forgot to explain why I called my die a "rough prototype"...I am a machinist and this is not my first time to turn dimple dies...it has been a long time since I made a "shade tree" dimple die.
An old timer taught me how to poor boy dimple when I was a youngster. All you need is some thick plate 1/2" or thicker, drill bit (or hole saw) of appropriate size and a conical shaped (30 to 45 degree taper is good) grind stone mounted on a drill motor or angle grinder & a ball bearing (larger than the drill bit size by 10 to 20 percent).
Fab process is simple if not quick, poor boy had more time than money, drill hole completely through the heavy plate (same size as you want ID of finished dimple)...then secure plate to a vise or clamp to a work table and start grinding with the tapered grindstone. If you were lucky enough to have a drill press, I wasn't, it's easier. Welders supply companys have these tapered "rocks" for pipe fitters etc. look for the ones that look like lava rock, extremely rough finish, very agressive cut and last a long time...well worth the price. Grind till you have a uniform shoulder that will accomodate the ball bearing at something less than half it's height (this will be your approximate finished outside diameter of the pressed dimple) & your finished with the female die! Drop a ball bearing in the hole and youv'e completed the male die!
This works well for hole sizes of 1 & 1/2" and greater...smaller diameter holes are automatically enlarged by the size of the grindstone tip as it penetrates the plate. On smaller diameter dies (1/2" to 1&1/2" use a tapered reamer to form. If you have a drill press you can mount the reamer in it BUT do not use the motor; turn the chuck by hand & feed the reamer into the work piece slowly. The reamer also works with the lathe but again don't use the motor, use the tail stock to feed into the work.
Pressing sheet metal is simple, place the female die on a press plate in you shop press, lay the sheet metal on top of this (with pre drilled holes) level, centered & supported...drop the ball bearing in the hole and press till it feels & looks right. Practice on scrap till you feel confident and then go make something. One draw back is that you must make sure everything is centered up before pressing or your dimples will not be uniform.
Axle truss, cage gussets, bumpers killer projects & more. Don't need bunch of high dollar gear to do super custom one off fabs that look great!
Thats why I used the ball bearing to test press the two holes I posted previously just didn't explain all that. Yeah I turned it in a lathe a lot quicker and I could have just bought one for $150. but wheres the fun in that?
