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Hi-Lok$^{®}$. An interference fit is typically used for aluminum and a clearance fit is used for steel, titanium, and composite materials. [Figure 4-107] 

## Lockbolt Inspection 

After installation, a lockbolt needs to be inspected to determine if installation is satisfactory. [Figure 4-108] Inspect the lockbolt as follows: 

1. The head must be firmly seated. 

2. The collar must be tight against the material and have the proper shape and size. 

3. Pin protrusion must be within limits. 

## Lockbolt Removal 

The best way to remove a lockbolt is to remove the collar and drive out the pin. The collar can be removed with a special collar cutter attached to a drill motor that mills off the collar without damaging the skin. If this is not possible, a collar splitter or small chisel can be used. Use a backup block on the opposite side to prevent elongation of the hole. 

## The Eddie-Bolt$^{®}$ 2 Pin Fastening System 

The Eddie-Bolt$^{®}$ 2 looks similar to the Hi-Lok$^{®}$, but has five flutes, equally spaced along a portion of the pin thread area. A companion threaded collar deforms into the flutes at a predetermined torque and locks the collar in place. The collar can be unscrewed using special tooling. This fastening system can be used in either clearance or interference-fit holes. 

## Blind Bolts 

Bolts are threaded fasteners that support loads through pre- drilled holes. Hex, close-tolerance, and internal wrenching bolts are used in aircraft structural applications. Blind bolts have a higher strength than blind rivets and are used for joints that require high strength. Sometimes, these bolts can be direct replacements for the Hi-Lok$^{®}$ and lockbolt. Many of the new generation blind bolts are made from titanium 

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