eski1
It sounds like the perf plate was punched with a large bottom clearance die. It is most likely that the smaller hole size is on the punch entrance side of the sheet.If you put the smaller size of hole to the face of the waste material, can you make the part work? If you have to have a parallel hole then you are going to have to go back to the perf sheet maker and ask them if they can tighten the tolerances for the bottom die on their machine, but I would not hold your breath waiting for an answer there.
B.E.

You are judged not by what you know, but by what you can do.

Some sort of electrolytic acid etch might be possible. You'd have a die with conic bumps, apply electricity and slowing bring the die toward the steel. The electric field would have it's highest concentration at the tips, so the steel closest to the tip would etch preferentially.

TTFN (ta ta for now)
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You can get straightish roundish holes
via laser cutting (with a small HAZ)
or via waterjet cutting (with a fine sand coating everywhere).
You provide a DXF file of the developed part you want.
Since the machines can run unattended, the cost may be less than you fear.
In fairness, you might ask for a quote from someone with a CNC drill.

Mike Halloran
Corinth, NY, USA

Tapered drill, water jet, laser (though the numerous hole starts make both WJ and Laser difficult), electrochemical etch (they would apply mask to both sides and then submerge in tank), or stamping.
There are few stamping methods to do this. It can be a combination of form and punch or I have seen a similar thing done by dimpling a plate and then machining the back of the 'bumps' off to open the holes.

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P.E. Metallurgy, consulting work welcomed

The general rule of thumb on perforated sheet is that holes are no smaller than sheet thickness. Stainless steel requires an even bigger hole than sheet thickness. It seems like these are unreasonable demands with hole diameters for a perforator. I would approach the client to make certain that they need this feature. You could still get the flat sheet laser perf'ed with conical hole geometry on a multi-axis laser.

There are perforators out there who can provide perforated sheets with dimpled hole geometry. By selectively installing punches it would be possible to perforate conical segments in the flat pattern. Get a discussion going with a perforator about what you need to make and then start a dialog between the client, perforator, and you. This doesn't sound like an unsolvable problem.

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eski1,
I have been assuming that the tapered holes are an undesirable side effect of the punching/perforating operation. But it just struck me that your client wants the conical holes and has specified them. Which is it?
B.E.

You are judged not by what you know, but by what you can do.

Hi

Thanks for the numerous replies , apologies i didn't make it clear but we Do actually need the conical Holes.
Sounds like we just need to find a perforater who can help us maybe although all the ones i've talked to thus far say its not something they can do :(

chris