Pre-punched Hole
A pre-punched hole is a hole made in textile in advance before attaching a press fastener or eyelet, and it is provided to pass the part leg through and achieve proper riveting.
Contents6 sections
Definition and Overview
A pre-punched hole is a pilot hole made in textile in advance when attaching a metal or resin fastener. It is used to pass the leg or tube of a part through the textile and then flatten or flare it with a setting tool and press. Some parts require a pre-punched hole at the time of setting.
Some parts can be set without punching a hole, but whether a pre-punched hole is needed depends on the part structure, leg shape, textile thickness, and setting tool specifications. In the specification sheet, confirm the pre-punched hole diameter, setting tool, and attachment position along with the part to be used.
Relationship to Part Structure
Press fasteners are generally assembled by combining the cap on the front side, the socket and stud parts that open and close, and the leg section that secures them. Pass the leg section through the pre-punched hole, then use a dedicated setting tool to properly rivet each part.
For eyelets, pass the cylindrical eyelet body through the pre-punched hole and combine it with a washer if needed. Because the tube section is flared and secured by setting, the holding strength and finish are affected by the pre-punched hole diameter and the textile thickness.
- With press fasteners, it is important not to mix different part combinations.
- With eyelets, confirm the combination of the eyelet body and washer, as well as the front and back orientation.
- A pre-punched hole is a hole for passing a fastener through, and its purpose is different from a decorative or buttonhole eyelet hole.
How Size Is Expressed
The size of a pre-punched hole is generally controlled by hole diameter. However, when selecting it, you must confirm not only the hole diameter but also the part leg diameter or tube diameter, leg length, and compatible textile thickness. If the hole is too large, the part will wobble; if it is too small, it may damage the textile or cause poor setting.
Part size indications may be shown by cap diameter or the inner diameter of an eyelet, but these are not necessarily the same as the recommended pre-punched hole diameter. Confirm the specified value for each part, the matching hole punch, and the setting tool specifications as a set.
Installation and Suitability for Textile
Mark the attachment position, then make the pre-punched hole with a hole punch of the specified diameter. Assemble the parts with attention to the front and back orientation, set the matching tool on a hand press or foot-operated press, and apply pressure. Perform a trial setting to confirm the riveted condition and opening/closing performance.
Thin fabrics and highly stretchable knits require care because the area around the hole can tear or stretch. If necessary, use interfacing or reinforcing fabric together with the part, and for thick fabrics confirm whether the leg length is sufficient for the textile thickness. The number of layered fabric plies and seam allowance should also be judged according to the actual specification.
- If the pre-punched hole is misplaced, it can cause the fastener to tilt or open and close improperly.
- Use a setting tool that matches the part type and size.
- Before mass production, test with the actual textile, interfacing, and number of layers.
Quality Control and Precautions
After setting, check for scratches, deformation, lifting, rotation, and detachment on both the front and back sides. For applications subject to pulling or lateral force, evaluate not only the part but also whether the textile itself will tear. For products expected to be washed or rubbed, discoloration, corrosion, and plating peeling must also be checked.
When using metal parts, select the material and surface treatment according to concerns about rust and discoloration. For products that undergo needle detection, confirm whether they are needle detector compatible, and for applications that come into contact with skin, reflect nickel-free requirements in the part specifications at the planning stage.
Frequently Asked Questions
Is a pre-punched hole required for all press fasteners?
Whether it is needed depends on the structure of the press fastener and the textile being attached. Even for types that pierce the textile with a leg, some specify a pre-punched hole. Check the part installation instructions and the instructions for the compatible setting tool, and perform a trial setting on the actual textile.
What happens if the pre-punched hole is too large?
If the hole is too large, a gap will form between the textile and the area around the leg, causing the part to wobble, rotate, or pull out. In particular, tearing may spread in thin fabrics or loosely woven textiles. Select a punch that matches the specified diameter for the part, and confirm the holding condition before mass production.
Is there a countermeasure if the area around the pre-punched hole tears?
First check whether the pre-punched hole diameter is too large and whether the part leg length matches the textile thickness. For thin fabrics or easily stretched textiles, using interfacing or reinforcing fabric may help. Misalignment of the setting tool or excessive pressure can also cause damage, so adjust the press conditions with a trial setting.
