Fastening sheet metal

Big job would require a big machine. For a small job try an awl to punch the holes. It should create the burrs you are looking for. It's a neat idea.

There are a few different ways to do what you're talking about, but I'm guessing that the one you are asking looks a little like this:

...where the edges of the hole are slightly extruded, allowing for more thread depth. This is accomplished simply by punching a hole with one size punch, and a die with a larger clearance (I'm not sure of the actual ratio but let's say for S&G that you were punching .059 steel for a 4-40 tap, (Bear with me and my inches, I'm american) you'd use a .089 dia punch, and a larger, say .135 dia die, giving you .023" of space around the punch. The metal, instead of shearing and leaving a fairly clean hole, would pull (extrude) into the larger die.) My shop doesn't use this method, so the numbers, ratios and obstacles are unfamiliar to me, but that's the general gist of it. The tools themselves aren't "special" but the mis-matching of them is just a trick of the trade, so to speak.

Ya thats sounds like a great idea. I'll try it out. Seems to be cost effective since we already have die sets for punching, but I guess i'll have to see the consistency & efficiency of the process. Though we use about as much as 10-20 holes in about 2 square feet, we only do this about 1x per month. We build customized automation machines, as such order volume is not very high, but variety is. Thanks for the inputs!

1- different manufacturers have in their catalogues indications about the dimensions as well for the bore as for the minimal length

2- there ia tool designed for the thermo forming of the hole and protrusion. It is a rotary tool made of tungsten carbide which can be used with a drilling normal machine. This tool was first developed by a dutch company but now is available almost everywhere. After the metal sheet was deformed either a thread is cut, if standard fasteners are to be used, or special thread forming or cutting fasteners are used. This approach is also used for profiles as tubes or corners. The advantage is that no punching tool is needed.

Hi, thanks for the inputs. Could you please give me a suggestion re # 1 - manufacturers? Also, what is the proper name of the tool in #2? It sounds very promising and would like to know more about it. Thanks!

Hi,

Topic head read as "Fastening sheet metal" …I wonder it is about fixing sheet metal with another sheet metal or other object…it can be permanent fastening or temporary fastening…each these have many options…yes, Pl look at what is the real problem? Is tapping & metric screws are needed at all? With few threads engaged in the burr can hardly withstand any load or can avoid leaks…can we look at the situation differently? Back to you….

Guruprasad.K,Mumbai

Pierce extrude the hole, you can pierce then extrude or do it in one hit then tap it or alternately use one of the wide variety of "nutserts" that are used in the sheet metal industry, these are swaged into a pierced hole. Our company "Sheetmetal Tooling Tech. Pty Ltd." in Sydney, { Ph 1300 668 156 },markets a machine to do just that on a volume production basis.

Brien.

Hi Brien, thanks for the suggestion. I'll look into it, though I dont think I'll need a machine to do it as we dont do this in volume. Thanks nonetheless!

Hi, thank you for your reply. I guess it should have read "Fastening to sheet metal". The application is mounting various brackets for sensors, holders, etc. i.e. it is not holding much force. I've also seen this done on commercially available home appliances such as bread toasters, small ovens, and the like, and I was wondering if we could use it in our company.

I know that Trumph make punch tools for this, see http://www.trumpf.com/3.img-cust/inno_gewinde_big.jpg. I'm sure that other companies do as well. I've also seen a rotating tool like a blunt drill that generates heat from friction to extrude the metal but I can't remember who made it.

"Flow Drill" I believe is a name of the thermal thread forming tool. We have used this tool to install 1/4" NPT threads in 1" IPS schedule 40 pipe wall versus welded half couplings.

That's the one.

thanks guys for all the help!