Screw hole punches are very well suited for the processing of sheet metal, stainless steel sheets, non-ferrous and light metals as well as plastics up to 4 mm thick. They are mostly used for sinks for the installation of fittings, or holes in fuse boxes.
How does a screw hole punch work?
A screw hole punch consists of punch, traction bolt, die, and possibly a ball-bearing.
The screw hole punch is clamped between the sheet to be cut. During tightening, the traction bolt pushes punch and die together.
The punch can have two or three cutting edges that cut the sheet metal to form a clean, effortless and burr-free circle.
Screw hole punches are available with and without ball-bearings. The ball-bearing ensures that the frictional force between the screw and die is significantly reduced and lower torque is required. At the same time, the cutting force acting on the sheet is not reduced.
The working procedure
First drill the hole for the traction bolt. You can also do this with a step drill to determine the diameter more precisely.
The diameter of the through hole should be at least 1.0 mm larger than the diameter of the tension bolt.
The diameter of the screw hole punch is specified by the fitting. If you have a fitting with a required hole of 35 mm, the screw hole punch with 35 mm diameter has a traction bolt MF 12 (means metric fine with 12.0 mm). Therefore you need a diameter of 12.1 mm or larger.
It is good enough if you get to about this diameter, so that the traction bolt fits through. Here you can adjust the seat of the screw hole punch and thus compensate for an inaccurate hole if necessary.
As a second step you punch the hole in the sink by tightening the traction bolt.
Insert the traction bolt with die and possibly ball-bearing from above into your drilled hole. Tighten the punch from below.
Now you can use the cutting paste. Lubricate the cutting edges with the cutting paste. This reduces wear and thus increases the service life of the screw hole punch.
Tighten the traction bolt with the wrench until the hole is punched out.
Done: The hole for the fitting is punched out.
Why don't I simply drill the hole with the twist drill?
You may wonder why you can't just drill the hole for the traction bolt or even the fitting with the twist drill.
A sink is very thin, up to approx. 1 mm thick. So it's easy to bend it. That would happen with the twist drill and you'd put an ugly hole in the sink.
If there is no way around the twist drill because you don't have a sheet drill or step drill at hand, you can pre-drill with a 3.0 mm twist drill. Then take a 12.1 mm HSSE-Co5 twist drill (minimum for MF 12.0 mm) and drill the hole for the tension bolt.
To get a clean cut for the fitting, you can't avoid using a screw hole punch.
Summary and conclusion
With a screw hole punch, the hole for the fitting is punched out in only two steps.
With the sheet drill (or step drill) you drill the hole for the tension bolt of the screw hole punch and in the second step you insert the screw hole punch and punch the hole for the fitting.
In addition to individual screw hole punches, we also have complete case sets in our range which include more sizes of screw hole punches, a sheet drill and cutting paste.
In addition to manual tightening, there are also hand and foot hydraulic punches. In the electrical or sanitary sector, where you have to punch several holes a week, the hydraulic punches make your work easier. You can find the complete assortment under Products > Screw hole punching.