Pullstud Bolts
Pullstud Bolts


The pullstud bolt is the only part connecting the machining center and the tooling. It is one of the most important components because this one bolt retains the tooling and it must stand up to severe cutting forces. Because the pullstud bolt is used under severe conditions it is regarded as a consumable item. This is why regular inspection and exchange is essential. However, in some cases pullstud bolts are used without regular inspection and because of the lack of inspection it may cause damage. Pullstud bolts suffer from clamping and unclamping during each automatic tool change as well as cyclical forces caused by vibrations during cutting. This cutting load can be the cause of breakage from fatigue. Generally speaking, a pullstud bolt has a three year lifespan due to the risk of breakage from fatigue. However, this life can be shorter depending on the operating conditions. There are two different methods of clamping a pullstud bolt. One method uses a collet and the other uses a ball lock system. In the case of the collet type the collets and pullstud bolt have face contact. With a ball lock type the pullstud bolt has only point contact. The ball lock type retention can cause dents on the pullstud bolt and tends to shorten the useful life. In production applications with very short cycle times frequent tool changes can shorten the pullstud bolt life and require more frequent replacement. In some cases the pullstud bolt may need to be replaced every six months if frequent tool changes are done with a ball lock type machine. There may be rare occasions where corrosion may be an issue. Coolant type, its management and the workpiece material may cause this problem. Water soluble coolant is generally alkaline in order to avoid rust and corrosion. However, during long-term use such coolant can become acidic and increase the rust and corrosion inside the coolant tank on the machine table, the work material or in other parts of the machine. The same can be said for pullstud bolts. With the increase of rust and corrosion its integrity decreases and can lead to fracture. In the machining of free cutting Steel’s the included sulfur components may be transferred to the coolant. Sulfur can corrode metal and may accelerate corrosion. Though it is rare, if the rust and corrosion of the machine, workpiece and tooling are evident, such corrosion may reach the pullstud bolt. We recommend regular inspection and replacement. Make sure to tighten the pullstud bolt properly so that it does not vibrate loose during cutting. After cleaning and degreasing the thread apply a thread lock adhesive. Tighten it to the appropriate torque. To use pullstud bolts with security, proper use, regular inspection and exchange are important. In addition, the quality of the pullstud bolt itself is important. BIG’s pullstud bolts are scrutinized for both dimensional control and material. Both hardened alloy steel and die steel are used depending on the application. As die steel is two times stronger than hardened steel in tension and 1.5 times in bending, you can use it for additional security. Regularly inspect the pullstud bolts for possible trouble and choose one with reliable quality for safe and secure production.

9 thoughts on “Pullstud Bolts”

  1. YourAnonymousGuy says:

    thank you for uploading, verry usefull, and helped me at uni.

  2. Sps Spindle says:

    Real good informational video.  The pull stud bolt is often an overlooked item that can have a huge influence in the accuracy of your tools. 

  3. gredangeo says:

    Why is there so many pull studs for? Where I work has 3 competing ones so holders are difficult to interchange. Two of them are way too similar. The grasp spot is at 90deg and the other is at 45deg. I don't see the point in having that kind of low difference.

    lol at the 3 years. We still have pullstuds that are over 10 years old or more.

  4. Metal Dawg says:

    Very good knowledge.

  5. CAD CAM 3D says:

    it's great

  6. Guds777 says:

    Inspection, not me, i just work here

  7. Matt Ruth says:

    They should make them out of 4340 steel. That shit got some insane strength and would be perfect for this application.

  8. luận van lim says:

    video mà chèn hết chu lên thì còn thấy cái gi chu

  9. Active Atom says:

    Great explanation and understanding to not take the retention knobs for granted. Nice advise on exchanging these devices.
    Lance & Patrick.

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