Everything you should know about flush bolt for aluminium door

Flush bolt for aluminium door have been widely used in construction sites, hydroelectric power stations and other fields in recent years. How much do you know about it?

The shaft surface of the bolt body is formed with axially extending threads, and at least one notch is provided at the tail end of the bolt body. The notch above the notch is then dug into the center of the bolt body with a chip removal groove. The chip groove is deep inside the bolt body and exceeds its centerline by a predetermined angle, providing the effect of preventing chips from blocking the notch.

What is flush bolt and countersunk head screw?

Mentioning flush bolt, some people will have doubts about the difference between flush bolt and countersunk head screw.

• Flushhead bolt: The axial surface of the bolt body is formed with axially extending threads, and there is at least one slot at the end. A chip flute is dug into the center of the bolt at the notch. The chip flute must penetrate into the bolt body and exceed the center line by a predetermined angle. The main function is to avoid the chip from blocking the notch.

• Countersunk head screw: The head of the boltis a 90-degree cone, and the head has a tool tightening groove, such as a slot, a cross groove, a hexagon socket, and a hexalobular socket.

The difference between flush head bolts and countersunk head bolts:

The contact surface is different, the contact surface of the flush head bolt and the workpiece is the bit plane, while the countersunk bolt is the bit cone;

The force is different, the force of the grub bolt is larger, and the force of the countersunk bolt is smaller;

The combination is different, flush head bolts can be used in combination with this flush washer, and countersunk head bolts can only be used in combination with tapered washer;

The use method is different. The flush head bolt can go deep into the counterbore or exposed to the outside, but the countersunk head bolt is generally only inside the counterbore.

The materials of flush bolt for aluminium door 

At present, the flush bolt for aluminium doors on the market mainly include carbon steel, stainless steel, and copper.

📌Carbon steel

We distinguish low-carbon steel, medium-carbon steel, high-carbon steel and alloy steel based on the carbon content of carbon steel materials.

• Low carbon steel.C%≤0.25%. It is basically called 1008, 1015, 1018, 1022, etc. abroad. Mainly used for products with no hardness requirements such as grade 4.8 bolts, grade 4 nuts, small bolts, etc.

• Medium carbon steel.25%<C%≤0.45%. It is basically called 1035, CH38F, 1039, 40ACR, etc. abroad. Mainly used for grade 8 nuts, grade 8.8 bolts and grade 8.8 inner hexagon products.

• High carbon steel. C%>0.45%. At present, it is basically not used in the market.

• Alloy steel. Adding alloy elements to ordinary carbon steel to increase some special properties of steel: such as 35, 40 chromium molybdenum, SCM435, 10B38.

📌Stainless steel

Performance level: 45, 50, 60, 70, 80;

📌Copper 

Commonly used materials are brass and zinc-copper alloy. The market mainly uses H62, H65, H68 copper as standard parts.

Features of flush bolt for aluminium door

The flush head can be divided into a full countersunk head and a half countersunk head. The flush head cone angle generally has 3 types of countersunk heads: 900, 1000 and 1200. In the Russian standard system, it is customary to use 900 and 1200 flush heads. The 1200 flush head is mainly used for thin-walled structures, but because the thickness of the head is thin, the depth of the bolting groove is not easy to control, the groove is too shallow, the bolting performance is too poor, and it is easy to "slip" when installing and disassembling the bolt; if the groove is too deep, it will weaken the strength of the nail head and easily turn around. In the ISO/TC2 standard system, there are only 900 flush heads, while in the ISO/TC20/SC4 standard system, there are only 1000 flush heads and 1000 small flush heads. Small flush head refers to the type with reduced head height. It is used for thin-walled structures of aerospace vehicles. Due to the characteristics of the flush head bolt structure, the head strength is generally lower than the bolt strength or thread strength. When flush head bolts are subjected to tensile failure test, the head of the bolt is usually destroyed first.

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