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MG Midget and Sprite Technical - Countersink punch and die for sheet metal

I want to countersink some sheet metal (actually on the front wings) so that I can use countersunk screws to secure a mesh that has speed clips that the screws secure to. Just countersinking with a drill bit won't give me the finish I am looking for. So I want a simple screw together punch and die that makes a small countersink for a countersink screw. Does anyone know of a product I can buy or a way to make something that I can use and screw together?

Daniel

Daniel. As you note, the standard center drill (sometimes called a drill-countersink), nor a standard countersink would not work in such an application. Both work by removing material from the workpiece. In the case of sheet metal, it is simply too thing to work--the heads of the screws could rip through the metal too easily.

There are two ways to do such a job as you desire--the right way and the "maybe will work" way. The right, or correct way, is to take the sheet metal, place it on a machine that will have a "die" on the bottom (having a pocket countersunk into it) and a "punch" on top (having the same shape as the die, but in reverse) which is forced into the hold where it forces the metal into the die and causes the sheet metal to deform into the shape allowing a countersunk screw to be used. Hydraulic pressure, a significant amount, is used to force the sheet metal to bend into the desired shape.

The "maybe" system, whic I have not tried in this particular application but have used in other forms, is to make a die having a hole drilled through it, then countersunk to the proper depth (trial and error), then threaded on the inside hole. A small punch, designed to fit into the countersunk area of the die, is drilled through, then the end is shaped to fit the die, then, the work piece is cut to length. In use, a hole is drilled in the sheet metal, the die is placed on the back side of the metal, the punch on its center bolt is placed through the hole and the bolt tightened until it forces the metal into the shape needed. Some form of device will be needed to stabilize the die on the back side of the metal. A hex nut welded on to allow the use of a socket (sockets work better than a wrench/spanner is this application), or a cross bar, both used to prevent twisting of the die as the punch is tightened into it. If possible, heating of the metal, to a dull red, and the use of an impact wrench or air wrench to tighten the punch into the metal, should work better than hand tools. In either event, a bit of experiment with sheet metal of similar size should allow you to come up with the proper depth of countersink in the die and the proper size of the punch, as well as to get some practice before actually using it on an automobile.

Hope this will be of use to you as I have enjoyed your posts for the last 25 years.

Les
Les Bengtson

I thinks it’s a dimple die you need but not sure how small they make them . I have seen them for sale for making a depression for Dzus fasteners.
Mike Fairclough

The wing metal must be pretty thin and I think a conical countersink could be formed pretty consistently with a single hammer strike if you can contrive the necessary die and punch combination.

I have a large sized punch with a conical end that would work. What is needed is the countersunk die component. For the number you need to form I think you could use a piece of hardwood simply drilled with a woodworking countersinking bit. Simple solution, easily arranged. Must be worth a try on a piece of scrap steel.
GuyW

Yep-they're called dimple dies--If you have access to a lathe they're easy to make a pair----Then drill your bolthole---Girl die on the inside, boy on the outside, then poke a fine thread bolt through the pair and tighten to form the dimple----pic of a sample pair

William Revit

Nice image Willy and shows what I usually do and have an area outside the dimple to squeeze the main panel sheet metal to correct localised distortion caused by the dimpling. Easy things to make on a lathe and I've made many but they often get re-used so can only find a large one but haven't taken a photo yet.
David Billington

The photos, a slightly more involved dimpling tool made for forming a 75mm shallow cone in 1.5mm stainless steel. It's assembled with the sheet metal clamped between the 2 halves and then placed in a press, a fly press in my case, and the 3 pins press on the steel centre piece to form the dish. Worked great but unfortunately I didn't take a photo of the completed item.




David Billington

Thanks for all the replies. I don't have a lathe but do have a floor standing pillar drill.

I have dimple dies (purchased) which I have used on various things but none small enough for this job.

I have used a 10-32 threaded counter sunk head screw, a couple of washers and a nut to make a basic dimple that is a big improvement on having nothing at all.

What I am going to do now is make a proper counter sunk head female die from some hexagon bar I will drill and tap 10-32. Then I will use that female die with the same counter sunk head 10-32 screw to improve the counter sinking in the sheet metal.
Daniel

This thread was discussed between 19/05/2025 and 20/05/2025

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