What are the four core parts of the punch?

2026-02-25 17:05:48

The punch looks like a "metal rod", but it is actually the "main force of the sharp blade" in the mold. The accuracy of punching, cutting, and punching, the amount of burrs on the parts, and even the service life of the mold all depend on whether the structural design of the punch is in place. ESPECIALly for the four core parts of the head, shaft, guide, and punch tip, the geometric design of each part is carefully considered. Even the slightest difference can result in substandard parts and accelerate punch wear and needle breakage.

The four core parts of the punch are not independent of each other, but a whole that is "interlocked and coordinated". The punch tip is responsible for "breaking the hole" punching, the head is responsible for "pressure bearing" force transmission, the rod is responsible for "connecting" positioning, and the guide is responsible for "guiding" anti deviation. Only when the geometric dimensions and shapes of each part are designed accurately, can the punch work stably in high-speed stamping, ensuring part accuracy and extending its own life. This is also the core idea of Jingbo's punch design - not ignoring any detail, allowing each part to form the best fit.

Next, let's disassemble each part one by one, starting from the most critical punch tip, and then going to the head, rod, and guide parts. We will explain the geometric design points of each part in a way that everyone can understand and use.

Firstly, there is the punch tip, which is the "cutting edge" where the punch directly contacts the material and is also the most critical part of geometric design. Its shape, angle, and blade thickness directly determine the punching quality and durability of the punch. Many people think that the sharper the punch tip, the better, but this is completely wrong. Different stamping materials and aperture sizes have completely different geometric designs for the punch tip.

When designing the punch tip, Jingbo first considers the stamping material - if it is a thin material (such as copper foil or aluminum foil below 0.5mm), the top angle of the punch tip will be designed to be sharper, generally between 30 ° -60 °, and the cutting edge should be ground extremely thin and sharp in order to easily cut the material and avoid burrs and pulling; If it is thick material (such as steel plates or stainless steel plates with a thickness of 2mm or more), the top angle should not be too sharp. It will be designed at 75 ° -90 ° and slightly chamfered because thick material has high resistance during stamping. Sharp corners are prone to breakage and wear. Proper passivation can actually improve the service life and reduce cutting force.

Next is the geometric design of the cutting edge. Jingbo does not make a "one size fits all" straight cutting edge, but instead makes micro arc or stepped cutting edges according to punching requirements. For example, when punching irregular holes, the punch tip will be designed to match the hole shape perfectly, while ensuring uniform thickness at all points of the cutting edge to avoid excessive local force that may cause needle breakage; If it is a precision small hole (with a diameter less than 1mm), the punch tip will be designed with a "tapered" shape, with the tip diameter slightly smaller than the target aperture, leaving a wear allowance to prevent the aperture from becoming smaller after the punch wears out. Here we would like to remind everyone that the surface roughness of the punch tip must be controlled below Ra0.4. Jingbo will go through multiple precision grinding and polishing processes to ensure smooth cutting edges and reduce friction with materials.

Next is the head, which is the part where the punch is connected to the die handle and punch slider. Its core function is to "bear the punch pressure and transmit power", so its geometric design focuses on "pressure bearing area" and "connection stability", and cannot be designed too thin.

Many small manufacturers produce punch heads with the same thickness as the shaft, or with sharp transitions at the head. During stamping, the punching force is concentrated on a small area, which can easily cause the head to break, deform, or even drive the entire punch head to shift. When designing the head of Jingbo, the principle of "high pressure and slow transition" will be followed: firstly, the diameter of the head will be 10% -20% larger than that of the rod, which will be adjusted according to the overall size of the punch and the cutting force to ensure sufficient pressure bearing area to evenly withstand the pressure transmitted by the punch and avoid local stress concentration; Secondly, the transition between the head and the shaft will not be designed as a right angle, but as an R-angle transition. The size of the R-angle is determined by the diameter of the punch, generally between 0.5mm-2mm. A gentle transition can effectively disperse stress and prevent the punch from breaking at the transition.

