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

Hello folks.
I am writing to get some suggestions for making an aluminum deck hatch
for a boat.
These hatches are mounted flush with the floor (deck) of a boat and are
watertight.
I am just in the thinking it out stage, but would appretiate any input
the group may have.
The product I am trying to duplicate is:
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is basically a piece of 1/4" diamond tread aluminum plate. This
plate has a series of "dogs" or latches which secure the hatch into a
stainless steel frame. the dogs are pieces of stainless flat stock
attached to a nut which is operated from above the hatch with a socket.
each dog has a corresponding divot in the hatch which serves to recess
the operating nut flush with the top of the hatch. The divots are
approximately 3" in diameter and 3/16" deep.
My question is this: is it possible to make these divots using a
hydraulic press (the sort with the hydraulic jack) and some dies? or
does this type of forming require a punch-press type of sudden impact
to get the desired results?
I have acess to a lathe to make the dies. I would like to produce say 8
hatches with 4 divots each.
any suggestions would be appretiated (including "go buy them you cheap
p.....")
Andy Hall
Lynn, MA
Reply to
andy
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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
Reply to
Robin S.
I can't say I've done that one but the principle is pretty easy: just use a suitable male and female die. Tonnage will vary with the exact shape of the angles and clearances you put in there. Large clearances will reduce the tonnage but make it more difficult to get the clean lines you would like. A quick calc for 6061-T6 says that it should be easy with a 50 ton shop press, suspect less would work
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Die design is a bit tricky. You need to have a retainer ring to hold the plate flat while you extrude though the center of the ring. If you don't hold it flat the plate will 'pucker'
andy wrote:
Reply to
RoyJ
6061 t6 will most likely crack before you complete the forming. If you anneal it it will eliminate the problem, but then you will have to get it retempered.
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
Reply to
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 20 degrees with 1/2" inside radius.
I agree that the beat it down with a wood block has possibilites, even if it is just for a quick sample. Making up the stock is probably a foregone conclusion though.
john wrote:
Reply to
RoyJ
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
Reply to
az_100
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
Reply to
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
Reply to
Ned Simmons
If it is the polished diamond plate it is probably a 3000 series aluminum and can be bent and formed fairly easily. If it is the dull mill finish it is 6061 and does not take bending or forming without annealing first.
john wrote:
Reply to
machineman
Drill holes, chamfer them, weld cover plates on the back.
Reply to
Don Foreman
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:
Reply to
john

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