Countersinking screw holes

Imagine you are designing a part that you wish to have laser cut and/or bent. The part contains one or more holes that need to be countersunk. At 247TailorSteel, we can laser cut, bend and drill holes for you. However, countersinking holes is a process that you must do yourself.

 In this blog post, we explain what you need to take into account when drawing the holes for Sophia®. 

Countersinking a hole

The process of cutting a hole with an angled edge for a screw head is known as countersinking. The hole is widened conically from the top. This is usually done so the screw head does not protrude above the surface. The screws can then be neatly concealed in the end product, as shown in figure 1.

Figure 1. Screw countersunk into sheet metal

Countersunk holes and Sophia®. What do I need to know?

At 247TailorSteel, we use CNC laser cutting machines. Because these machines cut downwards, any holes that are cut will have the same diameter on the top and underside. This means we cannot cut countersunk holes.

We can however cut the hole for you, which you can countersink yourself later by following the steps below.

Avoid countersunk holes in your drawing

Do not add countersunk holes to your drawings. Draw all holes with a single diameter, namely the lower diameter (see figure 2 below). You can then countersink the desired side of the sheet metal yourself to a wider diameter (so the screw fits in the hole).

Figure 2. Upper and lower diameter

When you use Sophia®, the best solution – in most cases – is to avoid adding countersunk holes to your drawing.

Leave countersunk holes in your drawing

However, in some cases you can leave countersunk holes in your drawing. When you upload your drawing in Sophia®, you will see the following warning:

Figure 3. Warning in Sophia®

This means we can process your drawing, but we can’t create countersunk holes. Instead, we will cut straight holes at the locations where countersunk holes are drawn.

Sophia® will use the diameter of the hole at the top of the sheet metal (which is shown in blue). The means:

• If the lower diameter of a countersunk hole is on the top of the sheet metal, we will cut the hole with the desired diameter.
• However, if the upper diameter is on the top of the sheet metal, the hole will be too large and it will not be possible to countersink it.

Figure 4. By using the ‘turning over plate’ feature, the countersunk holes will move to the correct side.

If all your countersunk holes (and thus also the upper diameters) are on the top side of the sheet metal in the drawing, you can select the ‘turning over plate’ option. The bottom side will be the new top side, and all lower diameters will now be on the top.

Please note:

1. If holes are drawn and the sheet metal is turned over, the circle representing the widest part of the hole must not touch the edge of the product. A minimum distance applies! For more information, please see the submission guidelines for laser cutting.

2.    If your drawing contains countersunk holes on both sides of the sheet metal, you cannot use this trick. In this case, you must replace the countersunk holes in the drawing with straight holes. This is the safest option in any case. 

Do you have any questions?

Please contact our Customer Service centre. We will be happy to assist you!