Split Expansion Anchor

The Split Expansion Anchor is a removable mounting component designed for the Broinwood CNC Spoilboard System.

It installs into a machined pocket in an MDF spoilboard and uses a Threaded Insert to expand the two halves of the anchor against the pocket walls. Once expanded, it creates a secure 1/4"-20 threaded mounting point for Low-Profile Hold-Down Clamps and other compatible workholding setups.

The anchor can be removed, repositioned, and reused anywhere within the same spoilboard grid.

How to Install

The Split Expansion Anchor consists of two different halves:

• One half has two small holes on the top surface
• The matching half has a flat top with no holes

Together, these two pieces form one complete Split Expansion Anchor.

1. Insert both halves into a properly sized spoilboard pocket.
2. Install the Threaded Insert into the center of the anchor.
3. Tighten the Threaded Insert using an Allen wrench.
4. As the Threaded Insert is tightened, the two halves expand outward and grip the walls of the MDF pocket.
5. Continue tightening until there is a gap of about 1 mm between the two halves on both sides and the head of the Threaded Insert sits flush with or slightly below the top surface of the anchor.

These are the easiest visual indicators that the Split Expansion Anchor has been properly installed and expanded.

Excessive torque is not required. If using a drill/driver, use a low clutch setting.

How to Remove

Before removing the Split Expansion Anchor, completely unscrew and remove the Threaded Insert. This releases the expansion pressure against the walls of the pocket.

If the anchor remains firmly seated in the MDF:

1. Insert the removal tool into one of the two small holes on the top of the anchor.
2. Gently move that half away from the pocket wall to release it from the MDF.
3. Insert the removal tool through the center of the anchor.
4. Engage the extraction slot located at the bottom.
5. Pull upward to remove the anchor from the spoilboard.

The Split Expansion Anchor can then be installed in another pocket and reused.

Specifications

• Height: 16 mm
• Recommended nominal pocket diameter: 25.3 mm
• Recommended pocket depth: 17 mm
• Thread: 1/4"-20
• Recommended bolt relief hole: 8 mm
• Installation: Removable and reusable
• Designed for: MDF CNC spoilboards
• Manufactured in: USA

Important

The 25.3 mm pocket diameter is a recommended nominal size, not an absolute requirement.

A slightly larger pocket is perfectly acceptable as long as the Guide Pin fits snugly without excessive play. The actual pocket diameter may vary depending on your CNC machine, tooling, calibration, and cutting accuracy.

Before machining the complete spoilboard, I recommend starting with a 25.0 mm test pocket and checking the fit with a Broinwood Guide Pin.

If the pocket is too tight, increase the diameter gradually in 0.1 mm increments until the correct fit is achieved.

The Guide Pin should fit snugly, but it should still be possible to insert and remove it by hand without excessive force.

The fit is more important than the exact diameter.

Strength

The Split Expansion Anchor has been tested for pull-out loads of up to 120 kg (265 lb) under my test conditions.

This is a test result, not a certified or guaranteed working-load rating. Actual holding strength depends on the MDF, pocket dimensions, machining accuracy, installation, material condition, and other factors.

The anchor is designed to act as a replaceable sacrificial component if excessive torque is applied. Excessive tightening should still always be avoided.