MB6/8 Split-Mold Clamping Bush

MB6 and MB8 are a custom-made evolution of the regular drill bushes that are often laminated into prepreg composite molds to serve as fixing points when bolting split-molds together.

Like regular drill bushes, MB6/8 are made of case-hardened steel but instead of a smooth outer profile they have two hexagon flanges to transfer the clamping load to the surrounding laminate and prevent rotation when using torque to remove the alignment pin or screws that have inadvertently become bonded to the bush after a cure cycle.

The bushes are designed to sit directly on the surface of the tool, rather than beneath one or two plies of laminate, which eliminates the burring of the laminate that can otherwise occur around the aperture after repeated use.

Further Information

How to Use

MB6/8 bushes are designed to be positioned on the pattern using extractable alignment pins (sold separately) which should be treated with release agent before use.

Positioning & Laminating

1. Patterns are designed with holes machined into the pattern where the bushes will be located.
2. Mold bushes are slid onto the alignment pins (with the hexagonal flanges at the top) which are then pushed into the positioning holes in the pattern.
3. Typically, a donut-shaped ring of lighter tooling prepreg is used to surround the mold bush on the tool surface and then a 45 strip of the surface prepreg is wrapped around the mold bush before the rest of the surface ply is laminated. A debulk is often undertaken at this point.
4. Heavier backing plies of tooling prepreg are then laminated around the mold bush and slightly up onto the sides of the alignment pin head.
5. The mold is then cured according to the processing requirements of the tooling prepreg.

Extracting the Alignment Pins

Alignment pins should be extracted before the mold is separated from the pattern.

The pins have an M8 thread in their cap and can be extracted by T-handle, slide hammer or cordless drill:

• T-Handle Hex Driver: Lock an allen cap M8 screw to the pin using an M8 nut and twist the pin free using a T-handle hex driver.
• Slide Hammer: Attach a slide hammer to the pin using an M8 thread (a thread adapter might be required).
• Cordless Drill: The chuck of a cordless drill can be tightened over the head of the alignment pin to provide a steady rotation and lifting action though it may be preferable to ‘crack’ the bond first with a slide hammer or T-handle.

Once the alignment pins have been extracted, the mold can be separated from the pattern and the laminate around the pins ground flat before the mold is post-cured ready for use.

Mold sections are bolted together using 30mm M6/M8 allen cap screws and dome head nuts (sold separately).

Dimensions

How to Buy

Our Split-Mold Clamping Bushes are sold individually but almost always used in pairs. They are available in MB6 (M6/6mm) and MB8 (M8/8mm) versions; in most cases we would recommend MB6 bushes for M6 fasteners which can provide more than enough clamping force for most molds.

Volume discounts are available and apply automatically.

For positioning, MB6/MB8 bushes require an alignment pin (not included) which is extractable and reusable.

MB6/MB8 mold bushes are also available to buy as a complete set of two bushes together with an alignment pin, 30mm cap head screw and dome nut.