In addition, the end face design of the head also requires attention to detail, ensuring absolute flatness and being perpendicular to the central axis of the punch. The Precision Expo uses high-precision grinding machines to ensure that the perpendicularity error is within 0.005mm. Because if the end face is not flat, the punching force will be biased, causing the punch to shake during the punching process, which not only affects the punching accuracy but also wears out the guide part. If a fixed punch is required, Jingbo will design steps, pin holes, or threads on the head to accurately match the geometric dimensions of the mold handle, ensuring a secure connection and preventing loosening during high-speed stamping.

Next is the shaft, which is the "torso" of the punch, connecting the head and guide, and also the "force support section" of the punch. Its geometric design core is "diameter matching" and "reasonable length", balancing strength and economy.

The diameter design of the rod should not be blindly increased or too small. The Jingbo Fair calculates based on punching force and punch length, following the principle of "sufficient strength and reasonable clearance": if the diameter is too small, the punch rigidity is insufficient, and it is easy to bend or break the needle during punching; A diameter that is too large will increase the difficulty of fitting the mold and waste materials. For example, for a punch with a diameter of 5mm and a length of 80mm, the diameter of the rod will be consistent with the base diameter of the punch tip to ensure overall rigidity; For ultra long PUNCHES (with a length exceeding 100mm), the diameter of the rod will be appropriately increased, or a "stepped rod" design will be made, with a slightly larger diameter near the head to enhance the overall bending resistance.

The length design of the pole is also a point that many people tend to overlook. The longer the rod, the better. An excessively long rod will reduce rigidity and increase the risk of bending; If it is too short, it cannot match the closing height of the mold. Jingbo will accurately calculate the length of the rod based on the customer's mold closure height, discharge plate thickness, and material thickness. Generally, the "effective working section" of the rod during stamping is just matched with the stroke to avoid excessive length and shaking. At the same time, the surface of the rod will undergo strengthening treatments such as titanium plating and nitriding, maintaining precise cylindricity in geometric shape. A small R-angle will also be made at the transition with the guide to ensure smooth force application.

Finally, there is the guiding part, which is the "steering wheel" of the punch, installed in the discharge plate or guide sleeve. Its core function is to "guide and prevent deviation, ensure concentricity". Its geometric design points are "sufficient length, precise fit", which is the key to avoiding punch offset and needle breakage.

Many stamping failures, such as punch misalignment, burrs that are larger on one side and smaller on the other, and broken punch pins, are caused by inadequate design of the guide part. For example, if the length of the guide part is too short, the punch will lose its guidance during stamping and be prone to deviation; The clearance is too large, causing severe shaking of the punch and inability to guarantee accuracy. When designing the guiding part, Jingbo first ensures the guiding length, which is generally required to be no less than 1.5-2 times the diameter of the punch. If it is a precision stamping or ultra long punch, the guiding length will be increased to 3 times the diameter to ensure that the punch is always in a precise guiding state before entering the material.

Next is the fitting accuracy of the guiding part. The Precision Expo designs different fitting clearances according to the stamping accuracy requirements: for ordinary stamping, the fitting clearance is controlled between 0.005mm-0.01mm; Precision stamping, with clearance controlled between 0.002mm-0.003mm. The geometric shape of the guide part will be designed as a "straight column type", with the surface finely ground and the cylindricity error controlled within 0.002mm, ensuring smooth sliding with the guide sleeve without jamming or shaking. In addition, a "taper transition" will be made at the transition between the guide part and the rod part, with a taper angle generally between 5 ° -10 °, to facilitate the insertion of the punch into the guide sleeve and avoid scratching the inner wall of the guide sleeve at the transition.

The punch is the "core vulnerable part" of stamping dies, and its structural design directly determines production efficiency and product quality. Instead of repeatedly replacing inferior punch heads and reworking parts, it is better to choose the right professional manufacturer from the beginning and do a good job in geometric design of each part. Jingbo has been deeply involved in the field of punch heads for many years, always putting "precise design and precision machining" in the first place. Each punch head undergoes strict design review and quality inspection to ensure accurate geometric dimensions of various parts and can adapt to various stamping scenarios, helping everyone solve the problems of punch breakage and insufficient accuracy.