How to make "divot" in 1/4" aluminum plate

This advice is worth exactly what you paid, but...

You'll probably run into issues with wrinkling, basically. A shop hydraulic press could probably do it, but anything just beyond the radius of your divots will probably wrinkle unless you have a binder on the die (perhaps called a "draw ring" or something similar. We call them binders).

Also, you'll have to do any other forming (for the diamond pattern, for instance) after the divots are made unless you don't mind the binder/draw ring leaving a ringed mark around each divot.

Lastly, and of least importance, you'll have to create your outside edges last as you will probably get a least some "draw" effect, even if your die is mostly stretching the material. Essentially your square blank will not be square after the divots and diamond patters have been produced as material will be drawn into these forms.

I'd wager the manufacturer uses a draw die to create the divots and pattern in one operation (maybe two) and then uses a pierce and trim die to complete the part. You would not be able to run the draw die on a shop press. Chances are you'd need a punch press (perhaps with a draw cushion for the binder) of over 100 tons, although I could be wrong with that number.

Boats are holes in the water into which you pour money. Didn't anyone tell you before you bought?

Regards,

Robin

A cheap and dirty way of making them is to make a form out of hard oak wood and pound it out with a ball-peen hammer into the form. Start from the middle and work outwards. You may have to anneal the metal as you go if you workharden it too much. Make sure you polish the end of the hammer so it will not leave marks in the aluminum.

John

He only wants to go down 3/16" of an inch on a 3" diameter divot. I was figuring that as a 3/16" offset over an inch or so span. Total bend of

I agree that the beat it down with a wood block has possibilites, even if it is just for a quick sample. Mak>

I would try the following idea first: since you have a hole in the centre of the divot why not use this with a suitable fine pitch HT screw to draw the two pieces of the die together? It certainly worked or me but that was in a little thinner material and not threadplate. You could always heat the area first (hot enough to blacken a piece of pine wood when touched to the area) and then quickly draw the die together. The heated alumunium deforms easily. You'd have to practise that on an offcut first to see if the overall flatness gets distorted by the process. Klaus

Thank you for all the replies. It sounds like a die with draw plate and a 100 ton punch press would be the way to get "factory type" results. I also gather that die design is not a trivial matter.

I did notice that the tread pattern on the store-bought hatches is not the same as the material I normally associate with diamond tread. It could be that they stamp the tread and divots in one operation as Robin suggested. I also did not think about the final shape of the hatch changing shape after divoting (makes sense)

The pound it into an oak form is right up my alley. I will have to give it a try.

Maybe I can latch this hatch down in some other fashion. As it type this i am thinking something involving a flathead fastener in a countersink. Any alternative latching ideas would also be gratefully accepted.

If all else fails, I could use plywood and epoxy for the hatch. (sheepishly admitting that I am more comfortable with this medium anyway) Thank you all again Andy

For the number of hatches you're talking about, I think welding in a boss machined from bar stock would be easier than forming the dimple. I like the flat head idea - how about a flat head socket cap screw as the actuator? A hex key is more convenient to store than a socket wrench, and cheap enough to keep a few spares around for when one inevitably falls overboard.

Ned Simmons

Drill holes, chamfer them, weld cover plates on the back.

You form a pocket in the wood and then start from the center of the metal and work outwards until the aluminum forms itself into the pocket in the wood.

John

RoyJ wrote: